Large long axis deep well pump vibration troubleshooting method

Through the vibration analysis of large-scale deep well pump and various reasons that may cause vibration, a simple method to judge motor and pump in the field is proposed.
Panzhihua Iron and Steel in the upper reaches of the Jinsha River has built a large deep-well pump station, the pump station consists of two 18m ID, deep 31m deep and the upper plant form. The Jinsha River flows into the deep well via 4 Dg1200 pipes. The upper part of the deep well houses 20 sets of 30JD-19x3 sand control deep well pumps on a reinforced concrete frame beam with a cross-section of 1450mm × 410mm. After a long period of installation and maintenance, we made some explorations on the causes of vibration.
A deep well pump related technical performance parameters Model: 30JD-19x3, three impeller flow: 1450m3 / h drive shaft length: 24.94m, a total of 9 shaft pump shaft diameter: 080mm shaft material: 40Cr speed: 985r / min thrust Oil temperature: <50 ℃ Cooling water pressure: 0.8MPa Jacking pipe diameter: 500mm Head: 80m Rubber bearing Lubrication medium: Clean water Without motor Single weight: 14t Vertical motor Model JKL15-6 Rated power: 500kW Rated voltage: 6000V Rated Current: 60A Motor rotor moment of inertia: 58kg · m2 Motor weight: 4t Motor and pump vertical and horizontal allowable amplitude: <0.l0mm This deep well pump water quality requirements of not more than 0.1% sediment, the particle size of not more than 0.2mm, And the first level of the impeller pump should be immersed in moving water level lm below. At present, during the floods in July and August, the highest concentration of water in the Jinsha River from deep-well pumps is nearly 20%.
2. Judgment of vibration failure Pump and motor vibration occurred during operation, when conditions, the first should disconnect the coupling between the two, the vibration source is from the pump or motor, and carefully check the vertical motor base and Pump connection bolts are tightened, the installation level is over tolerance.
1. Motor vibration source and determine (1) the rotor speed is close to the critical speed. It can be calculated by calculating the motor shaft torsional stiffness and torsional vibration motor frequency with the motor critical speed, pump frequency and frequency close to produce resonance. In particular, the first use of the motor, the occurrence of vibration failure, to be analyzed and calculated. Motor rotor speed should be at least below the critical speed 25% or above the critical speed of about 40%. In the analysis, we must also consider that the quality of the rotor of the motor can not be simplified into the concentrated quality situation but distributed along the rotation axis. Therefore, the critical speeds such as second and third order should be analyzed when analyzing the critical speed.
(2) Motor rotor imbalance. Motor rotor imbalance is the most important and common causes of vibration, such as: 17 #, 19 # motor speed vibration meter (displacement meter) measured motor vibration speed of 9.8-l0mm / s, control IS02372 vibration speed standard, Class III machinery should be less than 4.5mm / s, while in the 9.8-l0mm / s state, measured with a vibrometer amplitude of the motor reaches 0.30mm. In order to find out the unbalance degree of the rotor of the motor, we made two steel frames on the scene to set up two parallel rails (pay attention to the steel frame should have sufficient rigidity), the surface of the rails processed into smooth and clean, Face adjustment and fixed. Check the motor rotor placed on top of two rails, manually push the rotor inlet metering pump to scroll back and forth several times, to be stationary after each, under the rotor marked. With sticky paste in the emphasis position of the symmetry point, and then rotate the rotor several times until the rotor can stop at random position, make sure the motor rotor has reached a state of static equilibrium. To replace the paste with equivalent quality to complete the balance of the motor rotor. If using the above method still can not solve the problem, you need to motor balancing test motor. The two motors that increase the rotor side 45-5g balance weight, the amplitude reduced to 0.05mm, with a displacement meter measured vibration velocity value of 2.1mm / s or so.
(3) The motor that has been used normally for a period of time should check whether the bearing clearance is too large, whether the fixing screws of the shaft base are loose, whether the shaft is worn and bent or a part of the windings is short-circuited, and the air gap is not uniform. Stator ring gap between the general shall not exceed 10%. It is particularly noteworthy that when the motor amplitude value is close to the standard value, which is considered within the acceptable range, the amplitude of the motor tends to exceed the standard value after load. This is because the factors affecting the vibration of the entire deep well pump drive system are interdependent And work together to result.
