Are your pumps working as efficiently as they should?
When considering how to make a building more energy efficient, lighting always seems to be the first thing that comes to mind. However, as Greg Towsley explained at the recent PM Expo in Toronto, there are many savings opportunities related to pumps that aren’t being captured.
January 13, 2010 By Robert Colman
Towsley is the Innovation Intent Director, Zero Impact Buildings, for Grundfos Pumps. He notes that 72 per cent of the energy consumed in commercial buildings in Canada come from applications and services that have pumps in them. Therefore, it’s worth considering how those pumps are being used, and whether improvements can be made in your pump management practices.
So what should you look for when you are reviewing systems in an existing building? Where do you start with a review of your pumps? Towsley first suggests that you review what your system was originally designed to handle.
“Within existing buildings, systems were designed with a specific intent, a specific service, flow rates, heating and cooling loads, etc., and of course over time those things have changed,” says Towsley. “It’s very important that as we look to make our buildings greener that we reevaluate what those systems are doing, how they’ve changed and what has changed within them. You really need to get to know that system to bring down the energy consumption and increase the energy efficiency of those systems.”
Towsley explains that you should review flow rates and load to see how these might have changed with changes in the building.
The next step is to learn more about the pumps that are currently in the system and, if you are considering changing them out, what sort of equipment should replace it.
“What are the physical constraints of the room the pump is going to be put in?” asks Towsley. “How is it going to be operated — at a constant or variable speed? Installation cost — what’s involved? What is the downtime cost? Energy costs end up being the largest part of a pump’s lifecycle cost — up to 60-80% of the cost of a pump’s life. And yet, the initial cost is often the deciding factor when it comes to installation.”
5 maintenance missteps
Towsley notes that one area that is often overlooked is the proper maintenance of pumps, and he points out five ways facilities often mistreat their pumps.
1. Overworking a pump refers to “working it continuously at high capacities or flow heads that may not even be right for what it was initially designed for,” says Towsley. Again, when looking at your building, maybe some loads have been added over time that the pump wasn’t sized for, so may be continually working without the aid of a backup pump or an alternating pump.
2. Starving a pump — all pumps require either grease or oil at the bearings, and the lack of maintaining that, just like not maintaining your car, ends up injuring the bearings and may cause premature failure.
3. Choking the pump — not providing enough liquid to the pump to allow it to operate properly. “We have what is called ‘net positive suction head’ required on pumps, and this is the water or liquid entering a pump at a certain pressure to keep it from damaging itself,” Towsley explains. “If the proper amount of water for that pump is not kept flowing, damage can occur within the pump, causing premature failure to not only the bearings but the impeller as well.
4. Frying can very commonly happen to pumps. “Pumps are designed to do what the system that it is operating in wants it to do and it tells it to do, and it’s going to keep on operating no matter what happens, especially if no special controls are involved,” says Towsley. “A person fries a pump when the discharge valve is closed on it. The pump continues to operate, wants to push that water somewhere at a certain flow rate and pressure, but when that discharge valve is closed, there is nowhere for that water to go, and like anything that involves energy, it is sometimes transferred into heat, and what happens when you close that valve is that the water ends up boiling within the pump.”
5. Breaking its limbs refers to how a pump is installed. “Pumps are more sophisticated and more of a high-performance piece of equipment than people really think about or realize,” says Towsley. “Most of these pumps are operating at 3600 rpm or 1800 rpm at a constant speed. If you think about your car, you are not always operating it at 3600 rpm or 3000, you give it a break to cool down and slow down or even idle. One thing we’ve seen over time is how the pump is installed among the piping. What many don’t realize is that if there is any type of pipe strain put on pumps, that transmits to the mechanical seals, to the bearings, and puts stresses on those. It can actually put so much pressure on the bearings and the seal that, right at start up, they’ve failed. Some of the ways the pumps have been installed, they have caused damage not only to the pump but to the flanges, bearings and mechanical seals.”
Towsley says the most important thing you can do for managing your pumps is regular check-ups. Much like your car, your pumps will thank you for receiving some regular attention.
Doing inspections also allows you to know what kind of clearances are left within the pump — “as clearances open up, your efficiency starts to decrease, and that’s when you start to see more energy consumption,” Towsley explains.
Continuous monitoring of pumps is important, and Towsley notes that such monitoring can be very simple or very complex.
“Probably the most simplistic way is to put pressure gauges around the suction end of the discharge side of the pump,” he explains. “By regularly checking the differential pressure between the suction and discharge as well as looking at the amperage draw at any certain point in comparison to that, you can go back and look at the performance curve of the pump you have in place and see where it is — what was your system designed for, where was it initially designed to operate and what is it operating at currently? Is it because there has been changes in the system or is it because there is now wear in there?”
As Towsley explains it, from there you can look at the performance curve of the pump, what horsepower you should be drawing and what is currently being drawn.
“When you start diagnosing problems, the first thing that most people ask is where are we operating at, what is the pump pressure between the suction and discharge and what sort of amperage are we pulling?” says Towsley. Of course, with effective monitoring, it’s possible to put that all on the table from the beginning.
Have you reviewed your pumps’ performance levels recently? Towsley offers a compelling argument to revisit your existing systems to find greater efficiencies.
For more on Grundfos, visit the company website at www.grundfos.ca.
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