Dampened Movement Industrial Pressure Gauges - WIKA blog

In applications with vibration and pulsation, either a liquid-filled case or dampened movement industrial instrumentation will minimize pointer oscillation. The better choice depends on the application and, to a certain extent, a user’s risk tolerance for leaks.

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Pointer flutter is a common problem among industrial pressure gauges and dial thermometers found in applications with mechanical vibration and pulsation. As the instrument wobbles and shakes, so do all the internal parts, including the pointer. The results? Mechanical vibrations increase the wear and tear of the internal parts, and technicians cannot get a precise reading on the pressure or temperature.

Best Practice for Tackling Pointer Flutter: Liquid Filling

There are two ways to prevent pointer oscillation. One is to use a liquid case filling. In industrial pressure gauge, the liquid fill – usually glycerin or silicone oil – also:

• Cools the vibrating metal parts
• Lubricates the mechanism, thereby reducing wear and tear

The above benefits greatly increase the service life of the instrument and reduce downtime due to pressure gauge failure. In the long run, liquid-filled gauges are smart investments that ultimately save users money and time.

Customers may be concerned about potential leaks of liquid-filled cases. Some of our competitors’ gauges and thermometers do tend to lose their case fill over time, but not WIKA instruments. We use superior materials. For example, the Pocan® thermoplastic cases of our XSEL® process gauge line will not absorb moisture, an important consideration because moisture could lead to cracks. In addition, WIKA’s liquid-filled gauges undergo several leak tests to make sure they are 100% leak tight before being filled, either at the factory or in the field. Unless they are mishandled or abused, our liquid-filled gauges and thermometers will not leak.

When to Use Dampened Movement Industrial Instrumentation

However, some industries cannot tolerate even the smallest risk of leaks. These include pharmaceutical companies, paint manufacturers, and food and beverage plants – even if the case filling is FDA approved. In certain environments, such as barges, any type of spill is considered a safety hazard that must be documented and reported to the Coast Guard.

When mechanical vibration prevents these industries from using a traditional dry gauge or dry thermometer, a good option is dampened movement industrial instrumentation, especially when the gauge is coupled with one or more protective devices, such as a restrictor, snubber, and/or needle valve.

The Principle Behind Dampened Movement

Pressure gauge with dampened movement

In a WIKA pressure gauge, its Swiss movement is the most critical component for converting the pressure input into a precise indicator. The movement comprises a link connected to a segment gear that moves the pinion gear wrapped around the pointer shaft. In a standard movement instrument, vibration and pulsation are transferred to all moving parts, causing the pointer to flutter and making a precise reading nearly impossible.

With WIKA’s specially engineered dampened movement technology, the entire instrument still shakes – all except for the pointer shaft. This fully sealed capsule (circled in blue) is filled with a highly viscous silicone grease. The capsule has a brass inner drum that rotates inside the capsule housing on a thin film of that silicone grease, which isolates unwanted vibrations from the pointer shaft, thereby eliminating pointer flutter. In addition, the fully encapsulated disc keeps the dampening media in and the dirt out. Other gauge manufacturers use a sleeve design that allows the dampening media to dry out over time and to migrate under higher temperatures.

Bimetal thermometer with dampened movement

WIKA is the maker of the world’s first dampened movement bimetal thermometer. The dampening principle and technology are similar to those of a pressure gauge. But instead of a pointer shaft, a staff wire connects the bimetal helix with the pointer. This staff wire leads through a bearing that is filled with NyoGel®, an inert synthetic hydrocarbon grease with very heavy viscosity. This grease greatly minimizes pointer flutter caused by vibration, even in extreme temperatures.

This silicone-free instrument is available in temperature ranges not possible with case fill. Furthermore, its completely welded construction and hermetically sealed case eliminates the possibility of cross-contamination.

Pros and Cons of Dampened Movement

WIKA’s Dampened Movement is an excellent option for stifling vibration and pulsation in applications where liquid filling is not permissible. Our pressure gauges with this technology offer the same temperature range as standard dry gauges, from −40°F (−40°C) to 140°F (60°C). For bimetal thermometers, the upper limit for the silicone case filling is 500°F (260°C).

However, there is one main disadvantage of using a pressure gauge with dampened movement: By preventing the pointer shaft from shaking, other parts of the movement actually experience a higher impact from the vibration. As a result, such gauges in high-vibration applications will experience an even shorter service life compared to the same gauge with a dry case and standard movement, due to the increased wear and tear on the moving parts. Therefore, we recommend dampened movement technology only when liquid-filled gauges are not a viable option.

