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This is the May 2004 issue of the Engineered Software Fluid Flow Newsletter. This month’s e-Newsletter focuses on using PIPE-FLO to troubleshoot problems with fluid piping systems.

If you have any questions or comments about this or any previous newsletter, please feel free to send them to solutions@eng-software.com we enjoy hearing from you all.

FEATURED TOPICS - click on a topic below for details.

  1. BUILDING & PROOFING THE MODEL

  2. START WITH THE PUMP

  3. CHECK THE BOUNDARY CONDITIONS

  4. COMPONENTS & CONTROL VALVES

  5. PIPELINES

  6. ODDS & ENDS
1. BUILDING & PROOFING THE MODEL

After building a system model of an existing fluid piping system, it is important to compare the calculated results to that of the operating fluid piping system. The best way to accomplish this is to record the operation of the system under a variety of lineups.

First, record the system parameters from the operating system, such as the levels and pressures in each tank, set values of the various controls, determine the pumps' operation, and the status (open / close) of the pipelines.

Next, create a lineup in your piping system model replicating the operation of the system. Perform a system calculation with PIPE-FLO and compare the calculated results to the observed values indicated on the plant instrumentation. If the calculated flow rates and pressures in the piping system model compare favorably to the observed values in the plant, the model is an accurate representation of the physical piping system. 

To get an accurate benchmark you should compare the results of the piping system model to the system instrumentation for a variety of operating conditions.

If the calculated results do not reflect the operation of the physical system, the model doesn’t represent the physical piping system design, or something has occurred to the physical piping system that no longer reflects the original piping system design. The remainder of this newsletter describes how to discover the source of the problem(s) and develop an accurate system model.

TRAINING OPPORTUNITIES
MACKAY PUMP SCHOOL
The Mackay Pump School is dedicated to helping companies stop repetitive pump failure and eliminate expensive and unscheduled downtime. This is achieved by analyzing the hydraulic and mechanical aspects of the pump and system, and developing effective troubleshooting skills. Presented in an unbiased approach by a 40 year veteran of the pump business with a talent for keeping it simple. Targeted for Design, Operating and Maintenance Engineers and Technicians, Equipment Specialists and Pump Sales People.
Click one of the two dates available to find out more information:
ONE DAY PUMP TRAINING - FROM AN INDUSTRY EXPERT

Pumps are an integral part of every system involving water and wastewater, yet engineers and plant personnel are seldom fully trained to handle the pump problems they encounter daily. A good understanding of proper pump application, selection, operation and interaction with the system are vital to the success of your company.  Now you can learn most everything you need to know about pumps at a one-day course on June 24, 2004 at the Museum of Flight in Seattle, WA. (Enrollment limited to residents of Washington and Oregon)
Click here for registration information.
THREE DAY PUMP TRAINING - FROM AN INDUSTRY EXPERT

  • Are you confused by the variety of pump types?  Do you know how to properly size pumps?

  • Did you know that proper pump selection can reduce both maintenance and energy costs?

  • Do you understand what causes cavitation in pumps, and how can it be avoided?

  • How do you deal with systems involving multiple pumps, variable speed, or viscous liquids?
Answer these questions and more at this three day course in Long Beach, CA August 18-20, 2004.  For registration information click here.
2. START WITH THE PUMP
When checking the accuracy of a piping system model, the first thing to check is the operation of the pump. If available, you should use the manufacturer's supplied pump test curve; if that is not available use the catalog curve.

Compare PIPE-FLO's calculated pump suction and discharge pressures to the pressure gages located on the pump.

  1. If the physical pump's suction pressure is lower than the calculated suction pressure, you may have a problem in your pump suction piping.

  2. If PIPE-FLO indicates that the pump's NPSHr is not being met, the pump could be cavitating.

  3. If the pump suction pressure is correct, but the discharge pressure is too low, the pump performance may have degraded.

  4. If a power meter is available for the pump, compare the pump's actual power consumption with PIPE-FLO’s calculated results.

If the operation of the physical pump compares favorably with the calculated results of the piping system model, you can rule out the pump. The next step is to review the accuracy of the components and control valves.
3. CHECK THE BOUNDARY CONDITIONS

Boundary conditions such as tank levels & pressures, control valve settings, open / closed pipelines, pumps on/off definitely have an effect on the calculated results. Check to insure the lineup for the piping system model accurately represents the boundary conditions found in the physical piping system.

4. COMPONENTS & CONTROL VALVES

Next check the system components, such as filters, strainers, heat exchangers, and other devices in the piping system with a pressure drop for a given flow rate.&

Use the manufacturer's supplied pressure drop data when modeling a component. If the manufacturer’s pressure drop data is not available, you can measure the differential pressure across the component for a given flow rate, then enter the flow rate and pressure drop in the component dialog box and click the second order button. PIPE-FLO then approximates the pressure drop across the component for a range of flows.

Control valves provide an accurate indication of the flow rate through a valve. Valve manufacturers typically provide Cv values for a range of valve positions. When Cv data is specified for a control valve, PIPE-FLO calculates the valve position based on the set flow rate through the control.

If the actual valve position is greater than the calculated position, check the following items:

  1. The inlet pressure at the control valve may be lower than the pressure calculated in the model. This indicates a problem with something upstream in the piping system.

  2. If inlet pressure is correct, the problem may be due to a worn valve seat / disk.

ATTEND A FREE PIPE-FLO WEB SEMINAR

Do you want to see how you can effectively use PIPE-FLO on your next piping project? Then sign up for a PIPE-FLO Web Seminar!

Every Tuesday and Thursday, we conduct Web seminars demonstrating the PIPE-FLO program in operation.

All you need is:

  • A computer with Internet Access

  • A phone next to the computer and

  • One-hour

One of our application engineer’s is available to demonstrate PIPE-FLO and answers your specific questions. Sign up for a PIPE-FLO Web seminar today by calling your account representative toll free at 800-786-8545, or sign up on our Website http://www.eng-software.com/webdemo.

5. PIPELINES

If the calculated flow rates or pressure in a single pipeline or path is not correct, the problem more than likely is due to a problem in the pipeline. If the flow rate and pressure in the entire system is do not appear to be correct, the problem is common to all the pipelines. Items you should check in order or importance is:

  1. Fluid properties - Make sure your fluid viscosity and density are correct in your fluid zones.

  2. Pipe schedule – Check the pipe specification to insure the model is using the correct pipe schedule or wall thickness.

  3. Pipe diameter – This typically occurs on a single pipeline. If can also occur in the entire piping system if the inside pipe is diameter is reduced by scaling on the inside of the pipe.

  4. Valves & fitting – This typically occurs in a single pipeline. Check to insure the model has a correct types of valves (gate, globe, ball, butterfly).

  5. Pipe roughness – finally check the pipe roughness used in the calculations, especially if the actual pipe shows signs or pitting and corrosion.
6. ODDS & ENDS

The following pump manufacturers can now be downloaded from the Pump Manufacturers List:

  • Chempump

  • Finder Pompe

  • Goulds Water Technology (G&L and Commercial Products

  • Smart Turner

 

The following pump manufacturers have made updates to their Electronic Pump Catalogs:

  • Griswold Pump

  • Sulzer Process Pumps

  • Met-Pro Divisions Fybroc and Dean Pump