Blowdown vessel water inlet distinctions - Clarification needed

[MixBlender]

Hello,

Currently I'm scoping a new blowdown vessel for our facilities boilers. I am reading up on Blowoff designs, and including the existing one we have on site, there are 2 distinct inlets: one for Continuous blowdown and one for intermittent blowdown.

While the designs specify this, and companies that build these vessels make a conscious effort to separate them I cant find specifically why. I am on board with this design logically,but I know that the piping designers will want to consolidate the CBD and IBD lines to a single run of pipe to save on costs.

I want to avoid that from happening if at all possible, but I have yet to find any ASME codes or otherwise in CSA to justify it yet. Is there any other resources I can reference?

 

[chicopee]

"...companies that build these vessels make a conscious effort to separate them I cant find specifically why..." For a short reply, intermittent blowdown which are normally done manually(alto. automatic controls could be used at a cost) when the boiler load is consistent throughout day and night such as for heating purposes. When boiler load have a large variation (and if you graph the fluctuating load for let's for a month period, this load chart will have a seesaw appearance) it would be difficult for the operator to control contaminant levels therefore a continuous blowdown would be mostly beneficial. Such fluctuating loads would be mostly found in industrial facilities whereby steam production would be for processes and heating.

 

[MJCronin]

Remember, all steam boilers generate solids in the boiler water

In large boilers, continuous blowdown systems transport water from the main steam drum to a separate vessel where flash steam is harvested and returned to the system. Dissolved solids go to waste. This system is necessary to control boiler water purity and control internal corrosion.

Intermittent blowdown systems are taken from the bottom of the boiler (mud drums) and are the responsibility of the boiler operator. This system removes the "big chunks" that will accumulate and eventually ruin proper heat transfer and allow accelerated corrosion. All of this water and solids must go to a separate vessel and to waste

Your piping designers may want to turn these two separate systems into one ...... but they shouldn't

https://www.pennseparator.com/

MJCronin
Sr. Process Engineer