Standard Operating Procedure (SOP) Compressed Gas … Cylind… · Standard Operating Procedure...

Standard Operating Procedure (SOP)

Compressed Gas Cylinders Revision 2: 03/31/16/15

EWU EH&S SOP of 16 Original Doc 6/30/14

INTRODUCTION

Compressed gases can be toxic, flammable, oxidizing, corrosive, inert, or some combination of

these hazards. In addition to the chemical hazards, the amount of energy resulting from the

compression of the gas makes a compressed gas cylinder a potential rocket. Appropriate care in

the handling and storage of compressed gas cylinders is essential. For chlorine gas see the

guidance document Chlorine Gas for Water Treatment. The following are six general

recommendations.

1. Know and Understand Gas Properties: Know and understand the properties, uses, and

safety precautions before using any gas or gas mixture. Consult Material Safety Data

Sheets (MSDSs) for safety information on the gases that you will be using.

2. Check Equipment: Leak test lines and equipment before they are used. Lines and

equipment should be designed and maintained to handle full cylinder pressure. Materials

of construction should be compatible with the gases being used.

3. Develop Emergency Plans: Be aware of potential hazards and develop plans to cover all

possible emergencies. Include information about the types of gases used on your

laboratory’s Emergency Information Poster.

4. Provide Personal Protection: Wear suitable protective clothing, including gloves and face

protection. Safety equipment, such as self-contained breathing apparatus and fire

extinguishers, should be located near hazardous areas. Stay well informed of the potential

hazards of the gases with which you are working.

5. Follow Regulations: Follow all federal, state, and local regulations pertaining to the

storage and use of compressed gas cylinders. Follow the National Fire Protection

Association (NFPA) codes, especially for flammable products.

6. When in Doubt, Contact Environmental Health & Safety: If you are unfamiliar with the

hazards associated with a particular gas or unsure of the correct handling and storage

procedures, call Environmental Health & Safety at 6455.

PRIMARY HAZARDS

The following is an overview of the primary hazards to be avoided when handling and storing

compressed gases. (Note: Chlorine gas is covered under the chlorine guidance document;

Cryogenic liquids and cylinders are covered under the Cryogenic SOP).

Asphyxiation: Simple asphyxiation is the primary hazard associated with inert gases.

Because inert gases are colorless and odorless, they can escape into the atmosphere

undetected and quickly reduce the concentration of oxygen below the level necessary to

support life. The use of oxygen monitoring equipment is strongly recommended for

enclosed areas where inert gases are being used.

Fire and Explosion: Fire and explosion are the primary hazards associated with

flammable gases, oxygen, and other oxidizing gases. Flammable gases can be ignited by

static electricity or by a heat source, such as a flame or a hot object. Oxygen and other

oxidizing gases do not burn, but will support combustion of flammable materials.

Increasing the concentration of an oxidizer accelerates the rate of combustion. Materials

that are nonflammable under normal conditions may burn in an oxygen-enriched

atmosphere.

Chemical Burns: Corrosive gases can chemically attack various materials, including fire-

resistant clothing. Some gases are not corrosive in their pure form, but can become

extremely destructive if a small amount of moisture is added. Corrosive gases can cause

rapid destruction of skin tissue.




Chemical Poisoning: Chemical poisoning is the primary hazard of toxic gases. Even in

very small concentrations, brief exposure to these gases can result in serious poisoning

injuries. Symptoms of exposure may be delayed.

High Pressure: All compressed gases are potentially hazardous because of the high

pressure stored inside the cylinder (even low pressure cylinders). A sudden release of

pressure can cause injuries by propelling a cylinder or whipping a line.

Improper Handling of Cylinders: Compressed gas cylinders are heavy and awkward to

handle. Improper handling of cylinders could result in sprains, strains, falls, bruises, and

broken bones. Other hazards such as fire, explosion, chemical burns, poisoning, and cold

burns could occur if gases accidentally escape from the cylinder due to mishandling.

