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Safety Valve Calibration Method And Its Advantages And Disadvantages
Nov 23, 2017

It is necessary to perform full performance experiments to check all the technical performance indexes of the safety valve. The most basic requirement of the experiment is that it has practical operation status and even exceeds the practical operation condition. In addition to the equipment such as high temperature and high pressure vessel, the experimental device also has fast measuring instruments of various parameters, and ensures the high temperature and high pressure steam source with large flow, which is costly.

Calibration is a part of the safety valve experiment, and it is the most important item in the factory experiment. Usually the normal temperature safety valve calibration stand is used before the factory. The open pressure setting and tightness test of the air medium are carried out. The test room of the safety valve can only do the open pressure setting and sealing test.

(1) under what circumstances should the safety valve be checked?

1) long time storage or first use

2) periodic check

3) severe damage and corrosion valves

4) valve missing from valve nameplate

5) seal damaged valve

(2) the meaning and method of the adjustment of the back seat pressure

Standard definition refers to the safety valve back seat pressure reach emission status, medium pressure drop to a certain value, the valve head and valve seat that is open to the touch, height is zero, the static pressure at the inlet valve, the back seat pressure is too low, too much is not good, too low and medium energy loss will be formed. Was not too high to emissions, the formation of valve frequency hopping, is adjustable to reach the principle of emissions under the condition of high back pressure can decrease the energy loss and medium.

(3) adjustment measures

The back seat pressure is adjusted by the conditioning ring, the principle of the adjustment is the principle of void, the smaller the gap, the greater the resistance when ejecting, the greater the force to hold the spool down, the more difficult to return seat, on the contrary, the larger the gap, the more simple spool down, the higher the back seat pressure.

About as long as the safety valve and cut ring, adjusting ring to increase, back seat pressure drop, adjusting ring to cut, back seat pressure increased; a lower safety valve and ring, lower physical ring spacing decreases, the back seat pressure drop, lower physical ring spacing increases, the back seat pressure increase.

(4) verification method and its advantages and disadvantages

Safety valve calibration has two methods: field check (online check) and check desk verification. The condition should be as much as possible on the spot check, because the field check is more suitable for the actual operating conditions, so it is more reliable.

The advantages of field check: it is easy to check the welding safety valve, and can measure the back seat pressure and measure accurately.

The defect is that the verification time is long, the system should be repeated boost, uneconomical, dangerous, can not do sealing experiments.

Advantages and disadvantages of normal temperature calibration table for safety valve:

Safety valve setting and leak detection of C under normal temperature medium and operating temperature below 250 degree a..

B. determines the small error scale of the open pressure of the safety valve, saves the adjustment moment of the new safety valve, reduces the labor intensity, reduces the energy consumption and reduces the operation risk.

C. running temperature and room temperature error (spring under high temperature softening), can not check the back seat pressure.

The safety valve checking table black network can be divided into digital control to control and accounting machine, digital meter can end 1) collected off the pressure, back seat pressure 2) holding pressure time, pressure, set 3 seat selection) 4) clamping force completely ended the semi active pick examination, manual control type different from other manufacturer. Manipulation of accounting machine type safety valve checking table made by American NI company data collection software, powerful function, stable, all the experimental process can end the initiative in the accounting machine, can show the pressure curve, the experimental parameters can be set free, for example, the test pressure, pressure holding time, promised to drop.


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