What Is Water Quality Acceptance Criteria During Hydro-test of Oil and Gas Equipment? The A to Z of Related Codes, Standards and Specifications

Water quality is an important factor at hydrostatic test consideration so that many corrosion and cracking problems are resulted from improper water quality. The important factor in hydrostatic test consideration by code and standards are as follows:

• Total dissolved solids (TDS)
• Chloride content specially for austenitic stainless steel
• PH , Conductivity and other parameters
• Drying

By this Article we review 12 applicable code, standard and specifications as Follows:

• API 510 / 570
• ASME PCC2 /B31.1/ B31.3 / B31.4 / B31.8
• EIL / SAES / PTS / EEMUA

1- API 510 / Pressure Vessel Inspection Code

Clause 5.8.5.2 - API 510 2014

Hydrostatic pressure tests of equipment having components of Type 300 series stainless steel should be conducted with potable water or steam condensate having a chloride concentration of less than 50 ppm. After the test, the vessel should be completely drained and dried. The inspector should verify the specified water quality is used and that the vessel has been rained and dried (all high-point vents should be open during draining). If potable water is not available or if immediate draining and drying is not possible, water having a very low chloride level (e.g.steam condensate), higher pH (>10), and inhibitor addition should be considered to reduce the risk of pitting, chloride stress corrosion cracking, and microbiologically induced corrosion. For sensitized austenitic stainless steel piping subject to polythionic stress corrosion cracking, consideration should be given to using an alkaline-water solution for pressure testing (see NACE SP0170).

2- API 570 / Piping Inspection Code

Clause 5.11.2 - API 570 2018

Piping fabricated of or having components of austenitic stainless steel should be hydrotested with a solution made up of potable water (see note), de-ionized/de-mineralized water or steam condensate having a total chloride concentration (not free chlorine concentration) of less than 50 ppm. After testing is completed, the piping should be thoroughly drained (all high-point vents should be open during draining), air blown, or otherwise dried. If potable water is not available or if immediate draining and drying is not possible, water having a very low chloride level, higher pH (>10), and inhibitor addition may be considered to reduce the risk of pitting and microbiologically induced corrosion.

API 510 and API 570 Common Criteria :

As mentioned these two code have a similar criteria for water quality of hysdrostatic test and refer to Article 501 of ASME PCC2 2018 for more details.

3- ASME PCC2 / Pressure vessel and Piping Repair

Clause 6.1 (t) - ASME PCC2 2018

• The use of salt or brackish water should be avoided. Test water should be free from sediment and corrosive substances.
• The test water should be verified to be free of microbes. If the water contains an unacceptable level of microbes, it should be disinfected.
• Test water used for austenitic steel vessels or piping systems, or for components clad or overlaid with austenitic stainless steel, should be condensate, demineralized, or of potable quality, with a verified chloride content of less than 50 ppm.
• Test liquid should be drained immediately after completion of the hydrostatic test. Care should be exercised to provide proper venting to prevent the creation of internal negative pressure (vacuum) during draining.
• Pressure vessels and/or piping systems that will hold the test water for more than 10 days, whether or not the test liquid is pressurized, should be treated with a corrosion inhibitor and biocide. A corrosion engineer should be consulted.
• If further drying is necessary, the use of hot air or hot nitrogen should be considered.
• If complete drainage of austenitic stainless steel vessels and/or piping systems is not possible, the components should be flushed with low-chloride (less than 5 ppm) water.

4. EEMUA 168 / Pressure Testing of Equipment

4.1 Appendix III Test Fluids

For equipment lined or clad with austenitic should be as follows:

a) Where it is not possible to flush (that is where the last water to wet the internal surfaces was the test water), the test water should contain not more than 1ppm of chlorides if the equipment:

i. has a maximum operating temperature of more than 50 C

ii. includes austenitic stainless steel bellows

iii. includes crevices in which water can be trapped such as tube to tube plate joints, welded jackets

b) Where a)i applies and it is practicable to flush for example where the internal surfaces can be washed down or re-wetted by the flush water, the test water may contain up to 200 ppm of chlorides. However, this is only permitted by specific agreement with the competent person and the equipment must then be properly flushed after test with water containing not more than 1 ppm of chlorides.

c) If none of the conditions a)i, ii and iii applies, then test water with chloride content of not more than 200 ppm may be used.

