[Test Your Knowledge] Chemical Production Knowledge—Question and Answer (17) is now over! See floor 25 for the answer key

Give it a try; I usually don’t pay much attention to equipment. . . 1. The seals we use here are mostly mechanical seals, the type with a moving ring and a stationary ring; they wear out easily, and leakage tends to occur whenever the machine is stopped or started up. There’s also the oil seal; it’s likely to be less prone to failure, as I haven’t disassembled that equipment in these past few years and don’t know what its structure is like. Another aspect is magnetic stirring; it’s separated from the outside area and relies on a magnetic stirring shaft for mixing. The torque isn’t very high, which may cause the stirring to stop, but it won’t damage the equipment. 2. When parking my vehicle in winter, I usually empty the entire pipeline system, including the heat exchanger and water pumps, both inside and outside, fill it with nitrogen, and then seal it. If the machine is not stopped, the water will keep circulating.

What are the types of shaft seals for rotating shafts? What are their respective characteristics? Answer: There are packing seals and mechanical seals. Packing seals have the advantages of easy installation and maintenance, as well as low cost. However, its sealing performance is not very good. Mechanical seals have advantages such as good sealing performance and low likelihood of leakage, but they require high precision in installation and are expensive. How to prevent freeze damage to heat exchangers in winter? Answer: 1. All cooling water heat exchangers must be supplied with cooling water regardless of whether they are in use or not; the supply must not be interrupted. The upper and lower bypass valves are slightly open. 2. A small amount of steam is supplied to all unused steam heaters, with the condensate being continuously drained via drain lines. 3. For heat exchangers that are not in use for a long time, the medium inside them should be emptied.

a\There are packed seals and mechanical seals. Packing seals have the advantages of easy installation and maintenance, as well as low cost. However, its sealing performance is not very good. Mechanical seals have advantages such as good sealing performance and low likelihood of leakage, but they require high precision in installation and are expensive. b\1) All cooling water heat exchangers must be supplied with cooling water continuously, regardless of whether they are in use or not; if there are bypass valves for the inlet and outlet water, these should be kept slightly open. 2) A small amount of steam is supplied to all unused steam heaters, and the condensate is continuously drained via a drain line. 3) For heat exchangers that are not in use for an extended period, the medium inside them should be drained, and it is necessary to ensure that the pipelines carrying steam, condensate, or cooling water to and from the heat exchanger, as well as those leading to the main pipes, are protected from freezing.

There are stuffing seals and mechanical seals. Packing seals have the advantages of easy installation and maintenance, as well as low cost. However, its sealing performance is not very good. Mechanical seals offer advantages such as good sealing performance and low likelihood of leakage, but they require high precision in installation and are expensive. 1) All cooling water heat exchangers must remain supplied with cooling water regardless of whether they are in use or not; the bypass valves for the inlet and outlet water should be kept slightly open. 2) A small amount of steam is supplied to all unused steam heaters, and the condensate is continuously drained via a drain line. 3) For heat exchangers that are not in use for an extended period, the medium inside them should be drained, and it is necessary to ensure that the pipelines carrying steam, condensate, or cooling water to and from the heat exchanger, as well as those leading to the main pipes, are protected from freezing.

