Diaphragm seals also known as pressure diaphragms are used in industrial applications to protect pneumatic or electronic measuring devices.
Different mounting techniques of diaphragm seals are adopted in certain applications for specific reasons. The selection of diaphragm seals is related to the desired performance and functionality of the device.
Diaphragm seals are used in various industries to protect pressure instruments such as pressure gauges, transmitters, and switches from the process media they are measuring.
These seals act as a barrier between the instrument and the corrosive, abrasive, liquids comprising particles or high-temperature process fluid. There are several mounting techniques for diaphragm seals, each suitable for specific applications and requirements.
Common materials used for the construction of diaphragm seals are
Diaphragm seals are generally constructed using the above materials that are compatible with process fluids.
The fill fluid used inside diaphragm seals depends on the specific application and compatibility with the process fluid.
The most important factor regarding diaphragm seal performance is the integrity of the filled system. Regardless of proper diaphragm seal size and proper fill fluid selection, the filled system should not contain air packets.
Here below are two liquids used commonly apart from a few others.
Some common mounting techniques for diaphragm seals can be found below.
The choice of mounting depends on the specific application, process conditions (Corrosive, Hot, Clogging, Sanitary), and required maintenance.
In this technique, the diaphragm seal is directly connected to the process pipe or vessel. This is the simplest and most common mounting technique. It is suitable for most applications where the process conditions are not too extreme.
The pressure instrument connects directly to the seal via a threaded connection or a flange. It is in closer proximity to the source of the pressure source.
When the process conditions are extreme, such as high temperatures, corrosive fluids, or high vibration levels, remote mounting is employed.
The diaphragm seal is located away from the pressure instrument, and a capillary tube or a filled system is used to transmit the pressure from the seal to the instrument. This protects the instrument from the harsh process environment.
In some applications, a longer diaphragm seal is used to separate the instrument from the process fluid. This is especially useful when the instrument needs to be positioned farther from the process connection.
Extended Diaphragm Seals are available in various lengths to accommodate different installation requirements.
Instead of using threaded connections, diaphragm seals can be mounted using flanges. Flange mounting provides a secure and leak-free connection between the seal and the process pipe or vessel. It is commonly used in applications where a high level of sealing integrity is required.
The term “flange mounting” refers to how the transmitter is installed in a system. In a flange-mounted configuration, the transmitter is typically attached to a flange on the vessel or pipe that contains the process fluid.
The threaded-mounted diaphragm pressure or level transmitter is a specific type of sensor used in industrial settings to measure either pressure or liquid level.
Threaded diaphragm seals have threads on both ends or at one end permitting them to be directly screwed onto the process connection and the pressure instrument. This method is straightforward and suitable for many applications.
The choice of mounting technique depends on factors such as the process conditions, the type of process fluid, and the distance between the instrument and the process connection. It’s important to select the appropriate mounting technique to ensure the accuracy and reliability of pressure measurements and to protect the pressure instrument from the harsh conditions of the process fluid.
The selection of threaded diaphragm depends on the need for maintenance or replacement.
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