Types of Compressed Gases The types of compressed gas can be divided into three categories, each with unique

characteristics.

Liquefied Gas can become liquid at normal temperatures when they are inside a cylinder

under pressure. When gas is removed from the cylinder, enough liquid evaporates to replace

it, keeping the pressure in the cylinder constant Common examples include anhydrous

ammonia, chlorine, propane, nitrous oxide and carbon dioxide. Anhydrous ammonia is

covered under the anhydrous ammonia SOP. Chlorine gas is covered under the chlorine gas

SOP. Propane is covered under the propane SOP.

Non-Liquefied is also a compressed, pressurized or permanent gas. These gases do not

become liquid when they area compressed at normal temperatures or even very high

pressures. Common examples are oxygen, nitrogen, helium and argon.

Dissolved Gas can also be compressed. A common example of dissolved gas is acetylene.

Care should be taken when using acetylene or welding. Consult your supervisor before using

acetylene. Acetylene is covered under the Acetylene SOP.

Dangerously Reactive Gases

Some pure compressed gases are chemically unstable. If exposed to slight temperature or

pressure increases, or mechanical shock, they can readily undergo certain types of chemical

reactions such as polymerization or decomposition. These reactions may become violent,

resulting in fire or explosion. Some dangerously reactive gases have other chemicals, called

inhibitors, added to prevent these hazardous reactions.

Common dangerously reactive gases are acetylene, 1,3-butadiene, methyl acetylene, vinyl

chloride, tetrafluoroethylene and vinyl fluoride.

Cryogenic Liquids Gases condensed to liquid form at extremely low temperatures. Examples of liquefied gases

inclued helium, hydrogen, methane, nitrogen, oxygen and fluorine in temperatures between -150 oF to -450

oF. Cryogenic liquids are covered under the cryogenic liquid SOP.

HANDLING, STORAGE, AND USE OF GASES

Only persons familiar with the hazards should handle compressed gas cylinders.




All cylinder movement should be done Always secure the cylinders with a compressed gas cylinder cart. when in storage or use.

Cylinders secured with a chain or strap must have the chain or strap attached 2/3 of the way up on the cylinder.

Compressed gas cylinders should not be subjected to any mechanical shock that could cause damage to their valves or pressure relief devices. Cylinders should not be dropped, dragged, slid, or used as rollers for moving material or other equipment. Cylinder caps perform two functions. First, they protect the valve on the top of the cylinder from damage if it is knocked over. Second, if gas is accidentally released through the valve, the cap

Reduce the pressure of a compressed gas through a manufacturer's specified regulator attached to the cylinder valve.

Test cylinders for leaks each time you use them. Use an appropriate leak-test solution or detection equipment to check for leaks, never use flame. Make sure the solution is compatible with the gas being tested. Refer to the drawing on the right for examples of areas to test.

Service

pressure in

PSI

Material of the tank

3AA, Steel

3Al, Aluminum




will vent the gas out of both sides, minimizing the likelihood that the cylinder will topple. Cylinder caps should not be removed until the cylinder is secured in place and ready for use.

VALVES ON COMPRESSED GAS CYLINDERS Most compressed gas cylinders require the installation of at least one valve. This valve allows

the cylinder to contain gases and allows gas to be filled into or emptied from the cylinder.

The cylinder valve is the most vulnerable part of the compressed gas cylinder. Leaks can also

occur at the regulator, cylinder stem and at the hose connection.

TYPES OF VALVES

Check valves are mechanical valves that permit gases and liquids to flow in only one direction,

preventing process flow from reversing. Common types of valves include check, ball, disk,

butterfly, gate, diaphragm, needle and solenoid. Valves can be made of plastic, stainless steel or

other material. Valves serve unique requirements so it is important to select the specific type of

valve for your operation.

