Sharing of experiences and lessons on several issues in industrial pump selection 【Heavy rewards for detailed discussants】

High-chromium cast iron could be considered; our refinery uses this material for its catalytic slurry pumps. It has very high hardness and high wear resistance, but poor toughness, and requires preheating.

It is important to choose the material for the flow-through section, which should be resistant to wear and corrosion as well as have strong resistance to cavitation； For mechanical seals, it is necessary to choose those from reputable manufacturers, with a design suitable for the medium being transported ； The difference between the effective NPSH and the required NPSH should preferably be more than one meter ；

1. Choose standardized water pumps. Standardized water pumps are the **latest models of pumps that have been developed and introduced in accordance with ISO requirements**. Its main features include small size, light weight, excellent performance, ease of operation, long lifespan, and low energy consumption. It represents the latest trend in the current water pump industry. Under no circumstances should one purchase products that lack the necessary information (namely, no manufacturer, no production date, and no production license); otherwise, if problems arise, consumers will be at a loss. 2. Decide whether to use a single-phase pump or a three-phase pump based on the local power supply conditions. 3. Selection of water pump head: The term \"head\" refers to the required lift, not the height to which water is lifted; understanding this point is particularly important when selecting a water pump. The head of a water pump is approximately 1.15 to 1.20 times the height to which water is lifted. If the vertical height from a water source to the point of use is 20, the required head is approximately 23–24 meters. When selecting a water pump, it is advisable to choose one whose head indicated on the nameplate is as close as possible to the required head; this ensures the highest efficiency of the pump and makes its use more economical. However, it is not necessary for them to be exactly equal; as long as the deviation is within 20%, the water pump can operate in a more energy-efficient manner. 4. What should be the ideal head indicated on the nameplate? Choosing a water pump whose nameplate indicates a head that is much lower than the required head often fails to meet the user’s needs; even if water can be pumped, the volume will be extremely small, and the pump may end up being useless. Is it true that the higher the head pressure of the pump purchased, the better? That’s not the case. When a pump designed for high head pressure is used in applications requiring low head pressure, excessive flow rate occurs, causing the motor to become overloaded. If it operates for an extended period, the motor’s temperature rises, and the insulation layer of its windings gradually deteriorates, which can even lead to the motor burning out. 5. Choose a water pump with an appropriate flow rate. The flow rate of the water pump, that is, the amount of water it can deliver, should generally not be set too high, as this will increase the cost of purchasing the pump. Each specific issue should be analyzed on its own.

1. Implement the process parameters – it is essential to verify them thoroughly.
2. Determine the type of pump to be used based on the process parameters (centrifugal, axial flow, metering pump, etc.).
3. After deciding on the pump type, determine its material and sealing method. The pump material can be stainless steel, carbon steel, or duplex steel, depending on the medium being handled; the sealing method can be mechanical seal, packing seal, dry gas seal, etc., also depending on the medium.
4. Identify potential manufacturers – usually, 3 to 5 companies should be considered, and quotes should be requested from each of them.
5. Once the quotes are received, conduct necessary technical discussions with the manufacturers.
6. After these discussions, research the manufacturers’ past performance related to similar equipment.
7. Based on the research results, decide on the final manufacturer.
8. Clarify technical details with the selected manufacturer.
9. Prepare the technical attachments and terms of the commercial contract, which shall then be signed by both parties.
10. If the order quantity is large, 1 to 2 further meetings may be needed.
11. If necessary, follow up with the manufacturers to expedite delivery.
12. Upon arrival of the equipment, inspect it upon unboxing.
13. If the inspection is successful, proceed with the installation of the equipment.
14. Once the equipment is installed and ready for testing, carry out tests (individual tests and combined tests).
15. If there are no issues during testing, both parties sign to confirm this.
Lesson: When selecting equipment, the process parameters must be verified repeatedly – any mistake can have serious consequences. In mild cases, the vehicle is stopped for repairs; in severe cases, it is scrapped outright. After working on projects for a few years, this is what I’ve learned. Everyone is welcome to join the discussion! This post was last edited by zhangya*ong on 2009-3-17 11:02.]