2. Pump body vibration and judge (1) pump installation and assembly caused by vibration. After the installation of the pump body and the thrust level and vertical pipe overtemperature will cause the pump body vibration, while the three control values ​​have some relevance. After the pump body is installed, the total length of the pumping pipe and the pump head (excluding the filter) is 26m, all of which are suspended. If the vertical deviation of the pumping pipe is too large, the pump and the shaft will cause violent vibration . Yang pipe vertical tolerance is too large will be in the pump during the operation of alternating stress, causing Yang pipe fracture. Deep well pump assembly is completed, Yang pipe in the total length of the vertical error should be controlled at ± 2mm. Pump horizontal and vertical horizontal error <0.05 / l000mm. The pump head impeller static balance of tolerance is not more than 10g, after assembly should be 8-12mm up and down the string moving clearance. Installation and assembly gap error is caused by the pump vibration is an important reason.
(2) drive shaft whirl. Whirl, also known as "rejection turn", is a self-excited vibration occurring on the rotating shaft. It has neither the characteristics of free vibration nor the type of forced vibration. It is characterized by the axis of the shaft in the bearing performance of the rotation, this vibration does not occur when the shaft reaches the critical speed, but in a larger range and the rotation speed of the shaft itself less. Deep well pump rejection mainly caused by inadequate lubrication of the bearing lubrication, if the shaft and bearing clearance between the larger, then the direction of rotation and the axis of rotation in the opposite direction, this situation, also known as shaft jitter. In particular, deep well pump shaft is very long, the rubber bearing and the shaft with the gap of 0.20-0.30mm, when the shaft and the bearing there is a certain gap, the shaft and the bearing is not the heart, the center distance is large, the gap and lack of lubrication, such as deep well Pump rubber bearing lubrication Supply pipe rupture, plugging, misoperation caused by inadequate or inadequate water supply and other circumstances, the more prone to jitter. In a moment of rotation of the journal and rubber bearings in contact at one point, the journal by the bearing to its tangential force, the role of the direction of force and shaft speed in the opposite direction, the force to the axis of translation, the mechanical effect Equivalent to a counterclockwise torque and a force acting on the journal center parallel to the tangential direction of the contact point of the bearing wall and tends to move the journal downwards so that the journal will be pure along the bearing wall Rolling, equivalent to an internal gear, so that the formation of the axis of rotation in the opposite direction of rotation. This has been confirmed by our daily operation, which can last a bit longer and burn the rubber bearings.
(3) Vibration caused by overload. Thrust washer pump using tin-base Babbitt alloy, which allows the load of 18MPa (180kgf / cm2). Pump body at start-up, the lubrication of the thrust pad is in the boundary lubrication state. In the pump outlet were installed electric butterfly valve and manual gate valve. When the pump starts to open the electric butterfly valve at the same time, the valve plate can not be opened due to deposition of silt or the manual valve is closed due to human factors, the exhaust gas is not timely and so on, which will cause severe vibration of the pump body and quickly burn the thrust pad, #, 17 # pump that is the case.
(4) outlet turbulence vibration. Dg500 short tube, check valve, electric butterfly valve, manual valve, supervisor and water hammer eliminator are arranged at the outlet of the pump. The turbulent motion of the water produces irregular pulsation phenomena. With the blocking of each valve, the local resistance is larger, Caused by changes in momentum and pressure changes, the role of the tube wall and the pump to make it vibrate, which can observe the value of the pressure gauge pulsation to illustrate. The fluctuating pressure and velocity fields in the turbulent flow are continuously transmitted to the pump body energy. When the main frequency of turbulence is similar to the natural frequency of the deep well pump system, the system absorbs energy and causes vibration. To reduce the impact of this vibration, the valve should be fully open, short tube should be the appropriate length and add bearings. According to this treatment, the vibration value is significantly reduced.
(5) Deep well pump torsional vibration. Long axis deep well pump and motor coupling flexible coupling, shaft length 24.94m. During pump operation, there is a superposition of the main vibrations at different angular frequencies. The results of the two simple harmonic vibrations with different angular frequencies are not necessarily harmonic harmonic vibrations, that is, the two-degree-of-freedom torsional vibration exists inside the pump body, which is inevitable. This vibration mainly affects and impairs the thrust pad. Therefore, to ensure that each plane has a corresponding thrust pad thrust oil wedge case, we will be the original equipment specification random 68 # oil into a 100 # oil to improve the viscosity of the thrust pad oil, so that the thrust pad oil Dynamic pressure lubrication film formation and maintenance is not destroyed.
(6) The vibrations caused by the pumps mounted on the same beam interact with each other. Deep well pumps and motors are installed on two reinforced concrete frame beams with a cross-section of 1450mmx410mm. Each pump and motor have a mass mass of 18t. The operation of two adjacent pumps oscillating on the same frame beam is again a two Degree of freedom vibration system, when one of the motor vibration seriously exceeded without load test run, that is, the elastic coupling is not connected and idling the motor, the other normal operating pump motor amplitude rose to about 0.15mm, This situation is not easily noticeable and should attract attention.

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