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Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer can additionally be a part-time college professor. He is the principal reliability advisor for Fischer Technical Services. He could additionally be reached at
One of Dirty Harry’s well-known quotes was: “A man’s got to know his limitations.” This story illustrates why you want to know your control valve’s limitations.
A client lately known as for help downsizing burners on a thermal oxidizer. Changes within the manufacturing process had resulted in an extreme quantity of heat from the prevailing burners. All attempts to decrease temperatures had ended in unstable flames, flameouts and shutdowns. The greater temperatures didn’t hurt the product but the burners had been guzzling 110 gallons of propane each hour. Given เกจวัดแรงดันถังแก๊ส of propane at that plant, there have been, actually, tens of millions of incentives to conserve energy and reduce prices.
Figure 1. Operation of a cross connected air/gas ratio regulator supplying a nozzle mix burner system. The North American Combustion Practical Pointers guide could be found on-line at Fives North American Combustion, Inc. 4455 East 71st Street, Cleveland, OH 44015. Image courtesy of Fives North American Combustion, Inc.
A capital venture to retrofit smaller burners was being written. One of the plant’s engineers known as for a value estimate to vary burner controls. As we mentioned their efforts to reduce back gasoline usage, we realized smaller burners won’t be required to solve the problem.
Oxidizer temperature is basically decided by the position of a “combustion air” control valve. Figure 1 reveals how opening that valve increases pressure in the combustion air piping. Higher strain forces extra air by way of the burners. pressure gauge ออก หลัง ” transmits the air stress to one aspect of a diaphragm within the “gas management valve” actuator. As air pressure on the diaphragm increases, the diaphragm moves to open the valve.
The gas valve is mechanically “slaved” to the combustion air being equipped to the burner. Diaphragm spring pressure is adjusted to ship the 10-to-1 air-to-gas ratio required for secure flame.
The plant was unable to maintain flame stability at significantly decrease gas flows because there is a limited range over which any given diaphragm spring actuator can present accurate control of valve position. This usable management vary is named the “turndown ratio” of the valve.
In this case, the plant operators no longer wanted to completely open the gasoline valve. They needed finer decision of valve position with a lot decrease combustion air flows. The diaphragm actuator wanted to be able to crack open after which control the valve utilizing significantly lower pressures being delivered by the impulse line. Fortunately, altering the spring was all that was required to allow recalibration of the gas valve actuator — using the present burners.
Dirty Harry would definitely approve of this cost-effective change to the valve’s low-flow “limitations.” No capital challenge. No burner replacements. No significant downtime. Only a couple of inexpensive parts and minor rewiring had been required to save tons of “a fistful of dollars.”

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