Pressure Switches for High and Low Pressures

What are Pressure Switches and How Do They Work?

Pressure switches are devices that can translate a pressure change into an electrical signal at a predetermined set point.

In a common pressure switch design, media enters through a pressure port pushing up onto the diaphragm and gland. When the actuator moves up, the contact washer makes/breaks the electrical path of the snap-action contacts, spades or blades. Only the presence or absence of pressure is required for these switches to operate. When this occurs, the spring tension will operate to open or close the switch, therefore switching the process on or off.

In a live example:
 

• Process typically runs from 40 to 70 PSI during normal operation.
• If the process were to go above 100 PSI, the pump could overload causing excessive pressure in the system.
• A pressure switch is introduced and set at 95 PSI. If the process goes above 95 PSI, it will trigger an alarm (or relay or other electrical circuit).

Types of Pressure Switches

• OEM Pressure Switches - at cost-effective price points and manufactured for higher volume applications. These rugged and dependable pressure switches come in a variety of materials from stainless steel, brass, aluminium, zinc-plated steel and reinforced plastic. Wetted materials a diaphragm available in Buna N, Teflon® coated Kapton®, stainless steel, PTFE, EPDM or Viton® and a pressure port available in stainless steel, brass, zinc or aluminium.
   
• Differential Pressure Switches - are used to identify a change in pressure between 2 preset levels. They alert the user to a difference in pressure by sounding an alarm or cutting out to halt the preset flow level. These are often used to ensure rooms and areas remain sterile, free from dirt and dust.
   
• Pneumatic Pressure Switches - are used to monitor the air pressure within a unit. These switches can act as a control valve which activates when air pressure rises above or falls below the adjustable chosen level.
   
• Digital Pressure Switches - are used to monitor the preset pressure levels and to record pressure data to detail any changes in the pressure. This information can be reviewed in real time or retrospectively.

Selection Criteria for Pressure Switches

There are many factors to consider when identifying which switch is suitable for your application. These may include:
 

• Identify required set point - what pressure level should the application be performing at? When is the alarm/trigger point needed?
   
• Operating Standards - now the standard set point has been identified, what is the maximum and minimum pressure the switch may reach? What is to be expected during normal operation?
   
• Compatibility - are the wetted materials compatible with the media? This may include fittings, diaphragms and seals.
   
• Environment - what environment will the switch be used in? Can the switch still perform in humid, wet, corrosive, hazardous, boiling hot or freezing temperatures?
   
• Electrical Requirements - ensure the switch can operate with the required voltage and current.
   
• Additional Specifications - consider if the switch requires bespoke operating functions or certification standards.

We have an extensive choice of pressure switches available and our knowledgeable technical support team at Boiswood can support you in choosing the correct switch to fulfil the needs of your business.