Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer can also be a part-time college professor. He is the principal reliability consultant for Fischer Technical Services. He could additionally 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 should know your management valve’s limitations.
ไดอะแฟรม ซีล referred to as for assist downsizing burners on a thermal oxidizer. เพรสเชอร์เกจ within the manufacturing course of had resulted in too much warmth from the existing burners. All attempts to decrease temperatures had ended in unstable flames, flameouts and shutdowns. The higher temperatures didn’t hurt the product however the burners were guzzling one hundred ten gallons of propane each hour. Given the excessive price of propane at that plant, there have been, actually, millions of incentives to preserve vitality 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 e-book may 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 challenge to retrofit smaller burners was being written. One of the plant’s engineers called for a value estimate to change burner controls. As we discussed their efforts to reduce gas usage, we realized smaller burners might not be required to resolve the problem.
Oxidizer temperature is principally decided by the position of a “combustion air” control valve. Figure 1 shows how opening that valve will increase pressure in the combustion air piping. Higher strain forces extra air via the burners. An “impulse line” transmits the air pressure to at least one side of a diaphragm in the “gas control valve” actuator. As air pressure on the diaphragm will increase, the diaphragm strikes to open the valve.
The fuel valve is automatically “slaved” to the combustion air being supplied 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 maintain up flame stability at considerably lower gas flows because there’s a restricted range over which any given diaphragm spring actuator can present accurate control of valve position. เพรสเชอร์เกจ is identified as the “turndown ratio” of the valve.
In this case, the plant operators not wanted to totally open the fuel valve. They wanted finer resolution of valve place with a lot lower combustion air flows. The diaphragm actuator wanted to have the ability to crack open and then management the valve utilizing considerably decrease 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 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 cheap parts and minor rewiring were required to save heaps of “a fistful of dollars.”
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