The view from the 5th floor is \"impenetrable\" – impressive, an expert’s opinion.

All along, corrosion has been one of the most troublesome hazards for chemical processing equipment; a slight carelessness can lead to equipment damage, and in severe cases, it can cause accidents or even disasters. According to relevant statistics, about 60% of the damage to chemical processing equipment is caused by corrosion; therefore, when selecting chemical pumps, it is essential to pay attention to the scientific choice of materials. There is a common misconception that stainless steel is a \"universal material\" that can be used in any medium or under any environmental conditions; this is very dangerous. Below are the key points for material selection regarding some commonly used chemical media: 1. Sulfuric acid, as one of the highly corrosive media, is an important industrial raw material with a wide range of applications. Sulfuric acid at different concentrations and temperatures causes varying degrees of corrosion to materials. For concentrated sulfuric acid with a concentration of over 80% and a temperature below 10°C, carbon steel and cast iron exhibit good corrosion resistance; however, it is not suitable for sulfuric acid that flows at high speeds, and thus cannot be used as material for pumps and valves ； Ordinary stainless steels such as 04Cr18Ni9 and 16Cr18Ni12Mo2Ti also have limited applicability in sulfuric acid media. Therefore, pump valves for transporting sulfuric acid are typically made of high-silicon cast iron (which is difficult to cast and process) or highly alloyed stainless steel (grade 20 alloy). Fluoroplastics exhibit good resistance to sulfuric acid, and using fluorinated pump materials (F46) is a more economical option. Most metal materials are not resistant to corrosion by hydrochloric acid (including various stainless steel types); high-molybdenum, high-silicon iron can only be used in hydrochloric acid at concentrations below 10% at 50°C. Unlike metal materials, the vast majority of non-metallic materials exhibit good corrosion resistance to hydrochloric acid; therefore, rubber-lined pumps and plastic pumps (such as those made of polypropylene or fluoroplastics) are the best choices for transporting hydrochloric acid. 3. Nitric acid: Most metals are rapidly corroded and damaged by nitric acid, while stainless steel is the most widely used material resistant to nitric acid. It possesses good corrosion resistance to nitric acid at all concentrations at room temperature. It is worth noting that stainless steels containing molybdenum (such as 16Mn and 16L) do not have better corrosion resistance to nitric acid than ordinary stainless steels (such as 304 and 21); in some cases, their resistance is even lower. For high-temperature nitric acid, titanium and titanium alloy materials are typically used, with a p/H value of > 4. Acetic acid is one of the most corrosive organic acids; ordinary steel suffers severe corrosion in acetic acid at all concentrations and temperatures. Stainless steel is an excellent material resistant to acetic acid, and stainless steel containing 16% molybdenum can also be used in high-temperature and dilute acetic acid vapors. For demanding applications such as high-temperature, high-concentration acetic acid or solutions containing other corrosive agents, high-alloy stainless steel or fluoroplastic pumps can be used. Steel is widely employed for sodium hydroxide solutions at concentrations up to 100% below 80°C; many factories still use ordinary steel at temperatures up to 100°C and concentrations below 5%, as the increased corrosion is offset by cost advantages. Ordinary stainless steel does not have a significant advantage over cast iron in terms of corrosion resistance to alkaline solutions; it is not recommended to use stainless steel when only a small amount of iron is allowed to be present in the medium. For high-temperature alkaline solutions, titanium and titanium alloys or highly alloyed stainless steels are commonly used. 6. Ammonia (ammonium hydroxide): Most metals and non-metals suffer only mild corrosion in liquid ammonia and ammonium hydroxide solutions; however, copper and its alloys are not suitable for use. 7. Saltwater (seawater): Ordinary steel exhibits a low rate of corrosion in sodium chloride solutions as well as in seawater and brackish water, and coating protection is generally required ； Various types of stainless steel also have very low rates of uniform corrosion, but local corrosion may occur due to chloride ions; therefore, 316 stainless steel is generally a better choice. Alcohols, ketones, esters, and ethers are common types of media: common alcohol media include methanol, ethanol, ethylene glycol, propanol, etc.; ketone media include propane, butane, etc.; ester media include various methyl esters and ethyl esters; ether media include methyl ether, ethyl ether, butyl ether, etc. These media basically have no corrosive properties, and standard materials can be used for them. When making a selection, it is necessary to consider the properties of the medium and relevant requirements in order to make a proper choice. It is also worth noting that alcohols, esters, and ethers are soluble in various rubbers; this should be taken into account when selecting sealing materials to avoid mistakes

