1. For static sealing, there are usually only two forms of sealing: gasket and sealing ring, and the sealing ring is widely used as an O-ring; For dynamic seals, chemical pumps rarely use packing seals, mainly mechanical seals. Mechanical seals can be divided into single and double face, balanced and non balanced types. Balanced types are suitable for sealing high-pressure media (usually referring to pressure greater than 1.0MPA). Double face mechanical seals are mainly used for high temperature, easily crystallized, viscous, particulate, and toxic volatile media. Double face mechanical seals should inject isolation liquid into the sealing chamber, Its pressure is generally 0.07-0.1MPA higher than the medium pressure.
2. The sealing material for chemical centrifugal pumps is usually fluorine rubber, and in special cases, polytetrafluoro material is used; The material configuration of mechanical seal dynamic and static rings is crucial, and hard alloy is not the best choice for hard alloy. The high price is one aspect, and there is no difference in hardness between the two, which is not reasonable. Therefore, it is necessary to treat them differently based on the characteristics of the medium.
Key points for the construction and installation of chemical pumps:
The installation of pumps should comply with the national standard GB50275-1998 "Code for Construction and Acceptance of Compressor, Fan, and Pump Installation Engineering".
① This regulation is applicable to the installation of centrifugal chemical pump, well pump, vertical axial flow pump, guide vane mixed flow pump, motor driven reciprocating pump, steam reciprocating pump, metering pump, screw pump and water ring vacuum pump.
② The size, position, and elevation of the installation foundation of the pump should be checked and should meet the engineering design requirements.
③ The unpacking inspection of the pump should meet the following requirements: the parts and components of the pump should be counted according to the provisions of the equipment technical documents, and there should be no missing parts, damage, rust, etc., and the pipe mouth protection and cover should be intact; The main installation dimensions of the pump should be verified and should be consistent with the engineering design; The types and specifications of the main components, seals, and gaskets of pumps conveying special media should be checked.
④ The parts that have been assembled and adjusted perfectly before leaving the factory cannot be disassembled.
⑤ When connecting the drive machine to the pump, the alignment should be based on the axis of the pump. When there is an intermediate machine connection between the drive machine and the pump, the alignment should be based on the axis of the intermediate machine.
⑥ The installation of pipelines should not only comply with the provisions of GB50235-1997 "Code for Construction and Acceptance of Industrial Metal Pipeline Engineering", but also meet the following requirements: the inside and end of the pipeline should be cleaned and cleaned, debris should be removed, and the sealing surface and thread should not be damaged; The suction pipeline and output pipeline should have their own brackets, and the pump should not directly bear the weight of the pipeline; The flange end faces that are connected to each other should be parallel, and the axis of the threaded pipe joint should be centered. It should not be forcibly connected by flange bolts or pipe joints; After the pipeline is connected to the pump, the original alignment accuracy of the pump should be rechecked. When deviation is found due to the pipeline connection, the pipeline should be adjusted; After the pipeline is connected to the pump, welding and gas cutting should not be carried out on it. When welding and gas cutting are required, the pipeline should be removed or necessary measures should be taken, and welding slag should be prevented from entering the pump; The configuration of the suction and discharge pipelines of the pump should comply with the design regulations. When there are no regulations, they can be used. According to Appendix 2 of GB50275-1998.
⑦ The pipelines of lubrication, sealing, cooling, and hydraulic systems should be cleaned and kept unobstructed; The pressurized part should undergo a tightness test according to the provisions of the equipment technical documents. When there are no regulations, the current national standard "Code for Construction and Acceptance of Industrial Metal Pipeline Engineering" should be followed.
⑧ The trial operation of the pump should be carried out after the individual trial operation of its auxiliary systems is normal.
⑨ The pump should be tested in the presence of medium, and the test run medium or substitute medium should meet the design requirements.