How to choose chemical pump selection?

　　How to choose the right chemical pump has always been a concern for chemical people, different occasions, different media, different materials... Choosing the right chemical pump does not seem to be so easy.

　　In the selection of chemical pumps, the following three points are mainly considered:

　　Chemical pump selection

　　Considerations I: corrosion resistance

　　1、Sulfuric acid

　　As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a very wide range of uses.

　　Different concentrations and temperatures of sulfuric acid on the corrosion of materials vary greatly, for the concentration of more than 80%, the temperature is less than 80 ℃ of concentrated sulfuric acid, carbon steel and cast iron have better corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid, not suitable for use as a pump and valve materials; ordinary stainless steel such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) sulfuric acid medium is also of limited use.

　　Therefore, the pump and valve conveying sulfuric acid usually use high silicon cast iron (casting and processing difficulties), high alloy stainless steel (20 alloy) manufacturing, but its processing difficulties and expensive, so it is not favored.

　　Fluorine plastic alloy has a very good resistance to sulfuric acid performance, it is the Shanghai Institute of Organic Chemistry of the Chinese Academy of Sciences patented materials, by the Chinese Academy of Sciences experiments have proved that there has not yet been any chemical medium with which it can produce a reaction, and therefore the use of fluorine lined pumps (F46) is a more economical choice.

　　2、Hydrochloric acid

　　Most of the metal materials are not resistant to hydrochloric acid corrosion (including a variety of stainless steel materials), molybdenum-containing high-silicon iron can only be used for 50 ℃, 30% of the following hydrochloric acid.

　　And metal materials on the contrary, the vast majority of non-metallic materials have good corrosion resistance to hydrochloric acid, so lined pumps (such as engineering plastics, fluoroplastics, etc.) is a better choice for conveying hydrochloric acid.

　　3、Nitric acid

　　Most of the general metal in nitric acid is rapidly corroded and destroyed, stainless steel is widely used nitric acid materials, all concentrations of nitric acid at room temperature have good corrosion resistance, it is worth mentioning that the molybdenum-containing stainless steel (eg, 316, 316L) corrosion resistance of nitric acid is not only not better than ordinary stainless steel (eg, 304, 321), and sometimes not even as good as the high-temperature nitric acid, fluoroplastic alloys are usually used materials. For high temperature nitric acid, fluoroplastic alloy material is usually used.

　　4, acetic acid

　　It is one of the strong corrosive organic acids, ordinary steel in all concentrations and temperatures of acetic acid will be seriously corroded, stainless steel is an excellent acetic acid-resistant materials, molybdenum-containing 316 stainless steel can also be applied to high temperature and dilute acetic acid vapor.

　　For high temperature and high concentration of acetic acid or containing other corrosive media and other demanding requirements, you can use high alloy stainless steel or fluorine plastic pumps, such as CQB magnetic pump, CQ stainless steel magnetic pumps, etc. .

　　5、Alkali(sodium hydroxide)

　　General corrosiveness is not very strong, but the alkali solution may crystallize due to seasonal changes and specific gravity, etc. Therefore, IHF type fluorine alloy alkali pumps equipped with non-pressure sintered mechanical seals or CQB-F type fluorine alloy magnetic pumps can be used.

　　6、Ammonia(ammonia hydroxide)

　　Most metals and non-metals in liquid ammonia and ammonia (ammonia hydroxide) corrosion is very slight, only copper and copper alloy should not be used. It is better to use CQF engineering plastic magnetic pump and FSB fluorine alloy centrifugal pump.

　　7、Salt water (seawater)

　　Ordinary steel in sodium chloride solution and seawater, salt water corrosion rate is not too high, generally have to use paint protection; various types of stainless steel also has a very low uniform corrosion rate, but may be caused by chloride ions and localized corrosion, usually 316 stainless steel, F53, F55 a class of bi-directional stainless steel, fluorine plastic, polypropylene materials can be discretionary choice.

　　8, alcohols, ketones, esters, ethers

　　Common alcohol media are methanol, ethanol, ethylene glycol, propanol, etc., ketone media have acetone, butanone, etc., ester media have a variety of methyl ester, ethyl ester, etc., ether media have methyl ether, ethyl ether, butyl ether, etc., which is basically corrosive is not strong, and therefore can be selected from the general stainless steel, the specific selection of the media should also be based on the properties of the media and the relevant requirements to make a reasonable choice.

　　It is also worth noting that ketone, ester, ether on a variety of rubber solubility, in the selection of sealing materials to avoid mistakes, Schaederbauer pumps and valves recommended the selection of non-organic seals of fluoroplastic magnetic pumps.

　　There are many other media can not be introduced here one by one, in short, in the selection of materials must not be arbitrary and blind, should be more relevant information or draw on mature experience.

　　Precautions two: sealing problems

　　No leakage is the eternal pursuit of chemical equipment, it is this requirement contributes to the application of magnetic pumps is expanding.

　　However, there is still a long way to go to truly leak-free, such as magnetic pump isolation sleeve life, material pore erosion problems, static seal reliability issues and so on.

　　Now on the sealing aspects of some of the basic situation is briefly described below:

　　1, sealing form

　　For static seals, usually only gasket and sealing ring two forms, and sealing ring and O-ring is more widely used.