I would like to ask the moderator about the differences between slurry pumps in catalyst production units and those in oil refining production units. I’ll learn it too.

Replying to the person above: The medium in the slurry pump is a slurry containing catalyst particles, with a particle content of no more than 20%; this medium has strong self-lubricating properties. The medium in the catalyst transfer pump is a kaolin solution, with a particle content of around 70%, and it has weak self-lubricating properties.

Let me give another example of incorrect motor rotation direction: When purchasing high-speed centrifugal pumps, we specified the correct rotation direction of the motors in the technical agreement. However, the equipment supplier did not pay close attention to the issue of gearbox rotation direction and used motors designed for conventional centrifugal pumps. It was only during the trial run that it was discovered that the rotation direction was incorrect. Initially, it was thought that replacing the fan would solve the problem, but our electrical experts provided various professional insights, explaining that factors such as the flow path, excitation, and the magnetic interaction between the stator and rotor would all have an impact, and therefore a replacement of the motor was necessary. Since there is a certain lead time for supplying explosion-proof motors, it was necessary to first replace the cooling fan for temporary use, with the motor being replaced eventually. Those who are experts in motors can also explain it.

When selecting pumps, the following problems have arisen: due to the overly high flow rate and head specified for the pumps (a common issue in state-owned enterprises), the pumps generate significant vibration and noise when operating at lower flow rates, and in severe cases, they cannot function at all. During the inspection at the head office, many devices were found to be exceeding the standards. Ultimately, this issue is resolved through methods such as up-conversion or low-flow lines; therefore, when selecting a pump, one should pay attention to this problem and incorporate additional control measures if necessary.

In our opinion, pumps that last less than three months to half a year or more are considered unsuitable or indicate an incorrect selection. We later switched to stainless steel, but the situation didn’t change much – the good ones lasted only eight or nine days. Eventually we found duplex steel, and we collaborated with a company from the former Ministry of Armaments Industry; we used their patented products, and the lifespan of these pumps reached over one month, with the longest duration being three months. ”---------Why is it always considered from the perspective of metal materials? ? :L ceramic pump: special ceramics that are both corrosion-resistant and wear-resistant, solving related problems. Photos of disassembling the all-ceramic pump can be found at http://bbs.hcbbs.com/thread-420558-1-1.html

Replies don’t allow photos; one can only post new threads with photos. Considering I’ve gone to the trouble of disassembling the pump, taking photos, and creating new threads for you, let’s give you a reward :)

I think the main issue is abrasion, so you might consider using a plastic pump made of polyethylene. Experts conducted an experiment in which sand and water were mixed in a ratio of 3:2 inside a mixing tank, and the mixture was stirred at 1200 RPM for 24 hours. The blades used for stirring were made of polypropylene, polyethylene, and 316 stainless steel; the results showed that polyethylene had an abrasion resistance 8 times greater than that of polypropylene, and 3 times greater than that of 316 stainless steel.

