Answer MEP Question 3

Q. Abnormal vibration has been observed in an HFO purifier while in operation. Explain the areas you plan to investigate for rectifying the faults and put the purifier back to normal operations keeping in view that no reduction; In vibration has been noticed even after desludging the purifier couple of times.

1. Oil condition and level:-condition of oil in the sump to be checked for contamination with water leakage, resulting in loss of property of oil. The level of the oil is important to provide sufficient oil for the lubrication of running gears.

2. Brakes:- Check if accidentally engaging the brakes has taken place. Also, check for the brakes are intact and appropriately fitted at the required distance from the drum. 

3. Foundation:- Check for any loose or broken holding down bolt on the foundation. Check that the resilient mounting is in proper condition.

4. Motor:- Check the amperage of the motor. Should always be within the limit. abnormal amperage is an indication of improper operation of purifiers. Also check if the vibration is originating from the motor, that can be because of single phasing or bearing failure of the motor.

5. Bowl & de sludge port condition:- After stopping and properly isolating the motor electrically dismantle the purifier to check the condition of the bowl and desludging ports.

Heavy deposition of hard sludge can be a cause of vibration. Clean that thoroughly before fitting back.

6. Friction pad:- Worn out friction pads may result in vibration during the torque transmission. that has to be checked and if found worn all friction pads are to be renewed.

If no spare is available then the same pads can be used after roughening up the friction surface of the pad. use trichloroethylene or grease solvent for cleaning and course file to roughening of the pads.

7. Buffer springs:- They are fitted to reduce the bearing wear and to dampen the vibration transmitting from the bowl to the frame. A broken or improperly fitted bearing in the casing may result in the vibration of the purifier.

8. Worm and pinion gears:- A worn out or damaged gear will result in very heavy vibration. check for the condition of Worn and pinion gear and renew if found damaged.

9. Bearings:- Check for all the bearings with the bearing holders are fitted properly in place. check for their free rotation. Any damaged bearing to be renewed.

10. Attached pumps:- Attached feed pumps are generally fitted at the non driven end of the shaft through a safety joint. Any damage in the attached gear pump usually does not harm the horizontal shaft. Check the attached pump if it is free to rotate.

11. Bowl height:- In Mitsubishi purifiers; the height of the bowl with respect to the frame (A=68-69mm) and the height of the shaft with respect to the frame (B=28.5-29.5mm)is required to be measured and adjusted if required. The height of the lower bearing block is required to be maintained as per the manual (D=63.5mm). It comprises a lower spring retainer, steel ball and bearing case. Also, the height of flat spring (c) needed to be adjusted by using a proper spacer as per manual.

A height adjusting ring is fitted underneath the top bearing in the alpha Laval purifier. when height is measured between the spindle top and upper rim of the frame without o-ring it should be within the limit(16.5-18.5mm). Also, the height of the pairing disc in relation to the spindle top is adjustable and for this purpose, a height adjusting ring is provided underneath the distributor cover. This height is required to be maintained within the limit(148.5-149.5).

12. Shaft wobbling:- It can be an indication of bearing worn out, damaged springs or shaft bending. If the shaft is wobbling beyond the limit (0.04mm), the cause needed to be investigated and rectified.

Basic Checks while the machine running 

Check the brake- The brake may have been accidentally applied or the brake is installed too close to the drum.

Check the frame foot - Frame foot is installed on purifiers as vibration dampeners. Check if they have become hard and brittle.

- Cracked, damaged or worn-out frame foot causes vibration of the purifier to worsen.

Check for heavy sludge accumulation inside blow - If the accumulation of sludge is high in the bowl,  heavy vibration is noticed due to unbalanced moments in a rotating bowl.

Open and check the sludge port, usually, the sludge starts building up from there.

Another way of ascertaining sludge accumulation is by checking the capacity of the purifier for a known throughput, reduced volume processed indicates sludge accumulation.

Perform  a  chemical  cleaning  in  running  OR  perform  a physical  cleaning  and overhaul  if 

heavy sludge accumulation found.

Check drive side faults

- Check for motor amps, any deviation (High/low)  indicates a fault in the system.

- The  electrical   motor  malfunctioning,  check  for single phasing, loose connections, frequency setting ( Causes the motor too fast / too slow)

- Friction pad pads worn out if the clutch pads are unevenly worn or completely worn, oily - also 

creates a lot of vibration.

Check oil case & horizontal shaft

- Check the horizontal shifting, oil level, if the locking pin is in place.

- If the worm & pinion gear is worn out also causes heavy vibration.

Detailed inspection if no cause is ascertained.

Bearing failure

- Bearing failures are one of the most probable causes, vertical/horizontal shaft hearings have failed.

- bearings are too loose in the bearing cover.

Issues with bowl and bowl parts

Bowl height:

The bowl height position relative to the frame ring must be checked. The distance shall be within the limit prescribed by the manufacturer. If the height is incorrect  the bowl bottom may touch the water chamber and Cause  vibration and heavy damage

Radial Wobble

The bowl spindle wobble should be checked using a dial gauge. Permissible radial wobble is 

maximum 0.04mm if the wobble is too large, renew all the bearings on the spindle.

It is still excessive, the spindle is probably damaged and must be renewed.

Buffer springs:

Weakened  or broken  buffer springs or defective contact surfaces for the buffers on the ball 

bearing housing may give rise to separator vibration.

Disc stake pressure:

Ensure that the disc stack pressure is sufficient to maintain bowl balance. Insufficient pressure in the disc stack can cause vibration and reduce the lifetime of ball bearings.

The number of disc stacks also leads to issues with the pressure, ensure the correct number of stacks are installed and the locking ring is tightened as per manufacturer recommendation.