pressure test objectives and acceptance...

Pressure Test Objectives and Acceptance Criteria

Sheri Baucom

Director, Integrity Services

RCP Inc.

What’s a “good” pressure test?

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“ILI will detect any anomaly that would fail a hydrotest.”

- an ILI vendor who shall remain anonymous

Case Study 1

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Case Study #1

• Pipe specs: • 8-inch, Grade B, 0.188 wt. • Seam type: LF-ERW• 1950s vintage

• Goal: Re-establish MAOP at 400 psig; incomplete material records

• Test Details:• 8 hour test planned • Target test pressure: 765 • 26% SMYS• 113 feet of elevation change • ~1.55 miles, all 8-inch • Part of a much larger hydrotest project

Pressure Temperature

On Test 766 psig 66˚F

End Test 754 psig 68˚F

2 injects = 3.6 gallons

Calculated Loss 9.3 gallons

Allowable Loss 1.9 gallons

Case Study 1:PT Attempt #1

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Lost ~45 psi


On Test 765 psig 65˚

End Test 762 psig 64˚

5 injects = 8.9 gallons

Calculated Loss 7.6 gallons

Allowable Loss 1.8 gallons

Case Study 2:PT Attempt #2

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Lost ~75 psi1˚F = 15 psi

Leaking manufacturing defect in long seam =A potentially hazardous leak

Strength Test

Leak Test

Leaking Defect ID’dBy Hydrotest

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Lessons Learned(from the Operator)

1. A pressure test may ID defects that are not ID’dby ILI.

2. Verifying the absence of leaks is required to meet the test objectives.

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• The objective: 1. Reestablish MAOP (incomplete material records) per

CFR requirement

2. Assess manufacturing defects i.e ensure there are no defects present that could leak or rupture in-service.

192.503: No person may operate a new segment of pipeline, or return to service a segment of pipeline that has been relocated or replaced, until…

Desired MAOP 400 psig

Design Pressure 1098 psig

Test Pressure 1.9*MAOP (70% SMYS)

Test Plan:

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192.503: Each potentially hazardous leak has been located and eliminated.

Test Plan:

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Establish MAOP

Meet CFR Leak

Requirement

Strength & Leak

Test

ID defects that may rupture

ID defects that may

leak

Strength & Leak

Test

Test Plan

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Test Parameters

Objective: Reestablish MAOP; Assess ERW-LF

Test Type Strength & Leak

Test Duration 8 hours

Strength Pressure ≥ 765 psig

Leak Calculated loss ≤ 2 gallons

Allowable Loss = Temperature Measurement Accuracy = 1˚F

If calculated loss < allowable loss, no potentially hazardous leaks.

API 1110

Disclaimer

• This is not to say hydrotesting is “better” than ILI or vice versa.

• (I <3 ILI. Plug for my talk tomorrow.)

• The point is… if you’re not analyzing your pressure test data (like you analyze your ILI data), you risk wasting all that time and $$.

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1 mile = $1 million

Pressure TestsCost $$$$

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1. Objective (establish MAOP, satisfy IMP, asses SCC)2. Test Subject (what are you testing?)3. Test Type (strength, leak, spike)4. Acceptance Criteria5. Test Parameters

Pressure Test Design

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Test Objective Test Subject Test Type Test Pressures1. (Re)Establish MAOP

MAOP ≥ 30% SMYS

Strength & Leak Test, 8 hours

CL TF*MAOP

2. (Re)Establish MAOP

Fabrication, MAOP ≥ 30% SMYS

Strength & Leak Test, 4 hours

CL TF*MAOP

1. Category 1 allows above-ground leak survey to assess for leaks2. CL TF = Class Location Test Factor

Every Code-required test requires proving the absence of leaks.

Test Parameters for Steel Gas Pipelines

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100 psi ≤ MAOP ≤ 30% SMYS

Strength & Leak1 ≥ 1 hour

2CL TF*MAOP


1 psi ≤ MAOP ≤100 psig

Leak test, duration TBD3

90 psig


MAOP ≤ 1 psig Leak test, duration TBD3

10 psig

1. If NG, inert gas or air is the TM AND TP>20% SMYS, a leak survey must occur during the PT

2. CL TF = Class Location Test Factor3. Duration defined by GPTC guide material

The test procedure used must ensure discovery of all potentially hazardous leaks in the segment being tested.

