Pressure sensors for ammonia refrigerants

Pressure measurement sensors from AST are supplied for all refrigeration system requirements, including sensors for use on ammonia refrigerants

American Sensor Technologies (AST) offers a variety of pressure measurement sensors for integration into HVAC and refrigeration equipment.

The AST sensors have a one-piece, stainless steel construction that contains no internal seals or gaskets.

Additional features include a high cyclical life (>100 million full cycles), long-term stability and compound ranges with linear output through zero (i.e from -14.7 to +100PSI).

Each product ensures a high level of EMI/RFI protection, in addition to holding hazardous area approvals [for equipment installed in classified locations], RoHS compliance [when requested] and is listed under UL/cUL standards.

Due to customer demands, AST is responding to ammonia refrigeration pressure measurement requirements.

Refrigeration pump and compressor manufacturers are moving towards the improved efficiency of ammonia over Freon-based systems.

However, the thermodynamic behaviour of ammonia is very different from Freon.

When the refrigeration pump turns on, the ammonia temperature rapidly changes from 100F to -70F or below.

This accelerated change, along with the type of sensor diaphragm materials affects the pressure transducer performance and ultimately the control system.

O-ring sealed pressure sensors cannot withstand rapid thermal changes and over time the internal O-ring will fail.

Fluid filled sensors suffer from freezing effects, which lead to the rupture of the diaphragm membrane.

Thin film sensors [based on 15-5 and 17-4PH stainless steels] that have their diaphragm welded to a pressure port, will undergo thermal stresses that will eventually crack the steel.

Thermal Flash Protection is the technology applied by AST to reduce the effects of thermal flash transients when the medium is ammonia.

First, AST uses its one-piece stainless steel sensing element with 316L-wetted materials.

This element is free of welds, oil-fill and internal O-rings.

Next, a special non-clogging port design is used in order to minimise the extreme temperature change.

The sensor will recognize a uniform temperature as to maintain system stability.

To conclude, Thermal Flash Protection is the pressure sensing technology for ammonia refrigeration applications.

AST offers other HVAC/R solutions including an SAE4 (7/16-20 UNF) female pressure port that contains an internal Schraeder depressor pin.

This port allows the sensor to be easily removed or installed in service, eliminating the need for adaptors.

AST also manufactures additional pressure ports, such as 1/8'' NPT, 1/4'' NPT and SAE4 male.

Common applications for AST products are refrigeration pump controls, chillers, Freon and Ammonia cooling systems, high-pressure wells, boiler controllers and environmental testing.

For more information on pressure measurement, please visit our website or contact the factory direct.

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