Boiler Hydrotest Water Quality 4

[pootong]

Our boiler is 70 Bar.g/480 C 90 T/hr steam production is going to get hydrotest very soon but demin water plant is not yet ready for water production. Is it possible to use potable water (municilpal water)for hydrotest. Any recommendation is welcome.

 

[metengr]

For a boiler of this size, potable water should be ok for a hydrotest. The boiler should be filled, tested and completely drained soon after. Do not leave the potable water in the boiler for any longer time then is necessary.

Most likely, you will form a light layer of rust (iron oxide) on exposed waterside surfaces because the water will be saturated with oxygen. However, this oxide will dissolve once demin water is used, you de-oxygenate and fire the boiler.

 

[unclesyd]

I concur with the above post but would like to ask and add.

How long after the hydro will the boiler be commissioned?

During startup take some good blowdowns.

 

[GenB]

You may need to add some chemicals to the water to keep the ph right and ox scavenger for the corrossion.
your best bet is to consult a water /chemist specialist for the right dosis.
ER

 

[rmw]

If your boiler has any 300 stainless steel grades of tubing in it anywhere, you will want to check to see if the potable water has any chlorine in it. SCC problems can develop from the use of "city water" with chlorine or other chlorides present.

rmw

 

[pootong]

Thank you all for valuable advise, I would like to give you more information as follows. First firing and Alkaline boiled out will be 1 month after hydrotest because of the remaining work such as insulation and lagging. After hydrotest there would be some water left in superheater coil becuase there is no drain. Our boiler doesn't have 300 stainless steel grade tubing, only T22 superheater tube is the highest alloy grade.

 

[metengr]

Based on your last post, I would probably use a corrosion inhibitor if you can't completely drain the boiler after hydrotest, and you are going to leave stagnant water in un-drainable tube circuits. Otherwise, you should be fine.

 

[qualitypro]

Asme B31.1 137.4.5 states that the the required hydrostatic test pressure shall be CONTINUOUSLY maintained for a minimum time of 10 minutes.
When there are instances of valve packing leakages in the piping system the only way of maintaining the test pressure is by running the pump. I would like to know if this is acceptable by the code and satisfies a hydrostatic test requirement.

 

[metengr]

Yes, running the pump to maintain hydrostatic test pressure is permitted. You are looking for leaks visually during a hydrostatic test. In some cases, a pressure decay is used if you cannot visually inspect the component. If necessary, make sure that your Inspector is in agreement, and reviews your hydrostatic testing procedure.

 

[davefitz]

Don't forget to maintain the water and metal temperature of all parts above 70F, to avoid brittle fracture during hydrotest. This is espescially important on the P91 welds on the main steam line.