FMDS1202

April 2014Interim Revision April 2015

Page 1 of 31

VESSELS AND PIPING

Table of ContentsPage

1.0 SCOPE ..................................................................................................................................................... 31.1 Changes ............................................................................................................................................ 31.2 Superseded Information .................................................................................................................... 3

2.0 LOSS PREVENTION RECOMMENDATIONS ....................................................................................... 32.1 Recommendations Applicable to All Vessels and Piping Systems .................................................. 3

2.1.1 Introduction ............................................................................................................................. 32.1.2 Construction and Location ..................................................................................................... 32.1.3 Occupancy ............................................................................................................................. 32.1.4 Protection ............................................................................................................................... 32.1.5 Equipment and Processes ..................................................................................................... 32.1.6 Operation and Maintenance ................................................................................................... 52.1.7 Employee Training ................................................................................................................. 52.1.8 Human Factor ......................................................................................................................... 62.1.9 Utilities .................................................................................................................................... 62.1.10 Contingency Planning .......................................................................................................... 62.1.11 Ignition Source Control ......................................................................................................... 62.1.12 Electrical ............................................................................................................................... 6

2.2 Concrete Vessel and Piping Systems .............................................................................................. 62.2.1 Introduction .............................................................................................................................. 62.2.2 Equipment and Processes ..................................................................................................... 62.2.3 Operation and Maintenance .................................................................................................... 6

2.3 Metallic Vessels and Piping ............................................................................................................... 72.3.1 Open, Vented, and Atmospheric Pressure .............................................................................. 72.3.2 Low-Pressure Vessels (15 psig [100 kPa] and Vacuum) .................................................... 72.3.3 Pressure Vessels (15 psig [100 kPa] and Vacuum) ........................................................... 72.3.4 Pressure Vessels 3000 psig (20.7 MPa) and Vacuum up to 10,000 psig (68.7 MPa) ....... 92.3.5 Pressure Vessels 10,000 psig (68.7 MPa) and vacuum ................................................... 10

2.4 Wood Vessels and Piping ................................................................................................................ 102.4.1 Introduction ............................................................................................................................ 102.4.2 Operation and Maintenance .................................................................................................. 10

3.0 SUPPORT FOR RECOMMENDATIONS .............................................................................................. 113.1 Equipment and Processes: System Construction .......................................................................... 11

3.1.1 Metallic Systems .................................................................................................................... 113.1.2 Overpressure Protection ....................................................................................................... 12

3.2 System Operation and Maintenance ............................................................................................... 153.2.1 Metallic Systems .................................................................................................................... 153.2.2 Overpressure Protection Maintenance .................................................................................. 19

4.0 REFERENCES ....................................................................................................................................... 204.1 FM Global ....................................................................................................................................... 204.2 Recognized Vessel and Piping Codes ............................................................................................ 21

4.2.1 Pressure Vessel and Piping Construction Codes ................................................................. 214.2.2 Pressure Vessel and Piping Inspection and Repair Codes .................................................. 234.2.3 Tanks and Silos Construction Guides and Codes ............................................................... 244.2.4 Tanks and Silos Inspection and Repair Guides and Codes ................................................. 26

APPENDIX A GLOSSARY OF TERMS ..................................................................................................... 26APPENDIX B DOCUMENT REVISION HISTORY ...................................................................................... 29

FM GlobalProperty Loss Prevention Data Sheets 12-2

2014-2015 Factory Mutual Insurance Company. All rights reserved. No part of this document may be reproduced,stored in a retrieval system, or transmitted, in whole or in part, in any form or by any means, electronic, mechanical,photocopying, recording, or otherwise, without written permission of Factory Mutual Insurance Company.

APPENDIX C BIBLIOGRAPHY ................................................................................................................... 30

List of FiguresFig. 1. Collateral damage following catastrophic failure of a hot isostatic press ....................................... 11Fig. 2. Imploded tank caused by inadequate design ................................................................................... 12Fig. 3. Failure to anticipate internal pressure in tank design and no provision of system

overpressure protection resulted in liberation of process tank head .............................................. 13Fig. 4. A dip tank is an example of an open vessel; the salvage and the separator tanks are

examples of vented vessels ............................................................................................................ 14Fig. 5. A water supply suction tank is an example of a vented vessel ...................................................... 15Fig. 6. Plastic ducts of an emission-control facility, copper refinery .......................................................... 16Fig. 7. Manifolded tanks ............................................................................................................................. 16Fig. 8. Combination pressure-vacuum relief device using weighted pallet valves ..................................... 17Fig. 9. Eighteen in. (400 mm) diameter, weighted pallet vacuum relief valve ........................................... 17Fig. 10. Utility reheat steam lead failure in welded joint ............................................................................ 18Fig. 11. Erosion-corrosion or FAC likely led to failure of this power boiler feedwater pipe ....................... 20

12-2 Vessels and PipingPage 2 FM Global Property Loss Prevention Data Sheets

2014-2015 Factory Mutual Insurance Company. All rights reserved.

1.0 SCOPEGeneral recommendations and supporting information are provided for vessels and piping used in the storageor processing of solids (powders, granules, etc.) liquids, and gases.The term system as used in this data sheet refers to the combination of a vessel or vessels and theconnected piping and piping components.Note that the hazards of explosion, detonation, deflagration, and fire are beyond the scope of this data sheet.See Section 4.0, References, for resources regarding these hazards.

1.1 ChangesApril 2015. Data Sheets 12-66, High Pressure Forming Presses, and 12-26, Quick-actuating Closures, havebeen incorporated into this document.

1.2 Superseded InformationThis data sheet supersedes DS 12-66, High-Pressure Forming Presses, and DS 12-26, Quick-ActuatingClosures.

2.0 LOSS PREVENTION RECOMMENDATIONS

2.1 Recommendations Applicable to All Vessels and Piping Systems

2.1.1 Introduction

The scope of this data sheet is very broad. As a result, recommendations are usually also very broad. Inthe cases of a few vessel and piping types, more specific advice is provided, but not in great detail. For moreinformation, see the data sheets applicable to the specific service of the vessel or piping system.The following recommendations are, in general, for the vessel and associated piping system.Recommendations applicable to specific vessels are also usually applicable to the associated piping. Notethat in some specific systems, there may be relatively large diameter piping of comparatively thin wall usedfor collecting vapor or dust. This piping is commonly known as ducting.Use FM Approved equipment, materials, and services whenever they are applicable and available. For alist of products and services that are FM Approved, see the Approval Guide, an online resource of FMApprovals (www.approvalguide.com)

2.1.2 Construction and LocationFor construction and location recommendations, see the data sheets associated with the specific serviceof the vessel or piping system.

2.1.3 OccupancyFor occupancy recommendations, see the data sheets associated with the specific service of the vessel orpiping system.

2.1.4 Protection

For general fire protection and natural hazard recommendations, see the data sheets associated with thespecific service of the vessel or piping system.2.1.4.1 Develop and implement procedures to prevent corrosion or freeze damage during idle or shutdownperiods. Some actions to be addressed are passivation, filling with inert gas, dehumidification, ventingcorrosive gases from high points, and draining from low points.

2.1.5 Equipment and Processes

For general equipment and processes recommendations, see the data sheets associated with the specificservice of the vessel or piping system.

Vessels and Piping 12-2FM Global Property Loss Prevention Data Sheets Page 3


2.1.5.1 Construct systems to a recognized code (see Section 4.2, Recognized Vessel and Piping Codes).Include provision for natural hazards for the geographic system location (wind, earthquake, precipitation,flood, surface water and freeze).2.1.5.2 Specify a corrosion or thinning allowance or use of resistant materials to ensure system thicknesswill not be reduced below the minimum required for continued operation of the system components during theexpected operating life (internal and external thinning).2.1.5.3 Use materials and construction processes that are less susceptible to known failure mechanismsfor the intended service, such as chloride stress corrosion cracking of stainless steels or caustic stresscorrosion cracking of carbon steels (internal and external cracking).2.1.5.4 Specify system fabrication processes known to minimize in-service failure mechanisms, such as stressrelief of welds in carbon steel vessels, even if such processes are not required by jurisdictional code orconstruction code.

2.1.5.5 Retain all design, material specification, inspection, and repair records for critical piping. These recordswill be needed to evaluate the condition of the piping, determine if corrective action is needed, determineappropriate repair methods, and document any repair activity. These records will also be useful in determiningremaining service life.2.1.5.6 For sytems intended for operation at atmospheric pressure, provide the greater relief vent capacityrequired for overpressure relief during filling or required for relief during fire exposure. Also provide sufficientrelief vent capacity to prevent implosion during use (contents extraction, draining or collapse of vapor in thesystem) unless the system is designed for full vacuum service.2.1.5.7 Provide overpressure protection for sytems intended for pressure operation set at or less than theMAWP of the weakest system component with sufficient capacity to prevent exceeding the MAWP. Thisincludes vacuum relief for systems not designed for full vacuum that may be subjected to vacuum. Locatethese relief devices such that plugging by system contents is avoided.2.1.5.8 Provide instrumentation, controls, and safety devices to ensure critical piping does not experiencepressure, temperature, or flow in excess of design.2.1.5.9 Provide appropriate external corrosion protection for critical piping. If not insulated, select a coatingmaterial that will resist the expected ambient environment. If insulated, select an insulation material that doesnot contain elements that could damage the pipe if moisture is present. Provide a weather-tight covering forthe insulation. To avoid corrosion under insulation, it is vital that no moisture enter the insulation system frompipe system leaks or external sources.

