Ever wonder why some impellers, fresh and new from the factory have holes in them? Or… why some impellers have those funny mini vanes on the back side? The short answer is to reduce the axial thrust in the pump and also to reduce the pressure in the stuffing box. Whenever you operate a
We have all heard the term “flush” used when discussing mechanical seals. The definition of a flush is “a stream brought in from an external source to the mechanical seal.” This plan (API Plan 32) is almost always used in conjunction with a close clearance throat bushing. The flush fluid must be brought into
Snoring pumps… ever heard of such a thing? I knew that pumps could run, burp, leak, stall and die (people “kill” them all the time), but I didn’t know that pumps could snore. Kidding aside, by definition a pump that is pumping a mixture of liquid and air is technically snoring. The term originates from the
This issue compliments an earlier issue (Volume 1 issue 12 from April 2018) on the same subject. I am frequently asked; should the discharge valve be open or closed when the pump is started? My answer is….it depends, but regardless the suction valve better be open. First Things First Let me state that as visitors to client facilities we
Rolling Stone’s front man Mick Jagger’s second favorite song verse is “start me up”…”I’ve been running hot”. Did you also know there are restrictive limits regarding the number of times an induction motor can be started in a given time period? The restrictions are due to (“running hot”) temperatures and for that singular reason it
I don’t have one particular subject for this month’s issue, but instead a gentle reminder of several simple things. Just a list of pesky issues that keep popping up on a regular basis. These are things that should not be popping up. …but in the spirit of the season we’ll just call them stocking stuffers. Pumps
Be very careful on self-primer lift applications because the liquid temperature directly affects its vapor pressure and that… …changes the Net Positive Suction Head Available (NPSHA). Example: Self-Primer – two temperatures… two outcomes: For the example we will use two versions of the otherwise same application. The applications are identical in both versions except the temperature
For those of us living in the northern hemisphere winter is coming and this message will serve both as a reminder and a warning as to the inevitable arrival of temperatures below freezing. For folks like us who reside in the higher latitudes, we know from experience that at some point in time (someday
Open or Closed Tanks and the Effect on NPSHA Calculations When working through NPSHA calculations for pump applications we need to know if the suction supply tank is open to the atmosphere or not. If it is an open tank the calculation is easy; as we just convert the ambient pressure to head for the
Bringing Awareness to Pump Preservation Shelf Life: With the possible exception of Twinkies™*…all things have a finite shelf life. The purpose of this month’s SSWSP is not to go into the details of pump preservation, but to simply make you aware that it is required. For today we will only discuss new single stage pumps
