Hot Tapping - wahaoil.ly

WOC LP

WOC HSE

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Manual

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Standards

DOCUMENT NO: WOC-HSE-ST-0001

Section H003 — Hot Tapping

REV ISSUE PREPARED BY REVIEWED BY APPROVED BY ISSUE DATE

0 Issued for Use!.1v

/A 1 tel) (W. McIntosh

WO ExecutiveVice President

OperationsJune 2009LP & EP Manager

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HSE Standards Manual

Section: H003

TITLE DOCUMENT NUMBER REV DATE PAGEHot Tapping WOC-HSE-ST-0001 0 June 2009 2 of 12

PURPOSETo outline the practices required to safely perform a hot tap into a "live" line or equipment

without blinding or purging of equipment.

APPLICATIONAll WAHA worksites and facilities

DEFINITIONHot tapping is the technique of attaching a mechanical or welded branch fitting to piping or

equipment in service, and creating an opening in that piping or equipment by drilling or cutting a

portion of the piping or equipment within the attached fitting. Therefore, this work mainly covers

welding technique without a process stream shut down, as it is impractical to take the piping or

equipment out of service.

Note:

It should be noted that Hot-Tapping is not be implemented as a means of convenience. A formal

risk assessment shall be performed and Hot-Tapping should be done as a last resort. This

information shall be documented and signed off by the Area Superintendent prior to Hot-Tapping

taking place.

POTENTIAL HAZARDS

welding burns and radiation

fire and explosion

toxic welding vapors

5. REQUIREMENTS

5.1. General

5.1.1. Hot tapping is restricted to carbon steel piping systems. Plant systems are governed

by rules established by ASME, B-31.3, Chemical and Petroleum Piping Systems or

government regulation. Pipeline systems follow the requirements of API 1104, and

API RP 2201 Procedures for Welding or Hot Tapping on Equipment in Service as a

minimum.

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5.1.2. Before undertaking a hot tap, Form A, "Request to Proceed with a Hot Tap," must

be completed and approved by the area Operations Manager and engineering. A

copy of this form must be forwarded to Operations personnel responsible for this

area for approval. This approval must be obtained before the hot tap is started. It

should be noted that within this request to Hot Tap Pipeline form a Work Pack is

included that contains all the relevant job details such as scope of work, normal

operating pressure and temperature, specific product in pipeline, pipeline flow

velocity, QA/QC procedures, P & Ids, plus hot tap engineering calculations. In

addition to this a comprehensive risk assessment using a Job Safety Analysis (JSA)

process must be carried out and attached with all the relevant potential hazards

identified and the method of control to remove or mitigate these hazards are fully

understood by all parties.

5.1.3. Form B, "Hot Tap Check List," must be completed and signed off by the Company

(WAHA) representative in charge of carrying out the hot tap. This information should

be retained as QC documentation by the Operations Manager.

5.1.4. Waha employees carry out hot tapping operations, however, If a competent

Contractor carries out the hot tap, they shall have a Manual, which contains a Safe

Operating Practice describing the procedure for operating hot tap equipment, Quality

Control manual, Welding Procedure Specification for the materials to be welded, and

Welder Certificate for the welder that will execute the hot tap. The welder shall be

thoroughly familiar with the welding equipment and hot tap and welding procedures to

be used.

5.1.5. Competent Company representatives including HSE representative must be present

during execution of the hot tapping.

5.1.6. Suitable fire extinguisher shall be available.

5.1.7. The location to be hot tapped must have be identified and physically marked.

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5.1.8. All necessary gas and toxicity tests has been made to ensure a safe environment

that is free from flammable substance.

5.1.9. Signs and barriers have been provided to isolate the job area from the public and

unauthorized personnel.

5.1.10. Appropriate personnel protective equipment shall be used.

5.1.11. Written emergency procedures specific to the job are required in the event of failure.

This procedure shall indicate isolation points and response by rescue and fire-fighting

units.

5.1.12. Prior to the hot tap, the inspector shall ensure the fittings, valves, gaskets and

bolting, etc., are identified and meet all the required specifications for pressure,

temperature and service environment.

5.2. Limitations

5.2.1. The minimum pipe wall thickness for hot tapping plant piping shall be 6.4 mm (1/4") &

4.8 mm (3/16") for pipelines. The base metal to be hot tapped shall be properly

inspected for adequate wall thickness and the absence of imperfections such as

laminations, hydrogen attack, or stress corrosion cracking. Imperfections, which

might prevent a sound weld from being made, shall be evaluated by qualified NDT

personnel.

