Have you ever underestimated the seemingly simple yet profoundly significant instrument, the pressure gauge? In the chemical industry, selecting and installing pressure gauges is an intricate science. A suitable pressure gauge not only ensures accurate measurements but also impacts the safety and efficiency of the entire production process. Today, we’ll discuss some details you can’t ignore when selecting pressure gauges to help you enhance your understanding and application of these instruments, taking your expertise to the next level!
1. What Details Shouldn’t Be Overlooked When Choosing a Pressure Gauge?
Physical and Chemical Properties of the Medium The chemical properties of a substance include its behavior during chemical reactions, such as acidity, alkalinity, oxidation, reduction, thermal stability, and other characteristics. When measuring viscous or acidic/alkaline media, choose a diaphragm-type digital pressure gauge. Use stainless steel for the wetted parts according to the specific medium measured, selecting different wetted materials as necessary.
For special gases, the pressure gauge should be labeled with “oil-free” and indicate the medium measured. For ease of installation and management, choose an edged digital pressure gauge when mounted near walls and an edgeless one when mounted directly on pipelines.
Accuracy Class Accuracy class is defined by the permissible error as a percentage of the dial scale. Higher accuracy classes allow a smaller permissible error relative to the dial limit. For a larger range, gauges of the same accuracy class allow greater absolute permissible errors.
The accuracy class reflects the closeness of the reading to the actual value when compared with a high-precision digital gauge. The accuracy level, ranging from 1 (±1%) to 0.05 (±0.05%), is determined based on calibration errors.
Range For ranges below one-third of the maximum pressure, accuracy decreases, making it unsuitable for use. To ensure safe and reliable operation and extend the gauge’s lifespan, choose a range that exceeds one-third of the maximum pressure in use. For digital pressure gauges, selecting a range from one-third to two-thirds of full scale provides the best accuracy and stability under steady and fluctuating loads. The upper limit should not exceed three-fourths of the range.
2. How to Install a Pressure Gauge?
Before installation, calibrate the pressure gauge and ensure it is qualified for use. The gauge should be fixed to a specially processed fitting with a gasket and not directly attached to the valve with packing. Install the gauge in an accessible location for maintenance and operation.
For horizontal sections of the connecting pipe, maintain a certain slope to facilitate drainage of condensate or gas. If the medium is gas, the pipe should slope down toward the pressure source. If the medium is liquid, it should slope toward the gauge. For small differential pressures, a steeper slope is preferable.
Additionally, if there are bends in the piping, install drainage or venting devices at low and high points, respectively, to prevent condensate or gas buildup from affecting measurement accuracy. Drain or vent regularly to maintain accuracy.
Install the gauge vertically relative to the horizontal plane. Ensure the measurement point and installation point are level to avoid errors from height differences. Keep the distance between the installation and measurement points as short as possible to prevent delayed readings. Ensure a good seal without leaks, especially for flammable, explosive, toxic, or harmful media.