Pressure Testing of Plant Piping and Pipelines | SAES-L-150 [PDF]

This article is about SAES-L-150 standard, which outlines specific requirements for conducting pressure tests on newly constructed plant piping and pipelines. These tests are carried out when the construction follows the guidelines of the ASME (American Society of Mechanical Engineers) codes such as ASME B31.1, B31.3, B31.4, or B31.8, depending on the type of piping or pipeline.

1. Newly Constructed Plant Piping and Pipelines: The SAES-L-150 standard provides rules for pressure testing when you’re building new plant piping and pipelines. These rules are in addition to what’s outlined in the ASME codes mentioned.
2. Existing Plant Piping and Pipelines: The standard also covers requirements for pressure testing existing plant piping and pipelines. This is typically done to revalidate their safety and integrity or after making repairs.
3. Exclusions: There are some cases where this standard doesn’t apply, and those exceptions are listed in another document called SAES-A-004.

This SAES-L-150 standard complements ASME codes by specifying how pressure testing should be conducted for both new and existing plant piping and pipelines, ensuring safety and compliance with industry standards.

Pressure Testing of Plant Piping and Pipelines

General Requirements

Here we outline specific requirements and procedures for pressure testing piping systems in a plant or industrial setting.

5.1 General Test Requirements:

• This article refers to SAES-A-004, which contains general requirements for testing.

5.2 Pressure Test for New Pipelines:

• All newly constructed pipelines must undergo a hydrostatic test before being put into operation.
• The test pressure should comply with section 8 of this standard but cannot be less than the minimum requirements specified in ASME B31.4 or ASME B31.8, depending on the type of pipeline.

5.3 Hydrostatic Strength Test for New Plant Piping:

• New plant piping must undergo a hydrostatic strength test in compliance with this standard and ASME B31.3 or ASME B31.1, as applicable.

5.4 Pressure Test for Existing Plant Piping:

• When repairs or alterations that affect the pressure-containment integrity are made to existing plant piping or pipelines, they must pass a hydrostatic test.
• The test pressure should meet the requirements of the applicable code.

5.5 Exclusion for Skid Mounted Piping Systems:

• Skid-mounted piping systems that have been successfully tested in a shop, witnessed by an authorized inspector, are exempt from in-situ field strength testing.
• However, this exemption becomes invalid if the packaged piping system undergoes subsequent repairs, modifications, or damage.

5.6 Pressure Testing for Sampling Piping Systems:

• Sampling piping systems must be pressure tested as an integral part of the piping or equipment they connect to.

5.7 Tie-In Butt Weld Testing:

• Provisions must be made for conducting a strength test on tie-in butt welds connecting new piping to either new or existing systems.
• If a strength test is impractical, it may be replaced by 100% radiography, subject to approval.

5.8 Second Pressure Testing for Piping Systems:

• A second pressure test is required for piping systems that have already passed a successful pressure test if new welding activities and post-weld heat treatment (PWHT) are necessary due to these new welds.
• Some specific cases are exempt from the second pressure test.

5.9 Exclusion for Certain Piping:

• Piping such as drains, vents, and piping downstream of pressure-relieving devices discharging to the atmosphere with low internal pressure may be excluded from in-situ pressure testing.

5.10 Valve Seat Testing:

• When block valves are used for blocking or isolating hydrotest sections, the differential pressure across the valve seat during strength and tightness tests must not exceed specified limits.

5.11 Field Hydrotesting of Valves:

• Field hydrotesting of valves should follow SAES-L-108 requirements.

5.12 Instrument Impulse Lines Testing:

• Instrument impulse lines must undergo a leak test for at least 30 minutes.
• The test involves pressure testing at 1.1 times the design pressure using air or nitrogen.
• Instruments susceptible to damage during testing should be disconnected.
• Liquid testing is allowed when pneumatic testing is not practical.

5.13 Fusion Bonded Epoxy (FBE) Coated Piping:

• The test pressure should not damage the internal FBE coating but must meet the minimum requirements of the applicable code.
• Deviations from this requirement require approval from specific committees.

