How to choose right pressure gauge?
In order to correctly define pressure gauges, it is necessary to know in what conditions the exploitation takes place as well as the basic technical characteristics of the gauges. The most important characteristics for defining are:
– the measurement range, the highest operating pressure of the fluid should be in the second-third zone of the scale (display range) of the gauge. In higher pulsed fluid pressures, the measurement area must be in the first half of the scale. For example, if the maximum operating pressure is 10 bar, a pressure gauge of 16 bar should be selected.
– Diameter – size of gauge. Standard dimensions are ø40, ø50, ø63, ø80, ø100, ø160 and ø250 mm
– Accuracy class (percentage of error allowed throughout the measurement range)
– Ø 40mm…………………………………….kl.2,5%
– Ø50, Ø63, Ø80 (Ø 100) mm………kl.1,6% i kl.2,5%
– Ø100, Ø160 mm………….…kl.1% i kl.1,6%
– The position of the connection can be:
– radial / lower, along the periphery of the case
– axial / back, behind the axis of the hand
– Connection thread (In Europe, the most commonly used is tubed, so-called “Whitworth” thread with markings G (if cylindrical) and R (if conical / self-sealing), while in the USA is used the NPT thread.) The standard sizes depend on the size of the manometer. The most commonly used are: 1/8 “, 1/4”, 3/8 “, 1/2”. The thread may also be a metric M.
– Whether the measure is exposed to vibration and pressure pulsation. In this case, the gauge should be filled with glycerine and with a built-in choke. In the case of mechanical vibrations, it is recommended to install membrane capillary manometers.
– The type of fluid directly influences the selection of the material. If the pressure gauge is in an aggressive environment, it is recommended that gauge should be made of stainless material.
– For measuring dense and soiled fluids the membrane manometers are used.
– The elevated temperature of the fluid and the working environment disturbs the declared characteristics of manometers. The influence of hot working fluid T <150ºC is eliminated or reduced by the installation of a compensation tube, a siphon, between the gauge and the installation.
– If the gauge needs to be additionally verified, verification may be carried out in an officially accredited laboratory with the issuance of a certificate and the mark on the product.