WorldWide Drilling Resource

S.A.E. Pumps by Bill Corey I thought this month I might talk about what makes an S.A.E. pump different from a Close-Coupled Motor Drive (CCMD) pump. The most obvious thing is the driver. A CCMD pump has an electric motor for a driver, which has either a threaded or keyed shaft. So the impeller is directly mounted to the shaft of the driver. This is not the case with an S.A.E. pump. An electric motor pump has certain limitations, the biggest is the rpm (revolutions per minute) at which it can spin. Unless you are using a variable speed drive/variable frequency drive (VFD), you have a two-pole, four-pole, six-pole, or eight-pole motor. Each set of poles decreases the speed at which the motor will turn; therefore, two-pole equals 3450-3550 rpm, four-pole is 1750 rpm, six-pole is 1170 rpm, and eight-pole is 870 rpm. Remember there is slip built into electric motors. With the use of a VFD you can change the speed of the motor and have the pump spin at whatever speed you require. An S.A.E. pump is driven by an engine, usually a diesel engine, but it could of course be a gas engine if you wanted. Part of the difference between a motor and an engine is how rough it runs. A motor tends to be very smooth, whereas an engine, be- cause of the explosions causing it to run, is rough. Because it is so rough, if you were to put the impeller on the end of the shaft, with the weight of the water moving through the impeller you would be more likely to snap the impeller off the shaft. An engine is a variable speed device; the more fuel you give it, the faster it spins until it hits the speed which makes it fly apart. Of course, this is not what we are trying to do here; we are trying to run our pump with the engine. Most S.A.E. engine pumps run at about 1400-2400 rpm, some may do more. Here is why the impeller is not directly connected to the shaft and may snap the shaft - weight. To be straightforward with this, we are looking at 8.334 pounds per gallon of water. If you do the math, 1000 gallons weighs 8334 pounds. What you are doing is pulling the water up to the pump, then changing direction by at least 90 degrees. This is a lot of weight, and if you are picking up the vibration from the engine, you’re getting a lot of bounce. If the motor is in its sweet spot, the vibration is minimal. If you have someone who is inexperienced and has the rpm set wrong, it will cause the impeller to bounce and, with so much weight, snap the shaft at the impeller. This usually happens when the person in charge just stops the engine without slowing it down. It can also happen on start-up if you leave the engine in idle too long. So to protect the pump, there is something cal led a flywheel coupl ing which attaches the engine shaft to the pump shaft. I like to call it a sacrificial lamb, be- cause it is designed to break should the vibration become too much. I’ve always told my students it is cheaper and easier to replace the flywheel coupling than to replace the pump shaft and impeller. There are a couple of different types of couplings - one mechanical which uses springs to hold the two couplings together and absorb the bounce, and the other has the two couplings vulcanized together by rubber. I don’t want to tell you which one to use, but make sure you have them and you understand why they are so impor- tant. If you are a rental center and you rent these types of pumps, make sure your customers know why you use a fly- wheel coupling. And if you are a water truck company, your employees should understand how to use these types of pumps. Hope this helps, and let me know if you have a question. Bill Bill Corey may be contacted via e-mail to michele@ worldwidedrillingresource.com Hydraulic-Pneumatic tools in stock. Sizes 1” to 20”. 2547 W Success Way Emmett, ID 83617 (208) 365-3492 • Fax: (208) 365-3792 rauchmfg.com • rauchmfg@frontiernet.net Model 113HD Sizes 1"-13" Patent U.S.: 6,065,372 Canada: Pending 55 WorldWide Drilling Resource ® FEBRUARY 2017