Every water system typically consists of piping networks that distribute water from a source or storage reservoir to the end users. This frequently requires miles of piping mains along with pumps systems and controls that all have to be monitored and controlled somehow. Whether this control is to regulate pressure, a level or a flow, this usually will require some form of a valve that will have to be controlled. Essentially you have four options:
- A manual valve. This is an inexpensive option that works if you rarely have to change the settings. To ensure this is a good option for your application you need to determine how often you need to make adjustments, what time of day they have to be done and how accessible the valve is. If it’s frequent, time and labour costs can quickly add up.
- An electrically actuated valve. You can add a motor to a simple butterfly valve, but there are several reasons why this may not be the best option: a. What if you need to control more than one variable? b. Do you have power at the valve location? Running a new power line can be costly. c. Electric motors are not inexpensive, especially if you are purchasing a more robust, waterproof version.
- A pneumatically actuated valve. This is a great choice for a plant based valve where a good air supply exists, but not so easy if you need the valve to perform several functions.
- A diaphragm actuated, hydraulic controlled valve is the most common pressure reducing valve in city water systems and for good reason.
Here are the top 10 reasons why a diaphragm actuated control valve should be considered?
- A diaphragm valve will typically cost less money. They are also self-powered, as the energy required to open and close the valve is “borrowed” from the water in the pipeline. (Assuming you are not electrically actuating this valve).
- It can perform many functions. Once you have the main valve it is quite simply a function of what pilot controls are installed to determine exactly what the valve controls. For example you can very easily have a pressure reducing in one direction, pressure sustaining to ensure the upstream users always have enough pressure and check feature to close the valve to stop reverse flow, all in one control valve. Or you could have a level control altitude valve complete with pressure sustaining feature that ensures when the reservoir is filling you are not robbing the water main of too much pressure. Multiple functions are very common for these valves.
- They can be installed remotely away from any power if required and will operate and make necessary adjustments without any input whatsoever. Once the pilot controls have been set, they give years of trouble free service. They will continue to work underwater, which brings peace of mind should there be an unexpected calamity at the station.1
- Adding electronic control is simple. Rather than having to install a large motor to open and close a valve you can simply add a small pilot solenoid control that can run on DC power to close even the largest of pipeline valves. There is no need to run expensive 3 phase power supplies.
- They can be maintained in the pipeline. At some point you will have to do maintenance on every valve. Unlike butterfly valves that have to be removed to determine the wear and quality of the discs and seats, the main diaphragm valves can stay in the pipeline while you do it.
- They can be adapted later. Sometimes conditions change or functionality may require changes or modifications. It is incredibly easy to make changes to this type of valve in the field and not hard for the average operator to perform. It’s easy to add more limit switches or a visible indicator or motorize one of the pilots to tie into a SCADA system for remote control?
- They are globe valves, which mean they are perfect for throttling. Unlike a butterfly valve which exhibit an equal percentage flow characteristic (flow capacity increases exponentially with valve position), a globe valve tends to have a more linear characteristic (flow capacity increases linearly with valve travel) which makes them ideal for not only on/off applications but also excellent at fine controlled throttling, especially if installed with a rolling diaphragm.
- They can handle cavitation. With the right trim installed, cavitation can easily be controlled to ensure that damage will not occur to the valve. And not just to the valve, as frequently valve cavitation will move downstream and destroy the pipe. With the correct anti-cavitation trim installed this will never happen.
- They are usually installed with speed controls to give adjustable opening and closing speed of the valves. Sometimes you may want a valve to open faster than you want it to close. This type of valve gives you that flexibility.
- They are easily maintained by city personnel. Everything on these valves can be taken apart and serviced and spare part kits cover everything required that typically wears out.
In closing, while diaphragm control valves can at times look quite intimidating, they are really quite simple and are a very reliable and a cost effective method of control in the network.