In addition to a), b) and c) above, austenitic stainless steel equipment should be drained as soon as possible after testing. Also where possible it should be dried within 48 hours of draining using swabs, a flow of ambient temperature dried air or evacuation where the design pressure of the vessel permits. Drying techniques involving the application of heat should not be used.

4.2 AIII.2 Specific User Experiences

4.2.1 AIII.2.1 Oil Refinery / Austenitic Stainless Steel Equipment

For austenitic stainless steel equipment the test water is limited to less than 250 weight ppm chloride ion with a pH between 6 and 9. Usually potable water meets this requirement. For high pressure service, above about 100 barg, less than 50 weight ppm chloride ion is required. All such equipment should be drained immediately after test and dried by blowing through with warm air at less than 60 C.

For equipment that cannot be readily drained and dried, eg. a vertical tube furnace coil, a hydrocarbon liquid may be used or steam condensate/boiler feed water that has been demineralised and has less than 1 weight ppm chloride ion. In the latter case residence time is minimized.

4.2.2 AIII.2.1 Oil Refinery / Carbon Steel Equipment

Salt water is used at times for testing of carbon steel equipment, particularly for large systems that might otherwise have a very long fill time. Use of salt water is reviewed on a case-by-case basis with the Inspector. Again, residence time is minimized. For rare occasions of extended test periods or wet lay-up of more than three days the test water should be treated with a suitable biocide and corrosion inhibitor, taking due account of water disposal after test.

4.3 AIII.2.2 Chemical Plant

For hydrostatic pressure testing of austenitic steel equipment the requirements for the quality of the water are determined by the necessity to prevent stress corrosion cracking by the chloride present in the test water which remains in the equipment after the test. The water should not have a higher chloride content than any aqueous fluid used in the vessel.

The following clip shows a chloride stress corrosion cracking of austenitic stainless steel during hydrotest while the chloride limit is not followed by rules of code and standards which commonly limited to 50 ppm. 

https://www.dhirubhai.net/feed/update/urn:li:activity:6650166548126277632

5- PFI ES 4 / hydrostatic Test of Fabricated Piping

Clause 4.2 PFI ES 4

This clause doesn't emphasize any special requirement and mention that any special requirement of the chemical content of the water content shall be specified in the contract document.

6- ASME B31.1 Power Piping

6.1 Clause 137.4.3 Test Medium

Test water shall be clean and shall be of such quality as to minimize corrosion of the materials in the piping system. Further recommended precautions on the quality of test water used for hydrotesting of austenitic (300 series) and ferritic (400 series) stainless steels are contained in non mandatory Appendix IV, para. IV-3.4.

6.2 IV-3.4 Precautions at Hydro testing

Equipment fabricated from austenitic (300 series) and ferritic (400 series) stainless steels and requiring hydrostatic testing should be tested with deionized water, high purity steam condensate, or potable water, in decreasing order of preference.

NOTE: Potable water in this context follows U.S. practice, with 250 parts per million maximum chloride content, sanitized with chlorine or ozone.

After testing is completed, equipment should be thoroughly drained with all high point vents open during draining, and dried by air blowing, swabbing, or other appropriate means. If immediate draining and drying are not possible, hydrotest water should be circulated in the piping for at least one hour daily to reduce the possibility of pitting and microbiologically influenced corrosion.

7- ASME B31.3 Process Piping

Clause F345.4.1 Hydrostatic Leak Test

Consideration should be given to susceptibility to microbiologically influenced corrosion (MIC). This condition is especially prevalent in no-flow, high-moisture environments. Internal MIC may also depend on the characteristics of the treated or untreated test fluid. Internal MIC may be lessened or possibly eliminated by properly draining and drying systems and/or by proper selection of test fluid.

8- ASME B31.4 / Liquid Hydrocarbon Pipe Line

Clause 437.4 .1 (b)

The ASME B31.4 refer to API 1110 by this clause and no special criteria for water is mentioned

9- ASME B31.8 / Gas Pipe Line

A847.3 Test Medium

The only criteria which mentioned at appendix A which use for offshore pipe line.

The test medium for all offshore pipelines will be water. Additives to mitigate the effects of corrosion, bio-fouling, and freezing should be considered. Such additives should be suitable for the methods of disposal of the test medium.

It seems that it is essential to clear all water parameters by construction specification between owner and contractor for ASME B31.4 and B31.8 pipe lines.

