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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 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 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 referred to as for help downsizing burners on a thermal oxidizer. Changes in the manufacturing process had resulted in too much warmth from the prevailing burners. All makes an attempt to lower temperatures had resulted in unstable flames, flameouts and shutdowns. The larger temperatures didn’t harm the product however the burners have been guzzling a hundred and ten gallons of propane every hour. Given the excessive price of propane at that plant, there have been, actually, hundreds of thousands of incentives to preserve power and reduce prices.
Figure 1. Operation of a cross linked air/gas ratio regulator supplying a nozzle combine burner system. The North American Combustion Practical Pointers e-book could be discovered 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 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 discussed their efforts to reduce gasoline utilization, we realized smaller burners won’t be required to unravel the problem.
Oxidizer temperature is principally determined by the place of a “combustion air” control valve. Figure 1 shows how opening that valve increases strain within the combustion air piping. Higher strain forces more air via the burners. An “impulse line” transmits the air stress to at least one facet of a diaphragm within the “gas control valve” actuator. As air strain on the diaphragm increases, the diaphragm strikes to open the valve.
The gas valve is routinely “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 steady flame.
The plant was unable to keep up flame stability at significantly lower fuel flows as a end result of there’s a restricted range over which any given diaphragm spring actuator can provide accurate management of valve position. This usable control range is named the “turndown ratio” of the valve.
In this case, the plant operators now not needed to fully open the gas valve. เกจวัดแรงดันแบบแห้ง needed finer resolution of valve place with much lower combustion air flows. The diaphragm actuator wanted to have the flexibility to crack open after which management the valve utilizing significantly lower pressures being delivered by the impulse line. Fortunately, changing the spring was all that was required to permit recalibration of the gasoline valve actuator — using the prevailing burners.
Dirty Harry would positively approve of this cost-effective change to the valve’s low-flow “limitations.” No capital venture. No burner replacements. No vital downtime. Only a number of cheap elements and minor rewiring have been required to keep away from wasting “a fistful of dollars.”
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