Diaphragms

Diaphragms are flexible sealing element components that are used in pump, valve, and diaphragm seal applications. They provide a barrier between two chambers. Diaphragms move slightly up into one chamber or slightly own into the other chamber, depending on differences in pressure. They may also vibrate when specific frequencies are applied. Applications for diaphragms include pumps and diaphragm seals; separating, actuating, and dampening mechanisms; measurement products; and fuel supply systems.

Diaphragms provide high flexibility and low hysteresis, a constant effective area, and a short reaction time in the event of a change in pressure. They are also extremely resistant to pressure, and provide benefits such as temperature resistance, permeation resistance, and tear resistance. Some diaphragms are resistant to commercially-available fluids and gases. Others exhibit no frictional loss when starting or when in operations. Maintenance- free diaphragms, lubrication-free diaphragms, and diaphragms with long service life are also available.

There are several different types of diaphragms. Choices include flat, top hat, and dish shape. Flat diaphragms are used mainly for pressure regulators and dampers. They have a limited stroke capability and are made of different calendered rubber materials. Top hat diaphragms have the longest stroke capability, but are limited by their height. Dish shape diaphragms have a sidewall that slopes gradually. They are designed to be flexed in both directions. Other custom shapes for specialized applications are available. Typically, diaphragms are made of rubber, plastic, or fabric.

Product selection requires an understanding of the difference between diaphragm seals and diaphragms. Diaphragm seals are packaged devices that contain a diaphragm or bladder. The diaphragm, together with a fill fluid, transmits pressure from the process medium to the pressure element assembly of the instrument. Diaphragm seals may be attached directly to the instrument, or remotely connected via a capillary line. These devices are intended to keep the process medium out of the pressure element assembly and to prevent damage from corrosion or clogging.

Diaphragm suppliers can assist buyers with specifying various products. Considerations include piston diameter, up stroke, down stroke, cylinder bore diameter, cycle rate, minimum and maximum pressure, reverse pressure, minimum and maximum operating temperature, and the interval at high temperature. When selecting diaphragms, the fluid or gas that comes in contact with the product is also an important consideration.

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