REGULATOR SELECTION

Check the regulator before attaching it to the cylinder. Be sure you are using the proper regulator

for the particular gas that is inside the cylinder. If the regulator connections do not readily fit

together, the wrong regulator is being used. Do not force connections to fit, as you may

permanently damage the threads. See Regulator Selection, Installation, and Operation

Restrictive Flow Orifices

Restrictive Flow Orifices are used to limit the potential danger of an uncontrolled flow from a

compressed gas cylinder. Unchecked, the instantaneous flow from a 44 liter compressed gas

cylinder filled to 2,000 psig can be as much as 20,000 liters per minute. By inserting an RFO into

the outlet of the CGA connection the flow rate could be reduced by a factor of 100 to

approximately 200 liters per minute. The Restrictive

Flow Orifice is designed to thread into the outlet of

most CGA connections that have external male threads.

CYLINDER STORAGE PRECAUTIONS

Several precautions should be taken during storage of compressed gas cylinders. Full and empty

cylinders should be stored separately. Cylinders should be stored upright and secured at all times.

Cylinders should not be stored near radiators or other heat sources.

Gases should be used and stored only in a well-ventilated area.

Never store gases for longer than one year without use. Always screw on an appropriate

gas cap on cylinders that are not in use.

Protect cylinders from corrosion due to weather or chemicals.

Gases should be stored in the order in which they are received and will be used.

When in storage, empty or full the caps must be on and the labels viewable.

Segregate empty cylinders from full cylinders.

It is essential that when handling or storing cylinders containing toxic or corrosive gases

that the plug or cap nut is always replaced in the valve outlet when the cylinder is not in

use or connected to an operational system.

Use tables 1 and 2 below for proper segregation and storage amounts.




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Oxidizers and flammable gases should be kept at least 20 ft. away from combustible materials and/or incompatible gases or substances. Storage areas that have a non-combustible wall at least 5 ft. in height and with a fire resistance rating of at least 30 minutes may be used to segregate gases of different hazard classes in close proximity to each other.

Toxic/Poison gases must be stored in a chemical fume hood or in a properly ventilated gas cabinet. In addition to the general guidelines, the following measures should be taken when handling toxic gases: 1.Gases that have an NFPA Health Hazard Rating of 3 or 4 (e.g., hydrogen sulfide) must be stored in a continuously mechanically ventilated gas cabinet. 2.Gases that have an NFPA Health Hazard Rating of 2 without warning properties (e.g., carbon monoxide) must be stored in a continuously mechanically ventilated gas cabinet. 3.Gas detection systems may be required in laboratories using toxic gases. 4.The quantity of toxic gas in a laboratory should be kept to a minimum. 5.Flow restrictors are required on most toxic gas cylinders. 6.Ensure that pressure-relief devices vent directly to a laboratory exhaust system. See table 3 and 4 for Highly Hazardous Gas Storage.

Inert gases are compatible with all other gases and may be stored together. Inert gases, such as argon, helium, neon and nitrogen, are not toxic and do not burn or explode. Yet they can cause injury or death if they are present in sufficiently high concentrations. They can displace enough air to reduce oxygen levels. If oxygen levels are low enough, people entering the area can lose consciousness or die from asphyxiation. Low oxygen levels can particularly be a problem in poorly ventilated, confined spaces.

Dangerously Reactive Gases Some pure compressed gases are chemically unstable. If exposed to slight temperature or pressure increases, or mechanical shock, they can readily undergo certain types of chemical reactions such as polymerization or decomposition. These reactions may become violent, resulting in fire or explosion. Some dangerously reactive gases have other chemicals, called inhibitors, added to prevent these hazardous reactions. Common dangerously reactive gases are acetylene, 1,3-butadiene, methyl acetylene, vinyl chloride, tetrafluoroethylene and vinyl fluoride.

Corrosive Gases Some compressed gases are corrosive. They can burn and destroy body tissues on contact. Corrosive gases can also attack and corrode metals. Common corrosive gases include ammonia, hydrogen chloride, chlorine and methylamine.

