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CSA 4.9-2014 pdf free download
CSA 4.9-2014 pdf free download.Gas-fired low pressure steam and hot water boilers.
A bleed restrictor for a diaphragm type automatic valve on a boiler having a normal input rating of
400,000 Btu/hr (117 228 W) or less shall be integral and nonadjustable. A bleed restrictor may be
adjustable and supplied as part of the valve but does not have to be integral when provided on a boiler
having a normal input rating over 400,000 Btu/hr (117 228 W).
When there is a continuous pilot:
a) When required, a bleed line from a diaphragm type automatic valve and, when furnished, a vent line from the regulator shall vent into the combustion chamber. A common bleed line and vent line shall not be used.
b) When required, a bleed line or vent line shall terminate in a suitable burner tip constructed of metal having a melting point of not less than 1450F (788C). The tip shall be secured in a fixed position relative to the pilot burner and located so the escaping gas shall be readily ignited by the pilot and the heat liberated thereby shall not adversely affect the normal operation of the automatic gas ignition system.
When there is no continuous pilot:
a) A vent line, when furnished, from the regulator shall be vented according to the manufacturer’s instructions but not into the combustion chamber, except on a boiler where all combustion air is supplied by mechanical means and which is equipped with a combination control incorporating an integral vent limiter and two automatic valves, one of which is upstream of the regulator diaphragm.
b) When furnished, a bleed line from a diaphragm type automatic valve shall be vented in such a manner as to provide for burning of the bleed gas during normal operation. In the event of diaphragm rupture, the bleed shall not permit the escape of more than 1.0 ft3/hr (7.87 cm3/s) of 0.6 specific gravity (relative density) gas at 7.0 in wc (1.74 kPa) pressure for natural, manufactured or mixed gases or IP gas-air mixtures, and 0.5 ft3/hr (3.93 cm3/s) of 1.53 specific gravity (relative density) gas at 11.0 in wc (2.74 kPa) pressure for liquefied petroleum gases.
When a vent line is provided for a gas appliance pressure regulator, a No. 40 mesh brass, aluminum, or stainless steel wire screen, sufficient in size to provide free area equal to the area of the escapement orifice, shall be installed In and made a part of the connecting fitting for installation at the regulator vent tapping. The fitting, when tightened against the screen, shall provide no opening larger than the mesh of the screen specified. This provision is only applicable to gas appliance pressure regulators having escapement orifices larger than 0.0165 in (0.419 mm) in diameter.CSA 4.9-2014 pdf free download.
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