Water hammer can be a major concern in pumping systems and should be a consideration for designers for a quantity of reasons. If not addressed, it could trigger a number of points, from broken piping and supports to cracked and ruptured piping elements. At worst, it could even trigger damage to plant personnel.
What Is Water Hammer?
Water hammer occurs when there is a surge in stress and move fee of fluid in a piping system, causing fast changes in pressure or drive. High pressures can result in piping system failure, corresponding to leaking joints or burst pipes. Support parts also can experience strong forces from surges or even sudden move reversal. Water hammer can happen with any fluid inside any pipe, but its severity varies relying upon the situations of each the fluid and pipe. Usually this occurs in liquids, but it could also happen with gases.
How Does Water Hammer Occur & What Are the Consequences?
Increased stress occurs every time a fluid is accelerated or impeded by pump condition or when a valve position changes. Normally, this stress is small, and the speed of change is gradual, making water hammer virtually undetectable. Under some circumstances, many pounds of pressure could also be created and forces on supports may be nice enough to exceed their design specs. Rapidly opening or closing a valve causes strain transients in pipelines that may end up in pressures properly over regular state values, causing water surge that may critically injury pipes and course of management equipment. The importance of controlling water hammer in pump stations is widely recognized by utilities and pump stations.
Preventing Water Hammer
Typical water hammer triggers embody pump startup/shutdown, power failure and sudden opening/closing of line valves. A simplified model of the flowing cylindrical fluid column would resemble a metallic cylinder all of a sudden being stopped by a concrete wall. Solving these water hammer challenges in pumping techniques requires both decreasing its results or stopping it from occurring. There are many solutions system designers want to bear in mind when developing a pumping system. Pressure tanks, surge chambers or comparable accumulators can be utilized to soak up stress surges, which are all useful tools within the battle against water hammer. However, stopping the stress surges from occurring in the first place is often a better strategy. This can be achieved by using a multiturn variable speed actuator to control the speed of the valve’s closure price on the pump’s outlet.
The advancement of actuators and their controls present opportunities to make use of them for the prevention of water hammer. Here are three cases where addressing water hammer was a key requirement. In ราคาเกจวัดแรงดันลม , a linear attribute was essential for flow control from a high-volume pump. If this had not been achieved, a hammer impact 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 check valves for flow control. To keep away from water hammer and probably serious system injury, the appliance required a linear move attribute. The design challenge was to acquire linear flow from a ball valve, which generally reveals nonlinear flow traits as it is closed/opened.
Solution
By using a variable speed actuator, valve position was set to achieve completely different stroke positions over intervals of time. With this, the ball valve might be pushed closed/open at varied speeds to achieve a extra 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 speed actuator chosen had the capability to manage the valve place based mostly on preset times. The actuator could possibly be programmed for up to 10 time set factors, with corresponding valve positions. The velocity of valve opening or closing could then be controlled to make sure the specified set position was achieved on the right time. This advanced flexibility produces linearization of the valve characteristics, allowing full port valve selection and/or considerably reduced water hammer when closing the valves. The actuators’ built-in controls have been programmed to create linear acceleration and deceleration of water during regular pump operation. Additionally, in the occasion of electrical power loss, the actuators ensured fast closure through backup from an uninterruptible power supply (UPS). Linear circulate price
change was also supplied, and this ensured minimal system transients and straightforward calibration/adjustment of the speed-time curve.
Due to its variable speed capability, the variable speed actuator met the challenges of this installation. A journey dependent, adjustable positioning time provided by the variable speed actuators generated a linear circulate by way of the ball valve. This enabled fine tuning of operating speeds through ten different positions to forestall water hammer.
Water Hammer & Cavitation Protection During Valve Operation
Design Challenge
In the area of Oura, Australia, water is pumped from a quantity of bore holes into a collection tank, which is then pumped right into a holding tank. Three pumps are each outfitted with 12-inch butterfly valves to regulate the water flow.
To shield the valve seats from damage attributable to water cavitation or the pumps from working dry within the occasion of water loss, the butterfly valves must be able to speedy closure. Such operation creates big hydraulic forces, known as water hammer. These forces are adequate to cause pipework harm and must be prevented.
Solution
Fitting the valves with part-turn, variable pace actuators permits completely different closure speeds to be set throughout valve operation. When closing from totally open to 30% open, a speedy closure fee is ready. To keep away from water hammer, during the 30% to 5% open phase, the actuator slows all the way down to an eighth of its earlier speed. Finally, during the ultimate
5% to complete closure, the actuator speeds up once more to minimize back cavitation and consequent valve seat damage. Total valve operation time from open to close is round three and a half minutes.
The variable speed actuator chosen had the aptitude to alter output pace primarily based on its position of travel. This superior flexibility produced linearization of valve traits, permitting simpler valve selection and decreasing water
hammer. The valve pace is defined by a most of 10 interpolation points which may be exactly set in increments of 1% of the open place. Speeds can then be set for as much as seven values (n1-n7) based mostly on the actuator sort.
Variable Speed Actuation: Process Control & Pump Protection
Design Challenge
In Mid Cheshire, United Kingdom, a chemical company used a quantity of hundred brine wells, every utilizing pumps to transfer brine from the properly to saturator items. The circulate is managed utilizing pump delivery recycle butterfly valves pushed by actuators.
Under regular operation, when a reduced move is detected, the actuator which controls the valve is opened over a interval of eighty 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 make sure safety of the pump.
Solution
The variable speed actuator is ready to present up to seven totally different opening/closing speeds. These could be programmed independently for open, close, emergency open and emergency shut.
Mitigate Effects of Water Hammer
Improving valve modulation is one resolution to suppose about when addressing water hammer issues in a pumping system. Variable velocity actuators and controls provide pump system designers the flexibleness to repeatedly management the valve’s working velocity and accuracy of reaching setpoints, another task apart from closed-loop control.
Additionally, emergency protected shutdown can be supplied utilizing variable velocity actuation. With the capability of continuous operation using a pump station emergency generator, the actuation expertise can provide a failsafe option.
In different words, if a power failure happens, the actuator will close in emergency mode in various speeds using energy from a UPS system, allowing for the system to drain. The positioning time curves can be programmed individually for close/open path and for emergency mode.
Variable velocity, multiturn actuators are also a solution for open-close duty situations. This design can provide a delicate start from the start place and soft stop upon reaching the tip position. This level of control avoids mechanical strain surges (i.e., water hammer) that may contribute to premature component degradation. The variable speed actuator’s capacity to provide this control positively impacts maintenance intervals and extends the lifetime of system elements.
Share