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Choosing Among Dry, Liquid-Filled, or Dampened Movement Instruments

When buying industrial instrumentation, should you go with a traditional dry case, a dry case with dampened movement technology, or a liquid-filled case? Because each industry and process has unique requirements, the best approach is to contact the specialists at WIKA USA for expert advice. We will help you decide on the best pressure or temperature solution for your application and budget.

Depending on specific industries, a business may rely on tight pressure settings, such as operations and safety systems. The comparison of measured data of a unit under test (your gauge) with those of a more precisely calibrated reference instrument is required to find the right pressure gauge calibration.

 Pressure calibrators help in ensuring that the pressure devices are measuring and displaying accurate values. As a calibrated pressure gauge supplier, Nagman offers a range of well-built, rugged, reliable, easy to use, and friendly options of pressure calibrators that you can choose from based on your needs. It must be calibrated at regular intervals, just like any other process measurement instrument, to ensure that it is measuring appropriately.

Only by providing insight into the specifics of your workload can you fully modify and calibrate a pressure gauge. There are numerous factors that influence the pressure calibration standard you use. The accompanying are some critical questions to consider when selecting a pressure calibration standard for your application.

Do I need to use analogue pressure standards or digital pressure standards to calibrate my pressure gauge?

Most pressure calibration standards these days are digital, and the pressure gauges you’ll be calibrating are frequently a mix of analogue and digital. Digital pressure standards have generally superseded analogue pressure standards because they are more accurate, easier to maintain, and easier to read. As a result, using a digital standard for both analogue and digital pressure gauge calibration is extremely popular.

Which type of pressure media is used for calibrating the standard?

Liquids, gases, and compressed air are all used in various pressure calibration standards. Lower pressures are generally easier to attain using a gas, such as air or nitrogen, because it is compressible. Higher pressures are often easier to generate with the liquid medium because it is non-compressible (at minimum for practical purposes).

Are there any pressure ranges that need to be covered?

You could be allowed to get more out of less, relying on the standard your company chooses. On average, the more pressure band you will have to calibrate, the more expensive and complicated the standard you’ll need. A somewhat more precise calibration standard, on the other hand, may prove to be more effective and convenient in the long run than purchasing much lower-precision equipment.

A better accuracy instrument that substitutes three lesser accuracy instruments could charge less than the contract sum of the three standards, saving you money upfront. Furthermore, a more precise and sophisticated standard can help to simplify operations and eliminate errors. If your calibration workload can be handled by a single standard, it saves operators the time and effort of selecting the incorrect standard and potentially completing poor calibrations.

What is the best way to determine the accuracy I need?

It’s common for folks to mix up precision reading with resolution. The term “accuracy” in the realm of pressure calibration standards pertains to how much the standard differs significantly from the genuine value. The frequency of decimal points displayed by the calibration standard is referred to as resolution. Greater decimal places may not always imply greater precision. These are two distinct specifications.

Do those standards have a high cost of ownership?

Make sure to include in the cost of ongoing calibration standards maintenance when making your decision. Calibration standards must be calibrated as well. Calibration expenses for just a limited list of high standards will be less than those for a substantial number of lower-accuracy devices, allowing you to make up the shortfall in initial costs for several calibration cycles.

What is the recommended frequency of calibrating pressure gauges?

When it comes to calibrating pressure gauges, the fundamental guideline is to stick to the pressure gauge calibration equipment suppliers’ guidelines. Nevertheless, there may be a few exceptions where you would have to prolong the interval. If you have a demonstrated record of success in calibrating a particular device, this is an acceptable argument to do just that. To illustrate, you could perhaps record the deviation of a device over a term and conclude that, based on information, you no longer need to calibrate the device yearly and can safely stretch it to three to four years.

A whole other situation where you will be willing to stretch a pressure gauge calibration machine’s calibration cycle is if the gauge has a single application and is only used seldom. You may merely need to calibrate it before using it. You may save time and money by extending calibration intervals, but only if you are confident that you are not compromising the safety or accuracy of your equipment. Nagman offers customers a variety of differential pressure gauge calibration services and other pressure gauge calibration instruments based on their requirements.

Contact us to discuss your requirements of temperature measurement device. Our experienced sales team can help you identify the options that best suit your needs.