Regulation 41. Heating surface.

                                   P.U.(A) 5/70

FACTORIES AND MACHINERY (STEAM BOILER AND

                  UNFIRED PRESSURE VESSEL)

                            REGULATIONS, 1970

                     PART II - STEAM BOILERS

Regulation 41. Heating surface.

(1) For the purpose of determining the area of the safety valve and the inspection fee the heating

surface of a steam boiler shall be the total surface of all plates and tubes exposed to heat on one

side and in contact with water on the other, measured on the water or fire side, whichever is the

greater.

(2) The heating surface of an economiser other than a steaming economiser and of a superheater

shall not be included in the steam boiler heating surface for the purpose of determining the

inspection fee, but shall be considered when calculating the capacity of the steam boiler safety

valve.

(3) For a Lancashire or Cornish type steam boiler the total heating surface shall include the

wetted surface of the furnace between the end plates, the fire surface of the cross tubes where

fitted and that part of the external shell below the side flue covers. In estimating areas, any

furnace shall be considered as a plain cylinder and the area of its wetted surface shall be taken

as its mean external circumference multiplied by the length of the steam boiler between the end

plates. For the shell, the width of the part of the circumference below the flue covers shall be

taken as equivalent to twice the mean diameter of the shell and this width multiplied by the length

between the end plates shall be taken as the area of the shell heating surface. Any part of the

back end plate exposed to heat shall be ignored.

 

(4) For a water-tube steam boiler the heating surface of a steam and water drum shall be taken

as half its external mean circumference multiplied by the clear length between the outer brick

walls or centres of cross boxes, as the case may be. The heating surface of a tube shall be taken

as its external surface between tube plates or headers. The surface of any header shall be

ignored.

(5) For a marine steam boiler of the fire-tube type the heating surface shall include the wetted

surface of any furnace between the tube plates (considered as for a Lancashire steam boiler), the

wetted surface of any combustion chamber (less the area of the tube holes) and the wetted

surface of any tubes between the tube plates. Any part of the front tube plate exposed to heat

shall be ignored.

(6) For a traction (loco-portable) or a vertical steam boiler the heating surface shall include the

wetted surface of the fire-box above the foundation ring (less the area of the fire-hole and ring

and the tube holes) and the surface of any cross or other tube and uptake below a point half way

up the gauge glass.

(7) For a locomotive type steam boiler the heating surface shall include the wetted surface of the

inner fire-box plates ( excluding the surface covered by the foundation and fire-hole rings, the

area of the tube holes and the area within the junction of the plates in the case of a flange firehole)

and the wetted surface of the tubes between the

tube plates. The smoke-box plate shall be

ignored.

(8) No deduction shall be made for the area of any stay in calculating the heating surface.

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