Table 3) The amount of hazardous compressed gases with a hazard ranking of

3 or 4 permitted within a laboratory work area are regulated by NFPA 45.

Flammable

Gas

Oxidizing Gas Health Hazard

3 or 4 (NFPA)

Amount allowed

per 500 ft2

6.0 scf 6.0 scf 0.3 scf

Number of

cylinders allowed

per 500 ft2

3 cylinders

(9"x51"

cylinder)

3 cylinders

(9"x51"

cylinder)

1 lecture bottle

Amount of gas

allowed per ft2 of

lab space

0.012 ft3 0.012 ft

3 0.0006 ft

3

In addition to the maximum quantities listed in the table above, the number of

lecture bottle cylinders is limited to 25.

Blue is Health 4-deadly 3-extreme danger 2-Hazardous 1-Slight Hazard 0-Normal Material

NFPA diamond

Fire

Reactive




Table 4) Hazard Gas Reference

Gas

Flammable

Limits in Air

(Vol. %) (1) Oxidizer

Inert

Displaces

oxygen Corrosive

Toxic

NFPA

ranking

Acetylene 2.5 - 82

Ammonia 15-28

X 3

Argon

X

Arsine 5.1 - 78

4

Boron Trichloride

X 3

Boron Trifluoride

X 3

1,3-Butadiene 2.0 - 12

2

n-Butane 1.6 - 8.4

Butenes 1.6 - 10

Carbon Dioxide

X

Carbon Monoxide 12.5 - 74

3

Chlorine

X

X 3

Diborane 0.8 – 98

(spontaneously

ignites)

4

Dichlorosilane 4.1 - 98.8

X 4

Dimethylamine 2.8 - 14.4

X 3

Ethane* 3.0 - 12.5

Ethylene 2.7 - 36

Ethylene Oxide 3 - 100

3

Fluorine

X

4

Halocarbon-13

(Chlorotrifluoromethane)

X

Helium

X

Hydrogen 4.0 - 75

Hydrogen Bromide

X 3

Hydrogen Chloride

X 3

Hydrogen Cyanide 5.6-40

X 4

Hydrogen Fluoride

X 4

Hydrogen Sulfide 4-44

4

Isobutane 1.8 – 8.4

Iso-Butylene 1.8 - 9.6

Krypton

X

Methane 5.0 - 15.0

Methyl Chloride 8.1 - 17.4

2

Monomethylamine 4.9 - 20.7

X 3

Neon

X

Nitric Oxide

X

X 3

Nitrogen

X

Nitrogen Dioxide

X

X 3




Nitrogen Trifluoride

X

Nitrous Oxide

X

Oxygen

X

Ozone

X

4

Phosgene

4

Phosphine 1.6 – 99

(spontaneously

ignites)

X 4

Propane 2.1 - 9.5

Propylene 2.0 – 11.1

Silane 1.5 – 98

(spontaneously

ignites)

Sulfur Dioxide

X 3

Sulfur Hexafluoride

X

Sulfur Tetrafluoride

X 4

Trimethylamine 2.0 – 11.6

X 3

Vinyl Chloride 3.6 - 33

2

Xenon

X

CYLINDER SIZES High Pressure Steel

Low pressure steel and aluminum (AL)

Order the smallest possible cylinder for your work. Gas cylinders must be inspected at least every five years by the distributor or manufacture.

Lecture

bottle




LABEL EXAMPLES

1 Dangerous Goods Classification (Hazard Class)

2 Contents of cylinder at standard temperature and pressure (15°C @ 101.3 kPa)

3 Cylinder size

4 United Nations numbering system for safe handling, transport and storage

5 Gas name and grade

6 Nominal filling pressure at standard conditions (for permanent gas)

7 Caution - indicated major hazards*

8 General safety information*

* Always refer to Material Safety Data Sheets (MSDS)

May cause cancer, fertility issues, or

organ damage

Causes serious eye or skin

irritation Corrosive Other hazard classes that can be encountered

Labels must always be

visible to identify the

contents of the cylinder.

