How to choose pump mechanical seal？

The selection of pump mechanical seal requires comprehensive consideration of multiple factors such as operating conditions, medium characteristics, and installation space. The following are detailed selection methods and precautions:

1、 Core selection parameters
a. Stress factors
Low pressure condition (≤ 0.5MPa): Non balanced mechanical seal can be selected
High pressure working conditions: Balanced mechanical seals should be selected, and friction pair materials with high strength (such as impregnated metal graphite, tungsten carbide) should be chosen
Fluid with a specific gravity below 0.6: Regardless of the pressure, an equilibrium type should be used

b. Temperature factor
Room temperature (-30 ℃~100 ℃): Nitrile rubber O-ring
Medium temperature (-20 ℃~200 ℃): Fluororubber
High temperature (>80 ℃): Cooling needs to be strengthened, and metal bellows type mechanical seals should be preferred
Low temperature: Pay attention to material brittleness and choose alloy steel with good low-temperature performance

c. Speed factor
Linear velocity ≤ 20m/s: Spring rotating type can be selected
Linear velocity ≥ 20m/s: It is best to choose a spring static type
Priority should be given to using small springs and spring static structures for high-speed working conditions

d. Characteristics of the medium
Recommended sealing type for medium type
Single end sealing of cleaning medium
Toxic/flammable and explosive double end seal
Strong corrosive external sealing, corrosion-resistant materials (fluororubber, silicon carbide)
A flushing and filtering system is required for particles containing impurities
Easy crystallization/high viscosity anti blocking design

2、 Selection of sealing structure

a. According to the number of end faces
Single end face seal: simple structure, suitable for working conditions with clean media and low sealing requirements
Double end seal: Double protection, suitable for toxic, flammable, and highly corrosive media

b. According to the balance method
Balanced: High pressure working condition, reducing friction and wear
Unbalanced: Low pressure working condition, simple structure, low cost

c. In the form of a spring
Multiple springs: suitable for general working conditions
Single spring: suitable for media containing particles
Wave spring: in space limited situations

3、 Procurement selection steps
Determine the direction of motion: reciprocating, rotating, spiral, or fixed
Clear sealing focus: whether the active point is on the inner or outer diameter
Confirm temperature level: Refer to the original factory instructions or follow the actual working environment
Measurement size: It is recommended to measure the size of the metal groove instead of just referring to old samples
Verify pressure level: infer from the original factory instructions or observation of the original seal structure