This article specifies the proper selection and installation of pressure gauges, with key technical and operational guidelines for accurate measurement and safe on-site application.
Have you ever underestimated the pressure gauge—this seemingly simple yet profoundly significant instrument? In the chemical industry, selecting and installing pressure gauges is a sophisticated discipline. A properly chosen pressure gauge isn’t just about measurement accuracy; it’s also critical to the safety and efficiency of the entire production process. Today, we’ll dive into the unignorable details of pressure gauge selection, helping you fully enhance your understanding and application of pressure gauges, so you can take a bigger step forward in your professional journey!
Key Details Not to Be Ignored in Pressure Gauge Selection?
1. Physical and Chemical Properties of the Medium
Chemical properties refer to the characteristics exhibited by a substance during chemical changes. Examples include the general chemical properties of the substance category: acidity, alkalinity, oxidizability, reducibility, thermal stability, and other specific properties.
When a pressure gauge is used to measure viscous, acidic, alkaline, or other special media, a diaphragm-type digital pressure gauge should be selected. The wetted material is stainless steel, and different wetted materials should be chosen according to the measured medium.
For special gases, the words "Oil-Free" should be marked on the pressure gauge, along with the measured medium. Considering the installation location and ease of observation and management, a digital pressure gauge with a bezel should be selected when installed against a wall; a digital pressure gauge without a bezel should be used when directly installed on a pipeline.
2.Accuracy Class
Accuracy class is classified by the percentage of the allowable error relative to the full-scale value of the dial. The higher the accuracy class number, the larger the allowable error relative to the full-scale limit value of the dial. For the same accuracy class, the larger the measuring range, the greater the absolute allowable error of the measured pressure value.
The accuracy class of a pressure gauge reflects the degree of proximity between the indicated value and the true value when the tested gauge is compared with a high-precision digital pressure gauge. Its value is equal to the percentage of the absolute value of the maximum basic error to the upper limit of measurement, determined by the magnitude of the error generated during calibration.
Pressure gauges are divided into 5 accuracy classes: Class 1, Class 0.4, Class 0.2, Class 0.1, and Class 0.05. The allowable errors are ±1%, ±0.4%, ±0.2%, ±0.1%, and ±0.05% respectively.
3. Measuring Range
The accuracy of the range below 1/3 of the maximum pressure is relatively low and should not be used.
When selecting the upper limit of the digital pressure gauge's measurement range, to ensure the safe and reliable operation of the digital pressure gauge and extend its service life, the range should generally be greater than 1/3 of the maximum operating pressure.
When choosing the range of the digital pressure gauge, considering the versatility of the pressure-bearing condition of the digital pressure gauge, it is advisable to select 1/3 to 2/3 of the full range. This pressure range offers high accuracy and can be used under both stable and fluctuating loads. The maximum operating range shall not exceed 3/4 of the full scale.
How to Install a Pressure Gauge?
1. Before installation, the pressure gauge should be calibrated and can only be installed and used if qualified. During installation, the pressure gauge should be fixed on a specially processed joint with a gasket; do not use hemp thread winding or directly attach it to the valve. The pressure gauge should be installed in a location convenient for operation and maintenance.
2.The horizontal section of the connecting pipe should have a certain slope to facilitate the discharge of condensed liquid or gas.
When the measured medium is gas, the pipe should slope downward toward the pressure tapping port;
When the measured medium is liquid, the pipe should slope upward toward the pressure measuring instrument;
When the measured parameter is a small differential pressure value, the slope can be slightly increased.
In addition, if the pipe has bends up and down, a device for draining condensed liquid should be installed at the lowest point or an air vent device at the highest point according to the medium in the pipe, to ensure that the measurement accuracy is not affected by the accumulation of condensed liquid or gas in the pipe for a long period of time. Condensed liquid or gas should be discharged regularly.
3.The instrument’s measuring point shall be at the same horizontal level as the installation position of the instrument; otherwise, correction for the additional height error shall be taken into account. The distance between the instrument installation position and the measuring point shall be kept as short as possible to avoid slow response of the indication. Ensure tightness of the whole system and prevent any leakage, especially when the medium is flammable, explosive, toxic or harmful gas.
Model Selection
|
Model
|
Specifications
|
Nominal Diameter
|
|
Y-100
|
Radial, without bezel
|
100mm
|
|
Y-100T
|
Radial, with rear bezel
|
100mm
|
|
Y-100Z
|
Axial, without bezel
|
100mm
|
|
Y-100ZQ
|
Axial, with front bezel
|
100mm
|
|
Y-100TQ
|
Radial, with front bezel
|
100mm
|
|
Y-150
|
Radial, without bezel
|
150mm
|
|
Y-150T
|
Radial, with rear bezel
|
150mm
|
|
Y-150Z
|
Axial, without bezel
|
150mm
|
|
Y-150ZQ
|
Axial, with front bezel
|
150mm
|
|
Y-150TQ
|
Radial, with front bezel
|
150mm
|
Code Explanation:
Y - Pressure
Z - Vacuum (represents axial when after the number)
B - Standard (Explosion-proof)
J - Precision
A - Ammonia gauge
X - Signal (Electrical contact)
P - Diaphragm
E - Capsule
F - Corrosion-resistant (Stainless steel)
XC - Magnetic-assisted electrical contact
N - Shock-resistant
T - Bourdon tube
Examples:
YTF - Stainless steel Bourdon tube pressure gauge
YA - Ammonia pressure gauge
YXC - Magnetic-assisted electrical contact pressure gauge
YZ - Vacuum pressure gauge
YN - Shock-resistant pressure gauge
YTP - Diaphragm Bourdon tube pressure gauge
