Fulton Ancillary Equipment SteamPac Unfired Steam Generators - Manual (Page 47)

Fulton Thermal Corp.*SteamPac Unfired Steam Generators Manual* Version 2010-0201
Page 47
3. Safety Relief Valves
a) When the valves leave the factory, they have been carefully set and tested to ensure that
the seating surfaces are perfect. However, in service, and when the pressure in the
vessel is neat to the set pressure of the valve, the clamping force between the seating
surfaces is very light and any foreign matter lodged between the two surfaces will cause
the valve to leak.
b) Particles lodged on the seating surfaces are, therefore, the first things to look for in the
case of a leaking valve and it is usually sufficient to flush the seating surfaces. If
however, the seating surfaces have been damaged, it will be necessary to replace the
valve.
4. De-scaling
a) The need to de-scale the steam generator is indicated when steam generation becomes
slower and more difficult. Operation of the unit may become erratic.
b) De-scaling is normally carried out chemically by preparing a solution of proprietary
chemical such as “Scale Kleen”, and pouring it into the top of the generator. (Remove the
pressure gauge and use its connection). The pump is run so that the generator is filled. If
possible, some heat is added to warm the solution slightly. Note: It is the responsibility of
the customer to insure that during the descaling of the tube bundle, the tubes are not
chemically attacked and form leaks or cracks.
c) There are two basic ways of ensuring the scale dissolving process continues. Either keep
filling the generator with new solution and drain off the used solution, or use suitable
circulating pump, rubber piping and bucket to continuously circulate the chemical through
the exchanger. Usually the solution changes color, as an indication that the acid is spent.
If necessary, add more solution. Scale cleaning is only completed when no further color
change of new solution takes place. Finally, flush through with an alkali, such as soda
ash (1 oz. Per 250 pounds of nominal steaming rate of the unit) in solution. If desired,
remove the heat exchanger tube bundle and visually inspect the interior.
d) During the cleaning process, the equipment must be vented and no unshielded lights
allowed in the vicinity.
Warning
Follow all safety instructions provided by the manufacturer of the de-scaling
chemical. Read the MSDS sheets that are provided. Disposal of spent solution
must be done in accordance with local regulations.