| Pressure gauges are measuring instruments used in highly automated chemical processes; hydraulics, pneumatics or other mechanical applications; and power plants.
Well-calibrated pressure gauges work under normal operating conditions, such as weatherproof installations, non-hostile atmospheres, and shock-free environments.
Problems Associated with Short Service Life Cycles of Pressure Gauges
Factors shortening the life cycle of pressure gauges are:
- Hostile atmosphere, e.g., saliferous or acidic air, resulting in material fatigue and destruction of bearings, toothed gear and other components.
- Moisture penetration, resulting in condensation inside the gauge, or worse, rust formation and window fogging.
- Below zero temperature, icing the moving parts.
- Dust inside the pressure gauge, increasing abrasiveness and resulting in irregular run and inaccuracy of pressure indication.
- Extrinsic tube vibration and environmental shock.
- Shut-off cock, pressure limitation and pump condition, causing pressure impulse or process fluid pulsation.
These problems not only decrease the service life of the pressure gauges, but also add more repair expenses or result to new gauge purchases.
Gauge vibration can be reduced or eliminated in two ways:
1) Manual dismantling of the gauge by the user to determine the cause of the vibration; or
2) Partial dampening of the vibration, also called liquid filling.
The first method requires more time and money. The second method may be more appropriate to protect the pressure gauge from being destroyed.
Liquid-filling lengthens the service life cycles of pressure gauges. It is advantageous because it:
- Absorbs all amplitudes regardless of their origin. Good reading of the indication in case of fast dynamic loads and vibration is made possible by the transparency of the liquid-filling.
- Lubricates all moving parts (measuring element and movement), thus reducing component fatigue.
- Helps absorb shock.
- Seals out moisture and other hostile atmosphere.
- Prevents corrosion, rusting and icing of the measuring system.
Variety of Filling Liquids
For most applications, pure glycerine offers the optimum performance. Other filling liquids exist for different applications, based on the following considerations:
- If oxygen is used as process fluid, only halocarbon oils may be used as a filling liquid to avoid possible chemical reactions and explosions.
- If temperatures read at below zero (-60 deg. C maximum), Silicon oil-filling or other comparable liquids provide good viscosity values, thus preventing icing. Silicon oils are most suitable if pressure is measured at relatively great temperature fluctuations and if vibration of liquid-filled gauges is to be absorbed steadily.
- For liquid-filled gauges with electric accessories (e.g., contacts), insulation oils are used.
The higher the viscosity of the filling liquid, the higher the dampening. The suitable degree of dampening depends on the requirements to be met by the gauge such as velocity of indication, pressure extremes, vibration and pressure changes.
Liquid-filled pressure gauges are particularly suitable for the measurement of pressure at points of measurement associated with high dynamic loads such as those with fast and frequent changes of pressure, pressure extremes, vibration and pulsation. Examples of equipment that use liquid-filled pressure gauges are:
- High-pressure cleaning
- Hydraulic systems
Frequently-used Liquid-Filled WIKA Pressure Gauges
- Gauge versions with plastic case (ABS), wetted parts of copper alloy, for a measuring range of 0/6 000 psi maximum (type 113.13).
- Low Price Stainless Steel Pressure Gauges Casing (nominal sizes 63 and 100) and wetted parts of stainless steel measuring range up to 0/16 000 psi (type 133.14). These pressure gauges correspond to ANSI/ASME B40 1-1985.
- Pressure gauges for the oil and chemical industries, case and wetted parts of stainless steel, nominal sizes 100 and 160 mm, measuring ranges up to 0/16 000 psi (type 233.30). Electric accessories (e.g., contacts) may be added.
- Safety version according to DIN 16006 (solid front design, type 233.30).
- Process gauge, solid front design, with plastic case (phenol) and wetted parts of stainless steel; nominal size 4 1/2", measuring range up to 0/16 000 psi max.
- Series plus 2 000 with sturdy pressed brass case (case and pressure connection constitute an integrated whole), nominal sizes 63, 100 and 160; measuring ranges up to 0/16 000 psi (type 213.40).
Benefits of Liquid-Filled Pressure Gauge
- Increases service life under highly changing operating conditions.
- Renders accurate reading possible even in cases of vibration and pulsation.
- Prevents the entry of aggressive ambient air.
- Avoids formation of water condensation and ice inside the gauge.
Liquid-filled pressure gauges safeguard the reliability of the measuring system for longer periods of time under extreme conditions. Many users insist on this quality with regard to the increasing cost for service and maintenance.
Historically, liquid filings were only used for pressure gauges with bourdon tube. Today, they are used to a constantly increasing degree for diaphragm pressure gauges as well as for absolute and differential pressure gauges.
Call to Action
Call LabCommerce now for more information at (408) 265-6482 or email us at info@LabCommerce.com, and inquire about how we use liquid-filled gauges in our products or how you can order them separately with quantity discounts.