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
Here are some brief reminders about NPSHA and NPSHR. NPSH changes with: Impeller diameter: For the same flowrate on a given system an impeller of a smaller diameter will have a higher NPSHR. Clearance of impeller and wear rings: As clearances open up on the pump over time the NPSHR will also increase. This effect
“Your pump isn’t producing enough flow!” “I can’t get enough pressure out of your pump!” “Your pump is making noise!” We often get these calls from the field. While it is entirely possible, in reality, it is rarely the pump’s fault. From my almost fifty years of field experience with pump troubleshooting; I’ve found almost 80 percent of all centrifugal
No one specific subject or theme this month, just a random collection of tips. Kind of like the junk drawer in my desk. Pop Quiz: What pump company made the first ANSI (B73.1) Pump? Answer at the end. You’re Grounded: If electric arc welding near the pump, be certain a solid ground is installed
Several times a month we receive an inquiry from a concerned customer that the “stainless steel” they received from Summit Pump is magnetic and/or appears to be rusting. We assure them there is no issue, and explain as follows. In the case of plain/standard 316-SS, it is usually because the piece has been cold worked
What is slip? How does it affect Positive Displacement Pump performance? Is Your Pump Slipping? Fluid slip is a common term used to describe reverse fluid flow inside a pump or other turbomachinery. Slip is affected by internal clearances of the parts, temperature, pressure and viscosity. In a positive displacement pump, slip can be easily calculated just
Baseplates: Flat and Level Pump Alignments We all know that proper alignments between the pump and the driver are critical. Did you know that the bearing load increases in direct proportion with the misalignment? But even more importantly, a bearing load increase will decrease the bearing life by a cubic function. Simply stated, if the bearing load increases by a factor of two, due to misalignment, then the bearing life decreases by a factor of eight. Warning: All pumps must be final aligned in the field. No matter how precise the alignment from the factory, it will be lost when the unit
Truth: Pumps Shipped From the Factory are NOT Ready to be Started and Operated Once a year I attempt to remind all Summit Pump distributors of the “Plug and Play” myths that unfortunately persist in the pump universe, like fake moon landings and that the earth is flat. Please make sure you and others
You have choices In the horizontal pump world of ANSI, the (14) mid frame pump sizes offer you a choice of selecting an MTO (medium) or an LTO (large) frame size. See sidebar below for more info. Most often your competitor will choose the MTO over the LTO version because it is less expensive.
NPSHR and Impeller Diameter Okay, this may take longer than 60 seconds. Prior to computerized software for pump selection, manufacturers simply drew one NPSHR curve for the pump on the head versus capacity curve. It was used regardless of the impeller diameter chosen. This is not a good idea for the smaller diameter selections.
API versus ANSI Pumps API pumps are utilized in applications where pressures and/or temperatures are higher than ANSI standards allow. API pumps may handle fluids that are flammable, toxic, hazardous, and my favorite…explosive. API pumps should be used when safety is especially important. An example would be the release of toxic liquids or vapors
NPSHR versus NPSHA margins From several sources I have recently studied: The minimum accepted margin between NPSHR and NPSHA should be a factor of 1.35 times the NPSHRor a minimum of 5 (five) feet (1.524 meters), whichever is greater. To eliminate the risk of cavitation to an acceptable level, the margin really needs to be