Croos Pump (Shanghai) Co., Ltd.

The Common Problems and Selection Methods of Chemical Process Pumps

The cooling problem

The transmission of high temperature medium has higher requirements for the structure, material and auxiliary system of the pump, and the requirements of different temperature changes for cooling and the applicable pump type of the company are discussed below.

1. For medium temperature below 120 ℃, and they usually do not set up a special cooling system, They use their own medium for lubrication and cooling. It is worth mentioning that for the medium that is easy to crystallize or contain particles should be equipped with the cover wash pipeline.
2. For the temperature of the medium during 120 ℃ to 300 ℃, generally on the pump cover shall be equipped with cooling chamber, the sealing chamber should also be connected to the coolant (double end mechanical seal). When the coolant is not allowed to infiltrate into the medium, it should be used to cool the medium itself (which can be realized through a simple heat exchanger).
3. for the high temperature medium above 300 degrees, not only the pump head needs to be cooled, but also the suspension bearing chamber should be equipped with cooling system, the pump structure is generally center supported form, mechanical seal is best used in metal bellows type, but the price is high (the price is more than 10 times of ordinary machine seal).

The sealing problem

The absence of leakage is the constant pursuit of chemical equipment, which has contributed to the increasing application of magnetic pump and shielding pump. However, there is still a long way to go, such as the life of the magnetic pump isolation sleeve and shielding pump shield, the hole erosion of the material, the reliability of the static seal and so on. Some basic information about sealing is briefly introduced as follows:

1. The sealing form

For static seal, there are usually two forms of gasket and seal ring, and the sealing ring is most widely used with O ring; For the dynamic seal, the chemical pump rarely uses packing seal, mainly mechanical seal. Mechanical seal has single end face and double end face, balance type and non-equilibrium type. The balance type is suitable for sealing of high pressure medium (usually the pressure is greater than 1.0 mpa). Double end plane seals are mainly used in high temperature, easy crystallization, viscosity, particles and toxic volatile medium. The double end plane sealing should inject the spacer into the sealing chamber. The pressure is generally higher than that of the medium pressure.

2. The sealing material

The material of static seal of chemical process pump is usually made of fluorine rubber, in special cases they use the material of PTFE; The material configuration of mechanical seal and static ring is key. It is not the best for hard alloy. The high price is one thing, no hardness difference between the two is not reasonable, therefore, it is best to discriminate based on the characteristics of the medium.

The problem of viscosity

The viscosity of the medium has a great influence on the performance of the pump. When the viscosity increases, the head curve of the pump decreases, the head and flow of the optimal working condition decrease, while the power increases, so the efficiency decreases. The parameters on the general sample are the performance of the conveying water, and the conversion should be carried out when the viscous medium is conveyed (the correction coefficient of different viscosity can refer to the related conversion chart). For the transportation of the high viscosity slurry, paste and viscous liquid, it is recommended to use the screw pump.

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