2.1.5.10 Installing and properly maintaining insulation is critical to preventing corrosion under the insulation.Insulation should be selected and installed to prevent moisture from entering the system. Install insulationas follows:

A. Face all seams downward so water will be shed rather than providing a path for moisture to enter thesystem.

B. Install only dry insulation. If insulation becomes wet while in storage, dry it out thoroughly beforeinstalling.C. Install insulation only during dry conditions to prevent water from becoming trapped inside duringinstallation.

D. If installation is halted, seal off all openings to prevent wetting of the partially exposed insulation.E. If insulation is removed, cover the exposed surfaces to prevent wetting, and keep the insulation dry ifit is to be reused.

F. Reinstall insulation as soon as possible, being sure to dry previously exposed surfaces.2.1.5.11 Apply a protective coating to exterior surfaces of piping before installing insulation. This is the bestway to prevent corrosion. Effective coatings for prevention of corrosion are those that are suitable forimmersion in water. Technical organizations, such as the National Association of Corrosion Engineers (NACE),can be of assistance in determining the right type of coating to use for a specific application.It is not uncommon for a contractor to clean component surfaces in preparation for insulation and follow upwith a primer, assuming that this will provide adequate corrosion protection. Primers are not designed to



be protective coatings. Only coatings designated for immersion under water provide adequate corrosionprotection. Use of such coatings will also be beneficial during periods when insulation must be removed.

2.1.6 Operation and MaintenanceFor general operation and maintenance recommendations, see the data sheets associated with the specificservice of the vessel or piping system.2.1.6.1 Post the system operating instructions and precautions where operators can refer to them. Instructionsshould address any operating actions that could damage the system (e.g., maximum fill level or maximumwithdrawal rate).2.1.6.2 Calibrate and functionally test system interlocks and protective devices as recommended by thesystem supplier, or in accord with accepted industry practice. The maximum time interval should not exceed12 months. All testing should be documented.2.1.6.3 Establish and implement a facility-wide vessel and piping integrity assessment program.

A. Visually inspect (VT) all vessels and piping externally at least annually. More frequent inspection maybe recommended in other data sheets or necessary due to service conditions.

B. Visually inspect all vessels and piping internally at intervals appropriate for the system materials andservice. Inspection intervals and nondestructive examination (NDE) techniques may be recommended inother data sheets or required by jurisdictional authorities.

The scope of the assessment program should follow accepted industry practices for systems in similar service,be developed by a person familiar with both industry practice and the specific system (see Section 4.2,Recognized Vessel and Piping Codes), and be executed by a person having demonstrated the ability toassess vessel and piping condition. Revise the inspection program if system service conditions are modifiedin any way. Maintain written records of all inspections. It may be acceptable to substitute some externallyapplied NDE techniques in lieu of internal VT. See Data Sheet 9-0, Maintenance and Inspection, forrecommended types of maintenance programs. Also see service-specific data sheets, industry standards,and jurisdictional requirements.2.1.6.3.1 Evaluate a vessel or piping that has experienced an excursion beyond design parameters. Basethe scope of the evaluation on the extent of the excursion (pressure, temperature, flow, displacement of thesystem component, or combination). For relatively minor excursions, an expert may be able to determinethe condition of the system by analyzing operating records. For other excursions any of a variety of NDEtechniques may be employed and, for some excursions, material may need to be removed from thecomponent for evaluation. In some cases systems or structures associated with the component may alsorequire evaluation.

2.1.6.3.2 If hydrostatic or liquid pressure or pneumatic testing is required, use the lowest test pressurenecessary. For liquid pressure testing, confirm the temperature of both the component being tested and thetest fluid is maintained above the component material nil ductility transition temperature (to avoid brittlefracture during the test).2.1.6.3.3 Failure of pressure vessels and piping due to corrosion under external coating or insulation canbe avoided or mitigated. Facilities with susceptible vessels or piping should have a planned inspectionprogram to do the following:

A. Identify compromise of the coating or insulation jacket;B. Identify leakage under the coating or jacket;C. Confirm thickness of the pressure-containing material; andD. Promptly correct any deficiencies.

2.1.7 Employee TrainingThe scope of the training program is highly dependent on the system service. See specific service data sheets,industry standards, and jurisdictional requirements for additional guidance.2.1.7.1 Develop and implement a documented employee training program encompassing normal operationof the system, recognizing unfavorable conditions, and appropriate responses to emergency conditions.



2.1.8 Human Factor

The scope of emergency planning is highly dependent on the system service. See specific service datasheets, industry standards, and jurisdictional requirements for additional guidance.2.1.8.1 Establish an emergency plan for the prompt and proper response to fire or other emergency involvingthe system.

2.1.9 Utilities

For general utilities recommendations, see the data sheets associated with the specific service of the vesselor piping system.

2.1.10 Contingency PlanningFor general contingency planning recommendations, see the data sheets associated with the specific serviceof the vessel or piping system.2.1.10.1 Provide backup utilities for critical systems used for process cooling or heating if failure of the fluidflow may result in shutdown of the process, explosion, solidification of the process material, interruption ofnormal production, or similar events.

2.1.10.2 Develop and maintain a contingency plan for components of a critical system that are known torequire replacement or are suspected to be damaged. Either maintain material that will be needed to repairthe components or have a contracted supply source that guarantees delivery of the material within a timeperiod that will not extend the repair time. Include in the plan a means to complete the repair by qualifiedon-site personnel, or guaranteed prompt response from qualified contract personnel.

2.1.11 Ignition Source ControlFor ignition source control recommendations, see the data sheets associated with the specific service ofthe vessel or piping system.

2.1.12 Electrical

For general electrical recommendations, see the data sheets associated with the specific service of the vesselor piping system.2.1.12.1 Establish a program of electrical maintenance in accordance with the manufacturers instructionsand Data Sheet 5-20, Electrical Testing.

2.2 Concrete Vessel and Piping Systems

2.2.1 Introduction

The following recommendations are in addition to the preceding recommendations. For generalrecommendations, see the data sheets associated with the specific service of the vessel or piping system.Concrete is commonly used for construction of silos, bins, hoppers, and tanks primarily for holding solidmaterials. While piping associated with these vessels may be concrete, it is more likely to be metallic, withsome being plastic.

2.2.2 Equipment and Processes

2.2.2.1 When constructing a steel-reinforced or pre-stressed concrete vessel, apply the cement to at leastthe designers specified thickness. Typically, a minimum of 1 in. (25 mm) is needed to minimize corrosion.

2.2.3 Operation and Maintenance2.2.3.1 Periodically examine concrete vessels internally and externally for indications of cracking, spalling,or crushing of the vessel and to evaluate the condition of external or internal steel reinforcement to determinethe condition of the steel-reinforcing elements. If adverse conditions are identified, engage a qualifiedconcrete repair agency to restore vessel integrity. Until vessel integrity is restored, reduce the vessel fill levelsufficiently to avoid loss of integrity.



2.3 Metallic Vessels and Piping

2.3.1 Open, Vented, and Atmospheric Pressure

2.3.1.1 Introduction

The following recommendations are in addition to the preceding recommendations. These systems may becomprised of vessels or piping having square, rectangular, or circular cross sections. System elements maybe formed by from stamping, welding, bolting, or some combination. For general recommendations, see thedata sheets associated with the specific service of the vessel or piping system.

2.3.1.2 Operation and Maintenance2.3.1.2.1 Annually inspect accessible interior walls, floor, and roof of metal tanks. This is particularly importantwhen the tank is subject to corrosive or abrasive influence. Take corrective action when any parts or areasare thinned below the minimum required to maintain tank structural integrity.2.3.1.2.2 Semiannually examine fasteners securing the joints of bolted steel tanks. Tighten any loosefasteners. Restore the corrosion barrier on any fasteners that have corroded. Replace fasteners havingcross-sectional area reduced more than 25% by corrosion. Note that draining below the level of fastenersto be replaced may be necessary.

2.3.1.2.3 Remove any accumulation (dust, debris, snow, etc.) from tank roofs.2.3.1.2.4 Periodically examine steel supports, particularly for tanks containing corrosive liquids, for corrosion.Evaluate corrosion damage, repair as needed, and restore corrosion barrier.2.3.1.2.5 Routinely inspect tank linings. If a lining is compromised, determine the extent of corrosion damage,repair the tank as needed, and then restore the lining.

