The hydrostatic test is to fill the pipe with water and test its ability to maintain the specified pressure without leakage or rupture under pressure. Its operation includes three steps: flushing, pressure testing, and water control.
It is an indispensable link in the production process of seamless pipe, and its function is to detect the anti-leakage performance of steel pipes under standard test pressure and pressure stabilization time. Like ray, ultrasonic and other flaw detection techniques, it is an important means to test the overall quality of steel pipes.
Technical operation points
1. Parameter setting: set the test pressure value and the voltage stabilization time according to the specifications, steel grade and thread type of the pipe to be tested;
2. Perform a full-length hydrostatic test on each tube. The actual test pressure and minimum voltage stabilization time must comply with the requirements of the process card (sometimes, the voltage stabilization time can be appropriately adjusted according to the quality of the raw materials);
3. During the pressure test, check whether the seals are in good condition and whether there is leakage at any time;
4. The test pressure control range of the pipe is: ≥ standard hydraulic test pressure;
Calculation formula of hydrostatic pressure 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 - hydrostatic test pressure, Mpa;
f-factor, the J55 and K55 steel grades with specifications > 95/8″ are 0.6, and other steel grades and specifications are 0.8;
Ysmin - the specified minimum yield strength of the pipe body, Mpa;
t-specified wall thickness, mm;
D-specified outer diameter, mm;
1. If the actual hydrostatic pressure test pressure cannot reach the standard pressure due to equipment reasons, the technical department shall be notified in time to make corresponding process adjustments.
2. If the pressure stabilization effect is not good during the pressure test, check whether there is leakage in each seal and pipeline, and repair if necessary.
3. After the pressure test, pay attention to check whether the tube body is damaged.
The relevant provisions of API-5CT standard for hydrostatic test
1. The hydrostatic test pressure value of the pipe with coupling and thread is the lowest value of the hydrostatic test pressure of the flat-end pipe, the maximum hydrostatic test pressure of the coupling, and the internal pressure leakage resistance.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 the customer has special requirements, a higher hydraulic test pressure can be selected.
4. Hydrostatic pressure test leakage is the basis for rejection.
5. Unless otherwise agreed between the purchaser and the manufacturer, hydrostatic testing is not required for coupling stock, coupling material, adjacent material, or grade Q125 steel pup joints.