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TRANSPORTING COMPRESSED GASES ON SITE Personnel may move compressed gas cylinders under the following conditions only:

They have received and documented that they have adequate training. The valve is closed, the regulator has been removed and the safety cap is securely in

place. An appropriate cart is used. A cylinder card is required for tanks over 35"' in height,

another cart or dolly will work for smaller cylinders. The cylinder must be secured on the cart.

"Hand Rolling" cylinders is not permitted. Lab personnel may not move large (>35" in height) cylinders between floors of a

building or outside of a building. Contact the department technician or the vendor for transport.

Large cylinders moved by vehicle should follow the guidelines above as well as the following:

Transport large cylinders in an open or well ventilated vehicle. Properly secure the cylinder from moving.

Properly secured cylinder for transport

THINGS TO KEEP AWAY FROM CYLINDERS Several precautions should be taken to prevent the release of high-pressure gases, fire, and explosion. Compressed gas cylinders should not be exposed to sparks, flames, or temperatures above 125°F. Cylinders should not be places where they could come into contact with any electrical apparatus or circuits. Smoking and open flames should not be permitted in areas used for storage of oxygen or flammable gas cylinders. Never permit oil, grease, or other combustible substances to come into contact with oxygen or other oxidizing gas cylinders, valves, and systems.

When Cylinders are Received

Check that the name of the gas is clearly labeled on the cylinder. Check that the appropriate

hazard warnings are clearly labeled on the cylinder. Check that the hydrostatic test date is within

the last 5 years. Check that the valve cap is in place and can be easily removed. Get a material

safety data sheet (MSDS) for the gas and keep it in the lab.

RETURNING CYLINDERS When returning an empty cylinder, close the valve before shipment, leaving 25 psig of residual pressure in the cylinder. Replace the valve cap and any valve outlet caps or plugs originally

Not approved for

acetylene transport




shipped with the cylinder. If repair is needed on a cylinder or its valve, be sure to mark it and return it to the supplier.

Lecture bottles should always be returned to the distributor or manufacturer promptly when no longer needed.

In both cases contact the supplier for proper shipping. Improper shipping can result in large fines and possible prison time.

HANDLING OF LEAKING CYLINDERS Most leaks occur at the valve in the top of the cylinder and may involve the valve threads, valve stem, valve outlet, or pressure relief devices. Personnel should not attempt to repair leaking cylinders.

Where action can be taken, without exposure to workers, (if trained) move the cylinder to an isolated, well-ventilated area and contact EH&S at 6455 or 2788. If the cylinder contains a flammable or oxidizing gas move the cylinder away from combustible materials and contact EH&S at 6455 or 2788.

Whenever a large or uncontrollable leak occurs, evacuate the area/building and immediately call 911.

REGULATOR SELECTION, INSTALLATION, AND OPERATION (From Airgas web site; http://www.airgas.com/content/details.aspx?id=7000000000247) The primary function of a regulator is to reduce high-pressure gas in a cylinder or process line to a lower, usable level as it passes from the cylinder to a piece of equipment. A regulator is not a flow control device. It is used to control delivery pressure only.

Since there are numerous hazards and potential for contamination associated with specialty gases—hazards that vary with the gas, the equipment used, and with the particular application—it is necessary to take the proper precautions to assure safety in high-pressure gas control. Contamination can occur during cylinder change out or from an improperly specified regulator or other component in your gas delivery system.

Before performing any operation with which you are not familiar, seek the advice of an experienced individual. In addition to adhering to the safety and operating rules provided here, the user should be aware of the additional safe operating practices peculiar to each piece of equipment and each application.

Note: Never use any regulator for gases other than those for which it is intended.

The following is applicable to pressure regulators used with flammable, oxidant, corrosive, inert, or toxic gases, when it is necessary to reduce cylinder supply pressure to a lower use pressure.

