Why is the diameter enlarged after the steam trap?
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Steam heat exchangers often have steam traps on the condensate pipes where heat exchange takes place. Why is the diameter of the pipe at the outlet of the steam trap larger than that of the inlet pipe? What are the considerations? The flow velocity of the liquid decreases after diameter expansion; should the static head increase, wouldn’t this make backflow more likely?
The outlet of the steam trap isn’t enlarged, right? Unless several steam trap outlets are combined into one pipe, then the main pipe will be made larger.
The same is true when there is only one steam trap in the PID
Personal opinion: There’s no need for diameter expansion!
There is also diameter expansion at the site, which indicates that it must be necessary
Diameter expansion occurs due to the pressure difference before and after the check valve; the pressure behind the valve is low, which facilitates flashing. If the diameter is not expanded, proper drainage will not be possible
The pressure is different, and the flow rate is different too!
Before the steam trap, the pipe diameter and flow rate are determined based on the liquid. However, after the steam trap, due to the drop in pressure, steam will flash out; therefore, the flow rate and pipe diameter need to be recalculated. If these values remain consistent, there is no problem when no flashing or pressure drop occurs. But in the presence of flashing and pressure drop, the flow rate increases, which can cause severe erosion of the bends in the piping connections.
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 header 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. The steam discharged from the vent holes condenses due to the heat dissipation by the steam trap. 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 out through the drain valve. As the condensate is discharged, steam begins to flow back into the steam trap, and a new cycle starts.