Selection of pressure gauges

First, the choice of pressure gauge

01. Select according to the use environment and the nature of the measuring medium

(1) In harsh environments such as strong atmospheric corrosiveness, a lot of dust and easy spraying of liquids, closed-type all-plastic pressure gauges should be used.

(2) For dilute nitric acid, acetic acid, ammonia and other general corrosive media, acid-resistant pressure gauges, ammonia pressure gauges or stainless steel diaphragm pressure gauges should be used.

(3) Dilute hydrochloric acid, hydrochloric acid gas, heavy oil and similar media with strong corrosiveness, solid particles, viscous liquid, etc., should use diaphragm pressure gauge or diaphragm pressure gauge. The material of the diaphragm or diaphragm must be selected according to the characteristics of the measuring medium.

(4) For media such as crystallization, scarring and high viscosity, a diaphragm pressure gauge should be used.

(5) In the case of strong mechanical vibration, a shock-resistant pressure gauge or a marine pressure gauge should be used.

(6) In flammable and explosive occasions, if electrical contact signals are required, an explosion-proof electrical contact pressure gauge should be used.

(7) Special pressure gauges should be used for the following measuring media:

Gas ammonia, liquid ammonia: ammonia pressure gauge, vacuum gauge, pressure vacuum gauge;

Oxygen: Oxygen pressure gauge;

Hydrogen: Hydrogen pressure gauge;

Chlorine: chlorine-resistant pressure gauge, pressure vacuum gauge;

Acetylene: Acetylene pressure gauge;

Hydrogen sulfide: sulfur-resistant pressure gauge;

Lye: alkali-resistant pressure gauge, pressure vacuum gauge.

02. Selection of accuracy level

(1) The pressure gauges, diaphragm pressure gauges and diaphragm pressure gauges used for general measurement should be grade 1.5 or 2.5.

(2) Pressure gauges for precision measurement and calibration should be of grade 0.4, 0.25 or 0.16.

03. Selection of external dimensions

(1) The pressure gauge installed on the pipeline and equipment has a nominal diameter of φ100mm or φ150mm.

(2) The pressure gauge installed on the instrument pneumatic pipeline and its auxiliary equipment has a nominal diameter of φ60mm.

(3) For pressure gauges installed in places with low illumination, high position and difficult observation of indication values, the nominal diameter is φ200mm or φ250mm.

04. Selection of measuring range

(1) When measuring stable pressure, the normal operating pressure value should be 2/3 to 1/3 of the upper limit of the measuring range of the instrument.

(2) When measuring the pulsating pressure (such as the pressure at the outlet of the pump, compressor and fan), the normal operating pressure value should be 1/2 to 1/3 of the upper limit of the measuring range of the instrument.

(3) When measuring high and medium pressure (greater than 4MPa), the normal operating pressure value should not exceed 1/2 of the upper limit of the measuring range of the instrument.

05. Unit and scale (scale)

(1) All pressure instruments shall use legal measurement units. Namely: Pa (Pa), kilopascal (kPa) and megapascal (MPa).

(2) For foreign-related design projects and imported instruments, international general standards or corresponding national standards may be adopted.

2. Selection of transmitter and sensor

(1) When transmitting with standard signal (4~20mA), the transmitter should be selected.

(2) In flammable and explosive situations, pneumatic transmitters or explosion-proof electric transmitters should be used.

(3) For crystallization, scarring, clogging, viscous and corrosive media, flange-type transmitters should be used. The material in direct contact with the medium must be selected according to the characteristics of the medium.

(4) For occasions where the use environment is good and the measurement accuracy and reliability are not high, resistance type, inductance type remote pressure gauge or Hall pressure transmitter can be selected.

(5) When measuring tiny pressure (less than 500Pa), a differential pressure transmitter can be selected.

3. Selection of installation accessories

(1) When measuring water vapor and media with a temperature greater than 60 °C, a spiral or U-shaped elbow should be used.

(2) When measuring easily liquefied gas, if the pressure point is higher than the meter, a separator should be used.

(3) When measuring dust-containing gas, a dust collector should be selected.

(4) When measuring pulsating pressure, dampers or buffers should be used.

(5) When the ambient temperature is close to or lower than the freezing point or freezing point of the measuring medium, adiabatic or heat tracing measures should be taken.

(6) The instrument protection (temperature) box should be selected in the following occasions.

Pressure switches and transmitters for outdoor installation.

Pressure switches and transmitters installed in workshops with severe atmospheric corrosion, dust and other harmful substances.