Analysis of the vibration of the decanter centrifuge

Daqing Petrochemical Branch Plastic Factory low-pressure high-density polyethylene plant M-3301 centrifuge, model LWF-1050N, drum diameter 1 050 mln, speed 1450r / rain, differential speed 19r / rain, motor power 185 kW , Slag discharge capacity of 13 t / h, manufactured by Jilin Chemical Industry Machinery Factory.2001
l1 January 2002, M-3301 centrifuge feed side and differential vibration amplitude gradually increased to 50Llm, the maximum amplitude of the unit should not exceed 39 um. The use of the United States produced data acquisition analyzer bearing vibration signal spectrum analysis, the main component of the vibration signal is 24. O5 Hz ejector frequency, 24.375 drum rotation frequency and 48.512 Hz double drum frequency.
Because the drum support bearing housing loose will produce a double frequency and double frequency vibration, if the bearing clearance is too large, even a small excitation force, can cause significant bearing vibration. The poor lubrication of the shaft and shaft bearings can also cause friction, causing the bearing clearance is too large, causing abnormal propeller vibration. Several adjustments have been made to the amount of lubricant on the bearing drums on both sides of the drum, and the bearing pads for propulsion have been refilled but the vibration has not improved.Initial diagnosis for the drum balance accuracy worse, and the excessive wear and tear bearing pads and shaft caused by mild abrasion.

drum and ejector imbalance reason 

Drum due to material, quality, processing technology and operating conditions and other aspects, it is impossible to achieve “absolute balance”; drum attached to the mass unevenly distributed plasticizers , So that the drum along the centerline of the uneven distribution of quality, but also to balance the state of the drum formed a large residual imbalance in quality. The centrifugal force generated by unbalanced drum quality always acts on the rotating drum. When the rotating drum rotates for one week, a vibration response occurs on one side of the bearing. Therefore, the vibration frequency is the rotating speed of the rotating drum, i_ (1 / 60) × n = 1/60 ~ 1 450 24.375Hz This frequency component is easily observed on the vibration spectrum of the bearing, and the bearing vibration spectrum has similar characteristics.

Continuous production of the production line has developed several tandem grades that are prone to plasticization. The inner wall of the drum and the plasticizers deposited on the pusher make the drum and pusher unbalanced in mass distribution, resulting in an imbalance between the drum and the pusher. Vibration larger.

2 centrifuge disassembly of the centrifuge to open the lid to check the drum and pusher and found that the inner wall of the drum attached to a layer of plastic, the thickest at 5 mm, pusher screw plasticizer serious situation, the most Thickness of up to 7 mln.Bearing wear more serious, up to 0.25 mm, close to the replacement standard.Support thrust bearings showed no signs of wear. The demolition inspection
verified the cause of the unit vibration.

3 measures

(1) in the development of production plans, try to arrange a series of plastifiable plastic grades and plasticizers in parallel low cross-licensing cross-production, so that the production of tandem grades plastic products produced in the parallel license plate number can be washed out, Reduce the excess mass on the drum and pusher.
(2) Clean the inner wall of the drum and the plasticizer attached to the feeder to avoid the “snowball effect” during each overhaul of the drum. And drums and pushers should do 2.5 level dynamic balance test.
(3) In the production of tandem grades, the period of grease padding is changed from original 6 months to 2 months to reduce the wear on the pad due to unbalanced ejector lengthening the service life of the pad.