Case 1:
Solutions & Suggestions:
1. Drain the valve thoroughly when system unit shut down during wintertime.2. Add heat tracing system for the pipeline.
Case 2:
1. Installation place modification to guarantee the minimum upstream and downstream straight pipeline length.
2. Add damper device as buffer.
Case 3:
Solutions & Suggestions:Modify the installation orientation with maximum slope 45° for cryogenic liquid service valves
Case 4:
Inappropriate insulation height for cryogenic valve caused stem leakage.
Solutions & Suggestions:
Modify insulation height up-to vapor dissipation space for low temperature service.
Case 5:
Ball valve applied to regulate the flow in the pipeline caused the sealing performance failure.
Solutions & Suggestions:
1. Never use gate or ball valves to regulate the flow to ensure proper service life.
2. Globe and butterfly valves could be used for regulating function for pipeline.
Case 6:
Oxygen service valves are at risk of on-site accidents if not strictly cleaned and protected.
Solutions & Suggestions:
1. Valves will be totally cleaned, reassembled, retested and seal packed in clean room.
2. Before installation, do not open the package.
3. Keep the valve passage clean during installation.
4. Do not fast operate the valve under full pressure difference.
Case 7:
For toxic service valves, high attention is needed to the risk of stem packing leakage.
Solutions & Suggestions:
1. Valves will be totally cleaned, reassembled, retested and seal packed in clean room.
2. Before installation, do not open the package.
3. Keep the valve passage clean during installation.
4. Do not fast operate the valve under full pressure difference.
Case 8:
In harsh services like coal chemical, the valve cavity may get stuck and cause functional failure.
Solutions & Suggestions:
Disassemble the valve and clean, grind, and replace with spare parts regularly according to the specific service condition.
Pressure Testing
Valves requiring repair or modification will be pressure tested in accordance with applicable standard and requirements laid out as if it is a new valve.
1) Hydrostatic shell and backseat test: no visible leakage is allowed.
2) High pressure seat test:
Soft Seated Valves and Lubricated Plug Valves:
The maximum allowable leakage during seat test should not exceed ISO5208 Rate A (no visibly detectable leakage) or in accordance to API6D and EES Standards.
Metal Seated Valves
The maximum allowable leakage during seat test should not exceed ISO5208 Rate D, except during a double isolation and bleed, double block and bleed or twin seat test. During a double block and bleed or twin seat test, the maximum allowable leakage rate should not exceed two times the ISO 5208 Rate D.
3) Low pressure seat test:
The seat test will have a test pressure between 80psi and 100psi using air or nitrogen as the test medium. The acceptable leakage rate for low pressure gas seat tests is:
– Soft seated and lubricated plug valve
– ISO5208, Rate A (no visible leakage)
– Metal seated valves – ISO5208 Rate D
3) Verify end-to-end dimensions meet the requirements of ASME.
4) All welds should be liquid penetrant and visually examined in accordance with ASME B31.3, Section 341, with acceptance criteria in accordance with ASME B31.3, Section 341.3.2, for normal fluid service.
5) If disassembly is required for the modification, reassemble in accordance with manufacturers installation and operations manual.
Post Weld Heat Treatment
The PWHT performance and acceptance criteria should meet ASME B31.2 requirements including heat treatment.
Magnetic Particles
The procedure is for surface inspection on ferromagnetic materials, in accordance with ASME V Article 7 (and Article 25) – 2019, and may present in any shapes, and forms, including all types of welds; with or without maximum paint coating not exceeding 0.005 inch. The purpose is to expose flaws that are open or near to the surface examined and the extent of inspection will be as governed by jurisdictional standards.
Radiography
Non-destructive examination and evaluation is in accordance to manufacturer, repair, modification standards meeting industry codes. Non-Destructive testing and Inspector i.e., performing NDE should be ASNT-TCIA Level I or II. Results acceptance and report generation should be performed by ASNT-TCIA level II. This should be 100% in accordance with applicable EES standards.
1) For Castings, Forgings and Rolled Wrought Materials:
a) MT – ASTM E709 (Cast), ASTM A275 (Forging) – (Equivalent ASME V Article 7 & 25)
b) PT – ASTM E165 (Equivalent ASME V Article 6)
c) RT – ASTM E94
d) UT – ASTM A609 (Cast), ASTM A388 (Forging, Forged Bar), ASTM A435 (Plate); for ASME applications reference ASME V Article 5
e) Visual – ASME V Article 9
2) For Welded Joints:
a) MT – ASME V Article 7
b) PT – ASME V Article 6
c) RT – ASME V Article 2
i. UT – ASME V Article 4
ii. Visual to ASME V Article 9
Ultrasonic Testing
Ultrasonic Thickness Testing (UTT) uses high frequency ultrasonic wave detection to measure material thickness and identify metal loss due to corrosion or erosion of steel, as well as identify internal imperfections. UTT should meet requirements laid out in EES and API specifications.
Tagging and Documentation
Tagging:
Refurbishing tag is to be affixed to the repaired/modified valve. Add statement in effect, any changes that will affect the information on the name plate. Additional name plate should be permanently affixed to the valve.
Documentation:
1) Identification:
Valves should be marked with a tag identification number, that should be registered in logbook at valve repair shop and the same is to be used in all records.
2) Certification:
a) Materials used in pressure boundary applications should be 100% traceable with a material identification number and material test reports should be supplied.
b) Manufacturers of components will provide a certificate of compliance, that will be provided towards components such as gaskets, packing, seats, seals, and bolting/nut etc.
c) PT or MT NDE and PMI report shall be issued and filed in the work order file as well as in the modification management tools/software.
3) Design Verification:
A repair/modification shop performing repairs and modifications will provide design calculations (such as new bonnet installation), design calculations may be performed, and drawings provided by the original manufacturer of the valve being modified. As an alternative, one could have a responsible and qualified engineer capable of performing such calculations, or have the calculations reviewed by a qualified third party, unless this is done under the direction and oversight of an OEM.
4) Drawings:
A repair/modification shop performing repairs and modifications requiring design work shall create and maintain detailed dimensional drawings of the modification components. These drawings should be kept for the purpose of design verification and the replication of spare parts. A copy should be provided with the valve.
5) Material Test Reports:
The pressure testing chart sheet should be completed by the technician per test requirements and will be signed and sealed by a professional engineer of assigned inspector of Enbridge Inc.
Shipping
Upon completion of the all the required repair, modification, testing and painting the valve will be drained (prior to painting) of test fluid, dried and where applicable, lubricated prior to preparation for shipment according to EES specifications of Enbridge purchase order terms and conditions.
References
2. Industry colleagues, code committees author participates
3. API RP 621 – Reconditioning of metallic gate, globe and check valves
4. API 6DR – Recommended practice for the repair and remanufacturing of pipeline valves
5. MSS-SP141 – Multi-turn and check valve modifications