Maintenance of vibration and displacement probes
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The company’s turbine unit is going to undergo a major overhaul. As an instrument maintenance technician, how should I work together with the equipment team during this maintenance? Specifically, what concerns relate to the vibration and displacement sensors of the turbine unit, as well as the temperature instruments used in it? Please provide installation photos of vibration, displacement, and temperature for on-site unit maintenance.
Bring a marker; before disassembling, draw a line from the probe to the base to mark the initial position. During the removal process, count the number of turns; then mark the angle at which it was turned out by drawing a line at the position on the base corresponding to the black line on the probe. To reassemble, simply reverse the disassembly steps. Remember to bring a feeler gauge; after reinstallation, measure the distance between the probe and the shaft assembly to ensure it meets the requirements specified in the technical documents.
We now use lead wires to measure voltage values
Maintenance of the shafting instruments in the unit: 1. Before carrying out maintenance on the equipment, it is necessary to remove the shafting instruments, as these instruments are usually connected from the machine body to the unit’s wiring box via flexible tubes, which hinders the maintenance work. Markings should be made during this period to indicate the correspondence between the probe, extension cable, preamplifier, and system channels. Notify the equipment after removal. II. The instruments that are disassembled for inspection shall be checked and calibrated in accordance with the \"Inspection, Maintenance, and Repair Procedures\", and their appearance shall be inspected for any damage such as to the cable insulation and the epoxy resin surfaces ； Verify and plot the sensor calibration curve to confirm whether the requirements are met ； III. After equipment maintenance, and when the conditions are met, reinstall the instrumentation for the shafting system. Note: 1. The installation clearance of the probe (for vibration probes, adjust the clearance voltage, e.g., -10V; the specific value depends on the probe model; move the displacement to the neutral position or calculate the required clearance voltage) ； 2. Insulation on the outside of the probe and extension cable connectors ； 3. For the temperature PT100 sensor, an oil-resistant sealant should be used to secure it at the bottom of the opening in the tile, so that the sensor is in close contact with the tile and remains fixed in place ； 4. Fixing of the internal wiring in the machine to prevent contact with rotating parts ； 5. For the sealing of the instrument leads at the point where they exit the machine body, rubber rings and sealant are used to prevent oil leakage ； 6. Measure the resistance again before closing the cover to prevent individual wires from breaking during installation ； IV. Circuit debugging, alarm and interlock debugging, and recording.
The installation and calibration of the shaft displacement probe also require moving the shaft to one end, taking into account the play of the unit.
Just measure the voltage value, and that’s it. It’s not that complicated.
Not all probes need to be removed; only those that hinder equipment maintenance should be taken off and marked, with the installation openings covered with a clean cloth. When reinstalling, testing the zero voltage can determine whether it has been installed properly.
For the same unit, is the serial number fixed, or does it need to be set each time a probe is installed during maintenance?
As I understand it, each time maintenance is carried out and a different shaft displacement is applied, it varies; specifically, cooperation between the instrument technician and the fitter is required. Therefore, the zero point after starting up the machine, which is adjusted during each maintenance session, is only a reference zero point. The purpose of shaft displacement measurement is to protect the unit; it is sufficient to ensure protection of the unit within the interlock range of the reference zero point.
Use a multimeter to record the voltage value of the probe when it is shut down, then remove it and make a record of the calibration results for the probe. Check the insulation condition of the probe, and wait until it is ready to be reinstalled. When reinstalling it, position it according to the voltage value recorded, and use heat-shrink tubing to protect the wires of the probe