Lubricants are used within all industries to keep machinery, including pumps, from seizing and to ensure the cooling of all working parts. By lubricating and separating moving parts such as bearings, lubrication minimizes the friction that causes wear and tear. In addition, it can help control contamination and even facilitate the absorption and transformation of heat. The lubrication practices a centrifugal pump is subjected to influence its life span significantly.
Oiling Bell & Gossett Series 100 Pumps
Bell & Gossett recommends that the pump bearings be lubricated with 1 oz. of Bell & Gossett 20# weight non-detergent oil upon initial fill. The motor bearings should initially be lubricated by adding 1/4 oz. in each oil tube.
For re-oiling, Bell & Gossett recommends the pump bearings be lubricated with 1 teaspoon of Bell & Gossett 20# weight non-detergent oil at the start of each heating season. An SAE 20 oil or 10W-30 oil may be substituted if Bell & Gossett oil is unavailable.
Motor bearings should be lubricated as instructed on the lubrication decal once every four months (more often under adverse conditions). Use eight to ten drops in each oil tube.
The amount of oil used is a general measurement, not exact. Too much oil in the bearing bracket is messy, but it will drain. However, too much oil in the motor oil tubes can overflow and soften the rubber motor mounts. The effect is an out-of-alignment coupler, noise, and eventual coupler failure.
Be sure to check the manual for your Bell & Gossett pump for specific instructions.
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How to Lubricate a Circulating Pump
Step 1: Determine the Oil Level
Locate the oil level window on the side of the circulating pump. The pump needs to be shut off and leveled to determine the oil level properly. The oil level should be even with the center point of the lowest roller.
Step 2: Locate the Lubrication Ports
Turn off the circulating pump. Shut off the breaker to the pump to reduce the chance of electrocution while lubricating the bearings. There should be small holes in the circulating pump used to put oil in for the bearings. These holes are often conveniently labeled with the word “oil,” or they have caps to keep dust out.
Step 3: Determine the Proper Lubrication Oil
Before attempting to lubricate your circulating pump, it is essential to refer to the user’s manual to ensure that you have acquired the correct lubricating oil. Different bearings require different viscosity of the lubricating medium.
Step 4: Lubricate the Bearings
Once you have located the oil fill holes, add a drop or two of oil in each hole and remove any cap in place. You may need to use a pair of needle-nose pliers to remove the caps from the pump. If you use more than a few drops, the oil tends to attract dust that will cause a problem by gumming up the pump. Be sure to re-insert any caps that were in the holes.
Step 5: Finish Up
Once you have the oil inserted into each lubrication hole, wipe any excess oil from the openings. This will help reduce the collection of dust on the exterior of the circulating pump. Next, put the caps back into the fill hole. Turn the breaker back on for the pump, and then turn on the circulating pump. Ensure that everything is running smoothly and then turn the water back on.
Types of Lubrication
Different bearing types require different lubrication methods. They include:
Grease Lubrication
The advantage of grease lubrication is simplified maintenance. However, some disadvantages include over-pressurization and limited heat dissipation. As a result, the use of grease is primarily limited to lower-speed and horsepower pumps.
Oil Bath
Advantages of oil bath/splash lubrication include a more comprehensive range of speeds than grease, and visual verification of oil level is possible. Some disadvantages are sensitivity to oil level and contaminants remaining in the oil bath. Oil bath lubrication can be achieved by the bearing being in direct contact with the oil; oil rings contacting the lubricant and splashing it throughout the bearing housing, or slinger disks that splash the lubricant throughout the bearing housing.
Pure Oil Mist
The advantages of pure oil mist lubrication are lower operation temperature than oil bath, wear particles are not recirculated and lower oil consumption. However, some disadvantages are that it requires a higher level of application knowledge and higher initial costs than an oil bath. The basic concept of an oil mist lubrication system is a dispersion of an oil aerosol into the bearing housing. There is no oil reservoir in the housing, and oil rings are not used. Instead, the oil is atomized, and airflow transports the small oil particles into the pump bearing housing through a piping system.
Troubleshooting Lubrication Issues
It’s critical to be proactive in resolving any lubrication-related pump problems.
Contamination
Contamination can contribute to cavitation, a major cause of failed bearings. Contamination results from:
- Poor seals
- Improper venting
- Loose-fill plug
- Poor storage and handling resulting in dirty oil
- Delivery of dirty oil
To ensure clean lubricants:
- Follow proper storage, handling, and transfer procedures
- Test incoming oil deliveries for particle counts and water content
- Install desiccant breathers to help stop particle and water ingression from pump aspiration
- Replace worn lip seals or upgrade to bearing isolators
Mechanical Issues
The mechanical issues most typically associated with lubrication are vibration and cavitation.
Pump vibration can start for various reasons, but when it is caused by structural stresses on the bearing housing, which affects the alignment of the pump’s bearings, the lubricant may not be able to do its job. Pipe strain on suction and discharge flanges, hollow bedplates or soft foot on anchor bolts, and misalignment of pump and driver couplings are the most common culprits. Each of these conditions twists, tweaks, or pulls on the pump frame and bearing housing, causing changes in the small clearances of the bearing races. These clearance changes will harm lubrication film thickness and the ball’s track in its groove. Such situations lead to ball sliding or skidding and rapid overheating.
Cavitation—the implosion of gas bubbles on the interior surfaces of a pump or piping—is an amazingly destructive force. It can quickly erode and break impellers, volutes, pump cases, and piping.
Cavitation can be caused by leaking gaskets and O-rings that lead to air entrainment. A more common cause may be the effect of rising temperature and/or pressure on the vapor point of the liquid being pumped. Once vapor pressure is reached, some of the liquid flashes to a gas, and the remaining pressurized fluid compresses and implodes this gas bubble on the nearest surface. Pumps that are cavitating may sound like they are pumping rocks or marbles.
Best practices for early lubrication-related mechanical-problem resolution include:
- Monitoring pumps and drivers closely to recognize subtle changes in oil levels, color, foaming, and cleanliness
- Using infrared thermometers to check bearing and oil temperatures and inlet and outlet temperatures on oil coolers to determine efficiency
- Frequently draining small amounts of oil from bearing housings to inspect for particle ingression, wear debris, and water content
- Noting changes in vibration, unusual sounds, or oil leaks
- Being vigilant in contamination-control practices. (It can cost ten times as much to remove particle contamination from oil as it does to prevent contamination in the first place.)
- On oil-misted bearings, draining manifolds and collection bottles and regularly checking mist flow at lube points
- Learning the proper use of desiccant breathers, filter carts, and vacuum dehydrators