An expert in the field of gaskets - NINGBO SHINE SEALING MATERIAL CO.,LTD. Today, I will explain to you the performance test method of sealing gaskets. Our Graphite Gasket Reinforced With Tanged Metal series products have won the recognition of our customers with advanced production technology and excellent quality!
Using nitrogen or water as the sealing medium to measure the leakage rate of the gasket to evaluate the sealing performance of the gasket is a test method commonly used in the industry at present. Gasket leakage rate can directly reflect the gasket sealing performance, it is the most basic comprehensive index; it is also the main basis for evaluating the quality of gaskets.
In the GRIT 12385-1990 standard, two test methods A and B for the sealing performance of gaskets for pipe flanges are specified. Both test methods are applicable to asbestos rubber gaskets, PTFE clad gaskets, PTFE gaskets, metal clad gaskets, spiral wound gaskets and metal gaskets. Users can choose any one of the test methods according to different working conditions.
A more commonly used test method is described below.
Test device
The test is carried out on a dedicated gasket comprehensive test device. The test device consists of a gasket loading system, a medium given system, a leak detection system, a frame and a test flange. The schematic diagram of the test device is shown in the top figure. The requirements for the test device are as follows:
a. The gasket loading system should be able to provide the specified gasket preload stress, the fluctuation of the gasket load during the test process should be less than 5% of the specified value, and can control the constant loading and unloading speed;
b. The test medium given system should be able to provide the specified test medium pressure, and the medium pressure fluctuation during the test process should be less than 0.5% of the specified value;
c. The leak detection of the leak detection system adopts the state equation method. A closed annular leak-testing cavity is set on the outside of the gasket and between the upper and lower flange surfaces, and the initial volume V of the leak-testing cavity is measured. And the volume change correction coefficient K1 should be strictly calibrated, the resolution of the leak detection system should not be less than 10cm, and the system error should not be greater than 0.5%;
Test conditions
Test temperature: 15-25℃;
Gasket preloading stress: correctly selected according to the type of gasket;
Test medium: 99.9% nitrogen;
Test medium pressure: take 1.1 times the nominal pressure;
operating procedure
a. Carefully clean the flange sealing surface with acetone, and install the gasket in the center.
b. According to (test conditions) regulations, apply pre-stress to the gasket, and keep it for 15 minutes after reaching the specified value.
c. Calibrate the initial volume and volume change correction factor of the leak detection cavity.
d. According to the requirements of (test conditions), enter the test medium, and keep it for 10 minutes after the medium pressure reaches the specified value.
Leak rate calculation
1. Leakage rate;
2. Standard atmospheric pressure;
3. The absolute temperature of the atmosphere in the standard state;
4. The difference between the pressure in the leak detection cavity and the ambient atmospheric pressure;
5. The difference between the temperature in the leak test cavity and the ambient temperature;
6. The initial volume of the leak test cavity;
7. Leak detection time;
8. Volume change correction coefficient;
9. During the leak detection process, the variation of the gasket compression;
10. In the process of side leakage, the change of pressure in the leakage cavity is measured;
11. During the leak detection process, the temperature change in the leak detection cavity;