HOW REGULATORS WORK Single-Stage Regulators High-pressure media enter the regulator through the inlet into the high-pressure chamber. When the adjusting knob is turned clockwise, it compresses the range spring and exerts a force on the diaphragm, which pushes the valve stem open. This releases gas into the low-pressure chamber, exerting an opposing force on the diaphragm.

http://www.airgas.com/content/details.aspx?id=7000000000247




An equilibrium is reached when the spring force on the diaphragm is equal to the opposing force of the gas in the low-pressure chamber. In a single-stage regulator, delivery pressure increases as cylinder pressure decays, because there is less gas pressure exerted on the valve stem. Thus, frequent adjustment of the control knob is required to maintain constant delivery pressure. This does not pose a problem, however, with pipelines and liquefied gas products where inlet pressure is maintained relatively constant. Two-Stage Regulators A two-stage regulator functions similarly to two, single-stage regulators in series. The first stage reduces inlet pressure to a preset intermediate pressure, typically 350 to 500 psig. By adjusting the control knob, the second stage reduces the intermediate pressure to the desired delivery pressure.

Like the single-stage regulator, outlet pressure from the first stage of the two-stage regulator rises as cylinder pressure decreases. However, instead of passing out of the regulator, the gas flows into the second stage where the pressure is moderated. Thus, delivery pressure remains constant even as cylinder pressure decays, eliminating the need for frequent control knob adjustment.

SELECTING THE PROPER REGULATOR Line and Cylinder Regulators Line regulators are typically point-of-use regulators serving low-pressure pipelines. They are also used in conjunction with high-pressure cylinder regulators that limit the inlet pressure to 250 to 400 psig. Cylinder regulators are available in either single-stage or two-stage models for high-purity, general purpose, or special service applications.

High-Purity Regulators High-purity regulators are designed and constructed to provide diffusion resistance and easy cleanup. Metal diaphragms and high-purity seats and seals minimize or eliminate outgassing and inboard diffusion. These regulators should be capable of containing and removing contaminants during cylinder change out. Only bar stock body regulators should be used for these gases.




General Purpose Regulators General purpose regulators are designed for economy and longevity. They are recommended for noncorrosive general plant, pilot plant, and maintenance shop applications where diffusion resistance is not required. These types of regulators are not for analytical or high purity applications.

Special Service Regulators Special service regulators are specifically constructed for special applications including oxygen, acetylene, and fluorine service and high-pressure, ultra-high-pressure, and corrosion service. To make your selection easier, this catalog lists the proper regulator for almost every gas, pressure, and situation. Simply look up the gas or mixture for your application and you will find the appropriate regulator listed under “Recommended Equipment.” CGA valve outlets are also noted for each gas and gas mixture. The regulator must be equipped with the appropriate CGA connection for the cylinder valve outlet.

PUTTING THE REGULATOR INTO SERVICE 1. Identify the regulator. Check the label and the inlet and outlet gauges. Ascertain that the high-pressure gauge is suitable for the pressure of the cylinder or source system. 2. Inspect the regulator. Check the regulator for evidence of damage or contamination. If there is evidence of physical damage or foreign material inside the regulator, contact your customer service representative for return information. 3. Inspect the cylinder valve. Check the cylinder valve for evidence of damage or contamination. Remove any foreign material before attaching the regulator. 4. Attach the regulator. Fasten the regulator to the cylinder and tighten the inlet nut securely. 5. Close the regulator. To close the regulator, turn the adjusting knob to the full counterclockwise position. The regulator must be closed before opening the cylinder valve.

SAFETY-CHECKING THE SYSTEM With the regulator adjusting knob turned fully counterclockwise, place both hands on the cylinder valve and open it slowly, allowing the pressure to rise gradually in the regulator. Stand as shown with the cylinder valve between you and the regulator. When the high-pressure gauge indicates maximum pressure, open the cylinder valve fully.

