Email this pageStall Phenomenon #2: Methods for Preventing Stall
Methods for Preventing Stall
In the preceding article, we touched on the mechanism responsible for the occurrence of stall.
As a quick review of the stall phenomenon, 'Stall occurs when a lack of trap operating differential pressure (the difference between the pressure in front of the trap and the pressure behind the trap) causes condensate to no longer be discharged from the trap and instead to pool inside the heat exchanger.'
In this article, we will take a look at some methods for the prevention of the stall phenomenon.
What is required for the prevention of stall?
To prevent stall, we need to prevent the pooling of condensate inside the heat exchanger. So the removal of pooled condensate, by some means or other, constitutes the prevention of stall.
As previously discussed, if the trap primary (inlet) pressure is smaller than the trap secondary (outlet) pressure, condensate cannot be discharged. Which means that the problem can be solved by making sure the trap primary (inlet) pressure is larger than the trap secondary (outlet) pressure.
Following this line of thought, we can see that there are two possible ways of achieving this result:
a. Raise the trap primary (inlet) pressure
b. Lower the trap outlet (secondary) pressure
Method a. is achieved by means of a mechanical pump such as a PowerTrap, while method b. requires the use of a vacuum pump. Both of these methods are widely used for the prevention of stall.
In the method that makes use of a PowerTrap, steam or air pressure is applied to the pooled condensate to raise the trap primary (inlet) pressure so that it is higher than the trap secondary (outlet) pressure, and thereby forces the discharge of the pooled condensate. In contrast, in the method that makes use of a vacuum pump, the pressure in the trap outlet piping (condensate return line) is reduced to below atmospheric pressure, thereby maintaining the differential pressure required for the trap to operate.
Both of these methods are suitable for the prevention of stall, but the selection of which method to use should be made based on factors such as the conditions causing the occurrence of stall, the installation environment of the equipment and the number of pieces of equipment installed. It is strongly recommended that a qualified technician evaluate the site before any decision is made on which method to use.
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