WorldWide Drilling Resource

59 WorldWide Drilling Resource ® NOVEMBER 2015 Suction Lift by Bill Corey Pentair Water Training Institute Several years ago, I got a call from a guy who said he had ten feet of suction lift. I want to make sure you know the use of the word “lift”. When you are on the suction side, it is always called lift; the dis- charge side is called elevation. Now understand a centrifugal pump, he had a jet pump which is in part a centrifugal pump, has a suction lift of about 25 feet at sea level. Of course, as you go up in altitude you will lose the amount of lift you have. Every 2000 feet for the first 8000 feet you will lose 1 psi or 2.31 FoH (feet of head). This means, if you are in Denver which is at 5280 feet above sea level, here is what would happen. The first 4000 feet would cost you 2 psi, but you still have 1280 feet to go. The next 1000 feet will cost you ½ psi, and then there are 280 feet left. Not quite, but we’ll call it .2 psi. This is a total of 2.7 psi lost because of altitude, which if you multiply by 2.31 FoH, you will get 6.24 FoH. So subtract this from the 25 feet you have at sea level and you only have 19 feet of lift. Remember, he only had ten feet of lift. He was not in the mountains, so 25 feet is close to his pump’s lift availability, but he couldn’t get the pump to prime. I had him look at both the nozzle and venture tube to make sure they were correct and would work with one another. We offer a choice on some of our jet pumps because the nozzle and venture tube work together and can change the flow or head. They were correct for the pump he was using. Now what? I asked him to tell me more about his system. He said he was using a spring box. I had never heard of it, so I asked what it was. To which he tells me it is an open cube about four feet deep and set in the middle of a stream, and it gives a four-foot- deep area with clean water in it. Sounds great. It is set only 10 feet vertically below the pump. Finally, I asked how far it was from the pump to the spring box. He said 300 feet. Again, this should still work. Unless... I asked what size pipe he had and was told ¾-inch! I realized at this point the pipe size was too small and he couldn’t get the water all the way to the pump. Close maybe, but not there. When I explained this he said, “The old pump worked.” To which I asked what his old pump was. He told me it was a piston pump! A piston pump has a lift of 33 feet - 8 more than a centrifugal pump. When I told him the jet pump wouldn’t work without putting in bigger pipe, he got mad and said he was just going to put the old pump back in. I agreed with him and he hung up. The point: Not all pumps are the same! Know your lift and understand a centrifugal pump has limitations. Bill Bill Corey may be contacted via e-mail to michele@worldwidedrillingresource.com --- *+ )#)('-()$* !(& )(%#'" +)""+ ,'.*,+ -'"/ 0 . 1 1 1 1