Petrochemical industry in the national economy occupy a very important position, chemical process pump as a key ancillary equipment is also more and more people's attention. Due to the complex nature of chemical media, coupled with the continuous improvement of user requirements, and now to say chemical pump selection process should pay attention to the problem.
Chemical process pump selection should pay attention to the problem
First, the viscosity problem
The viscosity of the medium has a large effect on the performance of the pump. As the viscosity increases, the lift of the pump decreases, the head and flow of the optimum condition decrease, and the power rises accordingly, reducing the efficiency. General parameters on the sample are the performance of the transport of water, when the transport of viscous media should be converted (different viscosity correction factor can be found in the relevant conversion chart). For the viscosity of the pulp, paste and viscous liquid delivery, the proposed selection of screw pump, DFGG single screw pump medium viscosity up to 1000000cst.
Second, the cooling problem
The delivery of high-temperature media sets higher requirements on the structure, materials and auxiliary systems of the pump. The following is a brief talk about the cooling requirements and the applicable pump types for different temperature changes.
1. For media temperature below 120 ℃, usually do not set a special cooling system, use more of their own media for lubrication and cooling. DFL (W) H chemical pump, DFL (W) PH shield chemical pump (class H should be used for shielded motor over 90 ℃); DFCZ common type and IH chemical pump can make the temperature Up to 140 ℃ ~ 160 ℃; IHF lined with fluorine pump up to a maximum temperature of 200 ℃; only CQB ordinary magnetic pump temperature does not exceed 100 ℃. It is worth mentioning that for the easy-to-crystallize or media containing particles should be equipped with a sealing surface flushing pipe (design have left interface).
2. For media above 120 ° C and within 300 ° C, a cooling chamber is normally to be provided on the pump cover and the seal chamber is also to be filled with coolant (to be fitted with a double-ended mechanical seal). When coolant is not allowed to penetrate the medium , It should be taken after the cooling medium itself access (through a simple heat exchanger). The company has DFCZ chemical process pump, GRG high temperature pipeline pump and HPK hot water circulation pump (under development) for selection, the other CQB-G high temperature magnetic pump can be used within 280 ℃ high temperature medium
3 for more than 300 ℃ high temperature medium, not only need to cool the pump head part, the suspension bearing chamber should also be equipped with cooling system, the pump structure is generally the central support form, the mechanical seal is best to use metal bellows type, but the price is high The price is more than 10 times the ordinary mechanical seal). There are currently DFAY centrifugal pump temperature can reach 420 ℃ (under development).
Third, the sealing problem
No leakage is the eternal pursuit of chemical equipment, it is this requirement has led to the growing use of magnetic pumps and shielded pumps. However, there is still a long way to go without leakage, such as the life span of the magnetic pump isolation sleeve and shielding pump shielding sleeve, the material pitting problem, the reliability of static sealing, and the like. Now some of the basic aspects of sealing a brief introduction is as follows
Sealed form
For the static seal, usually only two forms of seals and seals, and O-ring seal is the most widely used; for dynamic seals, chemical pumps rarely use packing seal to mechanical seal-based, mechanical seal and A single-ended and double-ended, balanced and unbalanced, balanced type for high pressure medium seal (usually refers to the pressure greater than 1.0MPa), double-end machine seal is mainly used for high temperature, easy crystallization, viscosity, containing particles As well as the toxic volatile medium, double-ended machine seal should be injected into the sealed chamber isolation fluid, the pressure is generally higher than the medium pressure 0.07 ~ 0.1MPa.
2. Sealing material
Chemical pump static sealing materials generally use fluorine rubber, special circumstances only use PTFE material; mechanical seal ring static material configuration is more critical, not cemented carbide is the best on the cemented carbide, the price is high on the one hand, two No hardness difference is not reasonable, it is best to distinguish between the characteristics of the media treated.
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