The pressure gauge has a sensitive element inside the indicator. The sensitive details are Boden tube, membrane box, and bellows. The pressure gauge can display the pressure using the elastic deformation of the exposed part. Then, the pressure deformation is transmitted to the pointer by the conversion mechanism in the gauge movement, causing the tip to rotate. Today we will talk about oil-filled pressure gauges and non-oil-filled pressure gauges.
1. Non-oil filled pressure gauges
A pressure gauge without oil is the standard pressure gauge. The average pressure gauge belongs to the local indication type pressure gauge. It can display the size of the pressure locally, without remote transmission display and adjustment function.
1.1 Features of ordinary pressure gauges
The standard pressure gauge is suitable for measuring non-explosive, non-crystallizing, and non-condensing. It has no corrosive effect on copper and copper alloys in liquids, gases, steam pressure, and vacuum.
1.2 Applications of standard pressure gauges
In industrial process control and technical measurement, the elastic sensitive element of the general pressure gauge has high mechanical strength and easy production, simple installation, and easy reading, which makes the broad pressure gauge more and more widely used.
2. Oil-filled pressure gauges
A pressure gauge is an oil-filled pressure gauge, also called a shock-resistant pressure gauge. It has a mechanical pointer-type pressure gauge with filling liquid in the case.
2.1 Applications of oil-filled pressure gauges
The oil-filled pressure gauge is suitable for use in places with severe environmental vibrations. It can withstand the medium, impact, and sudden unloading pulsation, and the gauge indication is stable and precise. They are widely used in machinery, petroleum, chemical industry, metallurgy, mining, electric power, and other departments, measuring the pressure of non-corrosive media on copper and copper alloy.
2.2 Composition of an oil-filled pressure gauge
The oil-filled pressure gauge has a mechanical pointer (or rotary dial) type pressure gauge with liquid filling in the case and a damper. It is composed of a pressure guide system (including joints, spring tubes, restriction screws, etc.), a gear transmission mechanism, an indicating device (pointer and dial), and a housing (including case, cover, glass, etc.).
2.3 Features of oil-filled pressure gauge.
2.3.1 The oil-filled pressure gauge has good shock resistance.
2.3.2 It is particularly suitable for measuring fluid pressure where the medium has violent pulsations or transient shocks.
2.3.3 Its drive indication mechanism is in a viscous damping fluid, which significantly reduces the influence of mechanical vibrations of the environment in which the gauge is located on its work.
2.3.4 We usually use an umbrella-sealed construction to work in harsh conditions like high humidity, dust, and water.
2.3.5 It also has anti-clogging characteristics.
2.3.6 It can be used to measure high viscosity, easily crystallized and solidified media such as cement and slurry.
3. The function of pressure gauge oiling
Objects shorten longitudinally and expand when pressed in one direction, while the press pad restrains the lateral deformation of the object using friction on the contact surface. Suppose there is a conflict between the oil and the press on the pressure gauge. Its transverse deformation is almost unrestrained. Therefore the pressure measured by a pressure gauge without oil is higher.
4. Difference between oil-filled and non-oil-filled pressure gauges
4.1 Difference in use
The forbidden oil table uses the prohibition of contact with the oil medium, while the non-oil table is not explicitly restricted to use.
4.2 The pressure of the force table is different
The oil ban is for the work of the pressure table contact medium to speak.
4.3 The scope of work is different
The pressure gauge is the default contact with oil media work.
4.4 The nature of different
But part of the pressure table, such as the oxygen table, ammonia table, acetylene table, etc., are not allowed to contact the oil medium for work. Otherwise, an explosion and other dangers will occur. So it is called a no-oil gauge.
4.5 Measurement applications of oil-filled pressure gauges
Pressure gauge oil is mainly used for measuring oxygen and other gas pressure gauges, like oxygen and grease contact heating combustion or even the risk of explosion, so oxygen pressure gauges in the work or calibration process are absolutely prohibited from using oil (except for glycerine). The indicator’s name on the dial of the oxygen pressure gauge is underlined in sky blue and marked in red with the words “no oil.”
Oil-free gauges include oxygen pressure gauges, hydrogen pressure gauges, etc. The indicator’s name on the dial of the ammonia pressure gauge should be underlined in yellow. Therefore, the oil pressure gauges in the above dials can be distinguished from the standard pressure gauges.
5. The function of oil in pressure gauges
The “oil” in the pressure gauge plays a stabilizing role to prevent the indicator from vibrating. A pressure gauge to which we have added “oil” is often referred to as a “shock-resistant gauge.”
The pressure gauge is generally used in harsh environments, for example, in noisy environments or where the system pressure fluctuates strongly, to prevent the pointer from constantly shaking and affecting the value reading.
At the same time, the addition of “oil” to the pressure gauge in a highly fluctuating environment can prolong the life of the indicator, as the constant wobbling of the needle will certainly reduce the life of the hand.
6.The difference between oils
So, do all “shock resistant gauges” use one oil?
No, not at all.
There are two main types of oil used in pressure gauges to stabilize the needle. One is “glycerine,” and the other is “silicone oil.” Both types of fat are shock-resistant, but silicone oil is also more resistant to low temperatures than glycerine. For example, suppose the outdoor temperature reaches -20 degrees Celsius. In that case, the glycerine will crystallize, but the silicone oil will not, so the silicone oil gauge can be used generally in this environment.
Therefore, we can use glycerine and silicone oil. However, we should consider at least two things when making specific choices.
1. thermal expansion system, the smaller the coefficient, the better, mainly affected by the temperature.
2. Oil-filled pressure gauges are used in a variety of situations. However, the food industry cannot use it for this type of oil. Measurement of solid oxidants is also not recommended for use in places. Otherwise, it will cause an explosion.
