A bellows consists of several capsules. The capsule consists of two circular wound membranes (usually stainless steel) which are tightly sealed around the circumference. Bellows members consist of tubular membranes wound around the circumference. The membrane is attached at one end to the source and at the other end to a display or instrument. The bellows member can provide a long range of travel (stroke) in the direction of the arrow when pressure is applied. Bellows and individual capsules are used in many instruments. They are very useful for measuring small pressures.
Pressure Switch Bellows
Liquid filled temperature switches include a probe and a bellows element. The lamp is immersed in the process whose temperature is regulated. The bellows element detects the fluid pressure (liquid or gas) as the temperature rises in the process. The liquid in the sensor bulb responds to temperature fluctuations and increases the pressure in the bellows element as the temperature rises. An increase in the sensor bulb temperature compresses the bellows and moves the main spindle upward until the spring force and the bellows pressure are in equilibrium. This movement of the spindle is transmitted to the switch and causes depending on the setpoint of the temperature switch on or off operation.
You can not talk about metal bellows without considering the Quality Pressure switch manufacturers best manufacturing methods. All important performance parameters depend on how the bellows is molded or welded. Let's look pressure switch types. Two most common manufacturing methods are:
Seamless hydroformed bellows
Seamless Hydroformed Bellows
As the name suggests, seamless metal bellows expansion joints have no welded joints. Instead, they are produced in a multi-stage deep-drawing process. A second hydroforming step forms the folds. The thermoforming and hydroforming processes can maintain consistent dimensional tolerances.
For example, the wall thickness variation of a well-controlled deep drawing process is within ± 0.0001 inches.
In high volume applications requiring small package size and precise spring rate, seamless bellows are by far the most popular choice. These applications include many types of equipment, HVAC and industrial controls and sensors.
Seam-welded formed bellows
Manufactured from rolled, welded and formed sheet material, seam welding is characterized by the cost-effective production of large diameter bellows. Diameters of up to eight inches are not uncommon and would be costly with seamless deep drawing manufacturing processes. Welded bellow seal manufacturers design Seam welded bellows can also be made in any desired length. And they have low initial tooling costs.
Seam welded bellows are therefore ideal for applications where a large, low-cost bellows is needed, such as: B. Compensators or other connections that compensate for the movement of mating components.
However, seam welding bellows are not suitable for applications requiring a very accurate spring rate. The reason for this is that their wall thickness tolerances are determined not by the precision thermoforming process, but by the sheet metal material. The typical wall thickness variation for seam welded models is ± 0.0005 inches, or about five times more than a seamless bladder.
Pressure Switch Bellows Working Principle
The bellows pressure is a one-piece, collapsible, seamless metal unit that has deep folds of very thin-walled tubes. The diameter of the bellows ranges from 0.5 to 12 inches and can have up to 24 folds. The system or line pressure is applied to the inner volume of the bellows. As the input pressure to the instrument varies, the bellows expands or contracts. The movable end of the bellows is connected to a mechanical connection arrangement. As the bellows and hinge assembly move, either an electrical signal is generated or a direct pressure indication is provided. The flexibility of a metallic bellows is similar to that of a helical wound compression spring. Up to the elastic limit of the bellows, the ratio between load and deflection steps is linear.
Pressure Switch bellows Applications in Various Industries
Pressure switches can generally be used in any application where electrical contacts must be opened or closed in response to a system pressure change within the electrical and pressure values of the switch. Pressure switches are used in a variety of applications such as the following:
- Compressed air systems
- HVAC equipment
- Pumping systems
- Process equipment etc.
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