Feed into twin drum watertube boiler

[fredrosse]

An excerpt from the ASME Boiler and Pressure Vessel Code, which is used in the USA as well as several other countries:

PG-59.2 Requirements for Feedwater Connections.
The feedwater shall be introduced into a boiler in such a
manner that the water will not be discharged directly
against surfaces exposed to gases of high temperature or
to direct radiation from the fire. For pressures of 400 psi
(3 MPa) or over, the feedwater inlet through the drum shall
be fitted with shields, sleeves, or other suitable means to
reduce the effects of temperature differentials in the shell
or head.

Although the requirement for shields or sleeves is only for operating pressures above 400 PSIG, it is still a good idea to use them where possible.

[fredrosse]

When continuously steaming a boiler with the feedwater flow rate equal to the steam generation rate, there will be virtually no difference in steaming performance regardless of the location where feedwater is introduced, top drum or bottom drums. Steaming rate and steam pressure will be steady as long as firing rate and feedwater flow are steady. There however are the detrimental effects of thermal stress and Oxygen corrosion mentioned earlier if the introduced feedwater is not brought up to saturation temperature as rapidly as possible.

With intermittent feed supply, introducing feedwater into the turbulent steam - water drum will suppress temperature somewhat, and steam pressure will dip lower, and then recover shortly afterwards.

If intermittent feed supply,does not cause this temporary dip in steam pressure, then the introduced new feedwater is not mixing with the main boiler water inventory, a condition named "hideout". This water is indeed hiding from participation in receiving heat, and thus temporarily not at play within the game of steam generation. When this happens, the water, (high density cooler water as mentioned earlier) will eventually end up mixing with the main body of boiler water inventory, but during the relatively long time of "hideout", the cooler water will be reducing metal temperatures in the hideout area of the boiler, as well as exposing this area of the boiler to high oxygen concentration.

[johngriffiths]

As Mike is local I thought he might like to know the Daniel Adamson (3 furnace, coal, riveted Scotch weight about 20 tons) has been fitted with an electrically powered hydrokineter to overcome the problem of a "cold bottom" mentioned by Fred earlier. The original feed pipes were taken up to the water steam interface but I'm not sure where the new ones go. The hydrokineter has been fitted at the request of the insurers and the Maritime & Coastguard Agency.

The relaunch is on 6th May, I have my invitation and I will be there, being the first person to inspect the boiler after we moved the vessel from Ellesmere Post over to Liverpool. We dropped the covers, got some clean air moving through, and then I dropped down onto the tube banks thereafter going down between the banks to the furnaces, using hammer and camera.I won't go into the sessions doing prep for ultrasonics, crack testing etc except to say that using a scaling hammer and disc grinder inside a boiler is never pleasant. It was worth saving and it will be good to see in steam at Lairds later this month after the nine? month refit.

Off topic!

[Mike Cole]

As Mike is local I thought he might like to know the Daniel Adamson (3 furnace, coal, riveted Scotch weight about 20 tons) has been fitted with an electrically powered hydrokineter to overcome the problem of a "cold bottom" mentioned by Fred earlier. The original feed pipes were taken up to the water steam interface but I'm not sure where the new ones go. The hydrokineter has been fitted at the request of the insurers and the Maritime & Coastguard Agency.

The relaunch is on 6th May, I have my invitation and I will be there, being the first person to inspect the boiler after we moved the vessel from Ellesmere Post over to Liverpool. We dropped the covers, got some clean air moving through, and then I dropped down onto the tube banks thereafter going down between the banks to the furnaces, using hammer and camera.I won't go into the sessions doing prep for ultrasonics, crack testing etc except to say that using a scaling hammer and disc grinder inside a boiler is never pleasant. It was worth saving and it will be good to see in steam at Lairds later this month after the nine? month refit.

Off topic!

Thanks for the post John. The Steam in Liverpool event where the Daniel Adamson is to be unveiled to be public is hopefully going to be my first public steaming as well. John Puddy is also thinking of bringing his boat up as well.