Test Parameters forSteel Gas Pipelines

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Test Parameters for Plastic Gas Pipelines

1. Duration defined by GPTC guide material

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Plastic Gas Pipeline

Leak test, duration TBD1

1.5*MAOP OR 50 PSI (whichever is greater)

The test procedure used must ensure discovery of all potentially hazardous leaks in the segment being tested.

Code-Required Test Types

Liquid Pipelines: A Strength & Leak test

• Strength Test (& Leak Survey)• Strength & Leak Test • Leak Test

Gas Pipelines:

Notice that every PT req’d by Code requires a leak

test…

• No ruptures or significant leaks occur that prevent the pressure from being maintained above the minimum

• Minimum usually defined by desired MAOP

Easy!

Time Pressure

SuccessfulStrength Test?

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1. Visual Inspection• If all pipe is visible

2. Leak survey • Only allowed for Cat. 1

and sometimes Cat. 3

3. Engineering Analysis• Prove any loss <

allowable loss

Time Pressure Temp. Volume

I repeat: Every Code-required test requires proving the absence of leaks.

SuccessfulLeak Test?

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• IMP Pressure Test = MAOP PT • Impending Gas Mega Rule

• Spike @100% SMYS or 1.5*MAOP + MAOP PT

• Cracking due to SCC or mfg: Spike + Strength + Leak

• Metal Loss: Strength + Leak

Integrity PressureTests

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“I just know it’s a good test.”- every testing contractor I’ve ever encountered

Case Study 2

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Bad Temp. Data

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Calculated Loss = 500+ gallons

Increasing pressure doesn’t mean there aren’t any leaks!

1˚F = 25 psi (400 psi)

“I don’t have a good feeling about this one.”- person responsible for signing their name on the test when

they see appreciable pressure loss

Case Study 3

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• Pressure loss is acceptable • as long as it correlates with temperature loss

• is equivalent to a loss that is less than the allowable loss.

• We can prove this with scientific principles.

Temperature goes down, pressure goes down…




Calculated Loss = 0.5 gal

Allowable Loss = 1 gal

Pressure-Temp. Correlation

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“Looks good!”- California State Fire Marshal Model

Case Study 4

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Not all modelswork well…

CSFM*ALLOWABLE LOSS

RCP MODEL ALLOWABLE LOSS

PREDICTED LOSS PREDICTED LEAK SIZE

PREDICTED LEAK RATE

10.47 GALLONS 0.30 GALLONS 0.54 GALLONS 0.0025 IN DIAMETER

0.23 GAL/HR

* CSFM = CALIFORNIA STATE FIRE MARSHAL

Time 0 hours 409 psig Pipe Temp 64oFTime 8 hours 327 psig Pipe Temp 63.5oF

“I certify that no leaks exist on this meter station.”- Licensed PE working with an engineering firm that shall not

be named…

Case Study 5

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How was thiscertified?


On Test 1820 psig 79˚

End Test 1814 psig 82˚

Found multiple leaks!!

• “The P-V plot proves there aren’t any leaks.”

• P-V plots can:• Indicate yielding of

pipe• % of air entrapped• Correct P-V ratio• Pump efficiency…

Pressure-Volume Plots

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“The test is deemed acceptable if there is no evidence of leaks.”

• What about when the pipe is buried?

• What about when the pipe is laying on the ground?

Ineffective Acceptance Criteria

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“If the pressure drops below minimum specified, the test segment shall be re-pressurized and the test duration requirement be restarted.”

• So if you have a leak, as long as you keep re-injecting to keep the pressure above minimum, the test is acceptable?

Ineffective AcceptanceCriteria

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“It’s okay to have some leaks, right?”- ….

Engineering Analysis

Consequence of Not

$<1% $100k+++

What is your risk tolerance? What constitutes a failure?

Define “Hazardous”

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If we can show calculated loss is less than allowable, we can

prove there are no “potentially hazardous leaks.”

Summary

Engineering Standard• Objective• Acceptance Criteria

• If pipe is buried• If all pipe exposed

Confirm (in real time)• Test meets Acceptance Criteria• Otherwise, repair/adjust and repeat the test.

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Questions for you!

• What’s a “good” pressure test?

• One that meets the acceptance criteria!

• What’s your company’s acceptance criteria?

• Ensure you have a leak requirement!

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Thank You!

Sheri [email protected]

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mailto:[email protected]

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