Hardness of Boiler Blowdown Water

What is the boiler operating pressure?

• For a low-pressure boiler (<15barg), a blowdown TDS of 2000-2500 is not uncommon, and 3000 might be on the upper end of tolerability.

What does the boiler manufacturer recommend?

Hello, Thanks. Boiler operating pressure is 10.5 bar and generation is 6MT/Hr, I am interested in knowing the hardness of blow down water not TDS . Feed Water hardness is 1ppm. Pl give your feedback. joravi

Blow down water hardness is same as TDS in boiler since you are removing water from boiler. The TDS should not cross 3000ppm. You should adjust blowdown accordingly

You can maintain a higher TDS depending on your caustic alkalinity. A lot depends on what type of hardness you have in the Boiler. If you have a fairly high silica level then you will need to adjust your alkalinity.

This is a guide only, there are lots of variables. You need to test your water for nasties before making any decisions.

We are maintaining Boiler Water TDS below 3000ppm, here my doubt is, if we measure the hardness of that blowdown water then what will be approximate range that measurement. for Example Feed water hardness is 1ppm and Feed water TDS is 20ppm Boiler Blow Down water TDS<2800 , Boiler Blow down hardness= ? Steam generation rate =6MT/Hr at pressure 10.5Kg/Cm2

We also need to know if you are getting a large percentage of return condensate and if your demand is steady or in large gulps? How is your surface blowdown set up?

We are maintaining Boiler Water TDS below 3000ppm, here my doubt is, if we measure the hardness of that blowdown water then what will be approximate range that measurement. for Example Feed water hardness is 1ppm and Feed water TDS is 20ppm Boiler Blow Down water TDS<2800 , Boiler Blow down hardness= ? Steam generation rate =6MT/Hr at pressure 10.5Kg/Cm2

The blow down water characteristics are likely to be closer to boiler in feed water.Whereas in feed water conditions are to be monitered as per needs,is there any specific condition to moniter blow down water parameters?

If you are keeping the boiler TDS at 3000 you may be giving away a lot of BTUs. The main reason for keeping the TDS low is to prevent carry over. You can save fuel costs if you run TDS up to 4500 or even 5000.

If you can monitor your steam quality closely you need to raise the TDS until you find out when carryover takes place and adjust your TDS back down from there.

It doesn't sound like hardness is something to worry about because it is so low at the feed water tank. Consult with your water treatment guys.

We are maintaining TDS below 3000ppm only to keep the boiler water tubes in healthy condition & to get maximum life of the Boiler tubes.

As a curiosity, I have measured Hardness of blowdown water, it is coming 20ppm.

Now I am intersted to know whether this data is acceptable or not.

20PPM hardness is fine. However, why are you so determined to avoid hardness at the expense of everything else?

Hardness is only one consideration when operating your system.You may be paying more in excess fuel costs trying to avoid hardness than is really necessary.

Thanks Mr Beriberi, Ok now my doubt is cleared. I was thinking that ,as all hardness we are removing in softener, Boiler blowdown water hardness will be same as feedwater hardness. I was wrong. Thanks to all who participated in discussion in my apprehensiveness.