Stainless steel pressure gauges classification and installation precautions

Stainless steel pressure gauge is composed of pressure guiding system (including joint, spring tube, current limiting screw, etc.), gear transmission mechanism, number display device (pointer and dial) and shell (including watch case, watch cover, watch glass, etc.). The outer casing is an air-tight structure, which can effectively protect the internal parts from environmental influences and contamination. For the instrument filled with liquid (usually silicone oil or glycerin) in the shell, it can resist the violent vibration of the working environment and reduce the pulsation effect of the medium pressure.

The parts of the stainless steel pressure gauge are made of corrosion-resistant stainless steel and corrosion-resistant alloy materials, so that the stainless steel pressure gauge has good corrosion resistance. The stainless steel pressure gauge can be widely used in petroleum, chemical, mining, machinery, electric power and food industries. Directly measure the pressure of non-crystalline, corrosive gases and liquids.

Stainless steel pressure gauge common faults analysis

1. The pointer does not move or moves very little

The reasons may be the following:

(1) The calibrator valve is not open

(2) The pointer is loose, and one end of the pointer touches the dial.

(3) The central hole of the calibrator joint sealing gasket is blocked, and the working medium cannot be introduced into the pressure gauge.

(4) The medium in the calibrator oil cup is too dirty, blocking the spring tube or the transmission channel.

(5) The rubber cup at the top of the calibrator screw is damaged or the spring tube is broken, resulting in a large amount of oil leakage.

2. The pointer is reversed. The calibrator leaks oil or the needle valve of the oil cup is not smooth, resulting in poor sealing performance, or there may be cracks in the spring tube. These failures are common and easy to fix.

3. Jumping needle phenomenon. The teeth of the sector gears may be rusted, worn, or dirty. Or the pointer shaft is tilted, bent and rubbed on one side of the dial.

4. The pointer does not return to zero, the return error and the tap displacement are out of tolerance. The hairspring is not tightened or stretched enough, or the hands are loose.

Stainless steel pressure gauge types

1. Liquid column pressure gauge

The liquid column pressure gauge will convert the pressure into the height of the liquid column for display. The common liquid column is a stainless steel pressure gauge indicating liquid, including alcohol water and mercury. This pressure gauge is simple in structure and sensitive in response. It is used to measure low pressure and vacuum. If the liquid column type stainless steel pressure gauge is subjected to severe fluctuations, the liquid column detection effect is poor, so the use of the liquid column type stainless steel pressure gauge requires more counterattacks.

2. Elastic pressure gauge

Elastic pressure gauges usually use elastic elements such as spring tubes to measure pressure through the principle of force and deformation. Because the elastic pressure gauge is cheap and reliable in measurement results, it has become one of the hot-selling stainless steel pressure gauges. Nowadays, many high-quality stainless steel pressure gauges use mechanical pointer output, so they must be checked at the production site. Distance viewing must be equipped with an additional device.

3. Pressure sensor

Pressure sensors and pressure transmitters convert the measured voltage into various signals through different conversion elements, and judge the pressure in an indirect way. The signal from the pressure sensor in the stainless steel pressure gauge can be transmitted over a long distance, so that it can be easily displayed and recorded, and is now widely used in the field of automated production.

Stainless steel pressure gauge installation recommendations

1. Selection of the position of the pressure port

a. Make the sampling pipe and the flow direction of the medium perpendicular to each other, and avoid selecting valves, bifurcations, and elbows where vortices are easily formed;

b. When there is a protruding object in the pipeline, the pressure taking port should be taken in front of it;

c. When measuring the pressure of liquid and water vapor, the pressure point should be set on the lower side wall of the horizontal pipe, so that there is no gas in the pressure pipe, so as to prevent the sediment in the pipe from blocking the sampling nozzle;

d. It is a pressure gauge for measuring liquid and steam media, and is installed at the lower part of the instrument panel to prevent liquid or condensation from dripping onto other instruments.

2. The laying of the impulse pipe

The function of the pressure pipe is to transmit the pressure signal between the pressure point and the pressure gauge. Attention should be paid to its laying: First, the inner diameter of the pressure pipe is usually 6-10mm, and the length is less than 50mm, so as to reduce the measurement error and avoid the pressure caused by the medium lag. The indication of the meter is delayed; the second is that the horizontal section connecting the conduit should have a certain slope, and the slope of 1:10 to 1:20 should be maintained to facilitate the discharge of condensate or gas in the tube. Isolation valve for use when servicing the pressure gauge.

3. Determination of installation height

The installation height should be suitable for the staff to observe, at the same level as the sight of the average person, that is, 1.5m to 1.6m. For high pressure, it should be higher than the head of the average person, that is, about 1.7m to 1.8m. When the installation position of the pressure gauge and the position of the pressure measuring point are vertically far apart, the correction of the liquid column difference should be carried out. The correction value is equal to the pressure value generated by the liquid column in the conduit of the vertical height difference between the instrument and the pressure measuring point. When the meter is higher than the pressure measuring point, add this correction value; on the contrary, when the meter is lower than the pressure measuring point, this value should be subtracted.

4. Use sealing gaskets

In order to ensure the tightness, a suitable gasket should be selected for the seal between the joint of the pressure gauge and the table seat. When the working temperature and pressure are lower than 80℃ and 2MPa, use leather gaskets or rubber gaskets; at 80℃～45℃, use asbestos paper or aluminum pads below 5MPa; when the working temperature and pressure are higher, use annealed copper pads or Lead pad.

5. Use a desander to treat heavy drilling fluid, but a large-size desander with a separation particle size greater than 74 μm must be used. Since the subsidence diameter ratio of barite and drill cuttings is about 1:1.5, the sand remover that can remove drill cuttings above 74μm can also remove barite powder above 49μm. In barite, this part of the particles accounts for about 10%-15%. The weighted drilling fluid that has been pretreated by the desander enters the mud cleaner, which can greatly reduce the burden of the mud cleaner. The disadvantage is that some barites with larger particle sizes suffer some losses.

Notes during installation:

1. Before use, you should understand the model and function of the stainless steel pressure gauge, and operate it carefully and correctly according to the detailed requirements of the manual to avoid affecting the measurement results of the instrument.

2. Avoid using the stainless steel pressure gauge in the environment with chlorine, nitric acid and oxygen perchloride and other strengthening agents, otherwise it will damage the instrument.

3. Select a suitable pressure measuring point when measuring, and ensure that the selected pressure measuring point can obtain accurate pressure measuring results. Be sure to select the part where the medium flows along a straight line, and avoid choosing a curved place, otherwise it may not be accurate. As a result, when measuring flowing media, it should also be noted that the pressure should be perpendicular to the medium.