New diaphragm materials improve pressure switch life

The 901 range of pressure switches from Impress Sensors are suitable for monitoring overpressure, vacuum or differential pressure in both liquids and gases, including aggressive media. They can be used to monitor fluid levels and filters, as well as excessive or inadequate pressure, and pressure differentials in closed systems.

Switches are available in factory-set versions, in which the pressure setting and switching differential are set by the manufacturer, or adjustable versions (901 Prescal), where the customer uses a scaled adjustment knob to alter the trip and reset pressure - without having to use a screwdriver.

New additions

The two latest additions to the 901 range are a saturated steam-resistant version and a food handling version, both of which benefit from newly-developed diaphragm materials.

Conventional elastomer diaphragms on pressure switches very quickly lose their elasticity when used in saturated steam, which can alter the switching points. In extreme cases, the diaphragm can become brittle or even cracked, which could become a potential safety hazard if left unchecked.

The saturated steam-resistant 901 pressure switch therefore has a newly developed FKM (elastomer) diaphragm that makes direct contact possible with extremely aggressive saturated steam. The switch operates reliably in temperatures up to 130degC and, depending on the design of the springs fitted, operates from 100mbar up to a maximum of 12bar, without material fatigue. The switch is therefore suitable for steam generation applications, including medical equipment, disinfection devices or professional kitchen equipment such as steam-pressure cookers. Coffee vending machines are another potential application area.

FDA approval

In addition, the food-handling version of the 901 has a special FDA-approved EPDM elastomer diaphragm. This diaphragm, which can also be used for saturated steam applications, is suitable for almost any food processing application. The switch's dual benefits of being FDA-approved and steam-resistant make it a very attractive option for customers. Target applications include food and beverage processing, water treatment systems, bottling plants and drinks storage.

Sam Drury, Sales Director at Impress Sensors & Systems, comments: "We are delighted to be able to offer these low-cost pressure switches to our customers in the UK. Typically, the switches will be available on a 10-day lead-time. We are already selling units into the UK, including a manufacturer of industrial dishwashers and a manufacturer of medical sterilising equipment."

The factory-set 901 switch can be set according to the customer's specification at a fixed value between 5mbar and 12bar in the positive pressure range and between –5mbar and –900mbar in the negative pressure range. With the 901 Prescal switch, the switching pressure can be controlled using an adjustment knob. For pressurised connection, there is a choice of plastic or metal hose connectors or threaded couplings.