The mechanical seal of the asphalt pump is a shaft seal device that relies on a pair or several pairs of end faces that are perpendicular to the shaft to slide relatively under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism and is matched with an auxiliary seal to prevent leakage.
Common materials for mechanical seals
Clear water; normal temperature; (dynamic) 9Cr18, 1Cr13 surfacing cobalt-chromium-tungsten, cast iron; (static) dipped resin graphite, bronze, phenolic plastic.
River water (including sediment); normal temperature; (dynamic) tungsten carbide, (static) tungsten carbide
Seawater; normal temperature; (dynamic) tungsten carbide, 1Cr13 surfacing cobalt-chromium-tungsten, cast iron; (static) immersion resin graphite, tungsten carbide, cermet;
Superheated water 100 degrees; (dynamic) tungsten carbide, 1Cr13 surfacing cobalt-chromium-tungsten, cast iron; (static) immersion resin graphite, tungsten carbide, cermet;
Gasoline, lubricating oil, liquid hydrocarbon; normal temperature; (dynamic) tungsten carbide, 1Cr13 surfacing cobalt-chromium-tungsten, cast iron; (static) immersion resin or tin-antimony alloy graphite, phenolic plastic.
Gasoline, lubricating oil, liquid hydrocarbon; 100 degrees; (dynamic) tungsten carbide, 1Cr13 surfacing cobalt-chromium-tungsten; (static) immersion bronze or resin graphite.
Gasoline, lubricating oil, liquid hydrocarbons; containing particles; (dynamic) tungsten carbide; (static) tungsten carbide.
Types and uses of sealing materials
The sealing material should meet the requirements of the sealing function. Due to the different media to be sealed and the different working conditions of the equipment, different adaptability of the sealing material is required. The requirements for sealing materials are generally:
1) The material has good compactness and is not easy to leak the medium;
2) have appropriate mechanical strength and hardness;
3) Good compressibility and resilience, small permanent deformation;
4) No softening or decomposition at high temperature, no hardening or brittle cracking at low temperature;
5) Good corrosion resistance, can work for a long time in acid, alkali, oil, and other media, its volume and hardness change is small, and it does not adhere to the metal surface;
6) Small friction coefficient and good wear resistance;
7) It has the flexibility to combine with the sealing surface;
8) Good aging resistance and durable;
9) It is easy to manufacture, cheap, and easy to obtain materials.
Rubber is the most commonly used sealing material. In addition to rubber, graphite, polytetrafluoroethylene, and various sealants are suitable for sealing materials.
Technical essentials of mechanical seal installation and use
1) The radial runout of the shaft of the equipment should be less than or equal to 0.04 mm, and the amount of axial movement should not be greater than 0.1 mm;
2) The sealing part of the equipment should be kept clean during installation, the sealing parts should be cleaned, and the sealing end face should be intact to prevent impurities and dust from being brought into the sealing part;
3) During the installation process, it is strictly forbidden to hit or knock, so as to avoid friction and damage to the mechanical seal of the asphalt pump and the seal failure;
4) During installation, a layer of clean mechanical oil should be applied to the surface in contact with the seal, so that it can be installed smoothly;
5) When installing the static ring gland, the tightening screws must be evenly stressed to ensure the vertical requirements of the static ring end face and the axis line;
6) After installation, push the moving ring by hand so that the moving ring can move flexibly on the shaft and has a certain elasticity;
7) After installation, turn the shaft by hand, and the shaft should not feel heavy;
8) The equipment must be filled with the medium before the operation to prevent the seal from being ineffective due to dry friction;
9) For easy-to-crystallize and granular media when the temperature of the medium is less than 80oC, corresponding measures of flushing, filtration and cooling should be taken. For various auxiliary devices, please refer to the relevant standards for mechanical seals of asphalt pumps.
10) During installation, a layer of clean mechanical oil should be applied to the surface in contact with the seal. Special attention should be paid to the selection of mechanical oil. For different auxiliary seal materials, avoid O-ring expansion or accelerated aging, resulting in premature sealing. invalid.