Always close the cylinder valve when product delivery is not needed. Do not leave it open when the equipment is unattended or not operating.

Adjusting the Pressure Turn the adjusting knob clockwise and establish the required use pressure by referring to the low-pressure gauge. Make sure that the cylinder valve is easily accessible.

Precautionary Measures 1. Never exchange the discharge (low-pressure) gauge for one of lower pressure. The gauge may rupture if the adjusting knob is unintentionally turned too far. 2. Check diaphragm regulators for creep (leakage of gas from the high pressure to the low-pressure side when the adjusting knob is turned fully counterclockwise). 3. Provide check valves. Back-pressure protection is needed to prevent damage to the regulator. Gas from a high-pressure system can flow back into the regulator.




REMOVING THE REGULATOR FROM SERVICE 1. Close the cylinder valve. 2. Vent the gas. Vent the gas in the regulator and/or system, or isolate the system, and vent the gas in the regulator by turning the adjusting knob clockwise so that no pressure is tripped inside the regulator. If the gas is flammable, corrosive, toxic, or an oxidant, take appropriate measures to render it innocuous by employing a suitable disposal system before venting the gas to the atmosphere. 3. Close the regulator. After relieving all the gas pressure, turn the adjusting knob counterclockwise as far as it will go. 4. Disconnect low-pressure equipment. All low-pressure equipment connected to sources of high pressure should be disconnected entirely or, if not, independently vented to the atmosphere as soon as the operation is either over or shut down for an extended period of time. 5. Disconnect the regulator. 6. Protect the regulator. If the regulator is to remain out of service, protect the inlet and outlet fittings from dirt, contamination, or mechanical damage. 7. Replace the cylinder outlet seal and valve cap.

LIFE EXPECTANCY OF COMPRESSED GAS REGULATORS From David Gailey http://www.harrisproductsgroup.com/en/Expert-Advice/Articles/Regulator-Life-Expectancy.aspx Compressed gas regulators, when not performing optimally, can lead to many hazardous situations, such as the leakage of toxic, pyrophoric or asphyxiant gases into the atmosphere, or even the risk of explosions or fire. As such, regulators are devices that should only be used by persons experienced and aware of the inherent dangers.

Regulators are continuously exposed to high stresses due to cylinder pressures. In addition to that, the materials of construction are attacked internally by both mildly and severely corrosive gases. External corrosive environments can cause gauges and springs to rust, fittings to discolor and can severely tarnish the appearance of an otherwise brilliantly manufactured product

Because the applications for compressed gas regulators are so varied, the life expectancy is varied and proportional to the gas service and the environment in which the device is used.

FACTORS WHICH AFFECT REGULATOR LIFE Gas Service. Know the properties of the gas being regulated and contact a manufacturer or gas distributor for help in correctly selecting regulators for specific gases. Argon, helium and nitrogen regulators will, under a given set of conditions, have a longer service life than regulators used for hydrogen chloride and hydrogen sulfide simply because the gas service is more severe (corrosive). Some non-corrosive gases can be reactive in certain environments. For example, carbon dioxide can react with moisture or condensation inside a regulator to form carbonic acid. This is a relatively weak acid, but it can attack certain elastomeric components over time and reduce the service life of a CO2 regulator. To insure that the gas service will not adversely affect the expected life of a regulator, contact the manufacturer to discuss the application as well as the regulator’s metallic and non-metallic materials of construction.

Service Environment. Many applications require that regulators function outside; exposed to rain, snow, ice and high humidity/salinity. These are conditions that can reduce the service life of regulator components.

http://www.harrisproductsgroup.com/en/Expert-Advice/Articles/Regulator-Life-Expectancy.aspx




A significant percentage of gauges have steel cases, which will rust if exposed to the rain, snow or ice. Most pressure adjusting springs are also made of steel which, even though they are inside the regulator, will corrode over time in a humid environment. Steel and copper-based alloys (brass) are commonly in contact with each other inside and outside the regulator. Even though one or both components may be painted or plated, electrochemical (galvanic) corrosion cannot be ignored. Corrosion of parts and/or failure of components can be accelerated in harsh environments. Manufacturers as well as users who operate regulators in a critical service application, should consider these issues when recommending or purchasing pressure regulators.

