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Subchapter 2. Boiler and Fired Pressure Vessel Safety Orders
Article 4. Installation

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763. Low-Pressure Boilers.

(a) All low-pressure boilers shall be installed and fitted with the fittings and appliances required by the Code, and any additional appurtenances required in the following subsections.

(b) When a hot water heating boiler is equipped with an electrically operated circulating pump and electrically operated burner controls, the control switches shall be labeled to show which is for the burner circuit and which is for the pump circuit, or the electrically operated burner controls shall be connected in the electric circuit ahead of the automatic pump switch or the burner control switch shall be mechanically interlocked to the disconnect switch for the circulating pumps.

(c) All low-pressure boilers shall be equipped with one or more pressure relieving device adjusted and sealed so as to discharge at a pressure not to exceed the maximum allowable working pressure of the boiler. The combined capacity of these devices shall be such that with the fuel burning equipment installed and operating at maximum capacity the pressure cannot rise more than 5 psi for steam boilers or 10% for water boilers above the maximum allowable working pressure of the boiler. All pressure relieving devices shall be installed as required by the Code and be ASME stamped and rated and shall be installed with the valve spindle vertical and shall have a manual lifting device to permit periodic testing.

The discharge from all drains and pressure relieving devices shall be piped to a safe place of discharge and shall have no shutoff valves in the pipe between the pressure relieving device and point of discharge.

A safe place of discharge as used in this section shall be a location where:

(1) The discharge of steam or hot water will not present a hazard to employees.

(2) The discharge of steam or water will not be detrimental to any electrical or other machinery or equipment.

(3) The discharge pipe cannot be readily plugged or otherwise obstructed.

(d) All automatically controlled low-pressure boilers shall be equipped with:

(1) A low-water control that will close the main burner fuel valve when the water in the boiler reaches the lowest operating level, or for boilers with no fixed steam or water line, when the highest permissible operating temperature is reached.

(2) A low-water safety cutout that will shut off the fuel to the burner when the water in the boiler reaches a predetermined level which shall not be below the lowest permissible level, and manual resetting of the low-water control or of the fuel valve or of the emergency control system shall be required to place the boiler back in operation after it has been shut down due to the operation of the low-water safety cutout.

(3) An adjustable operating control and fuel valve to regulate the flow of fuel to the burner to maintain the pressure or temperature below the following limits:

(A) 15 psi gage pressure for steam boilers.

(B) 250 F water temperature for water boilers.

(4) A high-limit safety control that will shut off fuel to the burner when the pressure in a steam boiler reaches a predetermined maximum not to exceed 15 psi gage or when the temperature in a water boiler reaches a predetermined maximum not to exceed 250 F. The high-limit safety control mechanism shall be in addition to the operating control required in (d)(3) above and manual resetting of the high-limit control or of the fuel valve or of the emergency control system shall be required to place the boiler back in operation after it has been shut down due to the operation of the high-limit safety control.

(5) (A) A full safety pilot control on boilers equipped with standing pilot burners, other than those included in subsection 763 (d)(5)(B), that will shut off the fuel to the main burner and any extinguished pilot burners if a pilot light is extinguished.

Such device shall actuate to close the safety fuel shutoff valve required in Subsection 763 (d)(6) within the time limits specified for flame failure shutoff in Table 1.

(B) A programmed flame safeguard system on burners equipped with spark ignition that will include a flame failure shutoff time not greater than specified in Table 1. Such system shall require the services of the attendant to place the boiler back into operation if a flame failure should occur while in operation or if the flame is not established within the time limit programmed into the system. Such time limits shall not exceed that specified for flame failure shutoff in Table 1.

Maximum
Firing rate
Oil
Gal. per hr.
Maximum
Firing rate
Gas
BTU/hr.
Type of
Ignition
Maximum time until
valve is fully closed,
seconds
3 gallons
or less
Unaproved
Pilot
or
Ignition
90
Over 3 gallons
to 7 gallons
30 (2)
Over 7 gallons
to 20 gallons
10 (2)
Over 20 gallons Proved Pilot 60 (3)
400,000 BTU
and under
Proved or
Unaproved
Pilot
90
400,001 BTU
and over
Proved
Pilot (4)
10

NOTE 1. Flame failure shutoff as used in these Orders means the total elapsed time from the time of flame failure or other abnormal condition occurs until the fuel shutoff valve is closed.

NOTE 2. Where a burner is designed or equipped for a "starting firing rate" of less than the maximum firing rate of the burner, the flame failure shutoff time shown in Table 1 for the lesser firing rate may be used for establishing ignition, provided that firing rate cannot be increased until ignition is proven. The time limit for flame failure shutoff shall be determined by the maximum burner input.

