Pump vs. system curves provide an intuitive, graphic way to understand how a pump interacts with a piping system. These can be useful during pump sizing, but can also be informative when your pump must function in a variety of operating conditions. Understanding how changes to your pump or system affect your operating point can be invalua...

Any time a rapid transient occurs in a piping system, there is a chance for unexpected surge to impact the system. Though system shutdowns account for many surge events, pump startups can cause water hammer as well. For this blog I am going to cover the basics of setting up pump and valve transients for the startup case in AFT Impulse 7, as well as...

The pistons, or diaphragm of a reciprocating (positive displacement) pump causes a cyclical variation, typically in some sinusoidal form, of both flow in pressure in a piping system. The magnitude varies, depending on the type and design of the pump. What is acceleration head? Acceleration head is the energy required to change the velocity of the liquid in the system from an at rest, or zero condition, to some non-zero value. To help us understand acceleration head a little more clearly, you could compare it to a race car. In a drag race, the race car will accelerate to some maximum velocity,...

What comes to mind when you hear the expression “planning for failure”? For some, it carries the negative connotation that failure is the direct result of a design – intentionally or otherwise. Benjamin Franklin said; “If you fail to plan, you are planning to fail!” and I believe he would agree that any good plan addresses potential failures. In fact, not "planning for failure" as an element of a system is essentially failing to plan and therefore inviting unexpected and unmitigated failures. Life Cycle Cost One of the many reasons to avoid failure when possible is to reduce cost. When a...

This past week I and Jeff Olsen, AFT’s V.P. of Technology, attended the annual conference of the Hydraulic Institute. The Hydraulic Institute (HI) was founded in 1917 and is America’s premiere pump organization. At this year’s meeting HI held a centennial celebration. For a technology organization like HI, 100 years is quite a feat and was rightly celebrated at the annual meeting this year. Many of you are familiar with HI through the standards HI creates. These standards show up in AFT Fathom in several places: Intake design (pump submergence to avoid vortex formation)Pump viscosity correctionsSlurry pumps (SSL module) Jeff and I enjoyed...

AFT Fathom can easily generate a pump and system curve for your piping system.  Creating a pump and system curve for a simple system with a single flow path and no control features is an easy and typically well-understood process.  However, as piping systems are quite complicated with lots of branch points, control features, and dynamic interactions, creating a useful system curve can quickly become a common source of confusion.  This three-part blog series is going to help clarify concepts regarding pump and system curves to better understand them.   This Part 1 blog will discuss the basics of what pump...

In AFT Impulse you can directly model a submerged pump. First, you will define your pump data exactly as you would normally, however you will only draw the discharge piping and not a suction piping. After doing this, you will check the box “Submerged Pump” at the bottom of the Pump Specifications Window. You now have an additional required input field. The “Suction Pressure” can be entered as a Head (HGL) or a Pressure. When entered as a Head (HGL) value, this value is the actual liquid elevation in the supply reservoir. When entered as a pressure, this is the actual...