What are the classifications of hydraulic pump seals? And see how Dalan Hydraulics analyzes!
What are the classifications of hydraulic pump seals? And see how Dalan Hydraulics analyzes!
Seals are mainly divided into the following major categories:
1. Balanced and unbalanced seals
1 The balance of the mechanical seal has a great influence on the sealing pressure of the contact surface. This sealing pressure depends on the effective cross section of the seal itself and the pressure inside the packing box.
2 balance the mechanical seal to reduce the sealing pressure and extend the service life of the seal. The above purpose can be achieved by generally using a spindle with a step and a bushing to reduce the effective cross section of the rotating surface. However, do not adjust the net seal pressure to near zero, as this may result in unstable working conditions between the seal faces and may blow the seal off due to sudden changes.
3 The cross section on the opposite side of the rotating surface of the unbalanced seal is completely exposed to the pressure range of the packing box. This will cause a high sealing pressure between the sealing faces, which will increase the working temperature and accelerate the wear rate. . Under high temperature operating conditions or when the liquid is highly corrosive and abrasive, the service life of the mechanical seal is greatly reduced.
4 In some applications, it may be better to use a non-balanced seal to achieve better results than the life of the seal, perhaps with a greater emphasis on safety issues due to liquid leakage. In this case, the choice of seal may be understood to be more desirable to have a higher sealing pressure. Similarly, the increase in operating temperature may be negligible when using a seal with a cooler liquid.
5 Regardless of the consideration, a balanced seal is generally recommended when the packing box pressure exceeds 50 psi.
2, inner seal and outer seal
1 The most common practice is to install the seal inside the packing box. However, this practice requires the wet end of the liquid pump to be removed during the seal repair. The main advantage is that the environmental sanitation of the seal is easy to control.
2 The outer seal is installed by reversing the direction of the static sealing surface, and the rotating unit on the main shaft is located outside the packing box gland. The outer seal has the following five major benefits:
a, easy to install;
b, the cost is relatively low;
c, continuous monitoring and cleaning;
d, suitable for small packing boxes that cannot be sealed inside;
e. Due to its proximity to the bearing, the difficulty of the spindle deviation is less affected.
The main disadvantage is that the centrifugal force will pry solid particles from the underside of the seal to the sealing contact surface. Therefore, such seals are primarily suitable for cleaning liquids that do not contain abrasives.
3, cartridge seal
1 The cartridge seal simplifies the installation process while protecting the internal components from accidental damage.
2 The cartridge seal is a fully functional seal that includes all the sealing elements, glands and bushings. Since this type of seal does not require any rigorous installation measures, the installation procedure is greatly simplified, while the sealing faces and sealing elastomers are well protected against accidental damage. These advantages also mean that the repair and replacement time of the seal can be reduced.
4, double seal and liquid barrier device
A seal with a double seal face instead of a single seal has a higher degree of leak proof. Most of these double seals are used in liquids that are volatile, toxic, carcinogenic, dangerous and poorly lubricious.
2 Double seals are generally available in three designs, each requiring a liquid barrier system between the double seal faces to prevent leakage of liquids or gases.
3 A more common low-cost double seal is a back-to-back seal that has a rotating sealing surface aligned in opposite directions. It often requires a barrier liquid that is at a pressure higher than the packing box pressure of approximately 20 psi to ensure that the internal seal is always lubricated by the barrier liquid and that the sealing surface is sealed to a certain sealing pressure.
4 In a face-to-face type seal with a relatively complicated structure, the rotary seal faces are arranged in a face-to-face manner, and they tend to move in opposite directions of the same stationary seal face. This type of seal can be either a high pressure barrier liquid system or a low pressure barrier liquid system.
5 The third design type of seal is arranged in a serial arrangement, that is, both rotating sealing surfaces are separated from the impeller and arranged in the same direction. The barrier liquid pressure of such a seal is generally lower than the pressure of the liquid pump. In fact, it is equivalent to a combined working device with two seals and two stages of pressure reduction.
6 All types of double seals require a liquid system. They generally belong to an external closed-loop system, the liquid used inside is generally different, but must match the liquid in the process. The system includes a reservoir that is positioned as close as possible to the seal.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
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