The polyethylene cited above is not ordinary polyethylene, but rather ultra-high molecular weight polyethylene UHMWPE. The most wear-resistant type, 316 stainless steel, is not a wear-resistant material, and PP polypropylene is even less so. Here, 16Mn steel, which has better wear resistance, is used as a comparison material. The evaluation is based on the weight loss due to wear. The abrasive used is quartz sand with a particle size of 40–70 mesh; the grinding wheel is made of butyl rubber with a Shore A hardness of 62±. The linear speed of the wheel’s rim is 140 m/min, the friction distance is 700 m, the load applied is 130 N, and the rate at which the abrasive is supplied is 300 g/min. Based on the weight loss due to wear, 16Mn steel exhibits 35.7 times greater wear resistance than 95-grade wear-resistant ceramic, and 62.8 times greater wear resistance than 99-grade wear-resistant ceramic. When converted to volume wear, it is 16 times and 32.7 times respectively. Assuming that 316 stainless steel has the same wear resistance as 16Mn steel, then the wear resistance of ceramics is 11 to 22 times that of ultra-high molecular weight polyethylene UHMWPE; in reality, it is even higher. It’s easy to understand: if you use a plastic rod and grind it on a grinder, it will get polished after just a short time.:L

Ceramic pumps are essential in the following types of enterprises: those that produce SIC silicon carbide powder, as the acids used for transportation contain silicon carbide powder. The high hardness of silicon carbide leads to wear on the pump chamber and impeller, and since acids are corrosive, metal materials such as stainless steel can be damaged by them. In enterprises that produce abrasives, as well as in the stages prior to the formation of grinding wheels and sandpapers, there is also a need to transport very hard fine particles; therefore, pumps with high wear resistance are required. In the non-ferrous metal industry, nickel powder is present in pools of dilute sulfuric acid, and this powder needs to be pumped into filter presses in order to be separated from the rest of the mixture. The applications for such pumps are diverse – wherever acidic substances cause corrosion to stainless steel, or where the passivation layer on the surface of stainless steel is worn away by solid particles present in the acid, ceramic pumps come in handy. These enterprises rely on ceramic pumps because they cannot tolerate the situation where other types of pumps fail after just a few weeks or months of use; it’s simply too troublesome:@

Personally, I suggest that in a situation like yours, it’s best to install a filter before the pump.

For pumps such as heavy oil catalytic slurry pumps, a structure with an inner lining can also be chosen

Regarding this issue, let me start by talking about my work in oil refining catalysis. Take the slurry pump used in our position as an example. First of all, it is necessary to know the density, temperature, pressure, degree of corrosion, and whether the medium inside the pump is toxic or not. Ours has characteristics such as high temperature, flammability, and being a heavy oil. Therefore, when making a selection, the material used must be heat-resistant; given its flammability, it is essential to choose one that is well-sealed, as well as one with mechanisms that help to reduce the temperature of the bearings. In the end, we chose an oil slurry pump from the United States; I can’t remember the model number, sorry about that. It’s just my personal opinion

