Unsa ang Water Hammer?
Water hammer o hydraulic shock phenomenon nga mahimong maunserahan isip abrupto nga collision sa fast moving solid slug sa piping system uban ang anumang obstruction sama sa bend, valve, etc. Bisan unsa, ang water hammer adunay definisyon isip sudden increase sa pressure tungod sa hindrance sa fluid motion o direction-change.
Example Nagsugyot kini sa panahon sa charging o warming-up sa mas long na steam line sa initial start-up operation ug tungod sa pag-mix sa steam ug condensate. Ang water hammer adunay tendency nga mogawas sa atong daily routine life – bisan unsa ka oras nga mobag-o o mobukas nato ang water tap sa amoa nga bathroom sa panahon sa bathing results in water hammer. (act of turning on/off shower valve very fast).
Misunderstood Concept about Water Hammer
Daghan kaayo nga thermo-hydraulic phenomenon sama sa table nga kasagaran mischaracterized isip water hammer. Ang mga resulta gikan sa mga insidente naglakip sa shocks sama sa Hydraulic-and-thermal. Ang water hammer mahimong mag-occur tungod sa lack of awareness ug improper Operation and Maintenance practices. Sa kaso sa water hammer, ang proverb nga “prevention is better than cure” adunay kalihukan.
Thermodynamic Phenomenon |
Location of Occurrence |
Water hammer |
In Steam pipes and headers |
Water Piston (unstable horizontal waves) |
Storage tank (like Deaerator) |
Flash condensation and evaporation shock |
In Deaearators |
Water induction, distortion of rotor or casing |
In Steam turbine and steam piping |
Occurrence of Water Hammer
Kung ang steam mao'y nag-leave sa boiler, kinahanglan nia mogawas og distance aron makab-ot sa point of use (steam turbine o any other heat exchanger) ug sa proseso sa pagtravel sa distance, ang steam magsugyot sa pag-lose sa heat. Isip resulta, ang steam sa pipe magsugyot sa pagcondense. Sa panahon sa plant start-up, ang rate sa formation sa condensate (formed from the droplets of water) kay dako kaayo, tungod sa complete system mao'y starting from cold or cold start-up.
Sa panahon sa operasyon, ang mga droplets sa condensate magsugyot sa pagbuild up along the length of steam pipe net work ug thus forming a solid slug of condensate as shown in the given
Condensation results in formation of water droplets. Gradually condensate strats getting build up along the length of pipe and forms solis slug. When this slug come across any obstruction like orifice, valve or a bend, then these obstruction will result is sudden halt of the solid slug unexpectedly. During this process the K.E energy of the solid slug changes to the pressure energy and the pipe network has to be cope with it.
Impact of Water Hammer
Kinahanglan nimo nga maunserahan ang serious impact sa water hammer sa mga equipments used in the plants. Ang gibag-o nga example adunay clear explanation sa destructive nature sa water hammer:
For Saturated steam recommended velocity is 25 to 35 meters per second
For water in a pipe network recommended velocity is 2 to 3 meters per second
When water hammer occurs, condensate slug is dragged by steam and thus the water slug travels with a velocity equal to that of steam which is ten times more than that of water velocity. Thus water hammer is always associated with very high pressure.
Factors help in avoiding water hammer
Steam system is very complex and dynamic, thus avoiding water hammering is a challenging task. But with the help of following the best engineering practices its occurance can be easily surmount by adopting:
Proper inclination should be provided in the steam lines in the direction of flow.
Steam trap installation at regular interval and that too at the lowest points. Installation of the steam trap at the lowest points ensure the removal of condensate from the system.
Pipe sagging results in formation of condensate in the piping network and may result in increasing the chances of water hammering. Thus steam pipes should be properly supported to avoid any sagging.
Standard start up procedures are required for cold start of the plant. Operators should be properly trained to take care of the openly of isolation valve slowly.
Proper sizing of the drain pockets, to ensure that the condensate should not jump or pass it easily. The purpose of drain packet should not be defeated to collect all the condensate and pass the same through the trap.
Type of reducers shall be eccentric instead of concentric reducers.
Water Hammer in Power Plants
Water hammer occurs when water, accelerated by steam pressure or a low-pressure void, is suddenly stopped by impact on a valve or fitting, such as bend or tee, or on a pipe surface. Water velocities can be much higher than the normal steam velocity in the pipe, especially when the water hammer is occurring at startup.
When these velocities are destroyed by impact, the kinetic energy in the water is converted into pressure energy, and a pressure shock is applied to the obstruction. In mild cases, there is noise and perhaps movement of the pipe.
More severe cases lead to fracture of the pipe or fittings with almost explosive effect and consequent escape of live steam at the fracture. Fracturing of pipes or steam system components can propel fragments that can cause injury or loss of life on it.
