Aspen Rentals

Belt Press Maintenance Procedures

Routine Maintenance

1 Clean belts by running belt drive and wash system without sludge or polymer for a minimum period of 45 minutes.

2 Clean spray nozzles on wash boxes.

3 Check fluid level in hydraulic unit. Fill as required.

4 Manually extend and retract the tension cylinders to clean and oil the rods. This will greatly extend the life of the seals.

5 Cycle the steering cylinder in both directions by holding the steering paddle first one way and then the other. This will clean and oil the rods and greatly extend the life of the seals.

6 Inspect alarm sensors.

7 Check emergency trip cord by manually tripping circuit and resetting.

1 Inspect wear items specifically chicanes, scraper blade, gravity drainage grids, dewatering belts, rubber seals on the sludge restrainers and the wash stations. Replace as required.

2 Inspect frame and roller coatings for wear.

3 Inspect belt guides and wiper bars for cleanliness/wear. Clean as required.

4. Check for any loose bolts.

5 Check and adjust the belt tension.

1 Verify daily and weekly items have been completed

2 Clean belts with a soap/bleach mixture. To prepare the soap/bleach mixture, use 1-cup detergent and 3-cups bleach to mix with 5 gallons water. The soap can be any laundry type liquid detergent and the bleach can be any generic brand bleach containing sodium hypochlorite. The water can be tap water.

Use power wash system to spray the soap/bleach mixture on belt surface for cleaning. The spray pressure shall be about 1,000 psi and not to
exceed 2,000 psi.

3 Check belt seam wires for breaks. Replace if broken.

1 Verify monthly items have been completed.

2 Clean hydraulic filter screen.

3 Check oil level in drive unit gear box and lubricate bearings. Inspect polymer mixer/injection ring assembly and clean as required. 

4 Replace belt seam wires. Worn belt seam wires can break and cause the belts to be damaged.

Specific System Maintenance

Inspection Items:

a. Inspect frame and anchor bolts and tighten as required.

b. Inspect frame coating and repair corrosion as required.

Coating Repair Procedures: (Galvanized Frame only)

a. Clean corroded area with wire brush until base metal is exposed.

b. Coat area with spray or liquid galvanizing solution.

Inspection Items:

a. Inspect roller coating for damages.

b. Minor chips and scratches can be repaired using a touch up kit.

Roller Alignment:

Roller alignment can be checked and corrected in the field using simple tools. This would only need to be done if rollers were replaced or the bearing base was removed from the frame.

a. The basis of proper roller alignment is a square and level frame. Check the frame for square by measuring diagonally from the same points on both sides.

b. Use the drive roller as the primary alignment reference and check it and the frame to be level using a machinist’s level.
c. Wrap a plumb line around the drive roller and measure from the line to the base of the tension yoke bearing. The measurement must be equal on both ends of the roller.

d. Check each roller to be parallel to the drive roller by measuring to plumb lines wrapped around it and the drive roller at both ends. The difference must be less than 1/32 inch.

e. Slide the bearing housing to align each roller to the drive roller.

f. Check each roller with the machinist’s level and shim under the bearing housing as needed.
g. Torque all bearing base bolts to 115 ft-lb.

 

   Inspection Items:

a. Ensure grease is visible on bearing/shaft seal.

b. Check bolts.

c. Ensure roller flinger is in place.

d. Listen for unusual sounds.

   Lubrication Procedures:

Note: Lubricate bearings every six months with 3 to 5 ounces of grease per bearing. Failure to lubricate the bearings will invalidate the bearing warranty.

a. Attach grease gun to button grease fitting.

b. Inject three to five ounces of grease. Grease should be seen.

c. Disconnect grease gun and continue with remaining bearings.

d. Repeat until all bearings are lubricated.

e. If the grease displaced from a bearing is rust colored this is an indication this bearing has been damaged by water and must
be replaced.

