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Uses and Benefits of Filling Fluids in Pressure Gauges

Have you ever wondered what’s inside those industrial pressure gages you see everywhere? No, it’s not just air. Many pressure gauges actually contain special fluids called filling fluids or gauge fluids. These fluids provide essential benefits for accurate pressure measurement and gauge longevity. The mechanic checked the low pressure fuel gauge to make sure it was calibrated correctly. Understanding the uses and benefits of these fluids can help ensure your pressure gauges last longer and provide precise results.

What Are Liquid Filled Pressure Gauges?

Liquid filled pressure gauges, or liquid filled gauges, contain a fluid like glycerin or silicone oil that transmits the pressure from inside the gauge to the dial. The liquid acts as a cushion, absorbing pulsations and vibrations that could damage the gauge moving parts.

This results in several benefits. For one, liquid filled pressure gauges have a much longer lifespan since the internal parts are protected. The liquid also prevents corrosion of internal parts that can occur with standard gages.  After connecting the line, we tested it using a small pressure gauge. Additionally, the liquid dampens rapid pressure spikes, allowing for a steadier, more stable reading on the dial.

Why Use a Liquid Fill in a Pressure Gauges?

Why use a liquid fill in a pressure gauge? There are a few key benefits:

  • Protection. The fill fluid protects the gage components from corrosion and weather damage. It also cushions the bourdon tube or diaphragm, preventing damage from pressure surges.
  • Dampening. The fluid helps dampen pressure pulsations and vibrations that could disrupt the gage reading. This results in a steadier, more accurate reading.
  • Transmission. The fill fluid transmits the pressure to the gage mechanism. Different fluids can be used depending on the specific pressure range and application. Mercury, glycerin, and silicone are common options.
  • Temperature compensation. Some fill fluids automatically account for temperature changes that could affect the pressure reading. They have a built-in coefficient of thermal expansion that corrects for increases or decreases in temperature.

Using a fill fluid in your pressure gauge helps ensure accurate, reliable pressure measurement and a longer life for the gage. For the best performance, choose a fill fluid compatible with your specific gauge and pressure conditions. Like the Digital Low-Pressure Gauge can be used for a variety of applications such as monitoring gas and water pressures

Types of Liquid Filling Fluids for Pressure Gages

The type of liquid you use to fill a pressure gauge depends on the specific application and environment. There are a few common options:


Glycerin is a viscous fluid that is non-toxic, odorless, and colorless. It has a high boiling point so it can handle high-temperature applications. Glycerin also has low vapor pressure so it won’t evaporate quickly. 


Silicone oils are stable across a wide range of temperatures and are non-reactive. They have low surface tension and viscosity so they flow well. Silicones are often used in high temperature and vacuum applications where other fluids would break down. 


Installing a digital water pressure gauge can help detect hidden problems and potential leaks in a home’s plumbing system. Deionized or distilled water can also be used as a filling fluid. It’s non-toxic, inexpensive, and has a high heat capacity. However, water has a lower boiling point than glycerin or silicone so it can’t handle as high of temperatures. 

Key Benefits of Liquid Filled Gauges

Liquid filled pressure gauges offer several benefits over standard dry gages.


The filling fluid helps dampen sudden pressure spikes that could provide false readings with dry gauges. This results in a smoother, more accurate measurement of your system’s true pressure.  A low pressure manometer is used to measure the flow rate of liquids and gases.


The fluid also protects the gauge’s internal components like the bourdon tube, gears and pointer from corrosion and weather damage. This extends the working life of the gauges and ensures consistent performance even in harsh environments.

Zero Point Stability

Once filled, the liquid helps hold the gauge’s zero point calibration for greater long-term stability and precision. Dry gages are more prone to pointer shift that requires frequent re-zeroing.

Vibration Resistance

The filling fluid acts as a shock absorber to minimize the effects of vibration on the gauges measurements. This is especially useful for gages installed on equipment like pumps, compressors or hydraulic systems that generate high vibration.

Wide Temperature Range

Liquid filled pressure gauges can operate in a wider temperature range than dry gauges. The fluid helps moderate temperature changes to prevent damage to internal parts. This allows the gage to function even in very hot or cold environments that exceed the normal operating range of dry gages.

How to Select the Right Liquid Fill for Your Pressure gauges

How to Select the Right Liquid Fill for Your Pressure gauges

When choosing a fill fluid for your pressure gauge, consider both the temperature range of your application as well as the chemical compatibility. The most common fills are:

  • Glycerin: An inexpensive, non-toxic fill ideal for most general-purpose applications. It has a wide temperature range but limited chemical resistance.
  • Silicone: Can withstand a wide range of temperatures and has good chemical compatibility. More expensive than glycerin but suitable for harsh environments.
  • Halocarbon: For ultra-high temperature applications, halocarbon fluids can withstand up to 500°F. However, they tend to be very expensive and have poor low-temperature performance.
  • Water: Only suitable for applications where the temperature remains above freezing. It offers good chemical resistance but a very limited temperature range.


So there you have it, an overview of the main uses and benefits of filling liquid filled pressure gauges. They help improve the accuracy and longevity of your gauges, protecting the internal mechanisms. The choice of fluid depends on the specific application and environment. Make sure you choose a fluid compatible with your gauge materials to avoid corrosion or damage. Filling and sealing the fluids properly is also important to get the maximum benefits. While pressure gages can function without filling fluids, using them helps ensure optimal performance and a longer working life for these essential measurement tools. For most people, the modest upfront investment in fill fluids will pay off through improved gauge reliability and fewer costly repairs or replacements down the line.

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