The selection of pressure gauges should be based on the requirements for pressure measurement in the process and production process, combined with other aspects, and comprehensively considered and specific analysis. Generally, the following issues should be considered: the selection of the instrument type, the determination of the measuring range of the instrument, and the instrument Selection of accuracy level and consideration of use environment and media performance.
1.Selection of range
The selection of the range determines the range of the instrument according to the size of the measured pressure. For elastic pressure gauges, when measuring stable pressure, the maximum pressure value should not exceed 3/4 of the full range, when measuring fluctuating pressure, the maximum pressure value should not exceed 2/3 of the full range, and the lowest measured pressure value should not be lower 1/3 of the full scale.
2.Precision selection
Accuracy selection, according to the maximum measurement error allowed by production, determine the accuracy level of the instrument on the principle of economy and practicality. 1.5 or 2.5 grades for general industrial pressure gauges are sufficient.
3.Considering the use environment and media performance,
The environmental conditions are harsh, such as high temperature, corrosion, humidity, vibration, etc. The properties of the measured medium such as temperature, corrosiveness, crystallization, flammability, and explosion. To determine the type and model of the pressure gauge.
4.Selection of the shape of the pressure gauge
The choice of the shape of the pressure gauge: The pressure gauge indicated on the spot generally has a surface diameter of 100mm. In the case of higher standards or poor lighting conditions, the diameter of the surface is 200~250mm, and the diameter of the disc-mounted gauge is 150mm.
The selection of the pressure measuring point should reflect the true size of the measured pressure.
① Choose the part of the pipe where the measured medium flows in a straight line. Don't choose the pipe bends, bifurcations, dead ends or other places where vortexes are easily formed.
② When measuring the pressure of the flowing medium, the pressure taking point should be perpendicular to the flow direction, and the inner end of the pressure taking pipe should be kept flush with the inner wall of the connection point of the production equipment, and there should be no protrusions or burrs.
③ When measuring the pressure of liquid (gas), the pressure point should be at the lower (upper) part of the pipe so that no gas (liquid) accumulates in the pressure guiding tube.
Pressure guiding pipe laying
① The thickness of the pressure guiding tube should be appropriate, generally the inner diameter is 6-10mm, the length should be as short as possible, and the longest should not exceed 50m to reduce the slowness of the pressure indication. If it exceeds 50m, a pressure gauge capable of long-distance transmission should be used.
② When the pressure guiding tube is installed horizontally, the inclination of 1:10～1:20 should be ensured to facilitate the discharge of the liquid (or gas) accumulated in it.
③ When the measured medium is easy to condense or freeze, an insulation heat tracing pipeline must be installed.
④ A shut-off valve should be installed between the pressure port and the pressure gauge to prepare the pressure gauge for maintenance. The shut-off valve should be installed near the pressure tap.
Installation of pressure gauge
① The pressure gauge should be installed in a place where it is easy to observe and repair.
②The installation site should avoid the influence of vibration and high temperature.
③When measuring the steam pressure, a condensate pipe should be installed to prevent the high temperature steam from directly contacting the pressure measuring element.
The above information is provided by pressure gauges supplier.