Corrosion issues: Throughout the years, corrosion of sewage pumps has been one of the most troublesome problems associated with chemical processing equipment. Even a slight carelessness can lead to equipment damage; in severe cases, it can result in accidents or even disasters. According to relevant statistics, about 60% of the damage to chemical processing equipment is caused by corrosion; therefore, when selecting chemical pumps, it is essential to pay attention to the scientific choice of materials. There is a common misconception that stainless steel is a \"universal material\" that can be used in any medium or under any environmental conditions; this is very dangerous. Below are the key points for material selection regarding some commonly used chemical media: 1. Sulfuric acid, as one of the highly corrosive media, is an important industrial raw material with a wide range of applications. Sulfuric acid at different concentrations and temperatures causes varying degrees of corrosion to materials. For concentrated sulfuric acid with a concentration of over 80% and a temperature below 80°C, carbon steel and cast iron exhibit good corrosion resistance; however, it is not suitable for sulfuric acid that flows at high speeds, and it cannot be used as material for pumps and valves ； Common stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) also have limited utility in sulfuric acid media. Therefore, the pumps and valves used for transporting sulfuric acid are usually made of high-silicon cast iron (which is difficult to cast and process) or high-alloy stainless steel (grade 20 alloy). Fluoroplastics exhibit good resistance to sulfuric acid, making the use of fluorine-lined pumps (F46) a more economical option. The company’s applicable products include: IHF fluorine-lined pumps, PF(FS) highly corrosion-resistant centrifugal pumps, CQB-F fluoroplastic magnetic pumps, etc. 2. Hydrochloric acid: The vast majority of metal materials are not resistant to corrosion by hydrochloric acid (including various stainless steel materials); high-molybdenum high-silicon iron can only be used in hydrochloric acid at temperatures below 50°C and with a concentration of less than 30%. Unlike metal materials, the vast majority of non-metallic materials exhibit good corrosion resistance to hydrochloric acid; therefore, rubber-lined pumps and plastic pumps (such as polypropylene and fluoroplastics) are the best choices for transporting hydrochloric acid. The company’s applicable products include: IHF fluorine-lined pumps, PF(FS) highly corrosion-resistant centrifugal pumps, CQ polypropylene magnetic pumps (or fluoroplastic magnetic pumps), etc. 3. Most common metals are rapidly corroded and damaged by nitric acid; stainless steel is the most widely used material resistant to nitric acid, exhibiting good corrosion resistance in nitric acid of all concentrations at room temperature. It is worth noting that stainless steels containing molybdenum (such as 316 and 316L) do not have better corrosion resistance to nitric acid than ordinary stainless steels (such as 304 and 321), and in some cases their resistance is even lower. For high-temperature nitric acid, titanium and titanium alloy materials are typically used. The company’s applicable products include: DFL(W)H chemical pumps, DFL(W)PH shielded chemical pumps, DFCZ process pumps, DFLZP self-priming chemical pumps, IH chemical pumps, CQB magnetic pumps, etc., all made of 304 material. 4. Acetic acid is one of the most corrosive organic acids; ordinary steel is severely corroded by acetic acid at all concentrations and temperatures. Stainless steel is an excellent material resistant to acetic acid, and 316 stainless steel containing molybdenum can also be used in high-temperature and dilute acetic acid vapor environments. For demanding applications such as high-temperature, high-concentration acetic acid or environments containing other corrosive substances, high-alloy stainless steel or fluoroplastic pumps can be used. 5. Alkalis (sodium hydroxide): Steel is widely used in sodium hydroxide solutions at temperatures below 80°C and with concentrations up to 30%. Many factories still use ordinary steel at temperatures of 100°C and concentrations below 75%; although corrosion increases in such conditions, centrifugal pumps remain cost-effective. Compared to cast iron, ordinary stainless steel does not offer any significant advantage in terms of corrosion resistance to alkaline solutions; it is not recommended to use stainless steel when a small amount of iron is allowed to be present in the medium. For high-temperature alkaline solutions, titanium and titanium alloys or highly alloyed stainless steels are commonly used. The company’s standard cast-iron pumps can be used for alkaline solutions at normal temperatures and low concentrations; for special requirements, various stainless steel pumps or fluoroplastic pumps can be employed.

You can take a look at the industrial pump selection manual; this book is divided into three parts. It provides a comprehensive overview of the characteristics, structure, basic performance, and selection procedures of pumps and prime movers. Taking into account the requirements of chemical and pharmaceutical plants, it explains the characteristics and basic performance of special-purpose pumps commonly used in petrochemical industries, such as cryogenic pumps, slurry pumps, vacuum pumps, and shielded pumps. It also covers aspects related to piping requirements for pump systems, pump materials, shaft seals, flow regulation, performance testing, installation, and operation. It also covers the procurement of pumps, the preparation and filling out of quotation documents and pump data sheets, the review and evaluation of manufacturers’ quotes, as well as the issuance of orders