2.3.2 Low-Pressure Vessels (15 psig [100 kPa] and Vacuum)


The following recommendations are in addition to the preceding recommendations. These systems may becomprised of vessels or piping having square, rectangular, or circular cross sections. System elements maybe formed by stamping, welding, bolting or some combination. For general recommendations, see the datasheets associated with the specific service of the vessel or piping system.

2.3.2.2 Equipment and Processes

2.3.2.2.1 Construct vessels with a maximum allowable working pressure (MAWP) that is at least 115% ofthe maximum expected process operating pressure.2.3.2.2.2 Construct vessels that may be subject to vacuum for full vacuum to avoid having to provide andmaintain vacuum relief devices.

2.3.3 Pressure Vessels (15 psig [100 kPa] and Vacuum)


Adhere to the following recommendations in addition to the preceding ones. These systems may be comprisedof vessels or piping having square, rectangular, or circular cross sections. System elements may be formedby stamping, welding, bolting or some combination. Quick-actuating closures may be provided on thesevessels, particularly if operated in a batch mode. For general recommendations, see the FM Global datasheets associated with the specific service of the vessel or piping system.


2.3.3.2.1 Construct vessels with a maximum allowable working pressure (MAWP) that is at least 115% ofthe maximum expected process operating pressure.2.3.3.2.2 Construct vessels that may be subject to vacuum for full vacuum to avoid having to provide andmaintain vacuum relief devices.



2.3.3.2.3 In addition to Recommendation 2.1.5.7 (system overpressure protection), provide a processprotection scheme to begin shutoff of system inputs at 90% of system MAWP, and to open vents at 95% ofMAWP. The intent of this arrangement is to permit operation at the necessary process pressure and avoidoperation of safety relief valves or rupture disks, which may force interruption of the process.

An acceptable alternative to Recommendations 2.1.5.7 and 2.3.3.2.3 is implementation of overpressureprotection by system design. An example of this type of system is described in ASME BPVC VIII, Division1, Part UG-140, Overpressure Protection by System Design.2.3.3.2.4 Adhere to the following recommendations for quick-actuating closures:

A. Design the locking mechanism so the failure of one locking element will not result in the release orfailure of the other elements.

B. Arrange the locking and holding elements so a visual external examination can be made of theircondition and to confirm that the elements are fully engaged in the closed position.C. Where the locking mechanism or the closure is completely released by limited movement of the closureor locking mechanism and is hydraulically operated (by other than manual operation), design the unit(or provide protective interlocking devices) so the vessel cannot be pressurized until the closuremechanism is confirmed fully engaged (closed position interlock), and the mechanism cannot be releaseduntil the vessel has been depressurized to ambient pressure (internal pressure equal to external pressureinterlock).D. For manually operated locking mechanisms designed to release the vessel pressure before themechanism has been disengaged, provide an audible or visible warning device to alarm when an attemptis made to pressurize with an incompletely engaged mechanism, or to alarm when an attempt is madeto disengage a mechanism when the vessel is pressurized.E. Provide at least one safety device to prevent release of the locking mechanism until the vessel pressureis verified equal to ambient pressure. (Not applicable to multi-bolted closures.)F. Provide a pressure-indicating device on all quick-actuating closure equipped vessels, and ensure it isvisible from the operating area.

2.3.3.3 Operation and Maintenance2.3.3.3.1 Develop a system startup procedure to ensure the vessel is not pressurized until the shelltemperature is well above the transition temperature (to avoid brittle fracture).2.3.3.3.2 Adhere to the following recommendations for quick-actuating closures:

A. Examine all bearing surfaces for evidence of excessive wear. If found, discontinue use of vessel untilcorrective action is completed.

B. Examine gaskets for wear, damage, and leakage. Replace gaskets in accordance with manufacturersspecifications, including gasket material, with no deviations.C. Check closure hinge mechanisms for proper alignment and to ensure adjustment screws and lockingnuts are properly secured.

D. Examine closure-ring and locking-ring lugs for evidence of undue stress and for cracks at the junctionof the lug and closure or locking ring. Check locking ring and closure wedges to verify full engagementwhen closed, proper bearing surface contact, wear patterns, and condition. Consult the closuremanufacturer for replacement of missing wedges or securement of loose wedges.E. For closures using a contracting-ring locking device, check the ring for loss of flexibility, cracks at thepoints of attachment of the operating lugs, evidence of undue wear on the ring, and shear on the pinsin the lugs and on the operating mechanism.F. With clamp-type closures, check the surfaces of the clamps for wear, and examine the clamps fordistortion at the portions overlapping the shell ring and closure ring. Check hinge pins and locking-deviceparts for wear and evidence of shear.

G. With bar-type closures, inspect all bearing surfaces for undue wear and check the various parts forindications of undue stress as well as for distortion. Check arm-pivot pins to be sure they are securely heldin place and are not bent. Check pivot-pin mounting brackets for cracks at the point of attachment to the



head and evidence of undue stress in line with the pin holes. Check threads of the operating screw forwear and fit in the nut or hand wheel hub.

H. Check closures of the swing-bolt type for missing bolts. If any are missing, replace at once. Checkbolts for soundness, particularly at the eye, and check the threads for evidence of stripping or excessivewear. The bolt washers should be flat. Washers that are distorted to a dish shape tend to allow boltmovement out of the slot when the nuts are improperly torqued. Also inspect the closure when closedto be sure the nuts are fully engaged. Examine the pins for distortion and for secure fit.I. At each inspection of the vessel, check the closure safety-locking appliances and tested to be sure thatthey are operating properly and are in good repair.J. Anytime a locking ring binds or catches at some point during its movement, the point becomes a fulcrumand the entire ring tries to rotate around it. This may result in shifting of the ring position and cause unequaloverlap on the lugs. Therefore, it is important that any safety device that determines the positioning ofthe ring, such as micro switches, manually operated pins with two-way valves connected to steam signals,or any other type of device, be located at four equal quadrants of the ring. One safety device at one pointis not sufficient to properly indicate the position of the ring. Test these four devices.K. Check the closure and the locking mechanism both in a closed and in an open position. Observe theposition of the locking ring, the amount of overlap, and any shift in the ring position.L. Check the opening to the vessel for out-of-roundness at the outer edge. This is the difference betweenthe maximum and minimum inside diameter at any cross section. Under no conditions should it exceed1% of the nominal diameter of the cross section under consideration. Preferably, it should be zero.

2.3.3.4 Employee Training2.3.3.4.1 Provide the following training and operating procedures for vessels having quick-actuating closures:

A. Train operators in the proper operation of quick-actuating closures. Instruct operators in the potentialfor accidents involving the vessel and of the tremendous forces acting on the closure. Ensure operators areaware of and understand the importance of the following:

1. Ensuring the vessel is completely vented before attempting to open the closure2. The function of all operating controls and closure interlocking devices3. The danger of interfering with or bypassing any safety device

An operator who has not yet acquired sufficient knowledge and experience with quick-actuating closuresshould be closely supervised by a trained and experienced person.

B. Develop and implement safe and proper operating procedures. Incorporate the closure manufacturersoperating instructions. Implement a system to ensure procedures are kept current and operators continueto follow the procedures. These procedures should ensure the following:

1. The closure, the closure gasket, and the gasket bearing surfaces will not be damaged during loadingand unloading operations.2. Only trained operators engage or disengage the quick-actuating closure;3. Gasket and gasket bearing surfaces are examined for and cleaned of foreign matter prior to engagingthe closure.

4. Any difficulty encountered in actuating the closure is investigated and corrected immediately: beforethe closure cycle is completed.

5. No attempt is made to open the closure until the operator has determined all pressure has beenrelieved.

2.3.4 Pressure Vessels 3000 psig (20.7 MPa) and Vacuum up to 10,000 psig (68.7 MPa)


Adhere to the following recommendations in addition to the preceding ones. These systems are typicallycomprised of vessels or piping having a circular cross section. System elements are typically fabricated by



forging or welding. A system may incorporate bolted joints. Vessels in batch process applications typicallyincorporate quick-actuating closures. Fore more recommendations, see the FM Global data sheets associatedwith the specific service or application.

2.3.4.2 Construction and Location2.3.4.2.1 Consider pressure vessel rupture damage potential in design of building and location of vessels.Larger vessels containing fluid above its ambient boiling temperature or above its critical pressure may failcatastrophically, with extensive collateral damage.


2.3.4.3.1 Provide a fatigue analysis for vessels and piping. Follow practices described in a recognized codesuch as EN 13445 or ASME BPVC VIII Division 2.

2.3.4.4 Operation and Maintenance2.3.4.4.1 Do not exceed system design pressure and temperature limits when operating. If these limits areinadvertently exceeded, suspend operations until the vessel is examined and a new fatigue analysis isconducted. Results of the new analysis should be used to determine remaining cyclic life and new NDEfrequency.