5.2.2. The hot tap shall be at least 3" (7 cm) to a welded seam (including a longitudinal

seam of welded piping), or 18" (46 cm) to a flange or threaded connection. Other

spacing distances must be reviewed and approved by Facilities Engineering.

5.2.3. If a hot tap is installed upstream of rotating equipment or control valves, strainers or

other devices must be in place to prevent damage from metal shavings.

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5.2.4. Welding electrodes shall be limited to the low hydrogen type & as specified in the

WPS. In order to eliminate the occurrence of burn-through, the following steps shall

be followed:

5.2.4.1. The first weld pass less than 1/4" (6.4 mm) thick shall be made with 3/32" (2.4

mm) or smaller diameter welding electrode.

5.2.4.2. The subsequent weld passes be made with 1/8" (3.2 mm) diameter welding

electrode, or smaller if the metal wall thickness does not exceed 1/2" (12.8

mm). The larger diameter electrodes may be used for metal wall thickness

greater than 1/2" (12.8 mm).

5.2.4.3. Welding on compressed air lines under pressure is not allowed.

5.2.4.4. No Hot-Tapping shall take place on piping systems known to have a vapor/air

or vapor/oxygen content as the heat from welding may cause a vapor mixture

to enter the flammable range.

5.2.4.5. Hot tapping stress relieved piping systems is not allowed. Under special

circumstances, approval to hot tap a stress relieve system may be granted by

WAHA management provided job specific welding procedures have been

developed.

5.2.4.6. When the metal wall thickness is greater then what code will allow without

having stress relieving performed, Facilities Engineering shall be contacted so

as a thorough engineering evaluation may be performed. Max thickness for

most piping systems is 19mm (3/4") without PWHT

5.2.4.7. Cooling period shall be included between the completion of the full-

encirclement fillet weld and the completion of nondestructive testing. The

cooling period after welding and before testing provides for the assessment of

any delayed hydrogen-induced cracking. The length of time for the cooling

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period should be evaluated for each hot tap and approved by Engineering and

the Chief Inspector.

5.2.4.8. Unless specifically authorized by specialized procedures or following an

engineering evaluation, hot tapping is not permitted on in-service lines or

equipment with cladding, or with glass, lead, refractory, plastic, or strip linings.

5.2.4.9. Overheating of liquids and burn-through conditions during the welding of a

branch connection for a Hot-Tap is less likely when flow is maintained.

However too high of flow velocity increases the weld cooling rate and the risk

of cracking. Therefore, it is desirable to provide minimum level of flow if

possible. Minimum of 1.3ft/sec flow velocity in a gas line shall be maintained

to provide sufficient heat transfer. A maximum flow velocity does not appear

critical within the limits of practicability in a gas line. In liquid lines, the

recommended flow velocity range is 1.3 — 4.0 ft/sec.

5.3. Maximum Operating Pressure During Hot Tapping

5.3.1. In order to avoid the occurrence of burn-through during hot tapping, the operating

pressure in the pipeline shall be maintained at pressures not exceeding its critical

level by considering that the Heat Affected Zone (HAZ) reduces the strength of metal.

5.3.2. The MAOP can be calculated using the related ASME formulas (B31.3 for plant

piping, B31.4 for liquid lines and B31.8 for gas lines) with considering correction

factors as described below:

5.3.2.1. The base metal wall thickness (t) should be reduced by the depth of HAZ.

Due to there are no data available yet for the depth of HAZ, it is

recommended to consider as 60% of wall thickness for plant piping, and 30%

for cross country pipelines either gas or liquid services.

One laboratory test/ experiment showed that depth of HAZ is about 4.4 mm

(0.173") for the following welding parameters: base metal of 8" dia.pipe

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sch.40 API 5L gr.B and a plate of 9 mm thick, ASTM-572 gr.50, 3.2 mm dia.

Electrodes AWS E-7018, DCRP, 70 — 150 Amperes, and 20 — 35 Volts.

5.3.2.2. The specified minimum yield strength of base metal should be determined

based on the LMT (log mean temperature) as calculated below,

LMT = (T2 — T1)/ Ln T2/T1

Where, T1 is the temperature of fluid in the pipeline/piping. T2 is the

temperature of metal at HAZ, assumed 750 deg C.

5.4. Nondestructive Examination

5.4.1. Prior to welding, the hot tap location shall be verified for thickness and checked for

laminations and other defects using ultrasonic examination methods.

5.4.2. After completion of welding, the final weld shall be visually examined and subjected

to magnetic particle or dye penetrant examination.

5.4.3. All Hot Tap connections will be subjected to a hydro test prior to the cutting out of the

coupon.

