چی دەوڵامە؟
Kurkê daryayê an şok hydraulîk û çavkaniya ku bi serkeftin biafirandin da ku şakhsa sêdar ên derve di rêzên xanbûrda de bigire vêgera bend, valv, yana çi dike. Bi tenê ji bo ku kurkê daryayê ya wekî pirastina serkeftîna pêşeya wergerandina cihêre hatî.
Mînak Da dibe dema bikar bûna yana destkirina hêlka steam dergeha destpêk ên. Kurkê daryayê ya wekî ku her dem dikare biafirîne bi bilî ve yana bi bilindiyê - dema me tevala berdest bikin an biceribin da ku me tevala berdest bikin (dema me tevala berdest bikin yana vekirin).
Misunderstood Concept about Water Hammer
Çend fenomena termo-hydraulîk wê ne ku di cihêre de nîşan dide ku ku niha mischaracterized as water hammer. Digerandina daneyê yên ku wan jî dikarin şokan de neçin Hydraulic-and-thermal. Kurkê daryayê li gor dilgeha neçin û Operation and Maintenance practices nederbas bikin. Di navbera kurkê daryayê de proverb of “prevention is better than cure” ya wekî rasthatî.
Fenomena Termodynamic |
Ji reşeyê ku tê hilafkirin |
Kurkê daryayê |
Di lêmanên steam û headers de |
Water Piston (waves unstable horizontal) |
Tank storage (like Deaerator) |
Flash condensation and evaporation shock |
Di Deaearators de |
Water induction, distortion of rotor or casing |
Di Steam turbine and steam piping de |
Occurrence of Water Hammer
Dema steam ji boiler derkeve, divê distanekek bişe bike ta ku derbarê (steam turbine or any other heat exchanger) bibike. Lê dema steam bişe bike, steam di pipe de hate destkirin. Dema destpêka plant rateya formasyonê ya condensate (formed from the droplets of water) zêde ye, ji ber ku sistemê di destpêkê din de destpêk e.
Dema operasyonê droplets ên condensate hate binivîsina bi rojhilata pipe network û hate form kirina slug ên solid ên condensate wê ne ku di cihêre de nîşan dide.
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
It is necessary to understand the serious impact of water hammer in equipments used in the plants. Given below example clearly explains the destructive nature of 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
Kurkê daryayê 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.