Elastomers. Many industrial regulators have elastomeric components such as reinforced neoprene diaphragms, viton seals or seats, nitrile o-rings, etc. Elastomers can be very sensitive to extreme temperature shifts and to the elements. Over a period of time (normally years) these materials tend to become brittle and/or crack. This degradation can result in some form of leakage from the regulator.

Typical Modes Of Failure Failure of internal components generally results in leakage of the regulated gas to the atmosphere. There are no outward indications that failure of a major component is about to occur. In regulators, there are usually two areas of concern. The first is gas leakage to the atmosphere from the external ports or from the diaphragm. Leakage from the ports is rare unless factory fittings or gauges have been changed or torque settings are lower than recommended. Leakage can also occur if port threads have been damaged due to changing connections. Diaphragms are flexible, dynamic components that move axially as gas flows and pressures fluctuate through the regulator. When a diaphragm is pressurized and then relaxed, that constitutes one (1) sequence or cycle. According to the Compressed Gas Association Pamphlet E-4, diaphragms must have a minimum life of 25,000 cycles if made from an elastomer and 10,000 cycles if made from a metallic material (usually stainless steel). Leakage from the diaphragm can occur if it has exceeded its normal life. This is generally a greater problem for metal diaphragms than for elastomeric diaphragms. Excessive flexing of the metal diaphragm can cause a radial crack, which allows gas to escape to the atmosphere through the vent hole in the bonnet. The second and perhaps the most common type of regulator failure is the internal leak, sometimes called creep or crawl. This can occur when the seat becomes damaged or displaced due to a foreign particle such as a metal chip or other material. When the seat cannot close completely, delivery pressure will not be maintained and regulator pressure cannot reach a state of equilibrium. Downstream or delivery pressure will continue to climb until the safety relief mechanism on the regulator is activated (usually a relief valve or a diaphragm burst hole). Checking for this type of failure is relatively easy if the device has a gauge that reads regulated pressure. The gauge pressure will start to rise above the set point and continue upward. This creates a potentially hazardous condition where any downstream equipment would be subjected to pressures beyond the rated limit. Regulators should be visually checked for this type of failure often.




Long Regulator Life Starts With Good Maintenance To avoid unexpected downtime and to enhance safety in the work area, nothing can be more important than a routine regulator maintenance schedule. This will insure that the performance of the device is being checked at regular intervals where problems can be easily addressed. All compressed gas regulators should, at a minimum, be checked for external leakage and internal leakage (creep or crawl) regularly. In addition to this, the device should be removed from service at least every five years (more frequent in some cases) and returned to the manufacturer, or a competent agent of the manufacturer, to be inspected and/or refurbished as necessary. Regulators should also be tagged or labeled to identify the last date of inspection. Users should consult the manufacturer for specific procedures on how to check for external and internal leakage as well as the recommended frequency of the tests. In summary, compressed gas regulators do not have an infinite life span. Because some regulators are in severe service and some are not, it is difficult to say how and/or when a device will reach the end of its service life. Some companies publish guidelines in their literature, which attempts to define what to expect in terms of service life. Users should closely adhere to these guidelines to protect their equipment and themselves against the hazards regulator failures can produce.

CYLINDER DISPOSAL Large Cylinders need to be picked up by the company supply the gas. Small cylinders (lecture bottles) and calibration gas cylinders need to be given to EH&S for proper disposal. EH&S will make arrangements for vendor pickup or disposal of the cylinders as hazardous waste. Propane cylinders will be vented through a carbon filter to collect the residual gas. The empty cylinders will then be placed in the metal recycling bin.

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