What Are The Differences Between Different Types Of Refrigerant Pressure Gauges?

Different types of refrigerant pressure gauges differ significantly in structure, accuracy, and application scenarios. Correctly distinguishing and selecting them is crucial for the safe operation of refrigeration systems. The following table summarizes the key differences between the main types for quick comparison.

Classification Dimensions

Type

Core Features and Application Scenarios

Key Differentiators

Working Principle

Mechanical Pressure Gauges

Using mechanical components such as a Bourdon tube to drive the pointer, they offer a simple structure, high reliability, and require no power, making them suitable for most routine maintenance scenarios.

Relying on a physical structure, they offer strong interference resistance but relatively low accuracy. Digital pressure gauges offer high accuracy, multiple functions, and rely on power.

Digital Pressure Gauges

Convert pressure signals into digital signals, providing accurate and intuitive readings and a wide measurement range. They often include advanced features such as data logging and unit conversion, making them suitable for high-precision testing and data analysis.

Range and Applications

High-Pressure Gauges

The upper range limit is typically 3.8 MPa (approximately 38 kg/cm²). They are used to monitor the pressure on the compressor discharge side (high-pressure side). The gauge case is often red.

Different ranges have distinct measurement locations and functions, and they cannot be used interchangeably.

Low-pressure gauges

The upper range limit is typically 1.8 MPa (approximately 18 kg/cm²). They are used to monitor the pressure on the suction side (low-pressure side) of compressors. The case is often blue.

Environmental adaptability

Ordinary pressure gauges

Suitable for environments free of vibration or pulsation, and for measuring refrigerants that are non-corrosive to copper or copper alloys.

Vibration-resistant gauges resist vibration through liquid filling and optimized structure; stainless steel gauges are more corrosion-resistant.

Vibration-resistant pressure gauges

The case is filled with a damping fluid such as glycerin or silicone oil, which effectively absorbs environmental vibration and pressure pulsations, protecting the internal movement and ensuring stable pointer readings. They are suitable for applications subject to severe vibration, such as compressors. Vibration resistance ratings include V.H.4 and V.H.5.

Stainless steel pressure gauges

Wetted parts (such as the spring tube and fittings) are made of 304 or 316 stainless steel, making them suitable for measuring highly corrosive media or in harsh external corrosive environments. They offer excellent versatility, wide application, and a long service life.

Specialty Media

Diaphragm-Sealed Pressure Gauge

A chemically sealed diaphragm isolates highly viscous, easily crystallized, or highly corrosive media from the Bourdon tube at the heart of the pressure gauge, preventing clogging or corrosion.

Designed specifically for special and demanding media, it provides isolation and protection.

Understanding the Dial: The Correspondence Between Pressure and Temperature

The unique and key value of a refrigerant pressure gauge lies in the fact that its dial not only displays the pressure scale but also the temperature scale for various refrigerants. This is because in a refrigeration system, the saturation pressure and saturation temperature of a refrigerant during evaporation or condensation are uniquely correlated.

How to Read: For example, when reading a low-pressure gauge from the outside in, the first circle typically displays the pressure value (in MPa). From the second circle onward, the corresponding saturation temperature value (in °C) for each refrigerant at that pressure is displayed. These values are often color-coded, for example, green for R22 and red for R134a.

Practical Application: Maintenance personnel can directly read the saturation temperature of the refrigerant in the evaporator or condenser by measuring the system pressure. For example, a chiller using R22 has a low operating pressure of 0.4 MPa. By checking the R22 temperature scale on the dial, you can tell that its evaporation temperature is approximately 0°C. This is the key basis for determining whether the system is operating properly (e.g., whether the refrigerant charge is appropriate and whether the heat exchange performance is good).

How to Accurately Select a Pressure Gauge Based on Operating Conditions

Selecting the appropriate pressure gauge for different operating scenarios is essential for ensuring accurate and safe measurements.

Matching Refrigerant Types

The first rule is to ensure that the pressure gauge dial indicates the refrigerant type you are measuring (e.g., R410A, R32, etc.). Different refrigerants have different pressure-temperature characteristic curves, so mixing them is strictly prohibited. For example, the operating pressure of R410A is 50%-60% higher than that of R22. Using an R22 pressure gauge to measure an R410A system can result in serious reading errors and even lead to safety accidents.

Evaluating Environmental Conditions

Vibration Environment: Vibration-resistant pressure gauges must be used near vibration sources such as compressors and pumps. The damping fluid filled in the housing effectively stabilizes the pointer and protects the internal movement from damage.

Corrosive Environments: If the measured medium is corrosive (such as ammonia/R717) or in a humid or chemically charged environment, select a pressure gauge with stainless steel wetted parts. For example, when measuring ammonia, a pressure gauge made of 316Ti/316L stainless steel is essential, as ammonia reacts with copper and copper alloys.

Determining Accuracy and Range Requirements

Accuracy Grade: For general maintenance, a Class 1.6 or 2.5 pressure gauge can be selected; for precision commissioning or as a reference gauge, a Class 0.4 or higher accuracy gauge should be selected.

Range Selection: Normal operating pressure is recommended to be between 1/3 and 2/3 of the pressure gauge's range. For example, if the system's normal high pressure is 2.0 MPa, a high-pressure gauge with a range of 0-3.8 MPa is appropriate.

Quality Identification and Routine Maintenance

A high-quality pressure gauge requires proper use and maintenance.

Key Quality Identification Points: High-quality pressure gauges are constructed from pure SS304 stainless steel and 59-1 brass. Laser welding ensures airtightness better than manual welding. Each gauge undergoes rigorous pressure-holding testing and vacuum treatment to ensure performance and negative pressure indication capability.

Daily Maintenance Recommendations: Clean the dial regularly with a soft cloth to maintain legibility. Handle with care and avoid severe impact. Perform regular calibration. The recommended interval is generally one year, though this interval should be shorter for critical applications or harsh environments.

Summary and Key Notes

In general, selecting a refrigerant pressure gauge is a systematic decision-making process, focusing on medium compatibility, operating conditions, and satisfactory accuracy. One important caveat: Use a dedicated pressure gauge for each refrigerant; mixing is strictly prohibited. Understanding the pressure-temperature relationship shown on the dial is essential for effective pressure gauge troubleshooting.

We hope this detailed comparison will help you make the right choice. If you have a specific refrigeration system (such as automotive air conditioning, industrial chiller) or refrigerant (such as R32, R290) you would like to know more about, we can continue to discuss it in depth.