Product Overview | Impulse Multiplier
FOR DIFFERENTIAL PRESSURES A 7266A Impulse Multiplier converts a low differential pressure signal to a high static impulse pressure, which is then applied to a gas or oil ratio regulator. The 7266A can be set to multiply a differential signal between 3 and 4.5 times, e.g., an orifice plate (high fire) differential of 6"w.c. can be multiplied into a 27"w.c. impulse pressure to a 7216 or 7218 Air/Gas Regulator or a 7052 Air/Oil Ratiotrol. Used in this way the 7266A enables a pressure-balancing regulator to be used as a flow balancing device, assuming the fuel remains at a constant Btu value and temperature. A common use is with an orifice plate differential pressure on the inlet (cold air) side of a recuperator. As the recuperator temperature rises, so does the combustion air temperature, resulting in reduced air flow (scfh). With a conventional cross- connected regulator system, the air/fuel ratio would go increasingly rich. A 7266A eliminates this problem by responding to actual (cold) air flow across an orifice plate: As combustion air temperature increases, air flow and orifice differential decreases. The 7266A responds by proportionally reducing impulse pressure to the ratio regulator, thereby maintaining air/fuel ratio. The 7266A impulse multiplier can also be used to multiply a low static air signal. Straight cross-connected pressure balanc- ing ratio regulators cannot produce adequate fuel pressures on some burners with low combustion air pressures. The 7266A can multiply the static air signal by 3 to 4.5 times.
INSTALLATION/OPERATION The 7266A Impulse Multiplier is a pressure-balanced regulator that uses an adjustable bleed (about 1 cfm) to obtain the desired multiplied outlet (impulse) pressure: Increased bleed means higher outlet pressure (so inadvertent restriction of the bleed results in lower outlet pressures and leaner air/fuel ratios [a fail- safe situation]).
The 7266A is installed in a ¾ " air line with a supply pressure 4 osi above desired high fire impulse pressure.
Per Figure 1 (page 2), an orifice plate pressure differential is applied to the 7266A's lower diaphragm. If used for multiplying a low static air signal, the top side of the lower diaphragm is left open to atmosphere. Supply air to the 7266A can come from either a blower or a compressed air system. An 8645A-01 Filter/Separator is recommended in the supply line. If compressed air is the source, use a regulator (such as North American's R690-1407, see page 3) to assure constant inlet pressure to the 7266A. One 7266A can serve any number of ratio regulators in the same control zone. SPECIFICATIONS Body Size: ¾ " × ¾ " fpt Maximum inlet pressure:4 psi emergency 2 psi operating
Maximum outlet pressure: 48"w.c. Operating temperature: 180°F max Impulse connections and vent: ¼ " fpt Approximate weight: 26 pounds Dimensions: See Figure 2 Materials Body: cast iron
Spring case/cover: aluminum Diaphragms: DuPont Fairprene ® Diaphragm plate: steel Valve seat: brass Valve facing: Buna Internals: steel, cadmium plated steel, brass
Bulletin 7266A Page 2
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