Pressure instrument-pressure switch maintenance and repair procedure
1 General Rules
1.1 Subject content and scope of application
This regulation specifies the specific technical requirements and implementation procedures for the maintenance, overhaul, operation and safety precautions of pressure switches.
This regulation applies to BT series pressure switches (hereinafter referred to as meters) used online in power generation devices, and other models and pressure switches with the same function should also be used in reference.
1.2 Basic Working Principles
The instrument works on the principle of measuring the elastic deformation of components.
1.3 Composition and function
The sensing element of the measuring mechanism receives the pressure signal and converts it into a change in displacement.
The output contact converts the displacement change into a microswitch contact action for interlocking or alarm systems.
1.4 Main technical performance and specifications
1.4.1 Performance Indicators
Boost basic error: 0.5 level
Step-down basic error: 0.5
Two-point control basic error: 0.5 level
1.4.2 Specifications
Pressure control adjustment range:
Step-down adjustment: 1.10~21.73MPa
Voltage boost adjustment: 1.37 to 22MPa
Switching pressure differential value: 0.91 MPa
Mechanical life of spring tube: 106 times
Contact capacity: AC 380V, 220V 100W
Dc 220V, 110V, 24V 10W
Contact life: 106 AC times
Dc 6 x 106
Medium temperature: -50~70℃
Ambient temperature: -50~70℃
1.5 Basic requirements for maintenance personnel
Maintenance personnel should have the following conditions:
a. Familiar with this regulation and the corresponding product specifications and other relevant technical data;
b. Understand the operation process and the role of the instrument in it;
c. Master the basic theoretical knowledge of power generation measuring instruments and maintenance;
d. Master the basic skills of maintenance, overhaul, operation and troubleshooting of the instrument;
e. Master the use of commonly used test instruments and related standard instruments.
2 Sound condition
2.1 Parts are complete and meet technical requirements, namely:
a. The nameplate should be clear and unmistakable;
b. Parts should be complete and standardized;
c. Movable parts should be flexible;
d. Terminal wiring should be firm;
e. Adjustable parts are in an adjustable position;
f. Seals should not leak;
g. The protection and insulation facilities should be intact.
2.2 Normal operation, meet the requirements of use, namely:
a. When running, the instrument reaches the specified performance index;
b. Under normal working conditions, the instrument setting value should be 20% to 80% of the full range;
c. Contact load does not exceed the rated value;
d. The instrument should not misoperate or not operate.
2.3 The equipment and environment are tidy, clean and meet the working requirements, that is;
a. The whole machine should be clean, no rust, paint layer should be smooth, bright, no fall off;
b. The scale should be clear and the font should be regular;
c. Instrument pipelines and lines are laid neatly;
d. The line label should be complete, clear and accurate;
e. The instrument should be installed in a position with low vibration.
2.4 Complete and accurate technical data, in line with management requirements, namely:
a. Instruction manual, certificate of qualification, factory entry verification certificate should be complete;
b. Operation records, fault handling records, maintenance records, calibration records, parts replacement records should be accurate;
c. The system schematic diagram and wiring diagram should be complete and accurate;
d. Alarm, interlock switch setting value and change records should be complete and accurate.
3 Maintenance
3.1 Routine Maintenance
3.1.1 Itinerant inspection
At least two inspection Tours per shift, including:
a. To the on-duty operator to understand the operation of the instrument;
b. Check whether the pipes, lines and valves connected to the table body are leaking, damaged or corroded.
c. If problems are found, they should be dealt with in time, and records of inspection should be made.
3.1.2 Periodic Maintenance
Periodic maintenance content
a. Clean the outside of the instrument once a week.
b. Check the instrument spring tube, terminal and pressure guide tube once a month for leakage, corrosion and other conditions.
3.2 Periodic Calibration
3.2.1 Calibration period: 12 months.
3.2.2 Calibration instrument: Standard pressure gauge: level 0.25; Pressure calibration table; A multimeter.
3.2.4 Basic error calibration of boost voltage
Slowly increase the output pressure value of the pressure tester, observe the standard pressure indication value, and the microswitch should operate at the set value. If out of tolerance, the adjusting mechanism should be rotated until qualified.
3.2.5 Buck basic error calibration
Slowly reduce the output pressure value of the pressure tester, observe the standard pressure indication value, and the microswitch should operate at the set value. If out of tolerance, the adjusting mechanism should be rotated until qualified.
3.2.6 Two-point control basic error calibration
When using two-point accurate pressure control, adjust the two switches separately according to boost calibration or buck calibration, and then fine-tune the first and second microswitch 1 to 2 times.
3.2.7 Overload test
Add 1.2 times the upper pressure value of the instrument for overload test, keep for 5 minutes, and then calibrate the instrument, the instrument should reach the specified performance index. Otherwise, it should be readjusted.
3.2.8 Calibrating quality standards
The calibrated instrument shall meet the performance specifications specified in Article 1.4.1.
3.3 Troubleshooting
phenomenon
reason
Treatment method
The contact does not operate
Stop valve is not open
The pressure sensing element is deformed or damaged
Open stop valve
scrap
Abnormal movement
The stop valve or pressure guide is blocked
The microswitch contact is poor
The microswitch is broken
Clean valves and dredge pipes
Repair or replace the microswitch
Replace the microswitch
4 Maintenance
4.1 Maintenance Cycle
The meter is serviced every 12 months. It usually coincides with the annual overhaul of the plant.
4.2 Maintenance Contents
4.2.1 Cleaning pressure sensing components
4.2.2 Check whether the pressure sensing element is rusted, deformed or damaged.
4.2.3 Check whether the micro switch is flexible and reliable.
4.2.4 If the paint of the instrument shell falls off and rusts, rust removal and anti-corrosion work should be carried out.
4.2.5 Calibrate the instrument according to Article 3.2 of this procedure.
4.3 Maintenance quality standards
The instrument after repair shall meet the condition of good condition specified in Chapter 2.
5 Commissioning
5.1 Preparation before operation
5.1.1 The instrument for measuring the pressure of general gas and liquid medium first drains the pipe.
5.1.2 Check whether pipes leak.
5.1.3 Checking whether Cable connections are correct.
5.1.4 Interlock should be removed from interlocked instruments.
5.2 Operation procedure
5.2.1 Contact the operation before putting into operation.
5.2.2 Open the meter sampling stop valve.
5.2.3 Power supply to the instrument.
5.2.4 If the instrument with interlock is confirmed to operate normally, it should be put into interlock if the operating condition permits.
5.3 Acceptance
5.3.1 Check the completion of maintenance items one by one.
5.3.2 Check whether the instrument meets the maintenance quality standard.
5.3.3 After 72 hours of normal operation of the instrument, the relevant technical supervisor shall sign for receipt.
6 Safety Precautions
6.1 Security Precautions
6.1.1 Maintenance must be performed by more than two persons.
6.1.2 Operations that may cause fluctuations in operating parameters must be approved by the operator in advance.
6.1.3 Appropriate safety measures should be taken when discharging.
6.2 Maintenance Safety Precautions
6.2.1 For the maintenance of the operating instrument, the maintenance work ticket must be issued.
6.2.2 Remove the switch without pressure.
6.2.3 During pressure test, pay attention to slow pressure and do not overpressure.
6.2.4 When removing cables, pay attention to cable insulation protection.
6.2.5 After maintenance, contact the operation for linkage test or put into interlock.
6.3 Safety Precautions for operation
6.3.1 The operation must be carried out by more than two persons.
6.3.2 Contact the operator before putting into operation.
6.3.3 Put the instrument with interlock into operation and confirm that it is in normal operation before putting into interlock