Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical crops and refineries. Fischer can be a part-time faculty professor. He is the principal reliability marketing consultant for Fischer Technical Services. He may be reached at bobfischer@fischertechnical.com.
One of Dirty Harry’s well-known quotes was: “A man’s received to know his limitations.” This story illustrates why you should know your management valve’s limitations.
A client lately referred to as for assist downsizing burners on a thermal oxidizer. Changes within the manufacturing course of had resulted in an extreme amount of heat from the present 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 were guzzling a hundred and ten gallons of propane every hour. Given the high price of propane at that plant, there have been, literally, hundreds of thousands of incentives to conserve energy and reduce costs.
Figure 1. Operation of a cross linked air/gas ratio regulator supplying a nozzle combine burner system. The North American Combustion Practical Pointers guide could be found on-line 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 referred to as for a worth estimate to alter burner controls. As we mentioned their efforts to reduce fuel utilization, we realized smaller burners might not be required to resolve the issue.
Oxidizer temperature is basically determined by the place of a “combustion air” control valve. Figure 1 reveals how opening that valve will increase strain within the combustion air piping. Higher strain forces more air by way of the burners. An “impulse line” transmits the air pressure to one aspect of a diaphragm within the “gas control valve” actuator. As เกวัดแรงดัน on the diaphragm increases, the diaphragm moves to open the valve.
The gasoline valve is mechanically “slaved” to the combustion air being provided to the burner. Diaphragm spring tension is adjusted to ship the 10-to-1 air-to-gas ratio required for stable flame.
The plant was unable to keep up flame stability at significantly lower gasoline flows because there’s a limited vary over which any given diaphragm spring actuator can provide correct control of valve place. This usable control vary is identified as the “turndown ratio” of the valve.
In this case, the plant operators not needed to fully open the gas valve. They wanted finer decision of valve position with much lower combustion air flows. The diaphragm actuator needed to have the power to crack open after which control the valve utilizing significantly decrease pressures being delivered by the impulse line. Fortunately, altering the spring was all that was required to allow recalibration of the gasoline 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 venture. No burner replacements. No vital downtime. Only a quantity of inexpensive components and minor rewiring were required to keep away from wasting “a fistful of dollars.”
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