1. Keep boiler firing ( this fashion you may have a much better circulation of water within the boiler)
2. Normally 2 valves are given on boiler side and 2 valves on the sea side for blowdown purpose. The idea behind giving two valves for blowdown in each of the places is that, The valves attached to the ships hull and the boiler body are very difficult to overhaul, when ship is sailing or in port. These valves is overhauled once ship is in dock only( by adjusting list or processing down entire boiler you’ll try this , but you know how hard it is ). So normally dont play around with these valves and dont keep them throttled( throttling a steam valve or a high pressure line valve causes wire drawing effect which destroys valve seats and it starts leaking). Now, you would like to regulate rate for processing down, and the way do u reach that??? Throttle the valve which is not attached to the boiler body or the ships hull!! This is why 2 valves are given .
3.Open the valve attached to the ships hull and the boiler body fully first.
4.Open the sea side valve .
5.Throttle the flow rate using the second valve given after the valve attached to boiler body.Simple!!!
6. When water level reaches the normal level on guage glass, close the throttled valve first( see which valve is throttled from point no.5)
7. Close other valves.
8. Finish the blowdown.