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Basic knowledge of hydrostatic test of steel pipe

Views:2     Author:Site Editor     Publish Time: 2019-05-23      Origin:Site

Basic knowledge of hydrostatic test of steel pipe

Hydrostatic test is an indispensable part in the manufacturing process of steel pipe. Its function is to test the anti-leakage performance of steel pipe under standard test pressure and pressure stabilizing time. It is an important means to check the overall quality of steel pipe, as well as ray and ultrasonic inspection.

A popular description is a pipe filled with water under pressure to test its ability to maintain a specified pressure without leakage or rupture. Its operation includes three steps: flushing, pressure test and water control.

I. technical operation points of the post

1. Parameter setting: according to the specification, steel grade and thread type of the pipe to be tested, set the test pressure value, voltage stabilizing time, etc.;

2. Hydrostatic test for the full length of each pipe. The actual test pressure and minimum voltage regulation time should meet the requirements of the process card (sometimes the voltage regulation time should be adjusted appropriately according to the quality of raw materials);

3. Check the integrity and leakage of each seal at any time during the pressure test;

4. The test pressure control range of the pipe is: standard hydrostatic test pressure;

5. Fill in the hydrostatic test record carefully.

The hydrostatic pressure formula of steel pipe

The standard hydrostatic test pressure is calculated according to the following formula, and the calculated value should be rounded to the nearest 0.5mpa, and the maximum value is 69.0mpa

P = 2 (f * Ysmin * t/D

P - hydrostatic test pressure,Mpa;

F - coefficient, steel grade 0.6 for J55 and K55 with > 95/8 "specification, and 0.8 for other steel grades and specifications;

Ysmin- minimum yield strength, Mpa;

T - specified wall thickness, mm;

D- specified outer diameter, mm;

Example: 139.7*7.72 P110 steel grade

P = 2 (f * Ysmin * t/D

= 2 * (0.8 * 758 * 7.72) / 139.7

= 67.0

339.7 * 10.92 grade J55 steel

P = 2 (f * Ysmin * t/D

= 2 * (0.6 * 379 * 10.92) / 339.7

=14.6 -- -14.5 rounded to the nearest 0.5mpa.

193.68 * 12.70 P110 steel grade

P = 2 (f * Ysmin * t/D

= 2 * (0.8 * 758 * 12.7) / 193.68

=79.5, but the maximum value is 69.0mpa, so the hydrostatic pressure is 69.0mpa.

Three, the position operation matters needing attention

1. If the actual hydrostatic test pressure cannot reach the standard pressure due to equipment reasons, the technical department shall be informed in time to make corresponding process adjustment.

2. If the voltage stabilizing effect is not good during the pressure test, check whether there is leakage of all seals and pipelines, and repair if necessary.

3. Check whether the tube body is damaged after pressure test.

Iv. Relevant provisions of API-5CT standard for hydrostatic test

1. The hydrostatic test pressure value of pipe with collar and thread is the lowest value of hydrostatic test pressure of flat end pipe, maximum hydrostatic test pressure of collar and leakage resistance of internal pressure, but the standard maximum pressure is 69MPa, and the calculated pressure value is generally rounded to the nearest 0.5mpa.

2. According to API requirements, the hydrostatic test pressure measuring device should be calibrated within 4 months before each use.

3. If customers have special requirements, higher hydraulic test pressure can be selected.

4. Leakage is the basis for rejection in hydrostatic test.

5. Unless otherwise agreed by the purchaser and the manufacturer, hydrostatic testing of the collar blank, collar material, nearby material or Q125 steel grade nipple is not required.

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