May 08, 2003
AFT Fathom seminars to be held at Flowserve's Learning Resource Center
As part of a working alliance, Flowserve Corporation has added AFT Fathom to their Pumping System Analysis course held at their Learning Resource Center near Dallas, Texas.
Flowserve built their Learning Resource Center to provide the equipment, conditions, and expertise students need to experiment, test, modify, and verify the "what ifs" of the tools they use every day in operating and maintaining fluid handling systems. The Learning Resource Center means students receive the kind of training that is not just theory, not just hands-on, but a balanced combination.
The analytical side of this balanced approach includes "Pumping System Analysis – Level I" and "Pumping System Design – Level I". Augmenting these courses, Flowserve will be offering classes on AFT Fathom.
"Flowserve is expanding its training curriculum by adding a Pumping System Analysis - Level I course." explains Dan Wood, Flowserve Educational Services Manager. "The heart of this 3-day course is learning how to use the 10 Pumping Principles. By learning these principles, the student learns how to analyze an existing pumping system, determine problems, and recommend solutions to those problems. However, the true power and efficiency of the analyst's knowledge cannot be exploited without powerful tools, such as AFT Fathom. Therefore, a 1-1/2 day course on AFT Fathom is integrated in the same week as the "Pumping System Analysis - Level I" and "Pumping System Design – Level I" courses. By combining these courses, the true power of AFT Fathom is realized and the pump system analyst will quickly learn that AFT Fathom is the best tool in their troubleshooting toolbox."
The Learning Resource Center is located in Irving, Texas, right in the heart of the Dallas/Ft. Worth Metroplex within minutes of the DWF International Airport.
Course schedules and descriptions may be found at http://www.flowserve.com/education/schedule_cust.htm.
AFT Arrow / AFT Fathom Seminar held at Cape Canaveral
AFT conducted a combined AFT Arrow / AFT Fathom seminar earlier this month for United Space Alliance at Cape Canaveral, the prime NASA contractor for space shuttle operations. United Space Alliance has used AFT Arrow and AFT Fathom in the design of various ground systems including new systems, expanding existing systems and trouble-shooting systems.
United Space Alliance' website offers a wealth of information on space shuttle operations at http://www.unitedspacealliance.com.
Interesting Applications
Hickam Airforce Base jet fuel transfer systems transient analysis
Burns & McDonnell of Kansas City, Missouri, recently enlisted AFT's transient analysis expertise to answer a critical operation question for the jet fuel transfer systems at Hickam Airforce Base.
Two systems were involved, the 'Hydrant' and 'Truck Fill' systems. The first supplies jet fuel from a centralized pumping station to a network of ground mounted fueling hydrants while the latter supplies a network of points where truck mounted fueling systems connect. The systems include a main supply loop of more than 20,000 feet in length with several stations connected to the loop in parallel. Burns & McDonnell needed to assure that maximum allowable system pressures would not be exceeded when multiple station isolation valves were closed.
Models of both systems had been developed in KY Pipe's Surge transient software, but Burns & McDonnell discovered it was not capable of modeling these systems. Using AFT Impulse 3.0, models were easily developed and accurately simulated both systems verifying system design requirements would be met under these dynamic conditions.
Tips - Is this valve choked?
Under sub-sonic gas flow conditions, loss models can use the familiar K, Cv or resistance curve methods. At choked flow, however, the dynamics of compressible flow require a different method to characterize the loss, which AFT Arrow users will see as the optional 'CdA' input value on the valve and other junctions specifications window. The product of coefficient of discharge and effective flow area under choked conditions, AFT Arrow can directly calculate the CdA for some cases, such as at the discharge from a pipe. For other components, such as valves, determining these values is most commonly done through flow testing. Indeed, it is the product of Cd and area that is directly available from test results rather than the individual value of each, hence the term CdA. When a CdA value is included in the valve specifications window, AFT Arrow can determine if choked flow exists at the valve and, if so, calculate the choked flow through the valve.
So where do you obtain the CdA for a valve in your gas piping system? Most likely from the manufacturer. Unfortunately this data is not always available. AFT Arrow's output for junctions includes the 'Sonic Area', the CdA value at the junction that would result in choked flow, and in conjunction with the pipe flow area, can be used to make a reasonable judgement as to whether a valve may choked. ('Sonic Area' and 'Flow Area' may be selected to include in the output from the Junction and Pipe tabs of Output Control.)
Let's take an example of a globe valve with a sonic area of 0.5 in2 mounted in a 1-1/2", sch 80 pipe with a flow area of 1.767 in2. From specific data or experience, we know this valve's physical flow area is approximately 80% of the connected pipe. For CdA to equal the sonic are of 0.5 in2, Cd would have to be ~0.35 (0.5 / (1.767 in2 x 0.8). This is a very low value and we could safely conclude the valve will not be choked and we can model its loss using a K, Cv or resistance curve. On the other hand, if sonic area were, say, 1 in2, this would equate to a Cd of about 0.7. Given that an orifice has a high Reynolds number Cd in the range of 0.6, we would not reasonably expect the more convoluted flow path through our globe valve to have such a high Cd and would conclude flow is going to be choked through this valve. While we haven't determined the choked flow conditions through the valve, but we can conclude that we need to use a larger valve or a different type of valve to avoid choked flow at this location, and this is usually our goal in selecting isolation or stop valves for gas piping systems.
This example has focused on valves but is equally applicable to a wide range of piping system components.