The shaft seal is a sealing device installed to prevent leakage at the pump shaft and the housing. Common types of shaft seals include packing seals, mechanical seals, and dynamic seals. The shaft seal of a reciprocating pump is usually a packing seal. Diaphragm reciprocating pumps can be used when transporting media that must not leak. The shaft seals for rotary pumps (including vane pumps, rotor pumps, etc.) mainly include packing seals, mechanical seals, and dynamic seals. I. Packing seal: The packing seal has a simple structure, is inexpensive, and is easy to maintain. But it has a large leakage rate and high power consumption losses. Therefore, packing seals are used for transporting general media such as water ； It is generally not suitable for petroleum and chemical media, especially not for valuable, explosive, or toxic media. II. Mechanical Seals Mechanical seals (also known as face seals) offer excellent sealing performance, very low leakage rates, and a long service life. However, they are expensive, and their processing, installation, and maintenance require higher standards compared to ordinary seals. Mechanical seals are suitable for transporting petroleum and chemical fluids, and can be used with fluids of various viscosities, high corrosivity, or containing particles. Standard API610 (8th edition) of the American Petroleum Institute specifies that, unless specified by the user, a cartridge mechanical seal shall be installed. III. Dynamic Sealing Dynamic sealing can be divided into back vane seals and auxiliary impeller seals. When the pump is in operation, the centrifugal force generated by the back blade (or auxiliary impeller) reduces the pressure of the medium at the shaft seal to atmospheric pressure or a negative pressure, thereby preventing leakage during the pump’s use. When the machine is stopped, the centrifugal force disappears, and the sealing function of the back blade (or auxiliary impeller) is lost; at this point, it is the stop-sealing device that provides sealing. Packing seals are commonly used in the shutdown sealing devices associated with backplate types (or auxiliary impellers). Filler seals come in two types: the standard type and the mechanically adjustable type. A standard packing seal is similar to ordinary packing seal pumps, requiring a slight positive pressure at the shaft seal to prevent dry friction of the packing. Mechanical tension-type packing seals use weights to loosen the packing while the pump is running, and to compress it when the pump stops. It features reliable dynamic sealing performance, low cost, and easy maintenance, making it suitable for transporting media containing a high amount of solid particles, such as slurry pumps and pulp pumps used in the phosphate industry. The disadvantage is that the power loss is higher compared to mechanical seals, and the lifespan of its shutdown sealing device is shorter. 1) All cooling water heat exchangers must be supplied with cooling water continuously, regardless of whether they are in use or not; if there are bypass valves for the inlet and outlet water, these should be left slightly open. 2) A small amount of steam is supplied to all unused steam heaters, and the condensate is continuously drained via a drain line. 3) For heat exchangers that are not in use for an extended period, the medium inside them should be drained, and it is necessary to ensure that the pipelines carrying steam, condensate, or cooling water to and from the heat exchanger, as well as those leading to the main pipes, are protected from freezing.

Shaft seals are divided into mechanical seals and packing seals. Anti-freezing measures for heat exchangers in winter: 1. All cooling water heat exchangers must be supplied with cooling water, regardless of whether they are in use or not; the supply of cooling water must not be interrupted. The upper and lower bypass valves are slightly open. 2. A small amount of steam is supplied to all unused steam heaters, with the condensate being continuously drained via drain lines. 3. For heat exchangers that are not in use for a long time, the medium inside them should be emptied.

1. Packing seal (a packing seal device generally consists of packing, packing rings, and a packing gland)； 2. Mechanical seal (very low leakage, but complex structure and high maintenance costs) ； 3. Floating seal (leakage is greater than that of packing seals and mechanical seals); in winter, protection against low temperatures is necessary, and the ambient temperature around standby heat exchangers must be controlled ； Insulation layers can be applied externally using heat exchanger equipment

a. What are the types of shaft seals for rotating shafts? What are their respective characteristics? Answer: The types of shaft seals are: 1. Packing seal ； 2. Soft packing seal ； 3. Mechanical seal 4. Helical seal 5. Labyrinth seal 6. Jet seal 7. Floating ring seal b. How to prevent freeze-up of heat exchangers in winter? Answer: A drain valve is installed at the water inlet connection located at the lowest point of the heat exchanger. A collection pipe extends below the water inlet connection; all the branch water pipes are connected to this collection pipe horizontally or in the direction of water flow, from top to bottom. The collection pipe is connected to the drain valve. The water accumulated in the heat exchanger or the cleaning fluid flows directly into the unit’s condensate tray, from where it is then removed through drainage pipes. 1# zfy_80522

What are the types of shaft seals for rotating shafts? What are their respective characteristics? Answer: There are packing seals and mechanical seals. Packing seals have the advantages of easy installation and maintenance, as well as low cost. However, its sealing performance is not very good. Mechanical seals have advantages such as good sealing performance and low likelihood of leakage, but they require high precision in installation and are expensive. How to prevent freeze damage to heat exchangers in winter? Answer: 1. All cooling water heat exchangers must be supplied with cooling water regardless of whether they are in use or not; the supply must not be interrupted. The upper and lower bypass valves are slightly open. 2. A small amount of steam is supplied to all unused steam heaters, with the condensate being continuously drained via drain lines. 3. For heat exchangers that are not in use for a long time, the medium inside them should be emptied.

a. What are the types of shaft seals for rotating shafts? What are their respective characteristics? There are two types: packing seal and mechanical seal. The packing seal has a simple structure, but it requires frequent maintenance and consumes more power. Since such devices cannot completely prevent leaks, they are not suitable for transporting flammable, explosive, and toxic liquids. Mechanical seal devices are characterized by excellent performance, long service life, and low power consumption, but they require high standards for the machining and installation of their components. It is suitable for transporting acids, alkalis, and flammable, explosive, and toxic liquids. b. How to prevent freeze damage to heat exchangers in winter? 1. Steam tracing ； 2. Internal blowing in the tube bundle.