blow down
blow down
(OP)
Is there anybody know the meaning and purpose of "blow down"?
thanks,
thanks,
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RE: blow down
In relation to a boiler a blow down is to remove solids and reduce concentration of TDS in the boiler water.
For a pipe during commissioning it can be to blow out debris from the pipe.
There are probably some other applications for blow down that depend upon the industry/situation.
Mark Hutton
RE: blow down
For example, if you kept adding oil to your car engine without ever changing the oil, the contaminants would concentrate until your engine oil was a sludge.
With a boiler, the boiler system is closed and salts will accumulate in the blower over time as water is heated and turns to steam (leaving the salts behind). If the concentration of contaminants is too high, then the contaminants will plate out inside the boiler on the heat transfer surfaces and destroy the boiler. That is why boiler blowdown is used to control the salt concentration within a set operating range. You can do the blowdown continuously or as a batch process.
In a cooling tower system, water is evaporated in the cooling tower which also leaves the salts behind. A blowdown process is also used to control the salt concentration in a cooling tower recirculation system.
RE: blow down
what method can be applied for blowdown? how to blow out the contaminants inside system? by steam out or other pressure medias?
RE: blow down
A mass balance is used to determine the blowdown required to maintain the level of the contaminants in the system.
The actual blowdown mechanism is a drain line to waste controlled by a valve.
RE: blow down
A general CHEM ENG definition for blowdown:
The removal of liquids or solids from a process vessel or storage vessel or a line by the use of pressure.
A MECH ENG definition (I think) would be:
The difference between the pressure at which a safety valve opens and the closing pressure.
There are other definitions with other disciplines.
RE: blow down
RE: blow down
There are several kinds of blowdowns:
1. Steam Boiler. two blowdonwns here
continious blowdown. the goal is to reduce the conductivity of the boiler water (and related contaminats)
Bottom blowdown. the goal is to eliminate the solids that accumulate in the boilers.
2. Cooling tower. the goal is here to reduce the conductivity (and related contaminants) from the system.
3. Safety valves. Blowdown is in this context value of pressure drop to reseal after discharge.
In your second comment you wrote
"....blow out the contaminants inside system? by steam ...". This sounds more like you are trying to clean (aka flush out).
This comprehends a series of measures to clean process systems which may start with water flushing which may be a lot of water running down the system to clean it or blowout the pipes with steam which is also because afterwards you do not have tons of dirty water. some times you do both other only air etc. this depends on your application
rgs
RE: blow down
We also "blowdown" our boiler as others mentioned above, to help remove any build up from the boiler.
Lastly we are installing a "blowdown tank" to which we are piping the rupture disk from a couple of large reactors. Should the rupture disk go, the contents of the reactor will go to the tank, rather than spraying out in the process area.
RE: blow down