In the maintenance process, the diagnosis of pump failure is a key part of the following are given several common failures and elimination measures for you to set the pump fault diagnosis.
1, no liquid to provide, insufficient liquid supply or lack of pressure
1) Pump is not filled or not properly vented
Remedy: Check that the pump housing and inlet lines are completely filled with liquid.
2) the speed is too low
Elimination measures: Check the motor wiring is correct, the voltage is normal or the turbine steam pressure is normal.
3) system head is too high
Elimination measures: Check the system head (especially the friction loss).
4) suction is too high
Elimination measures: Check the existing net head (inlet pipe is too small or too long will cause a great friction loss).
5) impeller or pipeline blocked
Remedy: Check for obstructions.
6) The direction of rotation is wrong
Elimination measures: Check the direction of rotation.
7) Air or inlet piping leaks
Remedy: Check inlet piping for cavitation and / or air leaks.
8) Stuffing or seal wear in stuffing box to allow air to leak into pump housing
Elimination measures: Check the packing or seal and replace as needed, check the lubrication is normal.
9) Insufficient suction head when pumping hot or volatile liquids
Elimination measures: Increase the suction head, consult the manufacturer.
10) The bottom valve is too small
Elimination measures: Install the correct size of the bottom valve.
11) The bottom valve or inlet pipe immersion depth is not enough
Remedy: Consult manufacturer for correct immersion depth. Eliminate eddies with baffles.
12) The impeller clearance is too large
Elimination measures: check the gap is correct.
13) impeller damage
Elimination measures: Check the impeller, according to the requirements of replacement.
14) Impeller diameter is too small
Remedy: Consult manufacturer for correct impeller diameter.
15) Pressure gauge position is incorrect
Elimination measures: check the location is correct, check the outlet nozzle or pipe.
2, the pump will stop running for a while
1) Suction is too high
Elimination measures: Check the existing net head (inlet pipe is too small or too long will cause a great friction loss).
2) impeller or pipeline blocked
Remedy: Check for obstructions.
3) There is a leak in the air or inlet line
Remedy: Check inlet piping for cavitation and / or air leaks.
4) stuffing box packing or seal wear, so that the air leaked into the pump housing
Remedy: Check packing or seal and replace as required. Check the lubrication is normal.
5) Insufficient suction head when pumping hot or volatile liquids
Elimination measures: Increase the suction head, consult the manufacturer.
6) The bottom valve or inlet pipe immersion depth is not enough
Remedy: Consult factory for proper immersion depth and remove vortex with baffle.
7) Pump casing seal damaged
Remedy: Inspect the gasket and replace as required.
3, the pump power consumption is too large
1) The direction of rotation is wrong
Elimination measures: Check the direction of rotation.
2) impeller damage
Elimination measures: Check the impeller, according to the requirements of replacement.
3) rotating parts bite death
Elimination measures: Check the internal wear parts of the gap is normal.
4) Shaft bending
Remedy: Align the shaft or replace as required.
5) speed is too high
Remedy: Check the winding voltage of the motor or the steam pressure delivered to the turbine.
6) head below the rated value. Pump too much liquid
Elimination measures: to consult manufacturers. Install throttle valve, cut impeller.
7) The liquid is heavier than expected
Elimination measures: Check the proportion and viscosity.
8) The stuffing box does not have the correct stuffing (insufficient stuffing, incorrect stuffing or running in, stuffing too tight)
Elimination measures: Check the packing, packing stuffing.
9) Bearing lubrication is not correct or bearing wear
Remedy: Check and replace as required.
10) The running clearance between wear rings is not correct
Elimination measures: check the gap is correct. Replace the wear rings of the pump housing and / or impeller as required.
11) The pressure on the pump casing is too high
Elimination measures: Eliminate stress and factory representatives advice. After eliminating the stress, check the alignment.
4, pump stuffing box leak too much
1) Shaft bending
Remedy: Align the shaft or replace as required.
2) Misalignment of coupling or pump and drive
Elimination measures: check the alignment, if necessary, re-center.
3) bearing lubrication is not correct or bearing wear
Remedy: Check and replace as required.
5, the bearing temperature is too high
1) Shaft bending
Remedy: Align the shaft or replace as required.