NOTE 3. The 60-second time limit for flame failure shutoff may be used for burners having less than 20 gallons per hour input if equipped with a proved pilot.

NOTE 4. In case of pilot flame failure, the proved pilot shall de-energize the safety fuel shutoff valve electrical circuit and cause that valve to close within 10 seconds.

(6) In addition to the operating fuel shutoff valve(s) required in 763 (d) (1) and (3), an additional safety fuel shutoff valve that will be operated by the controls required by Section 763 (d) (2), (4), and (5). This valve shall be of a type that will close within 2 seconds after being de-energized if the burner input rating exceeds 400,000 BTU/hr.

(7) A means for obtaining adequate combustion chamber purging and for limiting the burner "trial for ignition" time during start up to 15 seconds or that permitted for flame failure shutoff in Table 1, whichever is greater.

(e) All low-pressure boilers shall be equipped with a pressure or altitude gage as required by the code. All water boilers shall be equipped with a thermometer to indicate temperature conditions at or near the hot water outlet. These devices shall be visible to the operator from the operating area.

(f) All low-pressure steam boilers shall be equipped with one or more water gage glass with shutoff valves and drain cocks. These devices shall be located on the boiler, or on a water column, within the permissible water level range for the boiler (unless specifically exempted by the Code).

(g) All hot water heating systems shall be equipped with a suitable expansion tank that will be consistent with the volume, temperature, pressure, and capacity of the system as required by the Code. All such expansion tanks shall have an allowable working pressure at least equal to the maximum allowable working pressure of the boiler with which they are used, and the maximum allowable working pressure shall be stamped on a nameplate visible after installation.

All expansion tanks connected into systems having boilers designed for more than 30 psi working pressure shall be constructed, inspected, and stamped according to the Code, Section VIII, unless it can be proven to the satisfaction of the Division that the design and construction will provide equivalent safety. Expansion tanks connected into systems having boilers designed for 30 psi or less shall be designed, constructed, and stamped according to the Code, Section VIII, or according to good engineering practices with a factor of safety of at least 4.

All expansion tanks shall be fitted with either: (1) a water gage glass or other means for indicating visually the water level in the tank, or (2) a bladder-type expansion tank provided the tank is fitted with an airtight bladder inside the tank and it is provided with a means of determining the presence of air cushion in the tank. The hot water heating system shall be installed, inspected, and equipped with the required safety relief and shut-off devices in accordance with the Uniform Mechanical Code, Chapter 10, February 1997 Edition.

Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.

(h) When low-pressure boilers are equipped with a float-type automatic water feeder, such water feeder shall be fitted with a valved drain on the float chamber. Float chambers of other control devices shall also be provided with valved drains on the float chambers.

(i) All valves, fittings, and controls shall be suitable for the pressures and temperatures expected in service and all such devices used in the fuel system shall be suitable for and compatible with the fuel and fuel pressures used. All electrically operated fuel valves shall be of the normally closed type to open only when energized. Fuel valves of a type that will fail to close due to abnormal fuel pressure shall not be permitted. Automatically operated fuel valves shall not be designed with integral manually operated by-passes unless such by-pass is of the constant pressure type.

(j) The electrical circuit for boiler controls shall not exceed 120 volts and shall be 2-wire with 1-conductor grounded and have the controls in the ungrounded conductor.

(k) After installation and before being placed in operation, the employer shall require all controls and burners to be checked for proper operation by a responsible person familiar with burner controls.

Instruction for the proper method of lighting, relighting, and shutting down the burner, type of fuel or fuels to be used, and the maximum fuel pressure shall be shown on a permanent and legible plate attached to the boiler or boiler casing and an operating manual giving complete boiler operating instructions, shall be furnished by the installer for each installation. The employer shall require operating personnel to become thoroughly familiar with these operating instructions before they are permitted to operate the boiler. These instructions shall include an instruction to the operator that the boiler shall not be placed back in service after having been shut down by the operation of the safety fuel shutoff valve required in 763 (d) (6) until the cause of such shutdown has been determined and corrected and the combustion chamber is properly purged.

HISTORY

1. Amendment filed 11-2-66; effective thirtieth day thereafter (Register 66, No. 38). Approved by State Building Standards Commission.

2. Amendment of subsection (c) filed 5-31-74; effective thirtieth day thereafter (Register 74, No. 22).

3. Amendment filed 8-12-76; effective thirtieth day thereafter (Register 76, No. 33).

4. Amendment of subsection (g) and new Note filed 12-2-97; operative 1-1-98 (Register 97, No. 49).

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