What should be paid attention to when changing the thermal dispersion booster pump and assembly of paper machinery?

Matters needing attention in replacement of paper-making thermal dispersion booster pump (assembly)

The thermal dispersion booster pump transports high-temperature and high-concentration waste paper pulp. The working conditions are: the temperature is 120,160℃, the system is under pressure, the pulp contains fillers, sand particles and sticky substances, and most of them are mechanical seals with sealed water flushing and cooling system; The risk points of assembly replacement focus on high-temperature scald, pressurized shotcrete, alignment deviation, seal flushing failure, thermal expansion dislocation and cavitation, and the LOTO tag and lock are strictly implemented throughout the replacement process.

A, downtime isolation and replacement (top priority, it is forbidden to take material with warm)

1. Stop the thermal dispersion system at reduced load, wait for the pump body and pipeline to cool down naturally, and then carry out disassembly and assembly when the shell temperature drops below 60℃. It is forbidden to quench water to prevent stress cracking of the shell.

2. Cut off the power supply of the pump motor and perform tag-out and locking; When closing the shut-off valve at the inlet and outlet of the pump, a blind plate must be added for physical isolation, and it is not possible to close the valve only to prevent the upstream and downstream slurry from flowing backwards and spraying out.

3. Open the sewage and pressure relief valve of the pump body, slowly release the pressure, and drain the slurry inside the pump cavity; Use clean water to flush and replace the pump cavity and short pipe, and flush the residual hot slurry to avoid splashing and scalding personnel when disassembling the flange.

4. Cut off the inlet and outlet valves of sealing water/flushing cooling water of mechanical seal, and release the pressure of flushing pipeline; Confirm that the pressure gauge is zero.

5. Operators wear high-temperature gloves, goggles and anti-cutting labor insurance shoes; The pump assembly is heavy, so the original lifting lug must be used for lifting. It is forbidden to lift the motor shaft and bearing box by bundling.

6. Photograph and mark the thickness of flange, coupling and base gasket before disassembly, and record the original centering state for easy reference during reassembly.

Second, the new assembly arrival check

1. Check the pump assembly model, shell material, impeller form, shaft diameter and flange pressure grade, which must match the original equipment; Thermal dispersion slurry has strong wear, and the wear-resistant materials of impeller and pump casing cannot be degraded.

2. Confirm that the complete set of containerized mechanical seal is in good condition, and the specifications of the supporting flushing water interface are correct; Thermal dispersion conditions can not be sealed with ordinary packing.

3. Check the oil level and oil seal of the bearing box; The sealing gaskets of import and export flanges are made of high-temperature resistant and wear-resistant flexible graphite composite gaskets, and ordinary rubber gaskets are not resistant to high-temperature slurry, so it is forbidden to use them.

4. Manually move the pump shaft, so that it can rotate smoothly without jamming, abnormal friction and abnormal noise, and make sure that the impeller has no bump damage.

Iii. Main points of dismantling the old assembly

1. Loosen the flange bolts diagonally by several times, and do not remove them all at once; Before the flange is completely loosened, make sure that there is no pressure residue inside, so as to prevent the internal residual slurry from being ejected instantly.

2. Dismantle the flanges of inlet and outlet pipelines first, then dismantle the coupling connection, and finally dismantle the foundation bolts of the base and lift the old pump assembly as a whole; Do not disassemble the internal parts of the pump on the frame.

3. Clean the flange of the pipeline, and clean up the residual slurry slag, welding slag and hard sand inside the pipeline. If the hard impurities are not cleaned up, the impeller and seal will be damaged quickly after the new pump is put into use.

4. Keep the original base adjusting gasket and put it in order, so as not to lose or confuse it.

Four, the new pump assembly in place to install the core points

1. Alignment of base and level

-Clean the base foundation, use the original adjusting gasket, and ensure the level of the pump body; Levelness control ≤0.05mm/m to prevent unilateral eccentric wear of bearings.