2.3.4.4.2 Maintain records of operating data, including number of cycles and the maximum pressure andmaximum temperature during each cycle. Record any unusual conditions during each cycle. Retain theserecords throughout the life of the system.2.3.4.4.3 Completely inspect the vessel at installation or when resuming operation after an extended periodof inactivity. Corrosion is likely in idle system, particularly for systems utilizing water as process fluid.2.3.4.4.4 Conduct at least annual visual and dimensional vessel inspections and examine high-stress areaswith liquid penetrant (PT) to ensure that the surfaces are free of defects.2.3.4.4.5 Conduct ultrasonic examination (UT) of the vessel after every 25% of the design cycle life or everyfive years, whichever comes first.

2.3.4.4.6 If cracks, pitting, corrosion, or other indications are found, perform appropriate corrective measuresand complete an evaluation of the repaired component using fracture mechanics techniques. This is todetermine MAWP, cyclic life, and NDE frequency.

2.3.5 Pressure Vessels 10,000 psig (68.7 MPa) and vacuum


Adhere to the following recommendations in addition to the preceding ones. These systems are typicallycomprised of vessels or piping having a circular cross section. System elements are typically fabricated byforging or welding. A system may incorporate bolted joints. Vessels in batch process applications typicallyincorporate quick-actuating closures. For more recommendations, refer to the FM Global data sheetsassociated with the specific service or application.


2.3.5.2.1 Provide a fatigue analysis for vessels and piping. Follow practices described in a recognized codesuch as EN 13445 or ASME BPVC VIII Division 3.

2.4 Wood Vessels and Piping

2.4.1 Introduction

Wood vessels and piping (penstocks) for liquid service are uncommon. Construction is typically wood stavewith external metal hoops, bands, or cables.

2.4.2 Operation and Maintenance2.4.2.1 Maintain fluid levels in wood systems to prevent wood shrinkage and potential for leaks.



2.4.2.2 Examine hoops or bands encircling wood vessels and piping at least annually for evidence ofdeterioration. This is particularly important when the vessel or pipe is subject to a corrosive atmosphere orwhen any protective coating has outlived its useful life. When appreciable deterioration is discovered, replacethe hoops or bands. If corrosion has already begun, remove the corrosion and coat the metal withcorrosion-resistant paint.

2.4.2.3 Periodically examine staves of older wood vessels and piping for signs of deterioration and replacethem as necessary.

3.0 SUPPORT FOR RECOMMENDATIONS

3.1 Equipment and Processes: System ConstructionConstructing vessels and piping to a recognized code better ensures the equipment will function as intendedover the planned equipment life, and will facilitate future repairs. Specific requirements for structural loadsbeyond pressure containment are generally not provided in pressure vessel construction codes. These loadsneed to be considered to minimize damage from environmental factors.Construction codes generally address minimum material thickness required for containing pressure, and donot provide specific guidance on material allowance for corrosion and erosion for specific service applications.Process fluids may be either highly caustic or highly acidic, leading to rapid corrosion. Process fluid maycontain erosive material (dirt, sand) that may accelerate thinning of vessel walls and piping (erosion-corrosionand FAC).

3.1.1 Metallic Systems

3.1.1.1 Pressure Vessels and Piping (+15 psig [+100 kPa] Minimum)Critical systems must be designed, fabricated and installed in accordance with established industry-recognized codes and standards. However, even with these prerequisites, there is the potential forunanticipated failures. Faulty layout and support design, poor welding practices, erosion or corrosion thinningdue to poor material choice and system design limits not consistent with process operating limits are a fewof the more common root causes of loss. When released, pressurized fluid is likely to cause collateraldamage to nearby systems and equipment.

Fig. 1. Collateral damage following catastrophic failure of a hot isostatic press



3.1.2 Overpressure ProtectionOverpressure protection is system and service design specific. For example, open-top vessels containingliquids do not need overpressure protection since neither positive or negative pressure can be developed andvessels containing pressurized gases do not need vacuum protection since negative pressure cannot bedeveloped. Following is general overpressure protection guidance for systems that can be expected toexperience either positive or negative pressures.Process upsets and external exposures can result in vessel pressure exceeding intended pressure. Provisionof fixed overpressure protection ensures the vessels do not experience pressure significantly above theMAWP, which could reduce the vessel life. Data Sheet 7-49, Emergency Venting of Vessels, providesguidelines for the evaluation of overpressure protection systems. It indicates the overpressure protectionscheme should be based on the evaluation of the worst credible case. The actual overpressure protectionsystem design should be left to specialists.Overpressure protection schemes become more complex as the hazard and risk increase. Common to allschemes is operator observation for indication of adverse conditions with a planned response. The next levelis system monitoring and operating controls to regulate within set operating parameters. Next level may beinterlocks and safety devices to stabilize the system if predetermined safe limits are exceeded. The finalelement in overpressure protection is fixed mechanical devices solely intended to relieve pressure fromnormal operation that exceeds the system design or maximum allowable working pressure (MAWP).Vessel and piping codes typically address overpressure only from normal system inputs. Overpressure maydevelop from reactive, non-reactive or other high velocity process reactions. Note that specific serviceapplications may require additional or emergency venting. See Data Sheet 7-49, Emergency Venting ofVessels, or specific service application data sheets for emergency venting guidance.Designing process controls to reduce inputs and to open vessel outlets at a pressure below overpressureprotection device set pressure reduces the probability that the overpressure protection device will operate.Process vessel contents in suspension will generally flow toward any opening in the vessel, includingoverpressure protection devices connected to the vessel vapor space. The vessel contents may plug therelief piping as the flow dissipates, and can be expected to cause sticking of a pressure relief valve. Suchplugging would require taking the vessel out of service until the overpressure protection system is restored.Also, safety relief valves or rupture disks are the final overpressure protection safety element. Unnecessaryoperation is to be avoided.

Fig. 2. Imploded tank caused by inadequate design



3.1.2.1 Overpressure Protection Methods3.1.2.1.1 Open VesselsOpen vessels, bins for solids, tanks for liquids, are typically not subject to overpressure during normaloperation. Bins or silos containing solids may develop an abnormal condition if the material bridges orsolidifies over the entire surface of the vessel. If this happens, there is potential for a vacuum to develop asmaterial below the bridge is withdrawn. There is no relief device for this hazard, only the acceptedpractices to avoid formation of a bridge by design of the vessel, provision of vibration to prevent formationand preventing the vessel contents from becoming compacted or agglomerated.3.1.2.1.2 Vented Vessels

Vented vessels may contain solids or liquids and are typically designed with sufficient vent capacity that nopressure can be developed under conditions that normally occur, such as filling or emptying of the container.Liquid-service vessels and vessels having connections to vapor systems (e.g., clean-in-place steam sterilizingsystem) also require evaluation of vacuum generated by potential vapor collapse (the sudden transition ofvapor to liquid with concomitant volume reduction).

Fig. 3. Failure to anticipate internal pressure in tank design and no provision of system overpressure protection resultedin liberation of process tank head



Note that many vented vessels are equipped with dust or vapor collection systems. These collection systemstypically operate under a slight vacuum. For the collection system piping (ductwork) overpressure protectionsee Data Sheet 7-78, Industrial Exhaust Systems, or other specific service data sheet.3.1.2.1.3 Low-Pressure Vessels (15 psig [100 kPa] Maximum)Low-pressure vessels are typically in liquid service with some solids applications. Note that liquids may includesub-cooled liquids (liquefied flammable gas). For very low system pressure, typical relief devices areweighted-pallet or weighted-lever valves for positive or negative pressures. When both positive and negativepressure protection are provided by a single device, the device may be called a pressure-vacuum relief valveor conservation vent.

As system pressures increase, direct acting spring-loaded valves become viable choices. Pin devices(buckling or breaking) also become an option if reclosing is not necessary or desired.Rupture disks may be used for all positive or negative pressures, but are non-reclosing devices.

Fusible link

Conveyor

Drain board

Note: The distance Atimes the specificgravity of the liquidmust be greater thanthe distance B

Note: Trap may be omittedwhen dump line terminatesin salvage or separator tank

Weir

Splashguard

Vent withflame arrester

6 in.(150 mm)

Overflowdrain

Trap

Or to safelocation

Or to safelocation

Ground line

Ground line

Level of bottomof dip tankWeight

(in closed position)Side view of quick opening dump valve

To fusible linkand manual release

Note: The distance C timesthe specific gravityof the liquid must begreater than thedistance D.