In summary, this passage details the procedures and requirements for pressure testing various types of piping systems in an industrial setting, emphasizing safety and compliance with industry standards.

Design Requirements

These are design requirements related to venting, draining, supports, and the use of expansion joints and spring hangers in a piping system for hydrostatic testing. Here’s a simplified breakdown:

6.1 Vents:

• High points in the piping system must have vents.
• For cross-country or submarine pipelines, vents may not be necessary if a scraper is used before the test to remove air from the lines.

6.2 Drains:

• Except for submarine and buried pipelines, drains should be placed at low points in the piping system.

6.3 Supports:

• For above-ground installations, the piping system must be analyzed to determine if temporary supports are needed during hydrostatic testing.
• These temporary supports are necessary to limit sustained longitudinal stresses to acceptable levels according to the code.
• If it’s more cost-effective to use temporary supports than permanent ones, this should be noted in the hydrotesting procedure.

6.4 Expansion Joints and Spring Hangers:

• When expansion joints and spring hangers are used in the piping system, temporary restraints should be added as needed during hydrostatic testing.
• These restraints prevent excessive movement or deformation of the expansion joints and spring hangers under the test loads.

In summary, these design requirements aim to ensure that venting, draining, supports, and expansion joints in the piping system are appropriately considered and incorporated to facilitate safe and effective hydrostatic testing while complying with code requirements.

Pressure Testing of Plant Piping

We outline specific requirements for pressure testing plant piping.

7.1 Test Pressure for New Constructed Lines:

• The hydrostatic strength test pressure for each section of newly constructed piping should create a hoop stress in the pipe equal to 90% of the specified minimum yield strength (SMYS) at the test temperature.
• Calculate the test pressure based on the pipe’s nominal wall thickness minus the manufacturer’s tolerance.
• The test pressure should not be less than the minimum required by ASME B31.3.

7.2 Duration of Test:

• The test pressure should be maintained for a minimum of 30 minutes to ensure there are no leaks.

7.3 Visual Leak Detection:

• All joints, including welded joints, should be left exposed during the strength test for visual leak detection.
• External coating and priming of joints are not allowed unless approved by the Inspection Department Manager and the organization’s representative. However, the pipe itself can be externally primed and coated.

7.4 Testing Jacketed Piping:

• For jacketed piping, the internal line should be hydrotested as per 7.1.
• Field welds should be visible for leak detection during the hydrotest.
• The jacket should be hydrotested according to ASME B31.3.
• The maximum allowable external pressure for the internal line should not be exceeded during the jacket pressure test, and differential pressure can be minimized by pressurizing the internal line.

7.5 Exemptions to Test Pressure and Duration:

• Specific cases of exemptions to the test pressure and duration are listed:
• Lube and seal oil piping has its own test pressure requirements.
• Underground process piping must be tested before backfilling.
• Flare lines of a certain size and design pressure may undergo pneumatic testing.
• Piping in vacuum service has specific test pressure requirements.
• Service tests are acceptable for certain types of piping services.

7.6 Revalidation of Existing Piping:

• For revalidating existing plant piping, the test pressure should be a minimum of what is required by ASME B31.3.
• Consider the actual wall thickness of the piping and the flange rating when calculating the test pressure.

In summary, these requirements outline how pressure testing should be conducted for various types of plant piping, ensuring safety and integrity in compliance with industry standards and codes.

Pressure Testing of Pipelines

This section outlines specific requirements for pressure testing pipelines.

8.1 Test Pressure for Newly Constructed Pipelines:

• The hydrostatic strength test pressure for each section of newly constructed pipelines should be calculated to create a hoop stress of 90% of the specified minimum yield strength (SMYS) of the pipe material, based on the nominal wall thickness.
• The test pressure at the lowest point of the pipeline, considering hydrostatic head, should not result in a hoop stress greater than the SMYS.
• The strength test pressure should be maintained for two hours.

8.2 Test Temperature:

• The test temperature should not result in a combined longitudinal stress (calculated based on 0.7 hoop stress at the test pressure, temperature stress, and bending stress) exceeding the SMYS.

