Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer is also a part-time faculty professor. He is the principal reliability advisor for Fischer Technical Services. He could also be reached at bobfischer@fischertechnical.com.
One of Dirty Harry’s famous quotes was: “A man’s obtained to know his limitations.” This story illustrates why you want to know your management valve’s limitations.
A client recently known as for help downsizing burners on a thermal oxidizer. Changes in the manufacturing course of had resulted in too much heat from the prevailing burners. All makes an attempt to lower temperatures had ended in unstable flames, flameouts and shutdowns. The larger temperatures didn’t hurt the product but the burners had been guzzling one hundred ten gallons of propane every hour. Given the high price of propane at that plant, there were, literally, millions of incentives to conserve power and cut back costs.
Figure 1. Operation of a cross related air/gas ratio regulator supplying a nozzle mix burner system. The North American Combustion Practical Pointers book could be found online at https://online.flippingbook.com/view/852569. Fives North American Combustion, Inc. 4455 East 71st Street, Cleveland, OH 44015. Image courtesy of Fives North American Combustion, Inc.
A capital challenge to retrofit smaller burners was being written. One of the plant’s engineers called for a worth estimate to alter burner controls. As we discussed their efforts to reduce gasoline usage, we realized smaller burners might not be required to unravel the problem.
Oxidizer temperature is basically determined by the position of a “combustion air” control valve. Figure 1 reveals how opening that valve will increase strain in the combustion air piping. Higher strain forces extra air via the burners. An “impulse line” transmits the air stress to 1 facet of a diaphragm within the “gas management valve” actuator. As air pressure on the diaphragm increases, the diaphragm moves to open the valve.
The gasoline valve is routinely “slaved” to the combustion air being supplied to the burner. Diaphragm spring pressure is adjusted to ship the 10-to-1 air-to-gas ratio required for steady flame.
The plant was unable to hold up flame stability at significantly lower gas flows as a outcome of there is a restricted range over which any given diaphragm spring actuator can present correct control of valve position. This usable control range is recognized as the “turndown ratio” of the valve.
In this case, the plant operators not wanted to fully open the fuel valve. เกจ์วัดความดัน wanted finer resolution of valve position with much decrease combustion air flows. The diaphragm actuator needed to have the flexibility to crack open after which management the valve using significantly lower pressures being delivered by the impulse line. Fortunately, altering the spring was all that was required to permit recalibration of the gas valve actuator — utilizing the existing 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 vital downtime. Only a couple of cheap elements and minor rewiring have been required to save lots of “a fistful of dollars.”
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