Pumped for Action
Industrial pumps may seem fairly simple, but they can cause as much trouble as the most complex machinery. To help you avoid maintenance headaches with the pumps in your facility, we sought out a few experts, who are happy to share their...
September 1, 2013 | By By Carroll McCormick
Industrial pumps may seem fairly simple, but they can cause as much trouble as the most complex machinery. To help you avoid maintenance headaches with the pumps in your facility, we sought out a few experts, who are happy to share their observations and experiences. Here is what we learned.
Tip #1: Low oil levels and lubrication deflectors: “You have to really keep on top of your oil levels,” says Marcus Wickert, engineering division manager, NTN Canada. Here is just one good reason why, he explains. “A lot of pumps are oil bath and have lubrication deflectors. The deflector dips in the oil bath as the shaft rotates, picks up the oil and hopefully splashes it on the bearings. But if the oil level is not high enough, the oil will not hit the bearings, causing a bearing failure.
“Sometimes the deflector is not set up properly and will not adequately splash oil on the bearings. We frequently see issues with them. This is usually the first thing I look at if there is a bearing failure.”
And if you are checking oil levels through a sight glass, beware, Wickert advises. “The sight glass may show that there is enough oil in the pump, but is it set up correctly?” You should check that it is.
Tip #2: Beware changing pump mediums: Particularly in a borderline situation where pump bearings are getting barely enough lubrication to keep them cool, if the thickness of the medium being pumped changes, that could cause the bearings to fail, Wickert says.
“If the consistency of what you are pumping changes, the load on the bearings can change dramatically. If there is not quite enough oil being delivered to the bearings in the first place, the bearings will begin to overheat and lubricant will oxidize and deteriorate. The production people need to stay on top of these things.”
Tip #3: Cycle your standby pumps: It is clever to have a cluster of pumps doing a job, both to save energy during times of low loads, and to have a spare ready to take over in case a pump fails or needs maintenance. However, the spare pump should not sit there for months without being used.
“For example, there might be three pumps, with two operating and one on standby. You need a good cycling program,” Wickert advises.
But what could go wrong if you don’t? “Two things can happen: If it is a moist area, you can get corrosion in the pump bearings as lubrication pools out. By cycling the pumps, you reintroduce lubrication to the bearings, preventing corrosion.
Also, the pumps that are running will likely transmit vibration to the standby pump. This can cause a fretting mode of wear (cyclical rubbing between two surfaces), also called false brinelling. Brinelling follows from an impact load on a bearing. In false brinelling, the rolling element is just sitting there, vibrating. It wears an indent on the raceway.
Cycling pumps is a best practice that we always talk to people about,” Wickert says.
Tip #4: Beware of moisture in air pumps: Air pumps are driven with air delivered from compressors. The compressing of air warms it, however, and moisture will condense out in the air lines as it cools. This moisture must not be allowed to reach the pumps.
“Moisture will cause rust in the air pump piston and valving,” says Bruce Bergen, owner, Production Supply Co. Ltd., Richmond, BC. “Water, oil and rubber do not mix. It becomes an oily, gooey mess in the pump,” he says.
The solution? Where air is taken off the main air line, position the ‘t’ fitting so the secondary line goes upwards first, not straight down. This will help limit the amount of moisture that gets to the air pump. As well, Bergen counsels, “Run a drain line going down from the lowest point in the main line and install a ball valve to drain off moisture.”
Tip #5: Air pumps need filtering and lubricating: Air pumps need lubrication. “This is a specialty industry and lots of people just don’t know this,” Bergen says. Air lines leading to air pumps have a trio of gizmos on them, referred to as the FRL (filter, regulator and lubricator).
“The filter traps dirt and impurities that come off the inside of the steel air line piping. Most air filters are usually water separators too, through centrifugal action. Any water that accumulates needs to be drained off from time to time,” Bergen recommends.
The lubricator gradually drips oil into the air line, then the oil is atomized and whisked into the pump. “Checking the lubricant level is an easy visual check. If you check it on a monthly basis, you will soon find out how often it needs replenishing,” Bergen says.
Tip #6: The dreaded 40/40 failure: Pumps built to API or ANSI standards dictate that manufacturers use 40-degree angular contact bearings for both the thrust and backup bearing. The backup bearing often runs unloaded and the balls will skid along the outer race. “This generates a lot of unwanted heat, lowering the viscosity of the oil,” says Jennifer Moritz, training manager, SKF Canada. “The loaded bearing begins to overheat. This can lead to a catastrophic and sudden failure.
“It fails nastily. People hate it. A solution to improve bearing performance is to switch the backup bearing to a 15-degree angular bearing. Switch from 40/40 to a 40/15 pair.”
Tip #7: This pump is too big: Once upon a time, the Neucel pulp and paper mill in Port Alice, BC, had a 200-hp slurry pump that was too big for the job. It always operated at 900 rpm and the only way to control the pressure and flow was to throttle the valve and keep it 80% to 90% closed. Too, the huge pressure drop from 25 psi to 8 psi on the downstream side of the pump caused all sorts of maintenance problems.
Using funds from BC Hydro’s Power Smart program, the mill downsized to a 150-hp model and added a variable- speed drive. The new pump uses 75% less electricity (800 MWh/year) and is saving the mill about $28,000 a year in electricity costs.
The moral of this story is that right-sizing your motors for a better fit to the tasks they must perform can save loads of money and maintenance.
Tip #8: Assorted energy-saving tips: Here are some other ways to lower pump operating costs, with suggestions from the experts at pumphealth.com.
Two or more pumps can be better than one big one, because you can run fewer pumps during low-demand periods.
Variable-speed drives might be an economical alternative to throttling your pumps, which is like driving with one foot on the gas and the other on the brake.
Consider ways to lower your flow capacity and head requirements. Possibilities include reducing the water velocity in equipment and spray nozzles, minimizing the elevation difference between the discharge and suction tanks, and using larger pipes, which will generate less friction.
Carroll McCormick, our senior contributing editor, is based in Montreal. He has been writing award-winning articles for us for the past 15 years.