   Bearing Replacement: Do not remove the bearing housing from the frame unless it is damaged. The roller alignment will be retained if the bolts holding the bearing on to the frame are not disturbed.
a. Provide a sling and hoist to raise and hold the end of the roller where the bearing is being replaced.
b. Support the roller and remove the shaft flinger (rubber splash guard) and the bearing cap.

c. Lift (or lower) the roller to get the bearing clear of the bearing base housing.

d. Remove the snap ring from the end of the shaft. Use a bearing puller to remove the bearing from the end of the shaft.
e. Remove and discard the old shaft seal assembly, but save the bearing spacer rings, if any. Spacer rings are only used in the bearings on the same side of the machine as the belt drive motor.

f. Thoroughly clean the bearing base housing and the cap. Clean and polish the journal of the roller in preparation for the new bearing. If the roller journal has been damaged, do not install a new bearing. Call Ashbrook Service for assistance.

g. Install the new seal assembly before installing the new bearing.

h. Heat the new bearing in an oven or in hot oil to 300 degrees F.

i. Immediately slide the heated bearing onto the cold shaft of the roller journal being certain to press it all the way to the shoulder.
j. Install a new snap ring on the end of the roller shaft.

k. Install the bearing spacer rings if the bearing is on the same side of the machine as the drive motor. If on the opposite side, do not install the spacer rings. This side must be free to float.

l. Move the roller with the new bearing installed back into the bearing base housing.

m. Coat the surface of the bearing cap that comes in contact with the bearing housing base with an RTV gasket sealant.
n. Reinstall the bearing cap and torque the bolts to 75 ft-lb.

o. Snap the seal assembly into the bearing housing.

p. Install the two piece rubber flinger (splash guard) around the shaft.

q. Grease the bearing while rotating the roller until grease flows out from under the flinger

   Inspection Items:

a. Ensure sensing paddle is moving with belt.

b. Ensure steering cylinder is responding to sensing paddle.

c. Ensure belt is tracking in approximately the center of the belt press.

d. Ensure belt misalignment limit switches are functioning 

  Wear Strip Replacement

a. Shut down belt press and lock out controls.

b. Unbolt wear strip from paddle.

c. Position new wear strip on paddle and replace bolts.

Belt Cleaning Instructions:

a. Run wash water and belt drive (no sludge or polymer) for a minimum of 45 minutes per day of dewatering.

b. If additional cleaning is desired, Apply mild soap directly onto the belts or inject into the spray wash system for one hour.

Note: Do NOT steam clean the belts. water at a maximum of 130 degrees F. will cause stretching.

Steam cleaning will damage the belts. Use a maximum of 1,500 psi Do not wash belts with hot water while they are under tension as this will damage the belts

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1 Belt Repair Procedures: 

a. Belt Puncture:

(1) Clean around the puncture and allow belt to dry.

(2) Using scrap belt material, cut a patch to size.

(3) Coat area with marine epoxy and apply patch.

(4) Allow epoxy to dry before operating press.

Note: When using marine epoxy, ensure belt is clean and dry before applying epoxy. Apply epoxy to both belt and patch as evenly as possible. Let epoxy thoroughly dry before operating. Dewatering will not occur in an area coated with marine epoxy.

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b. Belt Edge Fraying:

(1) Clean belt edge and allow belt to dry.

(2) Cut off excess strands.

(3) Apply marine epoxy and allow epoxy to dry.

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 Possible Causes for Belt Tracking Problems

Occasionally a problem will arise where one or both belts of a belt filter press will not track properly. When this happens look for these possible causes.

When both belts wander off track:

Uneven sludge distribution across the width of the machine will make the belts steer away from the heavy side because the higher sludge load between the belts makes the belt on the outside behave as though it were on a steering roller turned away from the heavy side. This occurs to both belts alternately as they go around the rollers. When the belt is on the inside against the roller it does not see the uneven sludge thickness, but when it is on the outside it will be steered “down hill” away from the heavy side. Correct the sludge distribution at the inlet spreader. In extreme cases of off center sludge loading the steering system will not be able to compensate and the belt will go into the over travel limit switches. Also, serious cases will cause diagonal creasing and destruction of the belts. If the belt seam is not straight across the machine this is evidence that the sludge loading has not been correct in the recent past. The seam will lag behind on the heavier loaded side and, if run this way long enough, will not recover even if the sludge distribution is corrected.

