Water hammer can be a main concern in pumping methods and ought to be a consideration for designers for several reasons. If not addressed, it could cause a host of points, from broken piping and supports to cracked and ruptured piping elements. At worst, it might even cause damage to plant personnel.
What Is Water Hammer?

Water hammer occurs when there’s a surge in strain and flow fee of fluid in a piping system, inflicting speedy adjustments in stress or force. High pressures may end up in piping system failure, corresponding to leaking joints or burst pipes. Support elements can even expertise strong forces from surges and even sudden flow reversal. Water hammer can happen with any fluid inside any pipe, but its severity varies relying 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 happens each time a fluid is accelerated or impeded by pump condition or when a valve place adjustments. Normally, this pressure is small, and the speed of change is gradual, making water hammer practically undetectable. Under some circumstances, many pounds of stress could also be created and forces on helps may be nice sufficient to exceed their design specifications. Rapidly opening or closing a valve causes stress transients in pipelines that may find yourself in pressures well over regular state values, causing water surge that can critically injury pipes and course of management equipment. The significance of controlling water hammer in pump stations is widely recognized 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 mannequin of the flowing cylindrical fluid column would resemble a metal cylinder suddenly being stopped by a concrete wall. Solving these water hammer challenges in pumping systems requires both decreasing its results or stopping it from occurring. There are many options system designers want to hold in mind when developing a pumping system. Pressure tanks, surge chambers or similar accumulators can be utilized to soak up stress surges, which are all helpful instruments within the fight in opposition to water hammer. However, preventing the pressure surges from occurring in the first place is often a greater strategy. This can be achieved by using a multiturn variable pace actuator to regulate the speed of the valve’s closure price at the pump’s outlet.
The development of actuators and their controls present alternatives to make use of them for the prevention of water hammer. Here are three cases the place addressing water hammer was a key requirement. In all cases, a linear attribute was important for circulate 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 verify valves for flow management. To avoid water hammer and probably serious system harm, the appliance required a linear move attribute. The design problem was to acquire linear flow from a ball valve, which usually reveals nonlinear circulate traits as it is closed/opened.

By utilizing a variable velocity actuator, valve place was set to attain totally different stroke positions over intervals of time. With this, the ball valve might be pushed closed/open at numerous speeds to realize a more linear fluid flow change. Additionally, within the occasion 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 control the valve position primarily based on preset occasions. The actuator might be programmed for as much as 10 time set points, with corresponding valve positions. The velocity of valve opening or closing may then be managed to make sure the desired set position was achieved on the correct time. This advanced flexibility produces linearization of the valve characteristics, allowing full port valve choice and/or considerably lowered water hammer when closing the valves. The actuators’ built-in controls were programmed to create linear acceleration and deceleration of water during normal pump operation. Additionally, within the event of electrical power loss, the actuators ensured speedy closure through backup from an uninterruptible energy supply (UPS). Linear circulate rate

change was also offered, and this ensured minimal system transients and simple calibration/adjustment of the speed-time curve.
Due to its variable speed functionality, the variable velocity actuator met the challenges of this set up. A travel dependent, adjustable positioning time supplied by the variable speed actuators generated a linear move by way of the ball valve. This enabled nice tuning of operating speeds via ten different positions to prevent water hammer.
Water Hammer & Cavitation Protection During Valve Operation

Design Challenge

In the area of Oura, Australia, water is pumped from multiple bore holes into a group tank, which is then pumped into a holding tank. Three pumps are each outfitted with 12-inch butterfly valves to control the water flow.
To defend the valve seats from damage attributable to water cavitation or the pumps from operating dry in the occasion of water loss, the butterfly valves must be capable of rapid closure. Such operation creates large hydraulic forces, known as water hammer. These forces are adequate to cause pipework harm and should be averted.

Fitting the valves with part-turn, variable velocity actuators allows different closure speeds to be set during valve operation. When closing from fully open to 30% open, a speedy closure rate is ready. To avoid water hammer, in the course of the 30% to 5% open section, the actuator slows right down to an eighth of its previous pace. Finally, in pressure gauge 10 bar of the last

5% to complete closure, the actuator hastens again to reduce cavitation and consequent valve seat injury. Total valve operation time from open to close is round three and a half minutes.
The variable speed actuator chosen had the capability to vary output pace based on its place of journey. This advanced flexibility produced linearization of valve traits, permitting easier valve selection and reducing water

hammer. The valve pace is defined by a most of 10 interpolation points which could be precisely set in increments of 1% of the open position. Speeds can then be set for as a lot as 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 several hundred brine wells, every utilizing pumps to switch brine from the nicely to saturator models. The flow is controlled utilizing pump supply recycle butterfly valves pushed by actuators.
Under regular operation, when a lowered 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 must be closed in 10 seconds to protect the pump. Different actuation speeds are required for opening, closing and emergency closure to make sure protection of the pump.

The variable velocity actuator is in a position to provide as a lot as seven completely different opening/closing speeds. These could be programmed independently for open, shut, emergency open and emergency close.
Mitigate Effects of Water Hammer

Improving valve modulation is one answer to consider when addressing water hammer considerations in a pumping system. Variable velocity actuators and controls present pump system designers the flexibility to constantly management the valve’s operating velocity and accuracy of reaching setpoints, one other task apart from closed-loop control.
Additionally, emergency secure shutdown could be offered utilizing variable pace actuation. With the capability of continuous operation using a pump station emergency generator, the actuation know-how can provide a failsafe choice.
In other words, if a power failure happens, the actuator will close in emergency mode in numerous speeds using energy from a UPS system, allowing for the system to empty. The positioning time curves can be programmed individually for close/open path and for emergency mode.
Variable velocity, multiturn actuators are additionally a solution for open-close obligation situations. This design can present a gentle begin from the beginning position and delicate stop upon reaching the top place. This degree of management avoids mechanical pressure surges (i.e., water hammer) that may contribute to premature component degradation. The variable velocity actuator’s capability to supply this control positively impacts upkeep intervals and extends the lifetime of system components.