Automatic sprinklersCarbon dioxide orfoam nozzle

Cable release hookHeat detector

Vent withflame arrester

Overflow samesize as dump line

(125% of dip tank capacity)

(125% of dip tank capacity)

Pump out line

Pump outline

Dump line

Dump line

Sewer

TrapOS&Yvalve

lockedopen

Quick openingdump valve

Dip tank

Separator tankKey

Salvage tankB

A

D

C

Cable to safe location formanual release of weight

Fig. 4. A dip tank is an example of an open vessel; the salvage and the separator tanks are examples of vented vessels



3.1.2.1.4 Pressure Vessels (+15 psig [+100 kPa] Minimum)Positive pressure relief for systems designed for a minimum 15 psig (100 kPa) may be provided by rupturedisks, pin devices or non-reclosing valves if acceptable for the process material. If a reclosing device isnecessary for the specific service, FM Global recommends use of direct-acting spring-loaded valves or pilotactuated spring-loaded valves. Use of weighted valves for this pressure range is not recommended duepotential for altering the valve set pressure, inadvertently or purposely. Negative (vacuum) pressure reliefmay also be needed for systems potentially subject to vacuum but not designed for full vacuum.

3.2 System Operation and Maintenance

3.2.1 Metallic Systems

3.2.1.1 Avoiding Temperature-, Pressure-, and Support-Related FailuresDue to operation at high pressure or temperature, a critical system is subject to pressure and thermaltransients (consequence of operation), fatigue (result of inadequate or improper support), and adverse

Fig. 5. A water supply suction tank is an example of a vented vessel



Fig. 6. Plastic ducts of an emission-control facility, copper refinery

Fig. 7. Manifolded tanks



Fig. 8. Combination pressure-vacuum relief device using weighted pallet valves

Fig. 9. Eighteen in. (400 mm) diameter, weighted pallet vacuum relief valve. Set pressure on order of inches of water(mm of water) with relief capacity on order of 20,000 scfm (566 m2/min) air.



metallurgical changes over time (resulting from operation in or near the creep regime). Operating andenvironmental factors may accelerate internal corrosion or erosion. The accumulation of creep (intergranularcracking due to high stresses and elevated temperatures), fatigue, and corrosion damage can lead toinitiation and propagation of cracks. If not detected by appropriate inspection and addressed by appropriaterepair, the result may be catastrophic failure.

Periodic inspection of a critical system and its supports assures the design bases are maintained, andequipment nozzle loads (forces and moments transferred to equipment by the piping system as a result ofoperation dynamics) are within limits, as well as forming a basis for remaining-life evaluations. Inspectiontechniques are selected to assure an acceptable probability of flaw detection. The success of any necessaryrepairs is ensured by employing experienced and qualified personnel who follow appropriate repairprocedures.

Piping support systems must be inspected and maintained to ensure stresses on critical equipment do notexceed the design limits. Systems normally are designed with low-point drains to permit the elimination ofcondensation. Long term operation of high temperature steam piping may lead to pipe creep and sag. Whensag occurs, condensation can accumulate in these new low points. Internal corrosion and steam hammerduring startup are common when sag has occurred.The high impact stress from steam hammer may cause cracking or rupture of system components. A pipingsystem typically moves during steam hammer, placing unplanned stress on the piping support system(hangers and snubbers). The supports, which may include major structural steel members, may be damagedand the pipe may be cracked at welded attachments for the supports. Common causes of this phenomenonin piping are rapid stoppage of flow, such as closure of steam turbine emergency stop valves, or theintroduction of a large quantity of water into a hot steam line. In the former case, the energy in the momentumof the flowing steam must be absorbed by the piping system. In the latter case, the water flashes to steam,

Fig. 10. Utility reheat steam lead failure in welded joint; timely inspection could have provided opportunity for correctiveaction prior to failure



causing shock waves in the pipe. Pipe systems are provided with snubbers at changes in direction to reducethe amount of displacement, but resultant forces are transmitted to the structure. Water hammer is similarto steam hammer except water is incompressible, which can increase shock forces. Proper vent, fill, drain,and pressurization can mitigate steam or water hammer in piping systems.Inadvertent entry of water into a hot steam pipe is a common cause of steam hammer in power generatingfacilities that incorporate reheat cycles. This typically results from leakage through a block valve. Leak-tightblock valve integrity can be extended by operating practice (i.e., terminating flow using a control valve, whichis designed for throttling service) before closing the block valve. Again, regular inspection and maintenanceof these piping system components can mitigate this hazard.Effective inspection of in-service systems, with appropriate repair or replacement of damaged components,can mitigate critical system failures. This is a lesson some electric generating companies learned the hardway, after suffering catastrophic failures of seam-welded hot reheat piping in 1985 and 1986. Subsequentinvestigations revealed that in some plants, seam-welded pipe had been substituted for the specifiedseamless pipe, and experience demonstrated seam-welded pipe was likely to develop cracks in the heat-affected zone of pipe material at the seam weld. Inspection programs for seam-welded pipe were initiated andreliable examination techniques have been developed. Many electric generating companies have replacedextensive seam-welded piping systems to avoid disastrous failures due to creep.

3.2.1.2 Avoiding Corrosion- and Erosion-Related FailuresCorrosion and erosion reduce the thickness, and thus the strength, of critical piping. Corrosion can damagefasteners holding piping together, and when combined with stress, can result in cracking. Without timelydetection and corrective action, the pipe will fail. Production may be interrupted and nearby equipment orstructures may be damaged.Corrosion and erosion occurring inside critical components is not readily apparent during normal operations.External corrosion of insulated components also is not readily apparent. Without an inspection program,undetected thinning leads to failure and an unplanned outage.Corrosion is a process of deterioration of metal. A common example is rusting of steel. The process iselectrochemical in nature, involving the transfer of electrons from the metal to something in the surroundingenvironment. Corrosion may be generalized, occur over a large area and appear uniform, or be localized,occur over a small area and appear as pits or cracks.

The electrons released from the metal by corrosion react with hydrogen, forming a thin, gaseous film onthe metal surface that impedes further corrosion. However, breakdown of this film increases the corrosionrate. For example, dissolved oxygen in boiler feedwater can react with the hydrogen in the film, forming waterand destroying the protective film. High fluid velocities, solid particles, or bubbles in the fluid also may disruptthe film. High temperature and extremes in pH (acid or caustic) can increase the corrosion rate. Corrosionthat occurs on insulated external surfaces is driven by trapped moisture and may be accelerated byconstituents in the insulation, or water that has leaked into the insulation. This type of corrosion is commonlyknown as corrosion under insulation (CUI).Erosion is a mechanical process. Typically, solid particles impact the metal surface and break the protectivefilm or scrape away metal, much as sandpaper or a grinding stone would. The simultaneous combinationof both processes is known as erosion-corrosion and is often called flow-accelerated corrosion (FAC).

3.2.2 Overpressure Protection MaintenanceThe scope of overpressure protection maintenance is highly dependent on the specific service. At least annualverification that vent lines are unobstructed and vent caps, when recommended, are in place.

All relief devices should be visually checked by system operators just to verify there is no leakage of processfluid from the device and no evidence corrosion or evidence of outlet or relief vent obstruction. Process fluidsthat are viscous or contain solids may obstruct the relief device inlet, outlet or prevent a valve-type devicefrom closing. For such processes it is prudent to inspect the devices immediately after operation in additionto set inspection intervals. See service specific data sheets and Data Sheet 12-43 for further guidance.



4.0 REFERENCES

4.1 FM GlobalData Sheet 1-40, FloodData Sheet 3-1, Tanks and Reservoirs for Interconnected Fire Service and Public MainsData Sheet 3-2, Water Tanks for Fire ProtectionData Sheet 5-8, Static ElectricityData Sheet 6-9, Industrial Ovens and DryersData Sheet 7-0, Causes and Effects of Fires and ExplosionsData Sheet 7-6, Heated Plastic and Plastic-Lined TanksData Sheet 7-9, Dip Tanks, Flow Coater and Roll CoatersData Sheet 7-12, Mining and Ore Processing FacilitiesData Sheet 7-13, Mechanical RefrigerationData Sheet 7-14, Fire Protection for Chemical PlantsData Sheet 7-17, Explosion Protection SystemsData Sheet 7-20, Oil CookersData Sheet 7-21, Rolling MillsData Sheet 7-22, Hydrazine and Its DerivativesData Sheet 7-25, Molten Steel ProductionData Sheet 7-26, Glass PlantsData Sheet 7-27, Spray Application of Flammable and Combustible MaterialsData Sheet 7-28, Energetic MaterialsData Sheet 7-30N, Solvent Extraction PlantsData Sheet 7-32, Ignitable Liquid OperationData Sheet 7-33, High-Temperature Molten MaterialsData Sheet 7-34, Explosion Prevention in Electrolytic Chlorine ProcessesData Sheet 7-35, Air Separation ProcessesData Sheet 7-36, Pharmaceutical Operations

Fig. 11. Erosion-corrosion or FAC likely led to failure of this power boiler feedwater pipe