-It is forbidden to press the weight of import and export pipelines on the pump shell, and the import and export pipelines must be independently provided with pipeline supports; Metal corrugated expansion joints must be provided for heat dispersion high-temperature pipelines to absorb thermal expansion displacement and avoid the stress caused by thermal expansion pulling the pump shell, resulting in seal leakage and pump body deformation.

2. Alignment of coupling (thermal expansion offset reserved for cold state of heat dispersion high temperature pump)

> thermal dispersion operation temperature is very high, the pump shell will expand axially to the motor side when heated, and only do cold zero alignment. After heating up, there will be serious misalignment, large vibration and rapid seal damage.

1. Use a dial indicator/laser to center the instrument in a cold state; Radial and end face runout shall be in strict accordance with the equipment instructions;

2. For cold-state timing, the thermal expansion pre-offset (generally 0. 050.12mm, refer to the original factory manual) is reserved at the pump end towards the motor to compensate the thermal displacement after heating.

3. After the coupling is aligned to be qualified, tighten the anchor bolt, and check the alignment after the fastening is completed to prevent the alignment from deviating after fastening the base.

3. Flange reassembly

The flange gasket shall be placed in the center, and the bolts shall be tightened step by step in 23 times diagonally, and tightened according to the specified torque. Unilateral one-time locking is prohibited to prevent flange deformation and slurry leakage. The flow direction is strictly marked by the arrow of the pump body and cannot be reversed.

4. Recovery of sealing water flushing pipeline (the most easily overlooked fault point of thermal dispersion pump)

1. Connect the mechanical seal flushing cooling water pipeline, and make sure that the filter is free of blockage; The pressure of flushing water must be higher than the working pressure of the pump cavity by 0. 20.3 MPa, so as to ensure that clean cooling water continuously enters the sealing surface and prevent high-temperature slurry from entering the sealing pair.

2. Purge the inside of the pipeline to eliminate rust impurities in the pipeline; Confirm that there is no reverse connection at the inlet and outlet of flushing water; Before putting into use, turn on the washing water to make sure that the water is smooth.

V. Inspection before commissioning

1. All bolts are rechecked and tightened; Re-check the coupling alignment; The coupling shield must be completely reset.

2. Fill the bearing box with lubricating oil of the specified brand, and control the oil level at 1/22/3 of the oil mark.

3. Dismantle all blind plates according to the ledger and restore the pipeline; The drain valve is closed; Instruments (import and export pressure gauges) are put into use.

4. First, introduce the sealed washing cooling water to confirm that the effluent is normal; The pump cavity is filled with slurry to prevent idling.

5. Turn the inching motor, and it is forbidden to reverse, which will directly break the impeller and damage the mechanical seal.

Six, commissioning and acceptance

1. Try running for a short time with no load, and observe the vibration and noise without abnormality; The vibration value refers to the standard of pulping pump.

2. Slowly put into the thermal dispersion system with load, and pay attention to the outlet pressure and current; Observe the leakage of mechanical seal: minimal dripping is allowed, and slurry leakage is a serious fault.

3. Observe the change of pump vibration during heating; After the heat engine has been running for a period of time, the coupling alignment can be checked in hot state if conditions permit.

4. Check the flange and sealing water interface for no leakage; Make records of equipment replacement, and record the models of gaskets and seals.

Seven, common mistakes and risk warning

1. Dismantle the pump directly without cooling and adding a blind plate: high-temperature and high-pressure hot slurry is ejected, resulting in scalding accident.

2. The pipeline has no independent bracket and expansion joint: the thermal expansion stress pulls the pump shell out of shape, and the seal fails for a short time and leaks slurry.

3. Only cold alignment, no thermal expansion deviation is reserved: after heating up, the alignment is out of tolerance, the vibration is large, and the bearing and seal are quickly damaged.

4. Insufficient pressure of sealing flushing water or reverse connection: hot slurry rushes into the sealing surface, and the sealing is burned for a short time.

5. The pump cavity is started directly without air discharge: cavitation, large pressure fluctuation and impeller erosion damage.

6. Use ordinary rubber gasket: the gasket will age rapidly at high temperature, and the flange will be sprayed.