What gauge valves and diaphragm seals are for
The pressure gauge is the most sensitive part of a measuring point. Without a valve, every replacement or calibration means draining the installation, and without protection, pulsation, steam and aggressive media quickly destroy the Bourdon tube. Correctly chosen accessories extend the life of a gauge several times over, improve operator safety and allow instruments to work on media they would not otherwise be suitable for.
Products in the Fadip range
Gauge cocks (DIN 16261, DIN 16262 and DIN 16263), two-way and three-way, in brass, are designed for pressures from 6 to 25 bar and medium temperatures up to 60 °C, on water, air and neutral gases.
Type A gauge valves (DIN 16270, DIN 16271 and DIN 16272) work at 250 to 400 bar and temperatures up to 120 °C, or up to 200 °C on request. Type B needle gauge valves withstand 400 bar and 232 °C. Both are available in brass or stainless steel.
The stainless steel two-valve manifold combines an isolating and a vent valve in one body, for pressures up to 400 bar and temperatures up to 240 °C. It is used when the instrument needs to be safely depressurised and checked on site.
Siphons (syphon tubes) to DIN 16282, in U and O (pigtail) form, protect the gauge from steam heat and pulsation. Galvanised steel siphons are rated to 60 bar and stainless steel ones to 100 bar, at medium temperatures up to 300 °C.
Diaphragm seals separate the medium from the gauge: versions with threaded process connection and PTFE coated for aggressive and contaminated media (-1 to 160 bar, stainless steel or titanium diaphragm), versions with threaded connection for pressures up to 600 bar, and hygienic versions with clamp connection and hygienic threaded connection for the food industry (up to 40 bar and 140 °C).
How to choose a valve or diaphragm seal
Start with pressure and temperature: gauge cocks are for low pressures and cold media, Type A and Type B valves for hydraulics, steam and high pressures, and manifolds for process installations where the instrument is checked without removal. The medium determines the material: brass for water, air and oil, stainless steel for aggressive and food-grade media.
For steam and hot media, a siphon must always be fitted between the valve and the gauge; condensate collects in it and protects the measuring system from heat. For viscous, crystallising, contaminated or aggressive media a diaphragm seal is used, and for hygienic processes a sanitary connection with no dead zones. The connection (1/4" or 1/2", BSP or NPT) must match both the process and the gauge.
Technical specifications
Connections range from 1/4" to 1/2" BSP or NPT. Gauge cocks work from 6 to 25 bar, Type A valves from 250 to 400 bar, and Type B valves and two-valve manifolds up to 400 bar, at medium temperatures up to 120, 232 and 240 °C respectively. Siphons have a nominal size of 3/8" to 1/2" and work up to 300 °C. Diaphragm seals cover ranges from vacuum to 600 bar, with a stainless steel or titanium diaphragm, and hygienic versions work up to 140 °C.
Applications by industry
In hydraulics and on high pressure power units, gauge valves up to 400 bar are used. Power generation, boiler houses and district heating rely on siphons and steam valves. The chemical and petrochemical industries use PTFE and titanium diaphragm seals and stainless two-valve manifolds, while the food and pharmaceutical industries use hygienic clamp and threaded connections. In water supply, heating and compressor stations, brass gauge cocks are the standard.
A complete measuring point from one supplier
Because Fadip manufactures pressure gauges, we supply the valve, siphon or diaphragm seal assembled and tested together with the gauge, with a calibration certificate from our accredited laboratory. You get one item, one warranty and the certainty that threads, ranges and materials all match.
See also our pressure gauges, thermometers and pressure transmitters.
For a quotation, send us the medium, working pressure, temperature, process connection and gauge type. Our technical team will recommend a suitable solution within 24 hours. Contact us.
