How To Prevent Liquid-Filled Pressure Gauges From Leaking?
Leave a message
The inside of the case of a liquid-filled pressure gauge is filled with a specific liquid (usually glycerin or silicone oil). The internally filled liquid can effectively buffer the mechanical vibrations from the working environment and the pressure pulsation of the measured medium, protect the precision measuring mechanisms (such as spring tubes and transmission gears) inside the pressure gauge from damage, and improve the stability of the pointer and the accuracy of readings. However, once the internal filling fluid leaks, not only will all the above-mentioned protective functions be lost, resulting in a decrease in measurement accuracy and a shortened instrument life, the leaked liquid may also pollute the working environment or affect peripheral equipment. Therefore, this article will focus on effective measures to prevent leakage of liquid-filled pressure gauges.
Correct selection
Selecting a pressure gauge suitable for a specific application is fundamental to preventing leaks. First, it must be ensured that the material of the pressure gauge will not be corroded by the medium being measured. For example, for corrosive media containing chloride ions or ammonia, avoid using 304 stainless steel spring tubes and choose materials with better corrosion resistance such as 316L stainless steel or Hastelloy or tantalum. Some highly acidic environments require the use of non-metallic materials such as polytetrafluoroethylene (PTFE) as sealing components. Otherwise, even if the pressure gauge has no abnormality in the short term, long-term immersion in corrosive media will cause its seal to rupture.
Secondly, the temperature range of the working environment must also be within the allowable range of the pressure gauge. Excessive ambient temperature will cause the volume of the sealing ring to expand and the pressing force to decrease; while in a low-temperature environment, the sealing material will undergo vitrification, become brittle and lose elasticity, and thus crack.
In addition, the range of the selected pressure gauge should be appropriate. It is generally recommended that the working pressure is between 1/3 and 2/3 of its full scale. Avoid long-term operation at high pressure or close to full scale, which will bring excessive and continuous stress to internal sensitive components and seals, accelerate their aging, and increase the risk of leakage.
Finally, for situations where vibrations are particularly severe, it should be evaluated whether the seismic resistance level of the liquid-filled pressure gauge is sufficient. When necessary, elastic mounting bases, rubber damping rings, external vibration isolation devices, etc. can be installed to minimize loosening of connections and leakage of filling fluid caused by long-term micro-movement.
Whether the installation process of the pressure gauge is standardized will also affect whether the filling fluid will leak. Improper installation practices are often the main cause of leaks occurring soon after a new meter or repair. During installation, it is necessary to ensure that the connecting threads are clean and intact. Avoid using a wrench to tighten directly on the watch case. Instead, use a suitable wrench to clamp the instrument joint (usually square or hexagonal) to apply force to prevent internal structural deformation or seal dislocation caused by torsion of the watch case.
The sealing treatment of threaded joints is also very important. Appropriate sealing materials should be selected according to the medium properties and pressure levels, such as polytetrafluoroethylene (PTFE) raw tape or special thread sealant. When winding the raw material tape, pay attention to the correct direction (tightening direction along the thread) and the uniform and moderate thickness. If it is too thick, it may cause excessive stress on the joint, and if it is too thin, the sealing will not be tight. When applying sealant, apply it evenly to avoid clogging the pressure channels.