A pressure roller bearing that has come loose from its mounting to the frame will allow the roller to get out of alignment and it will act like a steering roller and cause both belts to track toward one side. This may be detected by observing that the steering cylinders are staying off center or are hunting for their balance point. If the bearing housing has moved enough to cause this problem you should see the mark on the frame showing it has moved from its original place. Put the bearing back where it was and check all the bearing mounting bolts for tightness. Observe for correct tracking without hunting.

Check for bearings that have been moved in an attempt to “realign” the rollers. Sometimes this is done in the field by persons attempting to make a damaged or irregular belt track straight. When the belt wears or is later replaced, then tracking problems will begin. Put all the rollers back in their original places so they are parallel. Be sure to check that all the bearing bolts are tight.

When one belt wanders off track:

Uneven sludge distribution across the width of the machine will make the belts steer away from the heavy side because the higher sludge load between the belts makes the belt on the outside behave as though it were on a steering roller turned away from the heavy side. Uneven sludge distribution usually affects both belts, but in mild cases or if the belts have been stretched only one belt may be affected. Look for creases in the belts or belt seams that have been pulled in a diagonal. See the paragraph above.

An idler roller bearing that has come loose from its mounting to the frame will allow the roller to get out of alignment and it will act like a steering roller and cause one belt to track toward one side. This may be detected by observing that its steering cylinder is staying off center or is hunting for its balance point. If the bearing housing has moved enough to cause this problem you should see the mark on the frame showing it has moved from its original place. Put the bearing back where it was and check all the bearing mounting bolts for tightness. Observe for correct tracking without hunting.

Check for bearings that have been moved in an attempt to “realign” the rollers. Sometimes this is done in the field by persons attempting to make a damaged or irregular belt track straight. When the belt wears or is later replaced, then tracking problems will begin. Put all the rollers back in their original places so they are parallel. Be sure to check that all the bearing bolts are tight.

It is possible for the tension equalizing rack and pinion to get out of time. If the rack is clogged with dried sludge or there is any looseness in the assembly the pinion can jump a tooth and make the tension roller be out of line. Uneven sludge distribution can provide the force to cause this to happen. Observe when you fully retract the tension cylinders if one side hits bottom first; or you can measure the distance between rollers or count the teeth. Clean the rack and reset the timing.

Intermittent steering problems, those that return after you have “fixed” the problem and watched the machine run fine for hours, can be the result of trash in the hydraulic lines. Take off the steering valves and flush the lines. Try swapping the steering valves between the upper and lower belts to see if the problem goes with the valve. If the filters in the fittings on the valve are clogged with dirt it may not be obvious and you may not be able to clean them. Replace the fittings or the entire valve.

A dirty or damaged steering valve will not respond to the movement of the belt and the steering cylinder may stay at one end of its travel for too long and then switch completely to the other end. Clean or replace the steering valve. Also, look for a broken spring on the paddle arm. If the arm is damaged or loose on its shaft the same effect may be observed.

The early steering cylinders had chrome plated steel rods that can rust where there are microscopic pores in the plating. After a long time in service the rod can become so rough that it will stick in the rod seal or bushing and the cylinder action will be erratic, not responding immediately to movement of the steering paddle. Look for leaking seals and rough spots on the cylinder rod. Replace the cylinder. The new steering cylinders have solid stainless steel rods that will not rust and there is no plating to flake off.

Wear or damage to the steering bearing pivot assemblies can cause irregular tracking action. Make sure the pivots are in good condition and there is no looseness.

Sometimes a new belt gets stretched on one side by uneven sludge loading. When the belt tension is applied the belt will be tight like a drum head on one side of the machine and slightly slack on the other. A stretched belt will not track straight. Sometimes the belt can be straightened by running it for a while at maximum belt tension with only the wash water on. Apply hot water if it is available and the straightening will happen faster, but don’t over do it.

The basic steps in recovering from a belt tracking accident

1. turn off the power and disconnect the belt misalignment switches

2. turn on the power and start the hydraulic unit

3. retract the tension cylinders to loosen the belts.

4. turn off the power

5. manually pull the belts back to center

6. start the press and allow it to run without sludge until clean

7. observe the belt tracking

8. watch for proper operation of the belt steering

9. if belt tracks OK and steering is working, shut down the press

10. turn off the power and reconnect the misalignment switches

11. place the press back in service

12. watch for tracking problem to reappear

13. determine and correct the cause