Material (material).
The valves are to be used for a variety of common tasks. To the water. That must withstand high pressure natural gas applications. The high corrosion resistance and chemical And to withstand heat and high pressure steam, etc., so the materials used to make the valve must be selected to suit the material (medium) in the pipeline.
Of the PTT. The Check Valve Material used in natural gas should be a standard reference Cast Steel or Forged Steel ASTM A 216 Grade WCB standards ASTMA 105 Grade 2.
In addition, each type of material to withstand the pressure and temperature. (Pressure / temperature rating) are different, which is known to be resistant to a variety of materials with different materials, a Stress. When adding more pressure. Will withstand temperatures down. Or it can withstand higher temperatures when the pressure decreases. We need to bring the pressure and temperature were compared with actual use. pressure / temperature rating of the valves of each type of material so that the material can withstand the pressure and temperature conditions of use.
Major components of the valve is reversed and the renewal of the valve spring and the spring is a good idea I can not Stress fracture Life cycle has a high resistance to corrosion. And the pressure in the open or under a Range of Pressure drop of the spring stiffness to suit a wide range of applications. The material is Stainless steel springs in general, but if you use a high temperature over 300 should be a spring made from Inconel.
For selecting the material of the Seal, which determines the rate of leakage (Leakage rate) of the valve is to be divided primarily into two categories: Metal to metal seal and Soft seal by Soft seal the Leakage rate is better than Metal. Zero leakage to metal seal, or a material that is Soft seal must be selected to suit the material. Pressure and temperature inside the pipe. The materials used in the Seal Check Valve is widely used in the work.
Natural gas and BUNA-N or Nitrile Rubber, synthetic rubber, which is caused by the mixture. acrylonitrile (ACN) with Butadiene leak rate testing (Leakage rate) of the valve and return valve between the product manufacturer to do it. There are several standard benchmark tests, depending on each manufacturer to choose from. The popular standard is the European standard (EN), German Standard (DIN) and American standards (API).
Pressure drop (Pressure drop).
In the design of piping systems as well. Pressure drop across the pipe should not be more than 0.3 bar, the pipe length 100 meters, Pressure drop caused by friction of the surface of the pipe itself. Pipes, valves and fittings installed at all. Therefore, the valve is back to keep the pressure should not exceed 0.1 bar Pressure drop across the valve, or one of them.
Valves are to be classified into three main types.
1. Valve and back pressure drop across the valve between DISCO and DISCO to be most valuable when compared with the other two types because DISCO has obstructed the flow than others. Thus, it often does not produce an 8-inch valves of this type because it is too high Pressure drop Pressure drop through the valve will be different depending on the stiffness of the spring as well.
2. Valves and back pressure drop across the valve, Swing and Swing back to DISCO is lower than the valve is open and unobstructed flow of less than The opening angle is about 600 -700 but also Pressure drop than the Dual plate.
3. Valves Dual plate similar to a pressure drop across the valve and back Dual plate to a minimum. The valve opening and flow, very little obstacles. The opening angle of about 800 each.
Valve to return to the good quality.
- Pressure drop is constant and appropriate to the system.
- Sealed (Tightness of the valve) or Leakage rate is low.
- Lifetime of the spring (Spring life time) life does not crack.
- Requires a minimum flow rate (Min flow), to avoid problems Clattering.
The installation of Check Valve.
In the case of a Check Valve to prevent back pressure to the gas station. Turbine meter must be installed from a 5D (5 times the pipe diameter) standard AGA7.
Clattering is a phenomenon that the valve has a flow rate or pressure is not enough to cause the valve to the open position or the position is stable. Often resulting in a short time. At startup or stop the system. The valve will open - the frequency and causes wear and tear. If the valve has been selected the wrong size or type Clattering the time of normal use. The valve due to wear and short-lived than it should be.
The size of the valve to return (Size) is the size of the valve to return often overlooked by those who use it. Because the majority of the selected pipe size alone. The installation is convenient, but if we take into account the pressure drop across the valve should not exceed 0.1 bar, and to avoid instability problems, the valve opens. Clattering known that the short lifetime of the valve. Selecting a pipe, valve size alone is not sufficient to check the pressure drop and Clattering with
