TECH TALK demand . If downstream surge could be an issue , a downstream surge pilot can be added to the reducing valve that will close the control valve quickly should the downstream pressure rise slightly above the pressure-reducing pilot set point .
Some manufacturers will offer package solutions – for example , the Cla-Val Model XP2F offers full instrumentation that includes upstream pressure , downstream pressure , valve position , instantaneous flow , and totalized flow . When deployed across the system network the XP2F package allows for insight into pressure , leakage , flow , and system distribution management . The inlet pressure , outlet pressure , valve position , flow , and totalized flow can be retransmitted to SCADA or the AMI System , and logged to the internal SD Card .
The possible additions are numerous and specific requirements should be discussed with the control valve supplier to ensure you get the full benefit of all that is available .
4 . Layout of the valve station
There are some key items that every valve station requires , namely isolating valves , upstream and downstream of the control valves . These are required to allow for the isolation of the control valve when it is necessary to work on the control valve for maintenance . These valves can be either butterfly valves or gate valves and can be installed with handwheels or operating nuts depending on whether or not it is required to operate these valves from above ground . Most utilities will use non-rising stem gate valves as these are the valves that are typically located throughout the network . Everyone is familiar with them ; however , if space or cost is an issue , butterfly valves can be used , as long as there is space between the butterfly and the control valve to allow clearance for any equipment in the control valve , such as insertion strainers or flow meters .
The importance of protecting the control valve from foreign objects in the pipeline cannot be stressed enough , and this is where a line strainer is an excellent addition to the station . While most water supplies have screening at the intake point , it is common for objects to be introduced into the network , either by insufficient flushing after piping work or even open pipe ends that can attract animals during development . Everything – from welding rods , fish , rodents , pieces of wood , and even expensive tools – has been seen .
Each station should be installed with pressure gauges , either on the pipeline or sometimes supplied with the control valve . It is necessary to know the outlet pressure to set the reducing valve , and having an inlet gauge also allows the operator to see what the conditions are upstream .
Air valves should be strongly considered for every valve station . The operation of reducing pressure naturally allows air to form in the pipeline and , if this is not removed downstream of the control valve , it will move down the pipeline and potentially cause issues elsewhere . A good practice is to install an air release valve on the upstream side of the control valve – this will eliminate the possibility of air entering the pilot system , which can be a problem .
Cla-Station is used during planning to determine the right valve size based on velocities
5 . Practical and functional additions
Before a valve station is installed and operational , consider installing these items :
1 . Lifting eyes in the ceiling above major pieces of equipment . If this is a concrete chamber , these need to be decided upon before the concrete is cast to ensure correct capacity . They will make maintenance a much easier task for the operations crew .
2 . Spare pipeline connections , possibly for a hose bib connection . It is much easier to install before the line is pressurized .
3 . A sump drain . Chambers can flood and getting water out can be an issue . This may be as simple as a daylight drain , or a sump with an electric pump may be required .
4 . Protection from over-pressure for the downstream network . Consider adding a relief valve on the downstream piping inside the valve station . Typically , this valve will be a much smaller valve than the main line valve , and an angle style is most common . The outlet from this valve will require a drain connection to eliminate the flooding of the chamber , should the valve ever be utilized . However , it is a small cost compared to the potential damage that a burst water main may cause downstream .
While a valve station design is not necessarily difficult , poor design can certainly lead to operational issues down the road . Take the time to think it through and you will win friends in the operations department later . Regular maintenance , including inspections , calibration , and cleaning , is recommended to prevent malfunctions and extend the valve ’ s lifespan .
ABOUT THE AUTHOR
Mark Gimson is Director of Marketing and International Sales for Cla-Val . As a mechanical engineer with 40 years in the water industry , Mark has a passion for expanding markets and understanding customer challenges to provide the optimal solution .
www . valve-world-americas . net • October 2024 | Valve World Americas 33