Author: Ben Keiser, Applied Flow Technology Technical Sales Consultant
To all the engineers reading this article, we made it! Whew! Reading a three-part series is like running a marathon. Way to go!
If you are new to this series, we encourage you to read this article as well as the previous two: Part 1: Six Reasons Why Flow Analysis is Necessary and Part 2: Flow Analysis Is Neglected. In this article are six reasons engineers should conduct a flow analysis of their piping systems. The good news is there is no bad time to conduct one! In a perfect world, an analysis would be conducted during the design process. Not just the steady-state analysis, but you can use the same steady-state analysis model to jump start your waterhammer/surge transient analysis to see how the system will handle surge.
In another case, flow analysis is run to troubleshoot an issue. AFT understands troubleshooting. We help engineers troubleshoot issues on a regular basis. If we can’t help you find the solution, we can help you find a work-around. Regardless, running the pipe flow analysis will show us where the issues are occurring and put us all on the right track to fix them using your required criteria and project goals.
Regardless, the goal is Applied Flow Technology (AFT) would like to open the conversation and talk about why a flow analysis is necessary.
- Guarantee the system will work according to design
When performing a flow analysis, you can directly validate that the design requirements will be met. Since a flow analysis software tool would perform mass and energy balances all throughout the piping network, you would quickly determine if the design requirements are mathematically feasible. If they are not, it would indicate that the design will physically not perform as expected.
A flow analysis will also validate assumptions made for the design as well as any rules of thumb, hand calculations, spreadsheet calculations, proper equipment sizing and selection, etc.
In addition to simply validating design, a flow analysis can help you determine an optimal pipe sizing configuration throughout your network. This process is greatly streamlined if the flow analysis tool has automated pipe sizing capabilities. No one has the time to look at all possible pipe sizing configurations to determine the best possible performance while meeting requirements. Therefore, with automated pipe sizing capabilities, the flow analysis tool can help establish a more optimal design in an efficient manner.
- Understand complex system interactions
The ability to determine how system components interact for a complicated piping network is a key benefit to a flow analysis. It is easy to find potentially problematic parts of the system in unintuitive places. Perhaps the pipe size in a particular flow path causes a significant pressure loss. Identifying these types of bottle-necks becomes much easier.
Other important complicated system interactions to consider include the presence of control valves, operating multiple pumps in parallel or series, liquid levels changing in tanks, looping and branching flow paths, etc. One example showing how a flow analysis makes it is easier to understand complex systems is pumps operating in parallel. If the pumps are slightly different in any way (i.e., different pump curves, different impeller trims, different lots on the manufacturing line, or different models entirely), or if the suction and discharge piping and fittings are not the same, the pumps can “fight” each other. This means that as the pumps adjust to find their own operating point on their curves, it will cause both to potentially operate further from their best efficiency points. This decreases each pump’s reliability and will lead to excessive wear issues and high maintenance and repair costs.
- Ensure design requirements are still met in different operating cases
A system never operates in the same original design conditions during its lifetime. Even if nothing is ever changed, i.e., tank levels are always the same, temperatures remain constant, all equipment stays in operation, etc., the system will still degrade on its own. Corrosion can build up inside of pipes, thus scaling down the inner diameters. Heat exchanger tubes can get fouled up.
A flow analysis software with proper scenario management capabilities allows the designer to determine the system performance under any type of operating case. Scenarios to examine would include things like the modeling of high and low tank levels, peak vs. off peak flows, hot and cold extreme temperature cases, variable speed pumping cases, and many more.
Attempting to determine what will happen under all these differing cases with hand calculations or spreadsheets dramatically increases the difficulty and probability for mistakes when having to modify the governing equations. With flow analysis software, it is much easier to create different scenarios for these cases and simply change the input. This decreases the possibility of mistakes and by using a standard format, input and output reports are much easier for others to check, often preventing expensive re-work.
- Evaluate system dynamics of surge and non-surge related transient operation
Operation constantly changes as production levels fluctuate and flow demands change. Pumps go on and offline at different times, variable speed drive operating levels change, valves change position, control valves modulate to maintain set points, tank levels rise and fall, etc. It is important to evaluate how all these elements are changing over time because significant operational problems can arise when various components interact with each other in unexpected ways.
What happens when a valve slams shut or a pump trips? Does the pressure surge to unacceptable levels? Is cavitation present? Are the pipe supports strong enough to handle the loads? Severe pipe damage issues can arise during a water hammer or surge event. Careful analysis is required to ensure proper surge suppression equipment is in place.
Overall, conducting a transient analysis for changes in the system due to surge and non-surge related events is just as important as a steady-state analysis during the design phase.
- Easily plan for future expansions and system modifications
A detailed flow analysis of a system, ensuring it will operate according to design, makes it easy to plan for future expansions or other modifications. When a flow model properly calculates pressures, flows, and temperatures the system will deliver, it is easy to accurately predict what conditions will be for an expansion. Or, perhaps the system has been in operation for a long time and an opportunity exists to change some piping and equipment needing replacement. The flow model can help quickly determine which pipes may be significantly corroded, which heat exchangers might have a significant amount of tube fouling, etc. The impact of any system change can easily be determined with the flow model to ensure all components continue to work properly.
- Empower clients to better understand their system, perform effective troubleshooting, and determine impact of modifications
At the end of the design phase, handing off a detailed model of the piping system to the client provides a significant value to them. They will be empowered to better understand how their system operates. Manipulating the operation of pumps, valves, and control valve set points will never be a guessing game again. They will know exactly how to operate their system with great efficiency to avoid costly repairs, downtime, production losses, and expensive energy costs. The flow model would make it very easy for them to troubleshoot operational problems that arise and determine how modifications will affect system performance.
Overall, providing top quality service is a major responsibility of the engineer. With the added benefits and problem prevention provided by a proper flow analysis, it is easy to see how it is necessary to do this work, even when it is not required by code or requested by the client.
Thank you for hanging in with us. We are always interested to hear your feedback on this article or our pipe flow analysis software.
Applied Flow Technology engineers can show you real examples of pipe flow analysis as they pertain to your industry. Let us know what industry and types of projects you work on and we will contact you to schedule a time.AFT offers three main methods to analyze flow:
- AFT Fathom for incompressible flow: calculate pressure drop and flow distribution in liquid and low velocity gas piping and ducting systems
- AFT Arrow for compressible flow: calculate pressure drop and flow distribution in gas piping and ducting systems
- AFT Impulse for waterhammer/surge: calculate pressure surge transients in liquid piping systems caused by waterhammer
We look forward to working with you.