10- API 1110 / Pressure Testing of Steel Pipe Lines

10.1 Clause 5.3 / filling and cleaning

The quality and source of the test water should be determined. Water that contains sediment, non-neutral pH levels, or is high in salinity may be detrimental to the pipe, valves, and equipment and should not be used unless it is filtered or treated. The possible deleterious effect of additives or corrosion inhibitors on the processing of gas or hazardous liquids to be transported should be investigated.

10.2 Clause 5.9 / Disposal of the Test Medium

This clause addressing environmental issue. Prior to its discharge, water should be free of solids, acids, oils, and other products detrimental to the environment.

11. EIL 6314-00-16-71-SP-55 / Specification for Hydrostatic Testing of Onshore Pipelines

Clause 7.3 / Procedure

The test medium shall be soft non-aggressive water furnished by the Contractor. The water to be used shall be filtered, shall not be contaminated and free from sand of silt. Contractor shall submit laboratory test reports of water used for testing. The possible use of sea water shall be subjected to its degree of cleanness, the possibility of obtaining a pre-determined salinity neutralization and the use of corrosion inhibitors, this at the sole discretion of Company. Contractor shall provide Company approved corrosion inhibitors, oxygen scavengers and bactericides to be added to the test water. The Contractor shall furnish and install all temporary piping, which may be necessary to connect from source of water to its pump and manifolds/tankages.

12 . PTS 20.117 / Cleaning, Pigging and Hydrostatic Testing of Offshore Pipelines

Clause 3.2 - Consumable and Sea Water

All the seawater to be put into the pipeline system shall be first filtered through a mechanical filter having a screen of size 50 mesh and the filter shall be capable of being back flushed without disconnecting the piping. All the seawater put into the pipeline system, in addition to being filtered as stated here in above, shall be treated with 50 ppm of the bactericide "Petrolite XC-102". The use of a bactericide from other suppliers shall be subject to the COMPANY's prior written approval.

13. SAES - A007 / Hydrostatic Testing Fluids and Lay-Up Procedures

The most useful specification which is just related to water quality by 19 pages!. This standard establishes requirements to control corrosion and microbiological damage during and after hydrotesting of new, re-validated, and refurbished equipment. Equipment covered by this standard includes, but is not limited to, storage tanks, pressure containing equipment, plant piping, and pipelines both onshore and offshore.

The key points of this specification are as follows:

• Water quality of hydrostatic test waters shall be reconfirmed by testing as close to the time of the hydrostatic test as practicable.
• Suspended matter in the water shall be extracted, before use, by a filter capable of removing 99% of all particles 53μm (2.1 mil) in diameter and larger, or equivalent to using a 270 mesh wire mesh screen.
• Water may be reused for hydrotesting, as in a pipeline tested segment by segment. The water must have an oxygen level of less than 20 ppb, or additional chemical treatment will be required.
• When the equipment contact time with hydrotest water may exceed 14 days, an approved oxygen scavenger shall be added to the hydrostatic test water. Treat the water before it enters the system.
• Equipment must be laid-up after hydrotesting unless it can be ensured that it will be returned to service within 30 days from the first introduction of hydrotest water to the system. Use one of the lay-up methods detailed mentioned by :1- wet lay up 2- dry lay up 3- Inert Gas lay up 4- Ambient Lay-up.
• Type 300-series stainless steels shall be tested only with water that has very low chloride content in order to avoid pitting and stress corrosion cracking. The maximum allowable chloride concentration is 50 ppm
• Type-400-series stainless steels are highly prone to atmospheric corrosion. Type 400-series stainless steel trimmed valves shall be removed from pipelines before hydrotest. If it impossible to remove such valves from the line, then written hydrotest procedures must be prepared and approved ahead of time allowing the valves to remain in place
• For carbon steel open-roof tanks, floating-roof tanks, or API atmospheric cone roof tanks not designed for service above atmospheric pressure, treatment of hydrostatic test water shall not be required. Immediately after completion of the hydrostatic test, drain and remove all traces of visible water.
• For carbon steel open-roof tanks, floating-roof tanks, or API atmospheric cone roof tanks not designed for service above atmospheric pressure, treatment of hydrostatic test water shall not be required. Immediately after completion of the hydrostatic test, drain and remove all traces of visible water.
• For sour gas pipe lines immediately prior to re-commissioning new or existing lines, the lines shall be batch treated with a corrosion inhibitor. This shall be achieved by using a slug of corrosion inhibitor between two or more scrapers. The slug size shall be calculated as follows:

Gallons of inhibitor = Pipelines length (km) x Pipeline diameter (in) x 3

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