Data Sheet 7-37, Cutting OilsData Sheet 7-38, Loss Prevention in Ethanol Fuel Production FacilitiesData Sheet 7-41, Oil Quenching and Molten Salt BathsData Sheet 7-43, Loss Prevention in Chemical PlantsData Sheet 7-44, Spacing of Facilities in Outdoor Chemical PlantsData Sheet 7-45, Instrumentation and Control in Safety ApplicationsData Sheet 7-46, Chemical Reactors and ReactionsData Sheet 7-47, Physical Operations in Chemical PlantsData Sheet 7-49, Emergency Venting of VesselsData Sheet 7-50, Compressed Gases in CylindersData Sheet 7-51, AcetyleneData Sheet 7-52, OxygenData Sheet 7-54, Natural Gas and Gas PipingData Sheet 7-55, Liquefied Petroleum GasData Sheet 7-56, MAPP Industrial GasData Sheet 7-58, Chlorine DioxideData Sheet 7-59, Inerting and Purging of Tanks, Process Vessels and EquipmentData Sheet 7-64, Aluminum IndustryData Sheet 7-72, Reformer and Cracking FurnacesData Sheet 7-74, DistilleriesData Sheet 7-75, Grain Storage and MillingData Sheet 7-76, Combustible Dust ExplosionData Sheet 7-78, Industrial Exhaust SystemsData Sheet 7-79, Fire Protection for Combustion TurbineData Sheet 7-84, Hydrogen PeroxideData Sheet 7-88, Flammable Liquid Storage TanksData Sheet 7-91, HydrogenData Sheet 7-92, Ethylene OxideData Sheet 7-94, Ammonia Synthesis UnitsData Sheet 7-95, CompressorsData Sheet 7-96, Printing PlantsData Sheet 7-98, Hydraulic FluidsData Sheet 7-99, Heat Transfer by Organic and Synthetic FluidsData Sheet 7-101, Steam Turbines and Electric GeneratorsData Sheet 8-10, Coal and Charcoal StorageData Sheet 9-0, Maintenance and InspectionData Sheet 9-18, Prevention of Freeze-UpsData Sheet 10-3, Hot Work ManagementData Sheet 10-4, Contractor ManagementData Sheet 12-0, Applicable Pressure Equipment Codes and StandardsData Sheet 12-3, Continuous Digesters and Related Process VesselsData Sheet 12-6, Batch Digesters and Related Process VesselsData Sheet 12-43, Pressure Relief DevicesData Sheet 12-53, Absorption Refrigeration SystemsData Sheet 12-61, Mechanical RefrigerationData Sheet 13-2, Hydroelectric Power PlantsData Sheet 13-3, Steam TurbinesData Sheet 13-14, Electric Generating StationsData Sheet 17-1, Nondestructive Examination

4.2 Recognized Vessel and Piping Codes

4.2.1 Pressure Vessel and Piping Construction Codes

4.2.1.1 National Standards of the Peoples Republic of China GB 150, Pressure Vessels



4.2.1.2 ASME Boiler and Pressure Vessel Code Section VIII, Rules for Construction of Pressure Vessels Section X, Fiber-Reinforced Plastic Pressure Vessels Section XII, Rules for Construction and Continued Service of Transport Tanks

4.2.1.3 ASME Code for Pressure Piping, B31 B31.1, Power Piping B31.3, Process Piping B31.4, Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids B31.5, Refrigeration Piping B31.8, Gas Transportation and Distribution Piping Systems B31.9, Building Services Piping B31.11, Slurry Transportation Piping Systems B31.12, Hydrogen Piping and Pipelines

4.2.1.4 ASME PVHO-1, Safety Standard for Pressure Vessels for Human Occupancy

4.2.1.5 American Water Works Association (AWWA) C605, Underground Installation of Polyvinyle Chloride (PVC) Pressure Pipe and Fittings for Water C900, PVC Pressure Pipe and Fabricated Fittings C950, Fiberglass Pressure Pipe D100, Welded Carbon Steel Tanks for Water Storage D103, Factory-CoatedBoltedCarbon Steel Tanks for Water Storage D115, Tendon-Prestressed Concrete Water Tanks D120, Thermosetting Fiberglass-Reinforced Plastic Tanks D121, Bolted Aboveground Thermosetting Fiberglass-Reinforced Plastic Panel-Type Tanks for Water

Storate M9, Concrete Pressure Pipe M11, Steel Pipe: A Guide for Design and Installation M23, PVC Pipe - Design and Installation M55, PE Pipe - Design and Installation

4.2.1.6 Australian Standards AS 1210, Pressure Vessels

4.2.1.7 European Standards EN 13445, Unfired Pressure Vessels

EN 13923, Filament-Wound FRP Pressure Vessels

EN 13121, GRP Tanks and Vessels for Use Above Ground EN 14931, Pressure vessels for human occupancy (PVHO) - Multi-place pressure chamber systems

for hyperbaric therapy - Performance, safety requirements and testing



4.2.1.8 Japanese Industrial Standards JIS B 8242, Horizontal type cylindrical storage tanks used for liquefied petroleum gas - Construction JIS B 8265, Construction of pressure vessel - General principles JIS B 8267, Construction of pressure vessel JIS B 8266, Alternative standard for construction of pressure vessel JIS B 8241, Seamless steel gas cylinders JIS B 8248, Cylindrical layered pressure vessels JIS B 8278, Saddle supported horizontal pressure vessels JIS Z 2342, Methods for acoustic emission testing of pressure vessels during pressure tests and

classification of results

4.2.2 Pressure Vessel and Piping Inspection and Repair Codes

4.2.2.1 The National Board of Boiler and Pressure Vessel Inspectors

National Board Inspection Code (NBIC)

4.2.2.2 ASME PCC-1, Guidelines for Pressure Boundary Bolted Flange Joint Assembly PCC-2, Repair of Pressure Equipment and Piping

4.2.1.3 ASME PVHO-2, Safety Standard for Pressure Vessels for Human Occupancy: In-Service PVHO Acrylic

Windows Guidelines

4.2.2.4 American Petroleum Institute (API) Publication 510, Pressure Vessel Inspection Code: In-Service Inspection, Rating, Repair, and

Alteration

Recommended Practice 571, Damage Mechanisms Affecting Fixed Equipment in the RefiningIndustry

Recommended Practice 572, Inspection of Pressure Vessels. (2009, November). Recommended Practice 574, Inspection Practices for Piping System Components Recommended Practice 576, Inspection of Pressure-relieving Devices Recommended Practice 577, Welding Inspection and Metallurgy Recommended Practice 578, Material Verification Program for New and Existing Piping Systems Standard 579-1/ASME FFS-1, Fitness-for-service Recommended Practice 580, Risk-based Inspection

Recommended Practice 581, Risk-based Inspection Technology Standard 598, Valve Inspection and Testing Recommended Practice 750, Management of Process Hazards

4.2.2.5 ASNT SNT-TC-1A, Personnel Qualification and Certification in Nondestructive Testing CP-189, Standard for Qualification and Certification of Nondestructive Testing Personnel



4.2.2.6 MIT

129 4, A Practical Guide to Field Inspection of FRP Equipment and Piping Project 129-99 4, Self-help Guide for In-service Inspection of FRP Equipment and Piping Project 160-04, Guide for Design, Manufacture, Installation & Operation of FRP Flanges and Gaskets

4.2.2.7 NACE SP0590, Prevention, Detection, and Correction of Deaerator Cracking RP 0169 5, Control of External Corrosion on Underground or Submerged Metallic Piping Systems RP 0170, Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid

Stress Corrosion Cracking During Shutdown of Refinery Equipment RP 0274, High-voltage Electrical Inspection of Pipeline Coatings Prior to Installation RP 0275, Application of Organic Coatings to the External Surface of Steel Pipe for Underground

Service

4.2.2.8 Australian Standards AS/NZS 3788, Pressure Equipment - In-service Inspection

4.2.2.9 Welding Technology Institute of Australia (WTIA) Deaerator Cracking, May 1998

4.2.2.10 American Water Works Association (AWWA) D101, Inspecting and repairing steel water tanks, standpipes, reservoirs, and elevated tanks, for

water storage

4.2.3 Tanks and Silos Construction Guides and Codes

4.2.3.1 European Standards EN 1990, Basis of structural design EN 1991, Eurocode 1: Actions on structures

EN 1992, Eurocode 2: Design of concrete structures EN 1993, Eurocode 3: Design of steel structures EN 1994, Eurocode 4: Design of composite steel and concrete structures EN 1995, Eurocode 5: Design of timber structures EN 1996, Eurocode 6: Design of masonry structures EN 1997, Eurocode 7: Geotechnical design EN 1998, Eurocode 8: Design of structures for earthquake resistance EN 1999, Eurocode 9: Design of aluminium alloy structures EN 13121, GRP Tanks and vessels for use aboveground EN 14620, Design and Manufacture of Site Built, Vertical, Cylindrical, Flat-Bottomed Steel Tanks

for the Storage of Refrigerated, Liquefied Gases with Operating Temperatures Between 0C and-165C



4.2.3.2 American Concrete Institute (ACI) ACI 376, Code Requirements for Design and Construction of Concrete Structures for the

