Preventing Water Hammer With Variable Speed Actuators

Water hammer is often a main concern in pumping techniques and must be a consideration for designers for several reasons. If not addressed, it could trigger a number of issues, from broken piping and supports to cracked and ruptured piping components. At worst, it might even trigger injury to plant personnel.
What Is Water Hammer?
Water hammer happens when there’s a surge in stress and flow price of fluid in a piping system, inflicting rapid modifications in strain or force. High pressures may find yourself in piping system failure, similar to leaking joints or burst pipes. Support parts can even expertise robust forces from surges and even sudden move reversal. Water hammer can happen with any fluid inside any pipe, however its severity varies depending upon the conditions of both the fluid and pipe. Usually this occurs in liquids, however it can additionally occur with gases.
How Does Water Hammer Occur & What Are the Consequences?
Increased stress occurs each time a fluid is accelerated or impeded by pump condition or when a valve position modifications. Normally, this strain is small, and the speed of change is gradual, making water hammer virtually undetectable. Under some circumstances, many kilos of stress could also be created and forces on supports could be great enough to exceed their design specs. Rapidly opening or closing a valve causes stress transients in pipelines that can lead to pressures well over steady state values, causing water surge that can critically harm pipes and process control gear. The importance of controlling water hammer in pump stations is widely known by utilities and pump stations.
Preventing Water Hammer
Typical water hammer triggers embrace pump startup/shutdown, energy failure and sudden opening/closing of line valves. A simplified model of the flowing cylindrical fluid column would resemble a steel cylinder abruptly being stopped by a concrete wall. Solving these water hammer challenges in pumping techniques requires either decreasing its results or preventing it from occurring. There are many solutions system designers want to bear in mind when growing a pumping system. Pressure tanks, surge chambers or related accumulators can be utilized to soak up stress surges, that are all useful instruments within the fight in opposition to water hammer. However, stopping the strain surges from occurring in the first place is often a better strategy. This could be achieved through the use of a multiturn variable pace actuator to regulate the pace of the valve’s closure fee at the pump’s outlet.
The advancement of actuators and their controls provide alternatives to make use of them for the prevention of water hammer. Here are three circumstances where addressing water hammer was a key requirement. In all cases, a linear attribute was important for move management from a high-volume pump. If this had not been achieved, a hammer effect would have resulted, doubtlessly damaging the station’s water system.
Preventing Water Hammer in Booster Pump Stations
Design Challenge
The East Cherry Creek Valley (ECCV) Southern Booster Pump Station in Colorado was fitted with high-volume pumps and used pump examine valves for flow control. To avoid water hammer and probably severe system harm, the appliance required a linear move attribute. The design problem was to acquire linear flow from a ball valve, which generally reveals nonlinear flow traits as it’s closed/opened.
Solution
By using a variable pace actuator, valve place was set to attain different stroke positions over intervals of time. With this, the ball valve could probably be pushed closed/open at varied speeds to attain a more linear fluid move change. Additionally, in the event of an influence failure, the actuator can now be set to close the valve and drain the system at a predetermined emergency curve.
The variable pace actuator chosen had the aptitude to control the valve place based on preset times. The actuator might be programmed for as much as 10 time set points, with corresponding valve positions. The velocity of valve opening or closing could then be controlled to ensure the desired set place was achieved on the correct time. This superior flexibility produces linearization of the valve traits, allowing full port valve choice and/or significantly decreased water hammer when closing the valves. The actuators’ integrated controls had been programmed to create linear acceleration and deceleration of water throughout regular pump operation. Additionally, within the event of electrical power loss, the actuators ensured speedy closure by way of backup from an uninterruptible power supply (UPS). Linear flow rate
change was additionally provided, and this ensured minimal system transients and simple calibration/adjustment of the speed-time curve.
Due to its variable speed capability, the variable velocity actuator met the challenges of this installation. A journey dependent, adjustable positioning time offered by the variable pace actuators generated a linear move via the ball valve. This enabled nice tuning of working speeds through ten different positions to stop water hammer.
Water Hammer & Cavitation Protection During Valve Operation
Design Challenge
In the realm of Oura, Australia, water is pumped from a number of bore holes into a set tank, which is then pumped right into a holding tank. Three pumps are every geared up with 12-inch butterfly valves to manage the water circulate.
To shield the valve seats from injury attributable to water cavitation or the pumps from operating dry within the event of water loss, the butterfly valves must be able to fast closure. Such operation creates large hydraulic forces, generally recognized as water hammer. These forces are sufficient to cause pipework injury and have to be averted.
Solution
Fitting the valves with part-turn, variable speed actuators permits different closure speeds to be set throughout valve operation. When closing from totally open to 30% open, a rapid closure price is ready. To avoid water hammer, during the 30% to 5% open phase, the actuator slows right down to an eighth of its earlier pace. Finally, through the ultimate
5% to complete closure, the actuator hastens again to scale back cavitation and consequent valve seat harm. Total valve operation time from open to close is around three and a half minutes.
The variable speed actuator chosen had the aptitude to vary output pace based on its position of travel. This superior flexibility produced linearization of valve traits, allowing simpler valve selection and lowering water
hammer. The valve velocity is outlined by a most of 10 interpolation factors which could be exactly set in increments of 1% of the open place. Speeds can then be set for up to seven values (n1-n7) based on the actuator type.
Variable Speed Actuation: Process Control & Pump Protection
Design Challenge
In Mid Cheshire, United Kingdom, a chemical firm used a quantity of hundred brine wells, every utilizing pumps to switch brine from the well to saturator models. How-to is managed using pump delivery recycle butterfly valves driven by actuators.
Under regular operation, when a lowered flow is detected, the actuator which controls the valve is opened over a interval of 80 seconds. However, if a reverse move is detected, then the valve needs to be closed in 10 seconds to protect the pump. Different actuation speeds are required for opening, closing and emergency closure to ensure safety of the pump.
Solution
The variable speed actuator is ready to provide as a lot as seven different opening/closing speeds. These can be programmed independently for open, close, emergency open and emergency shut.
Mitigate Effects of Water Hammer
Improving valve modulation is one solution to consider when addressing water hammer concerns in a pumping system. Variable speed actuators and controls provide pump system designers the flexibility to continuously control the valve’s working velocity and accuracy of reaching setpoints, another process aside from closed-loop management.
Additionally, emergency protected shutdown can be supplied using variable velocity actuation. With the aptitude of constant operation using a pump station emergency generator, the actuation know-how can provide a failsafe option.
In different words, if an influence failure happens, the actuator will close in emergency mode in various speeds utilizing energy from a UPS system, allowing for the system to empty. The positioning time curves may be programmed individually for close/open path and for emergency mode.
Variable speed, multiturn actuators are additionally an answer for open-close duty situations. This design can provide a delicate start from the start position and gentle stop upon reaching the top place. This degree of control avoids mechanical pressure surges (i.e., water hammer) that may contribute to untimely element degradation. The variable velocity actuator’s capability to offer this management positively impacts maintenance intervals and extends the lifetime of system components.
Share

Leave a Comment