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AFT Product Tips

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Scott Lang

Start your engines! Modeling an Inertial Pump Startup

There are many (six!) ways to define a pump transient event in AFT Impulse . This gives you great flexibility in creating a model that behaves the way you want it to. One thing true for all pumps is that they must be started at least once. Pump startups often cause significant transient effects on the system so you may wish to model this with AFT Impulse. Even narrowing your pump transient down to a startup, there are still four models left to choose from: Without Inertia Startup With Inertia and No Back Flow or Reverse Speed Startup With Inertia -...
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Scott Lang

When to Begin? Time and Events in Transient Studies

To define any transient event in AFT Impulse or AFT Fathom XTS the application must know when it begins. To do so, the user should know how time and event logic is approached in AFT’s transient solvers. In this article, we will discuss the three different time bases used in the applications, the selection of a single or repeating event, and the many possible triggering events that can start the user defined transient. The user defines these items in the Initiation of Transient section of the junction’s Transient tab. The requirements for each junction can vary, but the general approach applies...
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Jake Miller

Calculating Pressure Drop Across Sharp-Edged Perforated Plates

Sometimes design engineers will install a screen to protect equipment like centrifugal pumps. Screens are available in a variety of configurations and each has its own head loss characteristics. As such, this article will strictly discuss thin-walled perforated plates with uniform diameter holes. AFT Fathom provides a screen junction that allows users to choose from four different screen types; Perforated Plate (Sharp-Edged), Perforated Plate (Round-Edged), Circular Wire, and Silk Thread Screen. Every screen has an open flow area that allows the working fluid to bypass the screen while restricting any foreign objects that are not able to pass through this area....
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Aaron Ren
This article is very good! I got much things from your articles. I think it is much better if you can add a tool in AFT Fathom t... Read More
Wednesday, 27 December 2017 08:44
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Jake Miller

Thank Your Machinist for Me

Cutting through the mysteries of impeller trimming Centrifugal pumps are a common and integral part of many industrial applications related to fluid flow of any kind. They require significant amounts of energy to operate. Unfortunately, many pumps are oversized for their applications. When pumps are not properly sized this can lead to operational difficulties that must be addressed. A pragmatic solution to this problem may be to reduce the outer diameter of the pump impeller to better meet flow requirements and avoid costly operating procedures such as throttling or expensive replacements. Changing the impeller diameter will affect the performance of the...
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Erin Onat

Inherent vs. Installed Control Valve Curves and How They Relate to AFT Software

As tech support engineers, we sometimes receive questions from users confused about what control valve characteristic curve (inherent or installed) they are inputting into AFT Fathom , AFT Arrow , or AFT Impulse . The inherent control valve characteristic curve plots the valve open percent versus the percent of maximum Cv. This curve is true regardless of the system effects on the valve. The installed control valve characteristic curve plots the valve open percent versus the flow through the valve, and this plot is dependent on the conditions specific to the system. For example, if the control valve flow setpoint is...
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Jake Miller

NPSH got you under pressure? This’ll get you pumped!

Cavitation is an important subject in piping systems. Quite often, cavitation is an operating condition that is to be avoided, such is the case with pumps. Not only can cavitation cause serious decreases in pump performance, but it is also a maintenance nightmare if left unaddressed. Such issues are costly and may lead a system to be deemed unsafe. As you are likely aware, cavitation exists when the local pressure falls below the vapor pressure of operating fluid. Overtime the pressure may increase again so that the cavity formed then collapses. When this collapse occurs on the vanes of a centrifugal...
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Jake Miller

Blast off with a revolutionary feature, Rotational Acceleration!

The success of rotating hydraulic systems could revolve around the methods employed, make sure to use only the best when modeling such a system. As the surge of space travel innovation continues, safety always comes to mind.  All too often the hazards of traveling through the colloquial final frontier prove the necessity of double checking calculations and the validity of the adage, units kill.  With the large number of piping networks that can rotate around an axis in the absence of the earth’s typical gravitational pull rotating objects involved in space flight, these systems are no exception to the hard-learned lessons...
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