Specific operation steps of fine adjustment of diaphragm pressure gauge

1. Modulus adjustment (sensor adjustment).

The main work to be done is complete fine tuning and zero fine tuning. Complete fine tuning requires three times the accuracy of a pressure gauge. In the menu of manual device: equipment settings-> diagnosis and maintenance-> inspection-fine adjustment of lower limit transmitter, operate.

If the accuracy of the pressure gauge is 0.25, the lower limit fine adjustment value is 0.06. During the whole operation, we only need to follow the instructions provided by the manual operator, and then fine-tune the upper limit sensor at the same position. Note that the fine adjustment of the upper limit should not exceed the large measuring range of the pressure gauge zui.

2. Zero point fine tuning.

First, open the pressure gauge to the atmosphere and connect it with the measuring circuit by manual device. Then, set the equipment-> diagnosis and maintenance-> inspection-> sensor fine-tuning-> zero fine-tuning. After zui, perform zero-point fine adjustment according to the prompt of manual device.

It should be noted that the pressure gauge must be within 3% based on the zero point before the zero point fine adjustment.

When fine-tuning, it is necessary to turn off the protection setting of the pressure gauge, usually the red switch in front of the meter, and the state is on and off. If the protection function is turned on, fine tuning will not succeed.

3. Digital-analog fine-tuning (output fine-tuning).

In the phone menu, device settings-> diagnosis and maintenance-> check-> output fine tuning-> digital/analog fine tuning.

Set the Control Loop to manual mode. Then according to the prompt of "Connecting Reference Table", connect an accurate reference ammeter to the pressure gauge, pay attention to the connection of positive and negative poles, and then select OK and zui to set the output of the field device to 4ma, at which time the output of the pressure gauge is 4ma. Then record the actual value of the reference table, input it in the prompt of "input instrument value", and observe whether the output of the hand operator is consistent with the value of the reference table.

If not, continue to input the reference value and check whether it is consistent with the output of the hand operator;

If they are consistent, change 4ma to 20ma, and then compare the reference value with the output value of the communicator until it is accurate.

Finally, set the "control loop" to automatic control, and then complete all operations.

Classification and troubleshooting of pressure gauges

A shock-resistant pressure gauge.

It is used to measure the pressure of gas or liquid that is non-corrosive, non-explosive, non-crystallizing and non-precipitating to copper and copper alloys. The earthquake-resistant pressure gauge is characterized by being able to measure pressure normally in the machine tool or equipment with violent vibration, and the earthquake-resistant grades are V.H.4 and V.H.5. It is suitable for measuring the pressure of machinery and equipment with frequent medium pressure pulses and long-term working conditions in places with violent vibration, and can be used as a substitute for general pressure gauges.

Second, stainless steel pressure gauge.

It is a pressure gauge made of corrosion-resistant stainless steel material and corrosion-resistant alloy material. The material of stainless steel pressure gauge can be divided into stainless steel 304, stainless steel 316 and stainless steel 316L.

Stainless steel pressure gauges can be widely used in petroleum, electric power, machinery, mining, chemical and food industries to directly measure the pressure of amorphous and corrosive gases and liquids.

Diaphragm pressure gauge is a kind of pressure gauge used to measure specific media. Diaphragm pressure gauge is made of a combination of pressure gauge and isolation device. The material used to make the pressure gauge has nothing to do with the measured media, because the pressure gauge itself does not contact those specific media, and it indirectly measures the pressure value of specific media in an isolated state. Therefore, this kind of pressure gauge has many excellent characteristics, and its accuracy can be higher. It can adapt to a wide range of media objects, as long as the corresponding dielectric isolation diaphragm is selected. The diaphragm pressure gauge provides a variety of connection structures, such as threaded connection, flange connection, etc., and its flange connection includes flat flange, angle flange, I-flange, etc. Because the diaphragm pressure gauge is a pressure gauge made by combination, it can provide a very flexible combination mode, which greatly improves its selection space.

Four, magnetic auxiliary contact pressure gauge.

Magnetic-assisted contact pressure gauges are widely used in petroleum, chemical industry, metallurgy, power station and other industrial departments or electromechanical equipment to measure the pressure of various fluid media without explosion danger of shock-resistant pressure gauges. Usually, the purpose of automatic control and sending alarm to the pressure system to be measured can be realized by matching the meter with corresponding electrical devices such as relays and contactors. In order to meet the different needs of the measured objects, this series of instruments is based on the original common and special types. More than 10 models and products of various types, such as anti-vibration, anti-corrosion, anti-vibration and isolation devices, have been developed one after another. Since this series of instruments not only has the characteristics of novel design, reliable structure, complete variety and specifications, good action stability and strong adaptability, but also has the advantages of combining measurement and control, simple installation and small maintenance of anti-vibration pressure gauges, it is incomparable for pressure controllers without instructions, switching difference adjustment and external setting devices.

1. Pressure interlock failure.

Fault phenomenon:

The pressure alarm interlock system of heavy oil main pipe in a petrochemical enterprise, because the pressure of heavy oil main pipe of boiler fuel oil drops and the standby pump can't start automatically, the pressure of heavy oil continues to drop until the boiler interlock action cuts off heavy oil and stops, resulting in failure.

Fault analysis:

Under normal circumstances, when the pressure of the heavy oil main pipe drops to a certain value, the standby pump should be automatically started to keep the heavy oil at a certain flow and pressure. Now, because the standby pump is not started, the electric contact pressure gauge indicates that the standby pump has not received the signal of pressure drop, which means that the pressure transmitter of this system has not felt the change of the main pipe pressure.

Treatment method:

Purge the pressure guide pipe with steam, clean the instrument membrane cavity with gasoline, and conduct static pressure test on the instrument before putting it into use again. After passing the inspection, refill the pressure guide pipe with isolation liquid.

2. The pressure indicator returns to zero

Fault phenomenon:

The pressure measuring pipe in a cracking gasoline pressure detection system in a petrochemical enterprise was closed shortly after heat preservation and heat tracing, and the pressure indicator returned to zero, the control valve was closed, and the cracking tower did not discharge, resulting in a shutdown accident due to the high liquid level in the tower.

Fault analysis:

Because the pressure fluctuation of the stainless steel pressure gauge system is large in normal operation, the method of opening the primary pressure-taking valve and controlling the resistance with a needle valve can reduce the fluctuation of the instrument indication. Because the instrument worker does not know the specific situation of the meter, the instrument indication fluctuates too much, that is, the primary pressure-taking valve is turned down, because the diameter of the primary pressure-taking valve is relatively large, which is difficult to control.

Treatment method:

Open the pressure-taking valve once to indicate that it will return to normal. It should be noted that for some detection control systems with high pressure, the detection fluctuation is often reduced by throttling resistance, but the resistance should be controlled properly, otherwise the above-mentioned faults will occur, resulting in serious consequences.

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