The key element of any effective preventative maintenance is establishing a schedule and checklist that are set in stone. Both of these items should incorporate recommendations from the manufacture and learned experiences.
One of the easiest and often overlooked parts of preventative maintenance is a simple daily inspection. Each piece of equipment will have a normal operational look, sound and feel.
Once you learn what the signs of normal operation are, problem conditions should stand out. To learn those normals, it takes everyday inspection and being physically around the equipment to establish the baselines for comparison.
A number of things show up as housekeeping issues that turn out to be indicators of equipment issues.
- Unexplained piles of material or leaking can point to worn components.
- A sump overflow may be an indicator of a worn Pump or a blocked Cyclone.
- A Cyclone overflow box pour over could also indicate a blocked Cyclone.
- Excessive splatter at the Cyclone underflow launder would point to a worn-out apex.
Not all leaking is a tell-tale sign of a problem. Depending on the type of seal gland used, water may be released at the seal point, but this is to be expected. You need to consider what is the normal amount.
In the case of a dry gland on a McLanahan Pump, five to 50 drips per minute is normal. Anything outside of that range would be cause for concern. Once again, this points out the need to see what is normal and what is an early warning sign of wear.
Up to this point, I have talked about what a person may see, but touch and sound can provide informative feedback.
A Pump and Dewatering Screen have a normal level of vibration, but a Cyclone has no moving parts except the slurry going through it. When a Cyclone shakes violently, something is definitely wrong. The most common source of the problem is air in the slurry. This is not only a problem for the Cyclone but most likely an issue with the Pump.
Vibration can be seen and felt, but when it is heard, there is going to be some damage. Both Pumps and screens operate at high RPM — and that means a lot of impacts per minute. A screen banging against a guard or handrail may not seem important, but when installed, a screen should have sufficient clearance to avoid contact. Contact with a guard or handrail means something has changed either with the structure around it or with the screen itself.
The cause of any banging on a screen or Pump should be immediately investigated and corrected.
In addition to everyday walkthroughs, weekly and monthly scheduled inspections can identify potential problems before they can become serious. This level of inspection will have a little more hands-on action and may involve written procedures to accomplish.
These inspections can normally be done while the equipment is operating as long as safety precautions are observed. In some cases, short downtime may be needed to check the torque on fasteners.
Indicators such as pressure, temperature, flow and amp readings should analyzed for sharp and gradual changes. Any sharp changes should be handled immediately, while gradual changes generally mean worn parts.
When a piece of equipment has moving parts, lubrication becomes an essential preventative maintenance task.
On a Pump, the bearing housing requires lubrication, as may the gland if it is a packed gland.
A packed gland uses graphite braiding (sometimes called rope) to keep the slurry from flowing out to protect the shaft. Because it is in direct contact with the shaft, it has to have some lubricating properties.
On a Dewatering Screen, the vibrating motors may have special lubrication requirements.
Because of the importance of maintaining the moving parts, lubrication instructions from the manufacturer should be completely understood. Assuming a lubrication plan can void the warranty and allow damage to an expensive piece of equipment.
Depending on the requirement, lubrication can be incorporated in the routine inspections. Automatic lubrication can help ensure timely doses but must be maintained with an adequate supply of lubricant.
Inspecting the equipment from the outside can only tell so much — there is a time to break out the tools and look inside. The wear parts on a Pump and Cyclone can only be seen when the unit is at least partially dissembled.
It is also difficult and unsafe to perform certain actions on operating equipment. Lock Out/Tag Out procedures need to be employed prior to any work being performed. This level of inspection is detailed in equipment manuals and should not be deviated from without good reason.
Winter has a way of doing its worst to idle equipment. The biggest issue is the possibility of freezing liquids, and the following two steps can prevent the damage it can cause:
1. Remove all standing water and prevent it from gathering or pooling up.
2. Protect/cover all electrical components and wire leads.
Although not thought of as much, the sun itself can damage equipment, so the addition of a third step (below) can go a long way in making sure the equipment is ready to run when you need it.
3. Cover rubber and urethane parts to prevent ultraviolet damage.
Pumps have a distinctive issue because of the possibility of residual water being contained within. During freezing temperatures, water increases its volume (in the form of ice) by about 9% under atmospheric pressure. Without room to expand, it will apply forces to the Pump casing and may cause damage.
If the unit has a drain plug, the solution is fairly easily. The removable plug allows the water to be drained while leaving the piping for the system in place.
In situations when a Pump does not have a drain plug or the Pump has been rotated for a different discharge orientation, then the best course of action is to crack open the casing. In order to crack open the casing, though, it is usually necessary to remove the suction piping and the discharge piping to allow enough of an opening to ensure complete draining.
I have been asked if anti-freeze can be used to avoid cracking open the casing, but I have never recommended it, especially with rubber lined pumps. While rubber does have a level of chemical resistance, the possibility of the chemicals attacking it when in contact for long periods can make the situation remarkably worse.
In addition, antifreeze is rated down to a specific temperature and Mother Nature does not read instructions. Removing the water is the only way to ensure the destructive expansion does not occur when it freezes.
Benefits of a preventative maintenance schedule
While a Pump, Cyclone and Dewatering Screen will have different issues, they all will benefit from a preventative maintenance program. The extended life of the equipment will provide payback in itself, but you will also have a more informed workforce because they see issues before they become problems.