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The shaft seal is a sealing device designed 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. 1. Packing seal: The packing seal has a simple structure, is inexpensive, and is easy to maintain, but it results in high leakage rates and significant power loss. 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 use with valuable, explosive, or toxic substances. 2. Mechanical seal: 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 specifications of the American Petroleum Institute ； Unless specified by the user, a modular mechanical seal should be installed. 3. Dynamic sealing: Dynamic sealing can be divided into back-vane sealing and auxiliary impeller sealing. When the pump is in operation, the centrifugal force exerted by the back blades (or auxiliary impeller) causes the pressure of the medium at the shaft seal to drop to atmospheric pressure or 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 vane (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 that accompany the back vane (or auxiliary impeller). Filler seals come in two types: the standard type and the mechanically adjustable type. A conventional 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. The mechanical tension-type packing shutdown seal uses a weight to loosen the packing while the pump is running, and to compress the packing when the pump stops. To ensure the lifespan of the parking seal device and reduce pump leakage, for pumps equipped with dynamic seals, the pressure at the pump inlet must be limited, that is: Ps＜10% Pd, where Ps is the pressure at the pump inlet, in MPa ； Pd—pump inlet pressure, MPa ； 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 in the phosphate industry and material transfer pumps. The disadvantage is that the power loss is greater compared to mechanical seals, and the lifespan of its shutdown sealing device is shorter.