　　For dynamic seals, chemical pumps rarely use packing seals, mainly mechanical seals, mechanical seals and single-end and double-end, balanced and unbalanced type, balanced for high-pressure media sealing (usually refers to the pressure is greater than 1.0MPa), double-end seal is mainly used for high temperatures, easy to crystallize, viscosity, containing particles, and toxic volatile media, double-end seal should be injected into the sealing cavity of the isolation fluid, the pressure is generally higher than the media pressure of 0.0 MPa. Its pressure is generally higher than the medium pressure 0.07~0.1MPa.

　　2, sealing materials

　　Chemical magnetic pump static seal material is generally used fluoroelastomer, special circumstances before the use of polytetrafluoroethylene materials, mechanical seals dynamic and static ring of the material configuration is more critical, not carbide to carbide is good, the price is high on the one hand, the two do not have a hardness difference is also unreasonable, so according to the characteristics of the medium to be treated differently.

　　Precautions three: viscosity

　　The viscosity of the medium on the performance of the pump is a great influence, when the viscosity increases, the pump head curve decreases, the ideal conditions of the head and flow rate are followed by a decline in power is followed by a rise in efficiency is reduced.

　　General parameters on the sample are conveying water performance, when conveying viscous media should be converted (different viscosity correction coefficients can consult the relevant conversion chart).

　　For the higher viscosity of slurry, paste and viscous liquid transportation, Schaederbauer Pump & Valve recommends the use of slurry pumps.

　　Chemical pump selection principles

　　In the device equipment, to determine the purpose of the pump and performance parameters and select the pump type. This selection must first start from the choice of the type and form of pump, then what principles to select the pump? What is the basis?

　　1, so that the selected pump type and performance in line with the device flow, head, pressure, temperature, cavitation margin, suction range and other process parameters.

　　2, must meet the requirements of the media characteristics

　　For pumps conveying flammable, explosive toxic or precious media, the requirements of a reliable shaft seal or leak-free pumps, such as magnetic drive pumps (no shaft seal, the use of isolation type magnetic indirect drive);.

　　For pumps conveying corrosive media, the requirement of convective components using corrosion-resistant materials, such as fluorine plastic corrosion-resistant pumps;

　　For pumps conveying media containing solid particles, requires convection parts using wear-resistant materials, if necessary, the shaft seal with clean liquid flushing.

　　3, mechanical requirements of high reliability, low noise, low vibration.

　　4, the correct calculation of the input cost of pump procurement.

　　5、Transportation of strong corrosive media (such as “concentrated sulfuric acid, concentrated nitric acid”), the transmission of flammable and explosive media, the use of the environment must not have any pollution: magnetic pumps can be used, such as the “CQB series of magnetic pumps, IMD series of magnetic pumps, such as the need for self-priming, you can choose the FZB fluorine self-priming plastic pumps.

　　6、IHF centrifugal pump and FSB centrifugal pump have the features of high rotating speed, small volume, light weight, high efficiency, high flow rate, simple structure, no pulsation of liquid, smooth performance, easy operation and maintenance, etc. If there is no special requirement for the working condition, centrifugal pump can be chosen.

　　7, pumps containing solid particles of chemical media, the requirements of convective components using wear-resistant materials: UHB mortar pump for the appropriate selection of objects, UHB corrosion-resistant wear-resistant mortar pump material for the new high-strength engineering plastics UHBWPE, which is a modified ultra-high molecular weight (more than 5 million) polyethylene. In plastics, it has excellent abrasion resistance, experimental comparison, its abrasion resistance is much higher than stainless steel, and impact resistance, creep resistance and excellent corrosion resistance (comparable to F4), there is no adhesion and other unique properties.

　　8、When the liquid level of the medium is below the installation position of the pump: FZB fluorine plastic self-priming pump should be selected, such as the need to meet the characteristics of the magnetic pump, ZMD fluorine plastic self-priming magnetic pump can be used.

　　9, according to the pump's performance curve to select specifications: when the use of requirements in the performance parameters of the table can not find a suitable model can refer to the pump's performance curve to select the appropriate pump type.

　　Chemical pumps common selection problems?

　　1 conveying acidic water containing solid particles, what pump to choose?

　　Q: We need to transport the medium is a little corrosive (acidic water), which contains about 20% of solid particles, want to choose a corrosion and wear-resistant pump?

　　A: If the corrosiveness is not very strong, you can choose UHB-ZK series of corrosion and abrasion-resistant mortar pumps, whose internal flow parts are all made of UHMWPE with good corrosion and abrasion resistance, which can transport corrosive media with solids content of not more than 40% and have a long service life and simple maintenance.

　　If the corrosiveness is very strong, fluorine plastic centrifugal pump should be used, supporting the corrosion and wear-resistant type of machine seal.

　　2 Our medium temperature is very high, very corrosive, with what pump good?

　　Q: We need to transport the medium temperature is very high (about 130 degrees), corrosive (glacial acetic acid), we want to choose a non-leakage, corrosion-resistant pump, please choose what pump?

　　A: We recommend IMD high-temperature fluorine plastic magnetic pump or IHF-NS high-temperature fluorine lined centrifugal pump, the specific material is: the pump casing is made of fluorine plastic alloy (F4/F46), impeller, isolation sleeve and other parts of the selection of PFA (soluble polytetrafluoroethylene), can withstand temperatures of up to 150 degrees, and good corrosion resistance.

　　3 transport medium is very corrosive, what pump to choose?

　　Q: We need to transport the medium for aqua regia, hydrofluoric acid, room temperature, what pump to choose?

　　A: Recommended selection of fluoroplastic pumps, fluorine plastic is one of today's corrosion resistance is very good, hydrofluoric acid belongs to a special medium, the demand for quotations should be specified.