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Understanding NPSH Part 3
Last time, we looked at how NPSH can be impacted by a poor pump selection, such as using a 3500 RPM pump selected near the end of its published curve. Sometimes this can be remediated by reducing the pump speed, but not always. If the NPSHr curve is relatively flat, the speed reduction may help. …
Read MoreUnderstanding NPSH Part 2
Last time, we saw that as we supply more pressure to the pump suction than what the pump manufacturer requires, we are OK. But that isn’t the whole story: most pumps in HVAC operate over a range of flows, meaning they will change flow rates based on loads or control strategies. So, what happens as…
Read MoreUnderstanding NPSH, Part 1
NPSH is probably the least understood part of a manufacturers pump curve. It’s easy to see why: we use atmospheric pressures as reference, the effects aren’t always audible, and it’s hard to tell pump cavitational noises from air entrapment. NPSH stands for Net Positive Suction Head. Roughly interpreted, it’s the amount of absolute pressure at…
Read MorePump Basics 2: Pump Curves
When a centrifugal pump is designed, the manufacturer will test the operation of the pump to the theoretical design. Pumps are tested for flow, head (pressure differential), power consumption, efficiency and minimum allowable suction pressures, also known as Net Positive Suction Head Required (NPSHR). Generally, as the pump handles greater flows, the pressure differential it…
Read MorePump Basics – Impellers and Volutes
Centrifugal pumps come in many configurations – in-line, base mounted, foot mounted, single and double suction, vertical and horizontal split case, close coupled and long coupled – the list goes on. No one style is best for all applications. So when should you use which? Over the course of the next few blogs, we are…
Read MoreGetting the Most, part 4: Cooling Tower Optimization
In the last part of this series, we talked about getting the most out of your Plate & Frame Heat Exchanger. One of the critical decisions to make about sizing a HX is the approach temperature. The approach temperature is the difference between the inlet temperature of one fluid and the outlet temperature of the…
Read MoreStainless Steel Choices in Cooling Tower Selection
The following is an excerpt from the LinkedIn page Cooling Tower Industry Topics, a very handy page to discuss the cooling tower industry or ask questions to professionals in this area, including our CT rep SPX Cooling Technologies. To request access to the group please visit this link. Engineers must choose from a variety of…
Read MoreGetting the Most, part 3 – Plate Heat Exchangers
Last time, we talked about pressure drop limitations and how they affect the sizing of a plate heat exchanger. Today we will discuss a couple of other key considerations. First: approach temperatures. Approach is the difference between the outlet temp of one fluid to the inlet temp of the other. Generally speaking for a given…
Read MoreB&G Centrifugal Pump Motor Speed Facts
Understanding electric motor speed is a vital part of the proper selection and application of B&G Centrifugal Pumps. The following is an explanation of how motors are designed to operate at a certain speed and how motors speed varies when installed to drive a centrifugal pump. “No Load” Motor RPM Every AC Induction motor has…
Read MoreGetting the Most – Part 2
Last time, we talked about the Bornquist IDEA (Integrated Design Engineering Assistance) team and the overall concept of using the equipment output capacities of some components, such as cooling towers, to reduce the sizes of other equipment. Since the most likely component to be affected would be a plate heat exchanger, let’s spend a little…
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