§ 14-12-55. Miniature boilers—Existing installations.

A.

Application of section. This section shall apply to existing miniature boilers.

B.

Maximum allowable working pressure. Rules and regulations, as adopted for power boilers applying to strength of materials and calculations to determine maximum allowable working pressure, shall be used for miniature boilers unless a special rule is stated herein. The maximum allowable working pressure on the shell of a boiler or drum shall be determined by the provisions of section 14-12-52.

C.

Construction. The construction of miniature boilers, including factors of safety, except where otherwise specified, shall conform to that required for power boilers.

D.

Safety valves. Each miniature boiler shall be equipped with a sealed, spring-loaded, pop type safety valve not less than one-half-inch pipe size, connected directly to the boiler.

The safety valve shall be plainly marked by the manufacturer showing name or identifying trademark, nominal diameter and pressure at which it is set to release.

The safety valve relieving capacity of each boiler shall be such that it will discharge all the steam that can be generated by the boiler without allowing the pressure to rise more than six percent above the maximum allowable working pressure.

In those cases where the boiler is supplied with feed water directly from a pressure main or system without the use of a mechanical feeding device, the safety valve shall be set to release at a pressure not in excess of 94 percent of the lowest pressure obtained in the supply main or system feeding the boiler. Return traps shall not be considered mechanical feeding devices.

E.

Gauge glass and water level indicator. Each miniature boiler shall be equipped with a water gauge glass for determination of the water level.

The lowest permissible water level shall be at a point one-third of the height of the shell, except where the boiler is equipped with an internal furnace, in which case it shall be not less than one-third of the tube length above the top of the furnace.

For small boilers where there is insufficient space for the usual type of gauge glass, water level indicators of the glass, bull's eye type may be used.

F.

Feeding and feed water piping. Every miniature boiler shall be provided with at least one feed pump or other mechanical feeding device except where the following conditions exist:

1.

Where the boiler is connected to a water main or system having sufficient pressure to feed the boiler at any time while under pressure;

2.

Where the fuel burned is such that all heat input can be discontinued instantaneously by the operation of a valve, cock or switch, thereby permitting the boiler pressure to be quickly lowered to a point where water can be introduced from the connection to the water main;

3.

Where the boiler is operated without extraction of steam (closed system) in which case the boiler is filled, when cold, through the connection or opening provided in accordance with the following rule.

Each miniature boiler shall be fitted with a feed water connection which shall not be less than one-half-inch iron pipe size. The feed piping shall be provided with a check valve near the boiler and a valve or check between the check valve and the boiler.

Feed water may be introduced through the blow-off connection where the boiler is operated without extraction of steam (closed system).

Feed water shall not be introduced through the water column or gauge glass connections while the boiler is under pressure.

G.

Blow-off pipe. Each miniature boiler shall be provided with a blow-off connection, not less than one-half-inch iron pipe size, directly connected with the lowest water space.

Blow-off piping shall not be galvanized and shall be provided with a valve or cock.

H.

Steam gauges. Each miniature boiler shall be equipped with a steam gauge having a dial range not less than 1½ times the maximum allowable working pressure. The gauge shall be connected to the steam space or to the steam connection to the gauge glass by a brass or bronze composition siphon tube or equivalent device that will keep the gauge tube filled with water.

I.

Stop valves. The steam piping from a miniature boiler shall be provided with a stop valve located as close to the boiler shell or drum as is practicable, except in those classes where the boiler and steam receiver are operated as a closed system.

J.

Gas burners. For installations which are gas-fired, the burners used shall conform to the requirements of the American Gas Association, as stated in the appendix of the A.S.M.E. Boiler Construction Code, section V.

K.

Flue connection. Each gas-fired boiler shall be equipped with at least four-inch vent pipe or flue, in no case less than the vent outlet from the boiler extended to and approved location outside the building or connected to a chimney flue. Where the horizontal run is more than ten feet the vent shall be increased to six inches. A draft hood of approved design shall be provided on each boiler.

L.

Stamping of boilers. Each boiler shall be stamped with a serial number of the city, followed by the letters "MFS," such letters and figures to be not less than 5/16 inch in height The stamping shall not be concealed by lagging or paint and shall be exposed at all times.

(Code 1967, § 45-85; Code 1985, § 42-90)