With the development of the times, many new industries and words are widely used, and gas pipeline engineering is gradually known by everyone. Gas pipeline engineering has been applied in all aspects of production and life, but are the construction technical requirements and acceptance standards of gas pipeline engineering superior? Here is a brief introduction:

Code for construction of gas pipeline engineering

1. Special gloves and protective equipment for clean and dust-free room must be worn during pipe welding.

2. The gas contact part of piping materials shall not be directly touched with dirty gloves or hands.

3. Ultra high purity argon must be used as the welding gas during piping. After construction, all pipelines must use ultra-high purity argon or nitrogen to continuously PURGE. PURGE exhaust must be connected to the outdoor for emission to avoid the risk of asphyxiation.

4. During pipe welding, all temporary pipes must be SUS 316 hard pipes.

5. Before the daily construction, all piping welding shall be conducted with each pipe diameter test piece, and the welding parameters, qualified test pieces and welding parameters of the welding machine shall be recorded. The construction personnel can start the construction only after the supervisor has inspected them as qualified.

6. Internal pressure management must be used during welding.

7. Pipe benders can be used for pipes less than 1/2 inch (inclusive), and the pipe bending radius R ＞ 5D (D is the outer diameter). If the above requirements cannot be met, ELBOW shall be used for construction.

8. When piping, cut the pipe, chamfer and end face. The pipe must be vertical and downward or parallel to prevent iron filings from adhering to the inner wall of the pipe, and feed carefully to avoid scratching the smooth surface inside the pipe.

9. After pipe cutting, clean N2 GUN gas must be removed, and the cutting surface of pipe inner wall shall be located in the downstream direction.

10. During the construction, the construction shall be carried out according to the drawings. If problems are found on the construction drawings or design changes are required, they shall be reported to the supervisor immediately for handling. Unauthorized decisions are not allowed.

11. When it is determined that all VCR connectors will not be disassembled or finally restored, install the Gasket lock, and mark a circle mark on the leak detection hole.

12. All completed pipelines shall be hung or labeled with the name of such gas and the direction of flow every 1.5 meters and after turning and crossing the wall. The labels shall be aligned with the scribed lines to ensure that they are neat and consistent.

13. The construction contractor shall clean up the machines, tools and environmental sanitation in the storage and construction areas.

14. The acceptance standards must be met. If the project violates or does not conform to this provision, it must cooperate with the re construction to meet the specifications and standards. The Contractor shall absorb the cost increase and schedule delay responsibilities arising therefrom.

15. Temporary clean shed shall be installed on site. During the pipeline work, all the prefabricated pipeline parts shall be carried out in the temporary clean shed to control the dust.

16. Welding work

I. The welding end is covered with a clean plastic cover with holes, and then connected with a differential pressure gauge for pressure control management in the welding pipe to isolate dust, moisture and impurities in the atmosphere.

II. Even if the welding is completed, continue to inject argon to maintain the circulation state and cool the metal substrate at the welding point.

17. Process of purity improvement

After the completion of the pressure maintaining test, the following processes can be carried out one by one in order to improve the internal purity of the pipeline.

A. During flushing, all secondary main pipes are repeatedly sprayed with pure argon or nitrogen, and the flow rate of gas used is about 15-20m/sec

B. Purification process

Continuous flushing with pure argon or nitrogen, and the flushing pressure shall not exceed the maximum inlet pressure of each test instrument.

Pipeline Analysis Testing and Acceptance Criteria

1. Inspection items before test

a) Before all pipeline tests, it is necessary to confirm whether the pipeline label is consistent with the actual gas pipeline, the gas flow direction of the label, and the weld bead quality.

b) Visually inspect to see if there is any deflection, distortion and pipe clamp is loose.

c) All testing instruments used on site shall have calibration records.

2. All pipeline field test results must be signed by the tester and relevant personnel of the Owner.

3. All welding points and VCR connection points must be pasted with Q.C. labels after passing the test.

4. Review of test results:

a) The test results shall be signed and approved by the Owner's on-site personnel before completion.

b) After the test is completed, the test report must be completed and signed by the corresponding owner's personnel.

