In industrial pressure measurement, many pressure gauges are internally filled with special liquids (such as glycerol or silicone oil). These devices are termed "liquid-filled pressure gauges" or "vibration-resistant pressure gauges." These liquids are not mere fillers but critical components that ensure stable gauge operation. Below is an analysis of the liquid types, functional principles, and application scenarios.
I. What Liquids Are Used in Pressure Gauges?
The most common liquids in pressure gauges fall into two categories:
1. Glycerol (Glycerin)
- Properties: Colorless, viscous, highly hygroscopic (absorbs moisture from air), capable of adsorbing harmful gases like hydrogen sulfide, and insoluble in organic solvents.
- Applications: Humid environments or scenarios with mildly corrosive gases.
2. Silicone Oil (Polysiloxane)
- Properties: High chemical stability, temperature resistance (-50°C to 200°C), strong hydrophobicity, and excellent insulation.
- Applications: High-temperature environments, waterproofing requirements, or electrical insulation needs, such as in chemical plants or power systems.
II. What Roles Do These Liquids Play?
The core purposes of liquid filling are damping vibrations, buffering shocks, and protecting the gauge, with specific functions including:
1. Damping Vibrations and Stabilizing the Pointer
- The viscous resistance of the liquid (glycerol/silicone oil) absorbs external vibrational energy, suppressing needle oscillations to ensure clear, stable readings.
- Example: In high-vibration environments like mining machinery or compressors, liquid-filled gauges prevent erratic needle movements caused by vibrations.
2. Pressure Transmission and Protection of Elastic Elements
- In chemically sealed gauges, silicone oil acts as a sealed medium. After vacuum filling, it forms a bubble-free environment. When external pressure acts on the gauge, the silicone oil uniformly transmits pressure to elastic elements (e.g., Bourdon tubes), preventing direct impact-induced deformation or damage.
3. Corrosion Isolation and Extended Lifespan
- Glycerol adsorbs corrosive gases (e.g., hydrogen sulfide), reducing erosion of internal metal components. Silicone oil's hydrophobicity blocks moisture, preventing rust.
4. Adaptation to Harsh Environments
- In extreme conditions-such as high/low temperatures, humidity, or severe pressure fluctuations (e.g., hydraulic systems, piston pumps)-the liquid-filled design significantly enhances gauge durability and measurement accuracy.
III. Why Choose Glycerol or Silicone Oil?
The choice between the two depends on practical conditions:
- Glycerol: Lower cost, suitable for standard vibration environments or scenarios requiring moisture absorption, but sensitive to high temperatures (>80°C).
- Silicone Oil: Offers comprehensive performance, wide temperature tolerance, and suitability for extreme temperatures, high pressure, or precision applications requiring insulation, albeit at a higher cost.
IV. Conclusion
The glycerol or silicone oil inside pressure gauges achieves core functions-vibration resistance, shock absorption, and corrosion resistance-through viscous damping and pressure transmission mechanisms. Liquid-filled pressure gauges have become indispensable "stabilizers" in industrial equipment, particularly in energy, chemical, and manufacturing sectors, ensuring operational safety and precise control.
(Note: Liquid-filled gauges require regular inspections of the liquid state. If cloudiness, leakage, or bubbles are observed, the liquid should be replaced promptly to maintain performance.)