In measuring instruments, the material selection for seals directly impacts the equipment’s sealing performance, corrosion resistance, and service life. Different operating conditions (e.g., media type, temperature, pressure) impose distinct requirements on seal performance. So we are introducing some common sealing ring materials and their differences, as well as how to select them according to different working conditions.

1. Common sealing ring materials and their differences

Nitrile rubber (NBR)

• Features: oil-resistant, wear-resistant, strong adhesion, but poor tolerance to low temperature and ozone, poor insulation, and general elasticity.
• Applicable scenarios: Suitable for sealing of grease products, but not suitable for use at high temperatures (over 80℃).

Fluororubber (FKM/VITON)

• Features: wide temperature resistance range (-20℃~200℃, some can reach higher), good oil resistance, suitable for a variety of media, but medium mechanical strength and high price.
• Applicable scenarios: commonly used for sealing under high temperature or special media conditions, such as petroleum, lubricating oil, hydraulic oil, etc.

EPDM

• Features: high temperature resistance, low temperature resistance, ozone resistance, water vapor resistance, etc., wide operating temperature range (-60℃~130℃), but not suitable for oils, solvents, etc.
• Applicable scenarios: widely used in non-oily media sealing such as automotive air-conditioning systems and oil systems.

Silicone rubber (SIL)

• Features: High and low temperature resistance (-70~260℃), ozone resistance and weather aging resistance, but low mechanical strength and oil resistance.
• Applicable scenarios: Suitable for sealing in high and low temperature environments, such as sealing in high-temperature equipment, but not suitable for making oil seals.

Polytetrafluoroethylene (PTFE)

• Features: Good chemical stability, heat resistance, cold resistance, resistance to various media, but poor elasticity.
• Applicable scenarios: Commonly used to make wear-resistant rings, guide rings, etc., suitable for a variety of corrosive media and high temperature environments. Material is used when the ultrasonic level transmitter 4-20ma output  is working for chemical tanks.

Metal sealing ring

• Features: High temperature resistance, high pressure resistance, corrosion resistance, high strength, but high manufacturing cost, complex installation and maintenance.
• Applicable scenarios: Sealing in extreme environments, such as high temperature, high pressure, strong corrosion, etc.

• Select the material of the sealing ring according to different working conditions

When selecting the material of the sealing ring, the following factors need to be considered comprehensively:

1. Medium properties: Understand the composition, temperature, pressure and other characteristics of the measured medium, and select the sealing ring material that is suitable for it. For example, oily media should use nitrile rubber or fluororubber with good oil resistance; corrosive media can consider using polytetrafluoroethylene or metal sealing rings.
2. Working temperature: For example, silicone rubber or fluororubber can be selected in high temperature environment; natural rubber or EPDM rubber should be selected in low temperature environment.
3. Working pressure: The working pressure will also affect the selection of the sealing ring. Under high pressure environment, metal sealing rings or high-strength rubber sealing rings may be more suitable, it should be considered for heavy duty oil pressure transmitter.
4. Sealing requirements: According to the accuracy requirements and sealing performance requirements of the measuring instrument, select the sealing ring material with corresponding sealing performance. For example, in situations where the sealing performance requirements are extremely high, metal sealing rings or high-performance rubber sealing rings can be considered.
5. Cost considerations: The prices of seals made of different materials vary greatly, and a reasonable choice should be made based on the actual application scenario and budget.

Selecting the right seal material is crucial to ensuring the accuracy and stability of the measuring instrument, no matter water pressure sensor for industrial applications or oil pressure transmitter for machinery. In actual applications, a variety of factors should be considered comprehensively according to the specific requirements of the working conditions to select the most suitable seal material.

Keywords：

1. ultrasonic level transmitter 4-20ma output
2. heavy duty oil pressure transmitter
3. no matter water pressure sensor for industrial applications
4. oil pressure transmitter for machinery