5. Pressure maintaining test

a) The recording mode shall be disc or electronic.

b) Continuous recording function is required.

c) The pressure of Bulk Gas and Specialty Gas shall be maintained for more than 24 hours during the test, and the positive and negative pressure shall not be greater than 2%.

d) All pipelines shall use PN2 as the test gas.

e) After the connection, the surface pressure on the pressure gage shall be observed for 30 minutes before the test, and the record shall be started after confirming that the pressure has not changed.

f) During the pressure maintaining test, make sure that the valve from the recorder to the test pipeline has been opened, otherwise, the airtight test is not being conducted.

g) It is forbidden to use leak detection fluid as a leak detection tool.

h) The pressure holding pressure is 1.5 times of the working pressure.

6. Pipeline purging - N2 Purge

a) The standard connection for pipeline purging is the same as the pressure maintaining test, and the purging must use UHP N2

b) N2 Purge must be discharged outside the plant or into General Exhaust, and it is prohibited to discharge N2 Purge to Fab or Sub fab.

7. Helium Leak Test

a) The Owner's personnel must be present during the test.

b) It must be confirmed that the helium leak detector has been pumped to 1X10-9atm * cc/sec before proceeding.

c) The tester shall obtain the welding spot list from the welding personnel and check the actual welding spot according to the list. During the He Leak Test, make sure that every weld bead and VCR contact are subject to helium injection test. After confirming that there is no problem, affix a He leak test pass ok label next to the weld bead and sign it, and record it on the welding point list.

d) When spraying He at the test point, be sure to follow the principle of "from near to far, from top to bottom" for leak detection to prevent He from drifting

However, it can not achieve the effect of leak detection and reflect the real leak rate.

e) During helium injection test, when the pipeline is long, spray He gas to test one weld bead, and wait 3 minutes to confirm that the value does not rise before testing the next weld bead. (Adjust and confirm the time when the value does not rise properly according to the length of the pipeline)

f) Helium leak test index: less than 5x10-9atm · cc/sec

8. Moisture content test:

a) PN2 must be used as purge gas.

b) During analysis, continuous records must be made to show the decreasing trend of micro moisture content. When the test value reaches less than 100 ppb, continuous records must be made for 30 minutes, and the test record can be ended only after confirming that the value has not risen again.

c) During the test, the pipeline shall not be equipped with Purifier, the connector shall be VCR connector, and the Teflon hose shall not be used.

d) Moisture content test index: less than 100ppb.

9. Micro O2 content test:

a) PN2 must be used as purge gas.

b) During analysis, the analysis value must be recorded continuously to show the decreasing trend of micro oxygen content. When the test value reaches less than 100 ppb, the test record must be continued for 30 minutes and confirmed that the value does not rise again before the test record can be ended.

c) During the test, the pipeline shall not be equipped with Purifier, the connector shall be VCR connector, and the Teflon hose shall not be used.

d) Micro O2 content test index:<100ppb (for reference, determined according to specific process requirements).

10. Particle test:

a) Use PN2 as purge sampling gas.

b) Before the test, all piping must be pressurized and depressurized (or cycle purged at least 30 times) to completely blow out the fine dust in the pipeline.

c) During the test, the rubber hammer must be used to tap the pipe wall to confirm that there is no particle residue.

d) The test time is 10 minutes, the test pressure is 30~90 psig, and the test speed is 7 m/s.

e) This test must pass the test standard (the standard is greater than or equal to 0.1 μ The number of parts cannot exceed 1).

f) Index: ≤ 1pcs/ scf@0.1 μ m

11. Connecting pipeline

a) N2 purge shall be kept as much as possible during connection, and N2 purge can be closed only after the pipeline connection is completed,

b) After the test is completed, when connecting the pipeline, the fragile sticker "QA/QC PASS OK" shall be posted at the pipeline contact to prevent irrelevant personnel from removing the contact, and the employee number shall be signed on the sticker for easy query.

c) Note: You must fill in the Tie in request form to apply to the Owner's personnel and strictly follow the requirements.