Preventing Water Hammer With Variable Speed Actuators

Water hammer is often a main concern in pumping techniques and should be a consideration for designers for several causes. If not addressed, it can trigger a number of points, from damaged piping and supports to cracked and ruptured piping parts. At worst, it might even trigger harm to plant personnel.
What Is Water Hammer?
Water hammer happens when there is a surge in strain and flow price of fluid in a piping system, causing fast changes in stress or force. High pressures can result in piping system failure, similar to leaking joints or burst pipes. Support elements can even expertise strong forces from surges or even sudden move reversal. Water hammer can happen with any fluid inside any pipe, however its severity varies depending upon the situations of each the fluid and pipe. Usually this happens in liquids, but it can also occur with gases.
How Does Water Hammer Occur & What Are the Consequences?
Increased strain occurs each time a fluid is accelerated or impeded by pump condition or when a valve position adjustments. Normally, this stress is small, and the rate of change is gradual, making water hammer virtually undetectable. Under some circumstances, many pounds of stress could additionally be created and forces on helps can be nice enough to exceed their design specifications. Rapidly opening or closing a valve causes stress transients in pipelines that can result in pressures well over regular state values, causing water surge that may critically injury pipes and course of control gear. The significance of controlling water hammer in pump stations is well known by utilities and pump stations.
Preventing Water Hammer
Typical water hammer triggers include pump startup/shutdown, power failure and sudden opening/closing of line valves. A simplified mannequin of the flowing cylindrical fluid column would resemble a metallic cylinder suddenly being stopped by a concrete wall. Solving these water hammer challenges in pumping systems requires either decreasing its results or stopping it from occurring. There are many options system designers want to remember when developing a pumping system. Pressure tanks, surge chambers or related accumulators can be utilized to soak up pressure surges, which are all useful tools within the fight towards water hammer. However, preventing the pressure surges from occurring within the first place is commonly a better technique. This could be accomplished by utilizing a multiturn variable pace actuator to manage the velocity of the valve’s closure price at the pump’s outlet.
The advancement of actuators and their controls present alternatives to make use of them for the prevention of water hammer. Here are three cases 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, probably 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 circulate control. To avoid water hammer and probably critical system harm, the applying required a linear circulate characteristic. The design challenge was to obtain linear circulate from a ball valve, which typically displays nonlinear flow traits as it is closed/opened.
By using a variable velocity actuator, valve place was set to realize completely different stroke positions over intervals of time. With this, the ball valve could presumably be pushed closed/open at varied speeds to achieve a more linear fluid move change. Additionally, within the event of a power failure, the actuator can now be set to shut the valve and drain the system at a predetermined emergency curve.
The variable pace actuator chosen had the capability to regulate the valve place based on preset times. The actuator could be programmed for up to 10 time set points, with corresponding valve positions. The speed of valve opening or closing could then be controlled to ensure the specified set place was achieved at the appropriate time. This advanced flexibility produces linearization of the valve characteristics, allowing full port valve selection 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 during regular pump operation. Additionally, in the event of electrical power loss, the actuators ensured speedy closure by way of backup from an uninterruptible energy supply (UPS). Linear flow price
change was also provided, and this ensured minimum system transients and straightforward calibration/adjustment of the speed-time curve.
Due to its variable speed functionality, the variable velocity actuator met the challenges of this installation. A travel dependent, adjustable positioning time offered by the variable pace actuators generated a linear flow through the ball valve. This enabled nice tuning of operating speeds via ten completely different positions to forestall water hammer.
Water Hammer & Cavitation Protection During Valve Operation
Design Challenge
In the world of Oura, Australia, water is pumped from multiple 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 regulate the water move.
To protect the valve seats from damage attributable to water cavitation or the pumps from running dry within the occasion of water loss, the butterfly valves should be able to rapid closure. Such operation creates large hydraulic forces, generally identified as water hammer. เกจวัดแรงดัน10bar are adequate to cause pipework harm and have to be prevented.
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 fast closure fee is about. To avoid water hammer, during the 30% to 5% open phase, the actuator slows right down to an eighth of its earlier pace. Finally, in the course of the ultimate
5% to complete closure, the actuator accelerates once more to reduce cavitation and consequent valve seat injury. Total valve operation time from open to shut is round three and a half minutes.
The variable speed actuator chosen had the capability to alter output velocity primarily based on its position of journey. This advanced flexibility produced linearization of valve characteristics, permitting easier valve selection and lowering water
hammer. The valve velocity is defined by a most of 10 interpolation factors which may be exactly set in increments of 1% of the open position. Speeds can then be set for up to seven values (n1-n7) based on the actuator kind.
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. The move is managed utilizing pump supply recycle butterfly valves pushed by actuators.
Under normal operation, when a decreased circulate is detected, the actuator which controls the valve is opened over a period of 80 seconds. However, if a reverse circulate is detected, then the valve needs to be closed in 10 seconds to guard the pump. Different actuation speeds are required for opening, closing and emergency closure to ensure protection of the pump.
The variable speed actuator is ready to provide as much as seven completely different opening/closing speeds. These may be programmed independently for open, close, emergency open and emergency close.
Mitigate Effects of Water Hammer
Improving valve modulation is one solution to consider when addressing water hammer considerations in a pumping system. Variable pace actuators and controls provide pump system designers the flexibility to constantly management the valve’s working speed and accuracy of reaching setpoints, another task apart from closed-loop control.
Additionally, emergency safe shutdown may be provided using variable pace actuation. With the capability of continuous operation using a pump station emergency generator, the actuation know-how can offer a failsafe option.
In other words, if a power failure occurs, the actuator will shut in emergency mode in varied speeds utilizing power from a UPS system, permitting for the system to empty. The positioning time curves can be programmed individually for close/open direction and for emergency mode.
Variable pace, multiturn actuators are also a solution for open-close obligation situations. This design can present a soft begin from the beginning position and soft cease upon reaching the tip position. This stage of management avoids mechanical strain surges (i.e., water hammer) that can contribute to untimely element degradation. The variable speed actuator’s capacity to offer this control positively impacts upkeep intervals and extends the lifetime of system elements.

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