Pneumatic and Vacuum Gauges
What are Pneumatic and Vacuum Gauges ?
Gauges are essential for monitoring systems that operate under pressure. Pressure gauges deliver key information about any potential problems in systems, such as industrial equipment, portable compressors and pressurised containers, ensuring optimal efficiency and timely repairs. They are often used in refrigeration units and heating, ventilation and air-conditioning. The accuracy of most pressure gauges ranges between 0.1 and 2 percent of the full scale depending on their quality, material and design.
Pneumatic pressure gauges are used to manage air systems. They are used in a huge range of devices to test metrics such as filter conditions, speed, fan efficiency and air supply. Pneumatic pressure gauges are normally dry and come in diameters of 40, 50 and 63 millimetres. They are either 0 - 1 bar or 0 -20 bar.
Pressure gauges are available with either a back connection for mounting or a bottom connection. Plus, they come with stainless steel or plastic casings. While stainless steel casing is stronger than plastic casing, it is more expensive and generally more prone to corrosion. You can opt for a modern digital pressure gauge or a more traditional analog gauge such as a Bourdon tube gauge.
Liquid vs. Dry Pressure Gauges
Pressure gauges are either dry or filled with liquid. No matter the type, however, they come with similar pressure ranges (this said, sometimes liquid gauges have a higher range). Nevertheless, it is important to select the right pressure gauge for the right environment.
Usually used in industrial settings, dry pressure gauges are perfect for dry environments without mechanical vibrations. This is because vibrations can move the pointer from position, making the gauge tricky to read. Dry pressure gauges tend to be cheaper than their liquid counterparts.
Liquid pressure gauges are normally filled with glycerine or a blend of glycerine and water. Standard glycerine gauges are ideal for temperatures above - 5 degrees Celsius. Gauges with two parts glycerine to one part water, on the other hand, can operate in situations where the temperature goes down to - 46 degrees Celsius and as such are ideal for harsh weather. Most liquid gauges are resistant to moisture and icing. In addition, they are usually airtight, which means that they can be used in corrosive environments. Plus, they absorb vibrations, which makes them precise and easy to read. Pressure gauges filled with glycerine are environmentally-friendly since glycerine is non-toxic and biodegradable.
Vacuum gauges are designed to measure pressure levels below atmospheric pressure. Since atmospheric pressure (101.325 kP) denotes zero, vacuum pressure measurements are negative in value (for example, - 1 barg, or - 15 psig, denotes a complete vacuum). Vacuum pressure and gauge pressure are measured differently. While vacuum gauges measure pressure as negative in value to atmospheric pressure, standard gauges measure pressure as positive in value to atmospheric pressure.
Vacuum gauges are used in a variety of environments such as manufacturing, chemical, automotive and nautical industries. When it comes to heating and cooling systems, vacuum gauges normally come as a combo with vacuum pumps. While vacuum gauges monitor the effective operations of a system, vacuum pumps ensure that such systems are free from contaminants, such as liquids and gases.
Gauges filled with glycerine are ideal for temperatures between - 20 and + 60 degrees Celsius (as such they can operate in conditions that are too harsh for dry gauges). Plus, they feature great vibration dampening qualities, which makes them easy to read. And since glycerine gauges are lubricated, they have a long lifespan. They are usually made from brass and stainless steel and do not experience condensation and corrosion. Glycerine gauges are normally used in a variety of equipment including compressors and pumps and applications such as measuring dynamic pressure loads.
Wika Pressure Gauges
Wika is a big name in the pressure measuring instrument industry. The brand offers a huge range of gauges for a variety of measuring requirements from 0.5 mbar to 7,000 bar. Incorporating materials such as copper alloys and stainless steel, Wika pressure gauges feature various technologies including diagrams, capsules and Bourdon tubes. Plus, they offer high accuracy of up to 0.1 %.
- Pressure Gauges with a Bourdon Tube (0.6 mbar to 7,000 bar)
Wika pressure gauges with a Bourdon tube are suitable for taking measurements in harsh but not highly viscous environments. Often made from stainless steel, they are filled with liquid to ensure precise results and easy readability, even in the presence of vibrations. Plus, they have an accuracy rate of between 0.1 and 0.6 of the full scale value.
- Pressure Gauges with a Capsule (2.5 to 600 mbar)
Suitable for extremely low pressure, pressure gauges with a capsule come with two joined circular diagrams. This gauge type is usually used in laboratory situations to measure contents and monitor filters. Plus, they have an accuracy rate of between 0.1 and 2.5 of the full scale value.
- Pressure Gauges with a Diaphragm (16 mbar to 40 bar)
Suitable for gaseous and liquid media, pressure gauges with a diaphragm feature high overload safety of three or five times the full scale value. Pressure gauges with a diaphragm are liquid-filled for precise readings in environments that feature vibrations and dynamic pressure loads.
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Different types of pressure gauges are suitable for different industries and applications. With this in mind, here are some of the most common pressure gauges on the market today.
- Differential Pressure Gauges: Differential pressure gauges work by measuring the difference between the pressure in two ports.
- Absolute Pressure Gauges: Absolute pressure gauges measure pressure in relation to a vacuum.
- Atmospheric Pressure Gauges: Atmospheric pressure gauges measure air pressure.
- Hydraulic Pressure Gauges: Hydraulic pressure gauges are capable of measuring high pressure ranges in hundreds of bar.
While both analog pressure gauges and digital pressure gauges have the same function, they have different features. Analog pressure gauges come with needles that point to numbers that correspond to the current pressure. Analog pressure gauges do not require a power source since they are mechanical. On the downside, analog gauges are more sensitive to corrosion, extreme temperatures and vibration than digital pressure gauges. They may also require periodic recalibration.
Also called electronic pressure gauges, digital pressure gauges are more modern and expensive than analog pressure gauges. They feature a digital display, which makes them easy to read. They normally run on batteries but can also be powered by loop or solar power. Digital pressure valves are calibrated digitally, which makes them more reliable than analog pressure gauges. They are also durable enough to operate in extreme temperatures and areas with heavy vibrations.
Pressure gauges are generally used to measure and monitor the characteristics of specific systems that function above atmospheric pressure. Meanwhile, vacuum gauges are used for systems below atmospheric pressure. In other words, they measure negative pressure as it stands in relation to atmospheric pressure.
Both glycerine gauges and silicone gauges are designed to dampen vibrations and pressure peaks to remain highly readable in dynamic environments. Liquid pressure gauges are sealed to prevent contamination with dust and other particles. They also do not experience condensation. While glycerine gauges are suitable for temperatures between + 60 degrees Celsius and - 20 degrees Celsius, silicone pressure gauges have even lower viscosity. As such, they operate well in temperatures between + 60 degrees Celsius and - 40 degrees Celsius.