Strange behavior of diaphragm pressure gauges – seeking expert help
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This post was last edited by sun_sjq on 2015-11-28 at 16:43. Our company purchased flanged diaphragm pressure gauges; after installing them using standard graphite metal wound gaskets, we noticed that the zero point shifted slightly upward. The zero point returned to normal as soon as the flange was loosened. Upon close inspection, it was found that the area where the diaphragm is under pressure is a central depression, making it completely impossible to come into contact with the sealing surface of the gasket. It is unclear why an increase in flange compression leads to a slight rise in pressure, of about 0.005 MPa. Could experts analyze the reasons and suggest solutions? Incidentally, another observation is that the flange surface at the pressure gauge end exhibits a slight, uniform inward slope; this slope was formed as a result of deformation even after the gasket was compressed.
This is a normal phenomenon; after installation, it is necessary to make fine adjustments to the pressure gauge to zero it out. Loosen a small screw slightly to reset the pointer, then tighten it.
The first two people are right; you can try opening the root valve in front of the pressure gauge – that should allow it to return to zero.
The sealing surface is inclined. One possible reason is that there is an issue with the material of the flange – the stress applied is insufficient; another reason could be a problem with the design of the flange’s sealing surface, specifically an insufficient thickness of the RF protrusion. The presence of pressure readings indicates that there is indeed force acting on the diaphragm. To ensure that there is no pressure at the ports, it is necessary to check whether any external forces are acting on the diaphragm