6. REFERENCESAPI Publication 2201API RP 74

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Section: H003

TITLE DOCUMENT NUMBER REV DATE PAGE

Hot Tapping WOC-HSE-ST-0001 0 June 2009 8 of 12

Form A - Request to Hot Tap Pipeline

Date of Request: WAHA QC #

Purpose of Hot Tap:

Length of cooling period:

Location:

Description of run pipe:

Pipeline No.:

MOP during hot tap (calculated): Psig

Operating Pressure : Psig F

Product in pipeline:

Pipeline Velocity: Ft/second

Description of branch pipe:

Hot Tap Contractor

- Procedures Manual :

Welding Contractor

- Quality Control Manual

- Welder MIGAS Certified

WPS#

Work Pack Complete

JSA Done

Approved :Operations Manager

Approved by: Engineering

Approved by: QC Personnel

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Section: H003


Form B - Hot Tap Check List

(To be completed by WAHA job supervisor and filed with Quality Control - Hot Taps)

Has the properly approved work permit been obtained?

Has the hot work permit been obtained?

Does the company carrying out the welding and hot tapping procedure have an

approved QC Manual?

Has the exact location on the line been identified and marked?

Has the location been inspected for thickness and imperfections or defects?

Has the pipeline material been identified and is it compatible with the connecting

fittings?

Is stress relieving required?

Do the flanges, bolts, gaskets, pipe, valves and fittings meet the piping code of

the line to be hot tapped? Is the hot tap machine correct pressure rating and has

it been tested?

Is there sufficient external clearance to accommodate the operation of the hot tap

machine?

Is there sufficient internal clearance to retract the cutter through the valve?

Is the hot tap fitting of the proper length to accommodate the operation of the hot

tap machine?

Have combustible and toxic gas tests been conducted in the area of hot tapping?

Will the contents of the line affect the metallurgy of the pipe during the welding

operation?

Is the material in the line stable under heated conditions and free of oxygen?

Has fire-fighting equipment been provided?

Yes

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Has suitable protective equipment been provided for all exposed personnel in the

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Section: H003


hot tapping area?

Is there adequate hoisting and support equipment for the hot tapping machine

and other equipment as well as room for operational and emergency access?

In the event of an emergency incident occurring during the hot tapping operation,

has a procedure to isolate the work area been prepared and are personnel

trained to implement this procedure?

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Date: Print Name: Signature:

WAHA QC#

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Section: H003


SAMPLE OF CALCULATION SHEET

Plant piping (Refer to ANSI/ASME B31.3).

Pipe material: 6.625" OD x 0.25" wall thickness, API 5L Gr.B.

Content: Liquid hydrocarbon

Internal pressure: 150 psi

Flowing temperature: 200 deg C

Flow velocity: 70 cm/sec (2.3 ft/sec is OK)

Base metal thickness measured at hot tap point, 0.25"

Depth of HAZ (assume 60%): 0.6 x 0.25" = 0.15"

Temperature of metal at base of HAZ; assume 750 deg C

Corrected base metal thickness 0.25" — 0.15" = 0.10"

Corrected OD: 6.625" — 2(0.15") = 6.325"

LMT = (750 — 200)/ Ln(750/200) deg C = 417 deg C = 782 deg F

Allowable stress at this temperature, S = 11,000 psi.

Apply hoop stress formula from ANSI/ASME B31.3,

P = 2 t S/ (D — 2 y t), y for temperature below 900 deg F is 0.4

= 2 x 0.10 x 11,000 / (6.625-2(0.4 x 0.10)) psi

= 336 psi

Since the internal pressure of piping is only 150 psi, which is far below the max. allowable operating pressure

of 336 psi, hot tapping can be done safely.

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Section: H003


SAMPLE OF CALCULATION SHEET

Cross country gas pipeline (Refer to ANSI/ASME B31.8).

Pipeline material: 18" OD x 0.375" wall thickness, API 5LX —X52.

Content: Natural gas

Internal pressure: 1,200 psi

Flowing temperature: 15 deg C

Flow velocity: greater than 5 ft/sec

Base metal thickness measured at hot tap area: 0.40"

Depth of HAZ is assumed 30% x 0.40" = 0.12"

Corrected wall thickness: 0.40" — 0.12" = 0.28"

Corrected diameter: 18" — 2 (0.12") = 17.72"

Temperature at HAZ is assumed: 750 deg C

LMT = (750 — 15)/ Ln(750/15) = 188 deg C

Allowable stress at this temperature is 28,600 psi.

Maximum allowable operating pressure during hot tapping,

P = 2 t S/ D = 2 x 0.28 x 28,600/ 17.72 = 903.8 psi.

This calculation concludes that in order to execute hot tapping safely,the operating pressure of the gas line should be reduced from 1,200 psito 900 psi or lower.

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