Membrane separators are essential accessories for pressure gauges. Their primary function is to protect the pressure sensor from harsh operating conditions. They are located between the working fluid and the sensitive element of the pressure gauge, transmitting the fluid pressure through a thin metal diaphragm to the intermediate fluid and then to the measuring mechanism.
In many industrial applications, process fluids can be corrosive, hot, dirty, viscous, or contain solid particles . When these fluids come into direct contact with the pressure gauge’s sensing element, there is a risk of rapid wear, corrosion, clogging, or contamination of the sensor . Diaphragm seals solve this problem.
General structure of the flood protection line
Flood protection membranes consist of several main parts:
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body
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The main body, which contains all the components, is usually made of stainless steel (316L or 304).
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membrane
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A very thin, flexible metal plate that absorbs the fluid pressure and transfers it to the intermediate fluid.
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Membrane materials such as stainless steel, Hastelloy, tantalum, Monel or even fluoroplastic coatings such as PTFE can be used to ensure high chemical resistance.
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Liquid filling
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A special fluid fills the space between the diaphragm and the pressure gauge element and is responsible for pressure transmission.
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Such a fluid is usually silicone, glycerin, fluorinated oil or another heat-resistant fluid.
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Technological connection
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The connection point of the sealing membrane to the process line or vessel can be a threaded connection, a flange connection or a clamp connection (e.g. Tri-Clamp in the food industry).
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Functional principle of a membrane separator
When the pressure of the working fluid acts on the surface of the diaphragm, it deforms slightly. This deformation transfers the pressure to the interstitial fluid behind it. The interstitial fluid transmits the pressure and displays it on the internal mechanism of the pressure gauge, without the fluid coming into direct contact with the sensitive element.
This avoids direct contact between the process medium and the pressure sensor and the measuring element remains completely insulated.
Use of membrane separators in industry
Membrane separators are used in almost all industries where certain liquids are used:
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Chemical and petrochemical industry
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It is used to measure the pressure of acids, alkalis, corrosive solvents and toxic liquids.
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Food and pharmaceutical industries
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Avoid contamination of the product and ensure hygiene (use hygienic connections such as Tri-Clamp).
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Oil and gas industry
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Under high pressure conditions and aggressive liquids such as H₂S.
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Pulp and paper industry
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For thick, viscous liquids that can clog small openings.
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Power plants and heavy industry
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Suitable for very hot steam or high temperature liquids.
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Advantages of using membrane separators
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Completely protects sensitive pressure gauge components from corrosion and mechanical damage.
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Prevents blockages and contamination of fluid channels.
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It can measure the pressure of high viscosity liquids or liquids containing solid particles .
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Extend the lifespan of your measuring devices and reduce repair costs.
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Thanks to the CIP/SIP design, it can be used in healthcare facilities.
Important points when choosing the right sealing membranes
When selecting a waterproofing membrane, the following factors should be considered:
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Type of process fluid
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The most important parameters are the chemical composition, viscosity, corrosivity and temperature of the liquid.
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Working pressure range
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The mechanical strength of the membrane must be guaranteed over the pressure range.
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Membrane and valve body materials
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By choosing the right material, chemical and mechanical damage can be avoided.
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Type of process connection
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Use threads, flanges, or installation methods in accordance with pipe standards.
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Liquid filling
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The selection should be made according to the temperature range and the properties of the liquid so that volume changes or evaporation of the intermediate liquid do not lead to errors.
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Maintenance and repair of membrane seals
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Check the diaphragm regularly to ensure there are no leaks or deformations.
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Avoid excessive shock and pressure on the membrane.
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If you notice bubbles or a change in the color of the fluid, replace the filling fluid.
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Carry out regular cleaning in a hygienic environment according to CIP standards.
Finally
Sealed diaphragm pressure gauges are an important tool for increasing the durability, accuracy, and efficiency of pressure measurement systems in harsh industrial environments. Selecting appropriate materials, designs, and connection types can improve device performance and significantly reduce maintenance costs. These devices meet pressure measurement accuracy requirements while providing comprehensive protection for sensitive equipment.