2) Misalignment of coupling or pump and drive
Elimination measures: check the alignment, if necessary, re-center.
3) bearing lubrication is not correct or bearing wear
Remedy: Check and replace as required.
4) The pressure on the pump casing is too high
Elimination measures: Eliminate stress and consult factory representatives. After eliminating the stress, check the alignment.
5) too much lubricant
Elimination measures: remove the plug, so that too much fat automatically discharged. If it is an oil-lubricated pump, drain the oil to the correct oil level.
6, stuffing box overheating
1) Filler or seal wear in stuffing box to allow air to leak into pump housing
Remedy: Check packing or seal and replace as required. Check the lubrication is normal.
2) The stuffing box does not have the correct stuffing (insufficient stuffing, incorrect stuffing or running in, stuffing too tight)
Elimination measures: Check the packing, packing stuffing.
3) Packing or mechanical seal design problems
Elimination measures: to consult manufacturers.
4) Mechanical seal is damaged
Remedy: Check and replace as required. Consult the manufacturer.
5) sleeve scratches
Remedy: Repair, re-machine, or replace as required.
6) The packing is too tight or the mechanical seal is not properly adjusted
Elimination measures: Check and adjust the packing, according to the requirements of replacement. Adjust the mechanical seal (refer to the manufacturer's instructions provided with the pump or consult the manufacturer).
7, rotating parts are difficult to rotate or have friction
1) Shaft bending
Remedy: Align the shaft or replace as required.
2) Running clearance between wear rings is incorrect
Elimination measures: check the gap is correct. Replace pump housing or impeller wear ring as required.
3) The pressure on the pump casing is too high
Elimination measures: Eliminate stress and factory representatives advice. After eliminating the stress, check the alignment.
4) Shaft or impeller ring swing too much
Remedy: Check rotating parts and bearings and replace worn or damaged parts as required.
5) There is dirt between impeller and pump casing wear ring, and dirt in pump casing wear ring
Remedy: Clean and inspect wear rings and replace as required. Cut off and eliminate the source of dirt.
A minor problem that can be easily overlooked when working on a pump
What I want to talk about is a trivial matter that can be easily overlooked when assembled after repair.
The middle of the impeller exit centerline of the impeller in the volute pump, ie, the exit of the impeller, should be aligned with the center line of the volute inlet. If not correct, should be in the impeller hub and shoulder by adding gasket adjustment. The two neutrals should be controlled within a 0.5 mm range. Pump slightly larger than the number of revolutions on the performance of the pump slightly less for medium and low pump speed due to the impeller exit is very narrow, such as the impeller exit width of only 10 mm, and if the shell center line deviation of 1 mm, the pump The performance has a significant impact. It is recommended to adjust the two midline (impeller and volute) error control within 5% of the exit of the impeller as well.
The same is true of the multi-stage vane pump, which controls the error of the midline of the impeller exit and the midline of the guide vane.
Space guide vane pump, it is best to use the data given in the assembly diagram to determine the position of the vane in the space guide vane. If there is no drawing, or by experience, or through the test results to adjust the position of the impeller.
Pump NPSH, suction stroke and their respective units of measure to express letters
Pump at work at the impeller inlet at a certain vacuum pressure will produce a vapor, vaporization of bubbles in the liquid particle impact movement, the impeller and other metal surface erosion, thus undermining the impeller and other metals, the vacuum pressure at this time Vapor pressure, NPSH refers to the excess energy of vaporization pressure per unit weight of liquid at the suction inlet of the pump. Units marked with meters, with (NPSH) r. Suction stroke is required NPSH Δh: That is, the degree of vacuum that the pump allows liquid to be sucked in, that is, the allowable installation height of the pump, in meters.
Stroke = standard atmospheric pressure (10.33 meters) - NPSH - safe amount (0.5 meters)
Standard atmospheric pressure pipeline pressure can be 10.33 meters in height.
For example: a pump required NPSH is 4.0 meters, suction Δh?
Then: Δh calculation also need to consider the vaporization pressure and tube loss
Δh = (Pc-Pv) / Ïg-NPSHa-hc (meter)
Discuss the Δh formula
The calculation of Δh also takes into account vaporization pressure and tube loss
Δh = (Pc-Pv) / Ïg-NPSHa-hc (m)
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