The selection of seals must take into account the working conditions, so as to select the appropriate type of seals, materials and installation structure. The working conditions to be considered generally include temperature, pressure and medium. Others also need to consider the selection of equipment according to the characteristics of the equipment itself.

Regarding temperature, for example, the working temperature range of NBR materials is generally - 40 - 120 C. It is necessary to consider using FKM or even PTFE materials when the temperature exceeds 120 C. Low temperature is relatively rare. Generally speaking, the use of cold-resistant NBR should be considered in the case of - 20 ~40 C. Normal NBR materials will cause hardening of materials under low temperature, leading to leakage, such as railway locomotives in winter in the north.

As for pressure, it affects the type of seal to be selected. Generally speaking, the choice of rubber or PU seals for low pressure and medium pressure will not be too big a problem. However, it is necessary to consider a problem of impact pressure, such as starting in construction machinery, when it is closed, its impact pressure is far greater than the normal working pressure, so HBY or SPGW, which can withstand up to 70 MPA, are often chosen as the main seals. PTFE combined seal is also a common choice.

The problem of medium is relatively simple. It is only necessary to pay attention to some special minor problems, such as the use of water-glycol and phosphate hydraulic oil in cylinders of metallurgical industry. Sometimes although the working temperature is not high, but the choice of materials still need to be very careful, hydraulic oil when using the latter or choose FKM.

The selection of seals is very important, or it must be combined with the equipment itself. For example, we need to be sensitive and precise in our control. Of course, we should choose the Steffengray Circle. Need high reliability, often choose Hunger's GD1000K series or NOK's SPGW. For example, construction machinery working in the field often has impact and low temperature weather, and its dust-proof ring will choose exposed metal skeleton to avoid falling off.

Cylinders, compressor piston rings, high-pressure oil seals, and oil pumps in various scientific instruments need special structures to meet the requirements.

All of these, not to mention, welcome to exchange with me the selection of seals.

What is the common sense of mechanical seals?

Mechanical seals are one of the basic mechanical components with high precision and complex structure. They are the key components of various pumps, reaction synthesis kettles, turbine compressors, submersible motors and other equipment. Its sealing performance and service life depend on many factors, such as type selection, machine accuracy, correct installation and use, etc.

Type Selection Method

According to the different working conditions and medium properties, mechanical seals have high temperature and low temperature resistance, high pressure and corrosion resistance, granular medium resistance and light hydrocarbon medium adaptable to vaporization. Different structural types and materials should be selected according to different uses.

The main parameters of type selection are: pressure of sealing chamber (MPA), temperature of fluid (C), working speed (M/S), characteristics of fluid and effective space for installation of sealing, etc.

What is the general knowledge of mechanical seals and the basic principles of type selection are as follows:

1. According to the pressure of the sealing chamber, the seal structure is determined to be balanced or non-balanced, single-end or double-end.

2. According to the working speed, the rotary or static, hydrodynamic or non-contact type are adopted.

3. According to the temperature and fluid properties, determine the friction pair and auxiliary sealing materials, and correctly select lubrication, flushing, thermal insulation, cooling and other mechanical seal cycle protection system.