what is start up vent valve ? why it is used in boiler?
Answer Posted / k.v.chandra mouli
Boiler start-up period can be a difficult period for a super heater particularly while the boiler water temperature is being raised from cold to the normal atmospheric boiling temperature (100oC). During this boiler start-up period, there is no steam available to pass through the super heater tubes and so to carry away the heat transferred from the flue gases. Therefore, the rate of heat input to the boiler should be carefully controlled to avoid tubes overheating.
So, in all super heaters attached to the boilers, there must be a provision to save the tubes from overheating while steam is raised, especially when the delivery of steam from the boiler is suspended, these tubes should be saved from overheating.
To save the tubes from overheating, the super heater may be flooded with water from the boiler. The startup vent valve is kept open while start up boiler and this valve is useful, to vent out low temperature & pressure moisturised steam as well as to raise steam pressure slowly.
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