Containment of Refrigerated Liquefied Gases ACI 371R, Guide for the Analysis, Design, and construction of Elevated Concrete and Composite

Steel-Concrete Water Storage Tanks ACI 372R, Design and Construction of Circular Wire and Strand Wrapped Prestressed concrete

Structure ACI 313, Standard Practice for Design and Construction of Concrete Silos and Stacking Tubes for

Storing Granular Material

4.2.3.3 Japanese Industrial Standards JIS B 8501, Welded steel tanks for oil storage JIS B 8502, Construction of welded aluminium and aluminium alloy for storage tanks JIS A 4110, Glassfiber reinforced plastic water tanks JIS K 7012, Glass-fiber reinforced thermosetting resin chemical resistant tanks

4.2.3.4 American Petroleum Institute (API) Specification 12P, Fiberglass Reinforced Plastic Tanks Specification 12B, Bolted Tanks for Storage of Production Liquids Specification 12D, Field Welded Tanks for Storage of Production Liquids Specification 12F, Shop Welded Tanks for Storage of Production Liquids Standard 620, Design and Construction of Large, Welded, Low-Pressure Storage Tanks Standard 650, Welded Steel Tanks for Oil Storage Recommended Practice 651, Cathodic Protection of Aboveground Petroleum Storage Tanks Recommended Practice 652, Lining of Aboveground Petroleum Storage Tank Bottoms Standard 2000, Venting Atmospheric and Low-Pressure Storage Tanks: Nonrefrigerated and

Refrigerated Recommended Practice 2003, Protection Against Ignitions Arising Out of Static, Lightning, and Stray

Currents Standard 2610, Design, Construction, Operation, Maintenance & Inspection of Terminal ant Tank

Facilities

4.2.3.5 ASME RTP-1, Reinforced Thermoset Plastic Corrosion-Resistant Equipment

4.2.3.6 ASTM International ASTM D3299, Standard Specification for Filament Would Glass Fiber Reinforced Thermoset Resin

Chemical Resistant Tanks ASTM D4097, Standard Specification for Contact Molded Glass Fiber Reinforced Thermoset Resin

Chemical Resistant Tanks

4.2.3.7 Underwriters Laboratories (UL) 142, Steel Aboveground Tanks for Flammable and Combustible Liquids

4.2.3.8 American Water Works Association (AWWA) D100, Welded Carbon Steel Tanks for Water Storage



4.2.4 Tanks and Silos Inspection and Repair Guides and Codes

4.2.4.1 American Concrete Institute (ACI) ACI 228.2R, Nondestructive Test Methods for Evaluation of Concrete in Structures ACI 222.2R, Corrosion of Prestressing Steels

4.2.4.2 American Petroleum Institute (API) Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction Recommended Practice 575, Guidelines and Methods for Inspection of Existing Atmospheric and

Low-pressure Storage Tanks

4.2.4.3 Steel Tank Institute (STI) SP001, Standards for Inspection of In-Service Shop Fabricated Aboveground Tanks for Storage of

Combustible and Flammable Liquids

4.2.4.4 American Water Works Association (AWWA) D101, Inspecting and repairing steel water tanks, standpipes, reservoirs, and elevated tanks, for water

storage

APPENDIX A GLOSSARY OF TERMSAutoclave: A pressure vessel used in processing materials. Depending on occupancy, it may be known asa sterilizer, reactor, extraction vessel, or isostatic press. In batch processing applications, it will have aquick-actuating closure.Brittle fracture: A fracture that occurs suddenly, with little or no plastic deformation such as stretching orbulging.Charpy impact test: A standard test of a materials resistance to fracture under impact loading. The test couponhas a notch machined in one side and is struck on the opposite side. The energy in foot-pounds requiredto break the coupon is recorded.

Caustic: Any of the hydroxide compounds, most commonly sodium hydroxide. Aqueous solutions areextremely basic, having a high pH, usually between 10 and 14.Caustic embrittlement: Also known as caustic cracking or caustic stress corrosion cracking (SCC). Whenexposed to aqueous caustic solutions, carbon and low allow steels can appear to have been embrittled whena sudden, brittle fracture occurs that is actually the result of gradual SCC.Corrosion: The electrochemical reaction between a material, usually a metal, and its environment thatproduces a deterioration of the material and its properties.

Corrosion, local: Occurs in a relatively limited area. Pitting and crevice corrosion are commonexamples. Erosion-corrosion, FAC, and cavitation are also examples.

Corrosion under insulation (CUI, a.k.a. under insulation corrosion): External corrosion due to moisturewithin the insulation system. The moisture remains in contact with the pipe for an extended periodof time, or may condense under the insulation covering and return to the pipe wall. The insulation maycontain chloride ions, making the moisture much more corrosive. Process fluids containing chlorides,acids, or caustics also may penetrate the insulation system.

Corrosion, uniform or general: Occurs over a relatively large area. May not be readily detected byvisual examination due to uniform appearance.

Environmentally-induced cracking: Stress corrosion cracking (SCC) is the more common form ofthis corrosion. SCC requires a material that is susceptible, a corrodent, and some level of stress.Carbon steel is susceptible to caustic SCC, and stainless steel is susceptible to chloride SCC.Choosing appropriate materials and taking care to minimize residual stress during construction canmitigate SCC.



Ductile fracture: A fracture that has associated with it some stretching, bending, or other deformationpermanently visible in the adjacent material.Erosion: A mechanical process resulting in thinning of pipe material. The rate of thinning for specific materialsis dependent on flow velocity and the water, steam, solid particles, or combinations of the three impactingthe pipe.

Cavitation erosion (CE): A specific type of erosion caused by formation of bubbles in a liquid streamthat impact the pipe (collapse at the pipe surface). Likely to occur at change in pipe size or direction.

Erosion-corrosion (EC): Thinning from combined mechanical and electrochemical process. The rateof thinning is more rapid than for either erosion or corrosion alone.

Flow accelerated (or assisted) corrosion (FAC): A specific type of erosion-corrosion affecting carbonor low-alloy carbon steels. The normally protective oxide coating is dissolved by the combinationof flow velocity and fluid chemistry. The fluid may be a liquid or liquid- vapor combination. The rateof thinning for a particular carbon steel is dependent on chromium content, fluid velocity, fluidtemperature, fluid pH, and two-phase flow.

FM Approved: References to FM Approved in this data sheet mean the product or service has satisfiedthe criteria for FM Approval. Refer to the Approval Guide, an online resource of FM Approvals, for a completelisting of products and services that are FM Approved (www.approvalguide.com).Fracture toughness: A material property that indicates its ability to resist propagation of a crack and fracturefrom a flaw, such as a void, inclusion, or preexisting crack.Isostatic processing: Batch processes completed at a constant pressure. May include heating of theprocessed material. Typically performed at high pressure in vessels having quick-actuating closures.Processing fluid may be liquid or gas. Examples are supercritical carbon dioxide extraction, diamond or quartzcrystal growing, food and drink processing, ceramic processing, and metal processing. Vessels may be calledextractors, autoclaves, reactors, or presses.

Listed: Equipment or materials included in a list published by an organization that maintains periodicinspection of production of listed equipment or materials and whose listing states that either the equipmentor material meets appropriate designated standards or has been tested and found suitable for a specifiedpurpose.

Low alloy steels: Those steel alloys with more alloying additions than carbon steels, and less than stainlesssteels. When compared with the less expensive carbon steels, some have higher strength, some bettercorrosion resistance, and some better high temperature properties.Nondestructive examination (NDE): The application of analysis methods to determine the condition ofmaterials without causing damage to the materials. Following are some types of NDE that may be appliedto vessels and piping.

Liquid penetrant test (PT): A penetrating liquid is applied to the material surface to detect corrosion-related cracking. Can only detect indications open on the surface.

Magnetic particle test (MT): A magnetic powder is applied to the material surface and a magneticfield is then generated in the material to detect corrosion-related cracking in magnetic materials.Wet fluorescent magnetic particle (WFMT) is the preferred method in most instances. Can only detectindication open on or very near the surface.

Pulsed eddy current test (pulsed ET): Pulsed eddy currents are induced in electrically conductivematerials to detect indications in the material. Can be applied without removal of insulation. Thecost is approximately US$3,000 to US$4,000 per day, but this method avoids the cost of removinginsulation (possibly asbestos). This test method, sometimes called Incotest (for insulatedcomponent test), can detect both CUI and FAC.

Radiographic test (RT): A radiation source is placed on one side of the vessel or pipe wall and asheet of film is placed on the other side. Variation in wall thickness affects exposure of the film. Bestresults require the film to be in contact with the examined surface. RT can be done through insulation,but the results are blurry and thus not conclusive. RT is more time-consuming and costly than UT.



Ultrasonic test (UT): A transducer transmits and receives an ultrasonic signal, revealing wallthickness, delamination, and cracks. A flaw detector-type instrument provides much more informationthan does a digital thickness gauge. UT requires access to a bare metal surface over the entire areato be inspected.

