Valve is an important component in the pipeline system of petrochemical equipment, its variety, large number, is one of the main leakage sources in the device, so the leakage requirements of the valve is very important. Valve sealing performance refers to the ability of each sealing part of the valve to prevent medium leakage.
The main sealing parts of the valve are: the anastomoses between the opening and closing parts and the seat, the packing and the stem and the packing box, the valve body and the valve cover. The first leakage is called internal leakage, which directly affects the ability of the valve to cut off the medium and the normal operation of the equipment. After the two leakage is called leakage, that is, the medium leaks from the valve to the valve, it directly affects the safety of production, resulting in the loss of working media and enterprise economic losses, environmental pollution, serious will cause production accidents. Especially for high temperature and high pressure, inflammable and explosive, toxic or corrosive media, the external leakage of the valve is not allowed at all, because the consequences caused by it are more serious than the internal leakage, so the valve must have reliable sealing performance, to meet the requirements of its use conditions for leakage.
One. Classification standard of Chinese valve seal:
At present, there are the following two classification standards of valve seal in our country.
1.1 China National standard for the classification of valve seal grade National standard GB/T13927 “Industrial valve pressure test”.
1.2 China Machinery Industry standard Classification of valve seal grade Mechanical industry standard JB/T9092 “Inspection and Test of Valves”.
Two. International standard for classification of valve seal grades:
At present, the commonly used classification standards for valve seal grades mainly include the following five kinds.
2.1 Classification of valve seal grades in the former Soviet Union
In order to select products according to the degree of seal of the valve and the specified use. Valves are classified according to the degree of seal.
2.2 ISO classification of valve seal grades
Iso standard ISO5208 “Industrial valve metal valve pressure test”.
2.3 American Petroleum Institute (APl) classification of Valve seal grades American Petroleum Institute Standard API598–2004 “Inspection and Testing of Valves”.
2.4 Classification of valve seal grades by the American Valve and Pipe Fitting Industry Manufacturers Standardization Institute (MSS) The allowable valve leakage requirements of the American Valve and Pipe Fitting Industry Manufacturers Standardization Institute standard “Pressure test of Steel valves” MSSSP61 are as follows:
(1) In the case of a sealing face in the valve sealing pair using plastic or rubber. There shall be no visible leakage during the duration of the sealing test.
(2) When closed, the maximum allowable leakage on each side shall be: the nominal size of the liquid (DN) shall be 0.4 ml per mm, per hour. Gas is nominal size (DN) 120 ml per mm, per hour.
(3) The allowable leakage of the check valve can be increased by 4 times.
2.5 American National Standard/American Instrumentation Institute (ANSI/FCI) Classification of control valve seal grades
American Instrumentation Institute standard ANSI/FCI70-2(ASMEB16.104) Control Valve Seat Leakage.
2.6 European Union standard classification of valve seal grades
European standard EN 12266-1 “Industrial valve testing” part l. Pressure tests, test methods and acceptance criteria – Mandatory requirements.