WorldWide Drilling Resource

11 WorldWide Drilling Resource ® MARCH 2016 NPSH by Bill Corey Pentair Water Training Institute NPSH s Net Pos t ve Suct on Head - some say t means No Pumps So d Here, but that s just a bad joke. It has a rea mean ng wh ch can affect how your pump works. F rst, et s po nt out there are two types of NPSH: Awh ch stands for Ava ab e and R wh ch means Requ red. There s a formu a for NPSHA that ooks ke th s: Pa - Pv ± Z - F = NPSHA Pa s the we ght of the atmosphere over the water. Remember from our ast art c e we saw th s can change. Pv s the vapor pressure po nt of the water. Aga n, th s changes as the tempera- ture of the water changes. Z says ± because t represents the he ght above or be ow a reference po nt, and of course s n FoH (feet of head). F s one of the th ngs I try very hard to he p nsta ers understand - fr ct on oss n the p p ng system. Often forgotten, t a ways has an affect on the system. It s a oss, wh ch means t s not he p ng us. The use of th s formu a g ves us the true amount of NPSHA. Remember, atmospher c pressure changes throughout the day. NPSHA can be changed! There was an rr gat on company from Wscons n, wh ch s ts about 1000 feet above sea eve . They won a b d to put a go f course rr gat on system n at Co orado Spr ngs, Co orado, wh ch s at about 6000 feet above sea eve . They p cked the pump, and the r team and went to Co orado and nsta ed the system. The system worked great when used n the morn ng, but every afternoon when t was on, there was cav tat on n the system. They ca ed us to see why the pump was hav ng prob ems w th cav tat on. We sent our sa esman there and the good news for them was he was from the area. He suggested a barometr c pressure read ng wh ch revea ed a ow pressure wou d cross the mounta ns every afternoon. What t ooks ke s th s: As ong as NPSHA s above NPSHR there s no prob em, but when the pressure drops, ke t d d every afternoon, the NPSH Ava ab e was ess than the Requ red, caus ng cav tat on. The quest on asked, of course, was, “How do we f x th s?” The answer was much s mp er than they thought - d g a ho e about two feet deep and set the pump that much c oser to the water. It ooked ke #2 . Now when the NPSHA dropped a tt e, t ooked ke #3 . As you can see, even though the NPSHA dropped t cou dn t affect the pump because the pump had been owered. The s mp e thought w th NPSHR s t s part of the pump and cannot be changed no matter where the pump s ocated, Wscons n or Co orado. Bill Bill Corey may be contacted via e-mail to michele@worldwidedrillingresource.com Morning: Afternoon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orthwest Flattanks manufactures sonic tender support trucks wh ch can be bu t w th r dged wa van or co aps b e van sty es. The f attank has water n the f rst 18 feet of the bed, 12 feet of bed for rod racks, 6 feet of bed for pa et storage, and 6 feet of bed for front pressure washer and we der mount ng. The ent re bottom of the tank s f tted w th hor zonta too boxes. Some of the many other deta s nc ude a rear fo d ng step p atform, b t ho ders mounted n front of the dr rod stopper, a um num adder w th removab e handra s, and a f ammab es cab net.