Overpressure: A pressure increase (either positive or negative) beyond a vessel design pressure or MAWP,or beyond the set pressure of a pressure relief device.

Plastic deformation: Deformation, such as stretching, bending, or bulging, that is permanent; is not recoveredwhen the stress is removed. As opposed to elastic deformation, which is fully recovered when stress isremoved.

Quick-actuating closure: A vessel closure designed to reduce the time to open and close the vessel,particularly for batch processing.Ultimate tensile strength: The stress level at which a material fractures under tensile (axial) loading.Vent, atmospheric: Pressure relief opening on a system to permit the intake and discharge of air duringemptying and filling operations and to permit expansion and contraction of vapor due to temperature changes.Sometimes called breather vent.Vent, emergency relief: Pressure relief opening on a system to prevent over pressurizing the system in theevent of upset in system operation, fire exposure or other adverse condition.

Vent, conservation: Pressure relief device typically of the weighted-valve type, minimizing release of systemcontents due to evaporation. Relief is provided for both vacuum and pressure. Vents usually open whenthe positive or negative pressure in the system reaches 0.75 to 1.00 in. water column (185 to 250 Pa) andare normally closed.

Vessel: Generic term used in this data sheet for containers used for storage or processing of solids, liquidsor gases. The general category of vessel is divided into subcategories of pressure vessel, silo and tank.Vessels may be constructed of a wide variety of materials.

Vessel, aboveground: A vessel installed above grade, at grade or below grade having access toall external vessel surfaces.

Vessel, underground: A vessel installed above grade, at grade or below grade not having accessto entire external vessel surface due to earth mounding or backfill.

Pressure vessel: Generic term for vessel containing solids, liquid or gas at a pressure significantlyexceeding ambient pressure. Pressure vessels addressed in this data sheet are limited to thoseconstructed of metals and some plastics. Pressure vessels are typically designed for a minimumpressure of 15 psi (100 kPa) and up to full vacuum.

Silo: Generic term for vessels containing solids. Silos addressed in this data sheet are expected tooperate at ambient pressure only, not subject to application of either positive or negative (vacuum)pressure.

Tank: Generic term for vessels containing solids, liquids or gases at essentially ambient pressure.Tanks addressed in this data sheet are primarily constructed of metals with some being plastic, woodor concrete construction. Tanks are typically designed for a maximum pressure of 15 psi (100 kPa)and up to full vacuum.

Aboveground tank: A tank that is installed above grade, at grade, or below grade without backfill. Atmospheric tank: A storage tank that has been designed to operate at pressures from

atmospheric through a gauge pressure of 1.0 psig (6.9 kPa) measured at the top of the tank. Double-skinned tank: See secondary containment tank, a term used in European Union (EN)

standards.

Floating roof tank: An atmospheric tank intended for storage of high vapor pressure liquids suchas crude oil and gasoline with vapor pressure exceeding 15 psig (103 kPa or 1 bar gauge) witha roof floating on the liquid surface. (Floating roof tanks are not covered by this standard.) Designaccording to the criteria in API 650, Appendix C or H, or other recognized equivalent standard.



External floating roof: A roof that sits directly on the liquid surface, usually on pontoons witha seal attached to the roof perimeter to cover the annular space between the roof and theshell. Design criteria are in API 650, Appendix C. This type has inherent buoyancy and aredifficult, though not impossible, to sink.

Internal floating roof: A roof similar to the external floater but with a fixed roof above, intendedfor weather protection or quality assurance. The internal floater is often a simple pan or plasticmembrane floating directly on the liquid surface with little or no inherent buoyancy and issubject to sinking. Design criteria are in API 650, Appendix H. Pontoon type roofs similar oridentical to external floaters are possible but not common. Unless the internal floater has theinherent buoyancy of a pontoon type, treat the tank as a cone roof tank.

Low-pressure tank: A storage tank designed to withstand an internal pressure of more than 1psig (7 kPa) but not more than 15 psig (100 kPa or 1 bar gauge) measured at the top of the tank.

Portable tank: Any closed vessel having a liquid capacity over 60 gal (230 L) and not intendedfor fixed installation. This includes intermediate bulk containers (IBCs) as defined and regulatedby the U.S. Department of Transportation in CFR Title 49, Part 178, subpart N, and the UnitedNations Recommendations on the Transport of Dangerous Goods, chapter 6.5.

Protected aboveground tank: An aboveground storage tank that is listed in accordance with UL2085, Standard for Protected Aboveground Tanks for Flammable and Combustible Liquids, oran equivalent test procedure that consists of a primary tank provided with protection from physicaldamage and fire-resistive protection from exposure to a high-intensity liquid pool fire.

Secondary containment tank: A tank that has an inner and outer wall with an interstitial space(annulus) between the walls and that has a means for monitoring the interstitial space for a leak.

Storage tank: Any vessel having a liquid capacity that exceeds 60 gal (230 L), is intended for fixedinstallation, and is not used for processing.

Weak seam roof (weak shell-to-roof joint construction): The attachment of the roof to the shell forms a frangiblejoint that, in the case of excessive internal pressure, will rupture before rupture occurs in the tank shell jointsor the shell-to-bottom joint. Design criteria can be found in UL 142 or API 650.Yield strength: The stress level at which a material begins to plastically deform (stretching under tensileloading).

APPENDIX B DOCUMENT REVISION HISTORYApril 2015. Data Sheets 12-66, High Pressure Forming Presses, and 12-26, Quick-actuating Closures, havebeen incorporated into this document.

April 2014. This data sheet has been completely rewritten. Major changes include the following:A. Changed the title from External Corrosion of Pressure Vessels and Piping to Vessels and Piping.B. Incorporated all relevant information from Data Sheet 1-25, Process Tanks and Silos.C. Incorporated all relevant information from Data Sheet 12-5, Critical Steam and Water Piping.D. Added guidance on process and storage tanks, silos, bins, pressure vessels and piping, in additionto the hazard of external corrosion.

E. Added text to direct the user to seek recommendations in other FM Global data sheets for the specificservice application.

F. For the Equipment and Processes section, made the primary recommendation to use a recognizedvessel or piping construction code for new vessels and piping. A list of codes is provided in Section 4.2,Recognized Vessel and Piping Codes, which can be expanded as other codes are determined to beacceptable.

G. For the Operation and Maintenance section, made the primary recommendations to implement a systemintegrity program and included text to direct the user to Data Sheet 9-0 for methodologies. A list ofacceptable industry inspection and repair codes is provided in Section 4.2, Recognized Vessel and PipingCodes.



H. Updated the Support for Recommendations section.May 2003. Minor editorial changes were made for this revision.January 2000. This revision of the document has been reorganized to provide a consistent format.

APPENDIX C BIBLIOGRAPHYAD Merkbltter: German standard, harmonized with the Pressure Equipment Directive.AIAA S-080-1998: AIAA Standard for Space Systems - Metallic Pressure Vessels, Pressurized Structures,and Pressure Components.AIAA S-081A-2006: AIAA Standard for Space Systems - Composite Overwrapped Pressure Vessels (COPVs).American Insurance Services Group, Inc. Fossil-Fired Utility/Industrial Boiler Life Assessment/Extension.Boiler and Machinery Engineering Report. New York: American Insurance Services Group, Inc. 1991.American Petroleum Institute (API)

910, Digest of State Boiler, Pressure Vessel, Piping & Aboveground Storage Tank Rules andRegulations. 8th ed. (1997, November 1).

941, Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineriesand Petrochemical Plants. 6th ed. (2004, February).

American Society for Nondestructive Testing (ASNT) Recommended Practice for Nondestructive Testing Personnel Qualification and Certification. ASNT

SNT-TC-1A. Columbus, OH: ASNT, 2001. www.asnt.org CP-189-2001, ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel.

ASNT CP-189-2001. Columbus, OH: ASNT, 2001.AS/NZS 1200: Pressure equipment.Autoclave Engineers. Bulletin No. 320. United States Patent 3,104,583.B51-09 Canadian Boiler, pressure vessel, and pressure piping code.BS 4994: Specification for design and construction of vessels and tanks in reinforced plastics.BS 5500: Former British Standard, replaced in the UK by BS EN 13445 but retained under the name PD5500 for the design and construction of export equipment.Cohen, P., ed. The ASME Handbook on Water Technology for Thermal Power Systems. New York: ASME,1989.

EN 13445: The current European Standard, harmonized with the Pressure Equipment Directive (97/23/EC).Extensively used in Europe.

EN 286 (Parts 1 to 4): European standard for simple pressure vessels (air tanks), harmonized with CouncilDirective 87/404/EEC.Feedwater Quality Task Group for Industrial Boiler Subcommittee of the ASME Research Committee on Waterin Thermal Power Systems. Consensus of Operating Practices for the Control of Feedwater and Boiler WaterQuality in Modern Industrial Boilers. New York: ASME, 1979.Ford, Sir H., E. H. Wats

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