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Low flow appliances represent a growing segment of the oil heating market as manufacturers work to develop more efficient systems. While the future looks good for low flow appliances, the present is rife with headaches for contractors and service personnel. “Particulates in the oil tend to be more of a problem in the low flow applications,” says Jeff Stembridge, Delavan Design Engineer. “Because of the reduced flow rates, particulates can easily plug a nozzle either reducing or prohibiting flow.” The result can be increased sooting, inefficient operation or a total shut down of the heating system. Some companies have resorted to monthly nozzle changes, increased filtration, or both.


Historically, extra filtration has been the only remedy available for low gallonage applications. The Del-O-Flo nozzle reduces plugging with patented technology that forces particulates and other contaminants through and out the nozzle. “The Del-O-Flo contains an extra-fine filter that stops larger particles that cause the problems in low flow situations,” says Delavan’s Stembridge. “The patented Del- O-Flo design keeps these particles in suspension and forces them out without plugging.”


With Del-O-Flo Nozzle, fluid flows through the filter into the slots and is metered prior to exiting. The slots are designed to force fluid into a swirling motion where particles are kept in suspension. The nozzle contains short slot openings that are perpendicular to fluid flow. “These short slots keep the fluid from slowing and maintain turbulence, which keeps particulates from collecting, settling, or clogging the nozzle,” says Stembridge.


In a test by Delavan engineers, both a standard hollow cone nozzle and an identical Del-O-Flo hollow cone nozzle were run continuously for 23 hours in a double adapter using the same oil supply. Clean oil was contaminated with a controlled amount of iron oxide (rust) and sand. Both nozzles had filters prohibiting particles over
40 microns so the contaminants utilized were under 40 microns. At the end of the test, the nozzles were disassembled. The photographs below demonstrate the dramatic difference. Contamination buildup on the standard nozzle was substantial while the Del-O-Flo nozzle remained contaminant-free and clean burning.

Capacity Charts

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