8.3 Tightness Test:

• After completing the strength test, a tightness test should be conducted at 95% of the strength test pressure.
• The tightness test pressure should be maintained long enough for the inspector to examine all exposed joints.
• For buried, insulated, or partially buried/insulated pipelines over a certain length, a 24-hour recorded tightness test is required.

8.4 Revalidation Pressure Testing for Existing Pipelines:

• For existing pipelines undergoing revalidation pressure testing, the test pressure should be a minimum of 1.25 times the Maximum Allowable Operating Pressure (MAOP) for pipelines with specific design factors.
• The flange rating should be considered when calculating the test pressure.
• The results of the latest pressure testing should be documented in the “Safety Instruction Sheet.”

In summary, these requirements ensure that pressure testing of pipelines, whether newly constructed or existing, is conducted with specific parameters to ensure safety, integrity, and compliance with industry standards and codes.

Pressure Testing for Minor Repairs

This section outlines pressure testing requirements for existing facilities undergoing minor repairs.

9.1 Small Diameter Threaded Piping:

• For small diameter threaded piping without pressure-containing welds (in all services and pressures), hydrostatic pressure testing is not required if the thread engagement and seal welding requirements specified in SAES-L-110 are met.
• However, a service test must still be conducted for these welds.

9.2 Socket Welded Piping:

• In the case of socket-welded piping, and when the Operations Engineering Unit determines that hydrostatic testing is not practical, the piping may be pressure tested with its own product at its operating pressure under certain conditions:
• A request for Non-Destructive Testing (NDT) in lieu of pressure testing must be processed as detailed in SAES-A-004 section 5.
• Qualified welders and welding procedures must be used.
• The weld gap should be verified and welding witnessed by the responsible Operation Inspection Unit.
• Welds should be subjected to either magnetic particle (MT) or dye penetrant (PT) testing (Operations Inspection decides the method).

9.3 Low-Pressure Steel Piping:

• Low-pressure steel piping used in water, instrument air, plant air, inert gases (Nitrogen, Argon, etc.), and steam systems operating at 1035 kPa (ga) (150 psig) or lower may be strength tested with its own product at its operating pressure (service test).
• This provision does not apply to firewater systems.

In summary, these requirements provide flexibility in pressure testing for minor repairs in existing facilities, taking into account the type of piping and the practicality of conducting hydrostatic tests while ensuring safety and compliance with relevant standards.

Test Procedures

This section outlines procedures and requirements for conducting pressure tests.

11.1 Test Procedure Preparation:

• Test procedures should be prepared and conducted following the guidelines outlined in SAES-A-004.

11.2 Test Water Quality and Lay-up Condition:

• The quality of the test water and the lay-up condition should meet the standards specified in SAES-A-007.

11.2 Disposal of Test Fluid:

• Prior to conducting the hydrostatic test, the sites where the test fluid will be disposed of should be reviewed and approved in accordance with SAEP-327, titled “Disposal of Wastewater from Cleaning, Flushing, and Hydrostatic Tests.”

11.3 Temperature-Related Pressure Variations:

• In cases where pressure variations occur due to changes in test water temperature, such as in cross-country pipelines, thermocouples should be installed to accurately measure the temperature of the pipe metal.
• These temperature measurements are essential for determining the acceptance of the pressure test.
• Deviations from standard procedures may be considered, but consultation with the Chairman of the Piping Standards Committee in the Consulting Services Department is required, especially for deviations related to the 24-hour pressure chart.

In summary, these procedures and requirements ensure that pressure tests are conducted with proper planning, water quality, disposal considerations, and temperature monitoring to ensure the accuracy and reliability of the test results while adhering to established standards.

International Codes & Standards for this Article

American Society of Mechanical Engineers
ASME B31.1 – Power Piping.
ASME B31.3 – Process Piping.
ASME B31.4 – Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids.
ASME B31.8 – Gas Transmission and Distribution Piping Systems.

FAQs: