As an important pressure monitoring and control component in industrial automation systems, the measurement accuracy of electric contact pressure gauges directly affects equipment operation safety and process stability. When accuracy abnormalities occur, a systematic investigation and repair should be carried out from four dimensions: pressure sensing system, electronic control contact system, installation environment, and maintenance process. The following is a complete diagnosis and solution:
1、 Fault diagnosis of pressure measurement system
1. Failure of elastic sensitive components
-Phenomenon characteristics: sluggish pointer, large return error, sudden change in indication under the same pressure
-Solution:
*Disassemble the header to check for plastic deformation or corrosion pits in the spring tube/diaphragm box
*Use a dial gauge to detect the rebound amount of elastic elements in a free state (should be ≤ 0.2mm residual deformation)
*Replace the annealed new elastic component and ensure that the axial perpendicularity error is less than 0.5 ° during assembly
2. Wear and tear of transmission mechanism
-Typical faults: Excessive gear mesh clearance causing pointer shaking, rusting of connecting rod pin causing backlash
-Repair measures:
*Inject clock oil to clean the gearbox, adjust the mesh clearance to the range of 0.05-0.1mm
*Replace the stainless steel material of the pin shaft and apply molybdenum sulfonate grease
*Verify the concentricity of the pointer gear, and the deviation should be controlled within 0.5mm
3. Blockage of pressure transmission pathway
-Identification method: Delayed response of oil filled pressure gauge, turbidity or bubbles in damping fluid
-Processing procedure:
*Rinse the pressure conducting capillary repeatedly with kerosene
*Replace the aging nitrile rubber sealing ring, inject oil and let it stand for 48 hours to defoam
*Check whether the silicone oil level height of the liquid level compensator meets the temperature compensation curve
2、 Troubleshooting of electrical contact control system
1. Poor contact of contacts
-Fault manifestation: signal intermittent, contact resistance>20 Ω
-Repair steps:
*Disassemble the magnetic assisted electrical contact device and polish the dynamic/static contacts with metallographic sandpaper
*Adjust the contact overtravel to 0.3-0.5mm and use a spring scale to detect the contact pressure (recommended ≥ 0.5N)
*Plating silver alloy contact layer in a vacuum environment, with a thickness controlled at 5-8 μ m
2. Set value offset
-Calibration method:
*Turn off the power and rotate the setting pointer to observe if the mechanical limit block has shifted
*Adjust the differential screw to ensure that the triggering pressure of the micro switch meets the nominal value ± 1%
*Verify the upper/lower limit contact action values point by point using a standard pressure source, and record the hysteresis
3. Signal transmission interference
-Anti interference modification:
*Lay the control line and power cable at a distance of ≥ 20cm
*Parallel connection of 0.1 μ F ceramic capacitors in the contact circuit to absorb surges
*Adopting a shielding layer single ended grounding method, with a grounding resistance of less than 4 Ω
3、 Optimization of installation environment
1. Mechanical vibration suppression
-Vibration reduction measures:
*Install rubber shock absorber pad (Shore hardness 60-70)
*Use flexible metal hoses to connect pressure interfaces
*The torque of the dial fixing bolt is controlled between 1.5-2N · m
2. Temperature impact compensation
-Temperature control modification:
*Add insulation sheath to ensure that the temperature fluctuation of the watch body is less than 3 ℃/min
*Select temperature compensated hairspring with a compensation coefficient of ≥ 0.03%/℃
*Regularly verify the accuracy of the pressure temperature correction curve
3. Media compatibility processing
-Protection plan:
*Installing a buffer bag in pulse pressure situations
*Liquid receiving parts lined with PTFE in corrosive media
*Installation of online filtration device for viscous media (filter aperture ≤ 0.2mm)
4、 Professional calibration and maintenance
1. Periodic verification process
-Calibration specifications:
*Use a 0.05 level piston pressure gauge as a standard
*Perform forward and reverse stroke calibration at four points of range: 25%, 50%, 75%, and 100%
*Record linear error and variation value, with maximum allowable error referring to JJG52-2013 standard
2. Preventive maintenance plan
-Maintenance content:
*Check the damping fluid level and transparency every quarter
*Disassemble and clean the transmission mechanism annually, and replace the seals
*Update the pressure spring tube component every two years
3. Management of faulty spare parts
-Key spare parts reserve:
*2 sets of elastic components (spring tube/membrane box)
*3 sets of electrical contact modules (including micro switches)
*Special lubricating oil (1L each for clock oil and silicone grease)