Drain valves and measures to reduce water hammer – German BETTE

Thread Content

I. Steam Traps In steam systems, traps are a very important component. Their primary function is to remove air and cold non-condensable gases from the steam system, as well as the condensate water generated as a result of steam use； It also automatically prevents steam leakage. II. Classification of Steam Trap Types
Basic Classification
Principle of Operation
Intermediate Classification
Sub-classifications

Mechanical Type
Density difference between steam and condensate
Float-type
Lever float-type
Free float-type
Free float with pilot piston type
Upward-opening float type
Bucket type
Differential pressure double-valve bucket type
Downward-opening float type
Inverted bucket type
Differential pressure double-valve inverted bucket type

Thermostatic Type
Temperature difference between steam and condensate
Steam pressure difference
Bellows type
Bimetallic strip type
Disc bimetallic type

Thermodynamic Type
Thermodynamic properties of steam and condensate
Disc type
Atmospherically cooled disc type
Air-insulated disc type
Steam-heated, condensate-cooled disc type
Orifice plate type
Pulse type

Principle of Operation of Steam Traps
These traps function by taking advantage of the density difference between steam and condensate, or by utilizing the physical properties changes that occur when the phase state changes, in order to open or close the valve. Commonly used traps include float-type, bell float-type, and thermodynamic types, among others. Steam traps are installed between steam heating equipment and the condensate return header. When turned on, the barrel is at the bottom and the valve is fully open. After entering the steam trap, the condensate flows to the bottom of the tank, filling the valve body and submerging it entirely; thereafter, the condensate is discharged to the return water manifold through the fully open valve. Steam also enters the steam trap from the bottom of the tank, occupying the upper part of the tank and creating buoyancy. The barrel rises slowly, moving the lever toward the valve seat until the valve is completely closed. Air and carbon dioxide gas gather at the top of the drain valve through the exhaust holes in the barrel. http://cdn037.yun-img.com/static/upload/dsc86/news/20190703154734_16786.jpg The steam emitted from the exhaust vents condenses due to the cooling effect of the steam traps. When the incoming condensed water begins to fill the tank, the tank starts to exert a pulling force on the lever. As the condensation level continues to rise, the force generated increases until it is sufficient to overcome the pressure difference and open the valve. As the steam trap valve begins to open, the pressure difference acting on the valve disc decreases. The barrel body will drop rapidly, causing the valve to open fully. The non-condensable gases accumulated at the top of the steam trap are discharged first, followed by the condensed water. As the water flows out of the tank, it carries the dirt with it and exits through the drain valve. As the condensate is discharged, steam begins to flow back into the steam trap, and a new cycle starts. III. Water hammer: Due to heat loss in the pipes, steam condenses into water, and these droplets of water form on the inner walls of the pipes. The water droplets are swept by the steam flow to form a water film. Due to gravity, the condensed water flows toward the bottom of the pipe, causing the thickness of the water film to increase continuously. The condensation droplets flowing along the steam pipes keep accumulating and eventually form water pellets (as shown in the figure). http://cdn065.yun-img.com/static/upload/dsc86/news/20190703154754_67348.jpg Such water bombs have a high density and are incompressible; they possess considerable momentum when moving at high speeds. When encountering obstacles such as pipe bends or tees, the kinetic energy of the water is converted into pressure energy, and pressure waves act on the obstacle. Condensate also accumulates at the lowest points in the pipes, and steam carries these droplets of condensate, which then impact the valves and pipe fittings downstream. These low points include the subsidence of the main pipe, which may be caused by a lack of sufficient support or damaged pipe racks. Other possible causes of water hammer include the use of improperly designed concentric reducing pipes or filters, or insufficient drainage of condensate before the rising steam main. The noise and vibrations resulting from collisions between the condensate droplets and obstacles are known as \"water hammer\". Water hammer **reduces the lifespan of pipe fittings; in severe cases, the pipe connections can break, resulting in an effect similar to an explosion.** Steam will leak from the cracked pipe, which is very dangerous. http://cdn065.yun-img.com/static/upload/dsc86/news/20190703154705_30064.jpg Valve damage caused by water hammer. IV. Measures to reduce the effect of water hammer: Proper steam pipeline or equipment valves as well as appropriate discharge capacities must be selected to ensure that condensate can be discharged quickly. The installation of the hydrophobic station must be proper. If the pipeline steam trap station must be designed as an equal-diameter tee steam trap station, otherwise the steam trapping effect will be poor and water hammer will be inevitable. The installation of valves and pipe reducers in the pipelines should be as reasonable as possible, to avoid creating artificial low points that could lead to the accumulation of condensate water and thus water hammer. A drain station must be installed at the lowest point of the steam pipeline. A steam trap station and an air release valve are installed at the end of the steam pipeline. If all of the system’s condensate water is recovered, a check valve must be installed downstream of the steam trap. Try to avoid recycling condensate water under different pressures into the same condensate pipe. Represented brands: German BETTE, Taiwanese NWYANG, Japanese KANEKO (stk), Taiwanese DSC, as well as various other brands from Japan, Taiwan, the United States, and Germany.