Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer can be a part-time college professor. He is the principal reliability consultant for Fischer Technical Services. He could also be reached at bobfischer@fischertechnical.com.
One of Dirty Harry’s famous quotes was: “A man’s received to know his limitations.” This story illustrates why you need to know your management valve’s limitations.
A client just lately known as for assist downsizing burners on a thermal oxidizer. ตัววัดแรงดันน้ำ within the manufacturing course of had resulted in too much warmth from the existing burners. All attempts to lower temperatures had led to unstable flames, flameouts and shutdowns. The higher temperatures didn’t hurt the product but the burners have been guzzling one hundred ten gallons of propane every hour. Given the high value of propane at that plant, there were, literally, hundreds of thousands of incentives to conserve energy and scale back prices.
Figure 1. Operation of a cross connected air/gas ratio regulator supplying a nozzle combine burner system. The North American Combustion Practical Pointers book can 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 known as for a price estimate to change burner controls. As we mentioned their efforts to reduce gasoline utilization, we realized smaller burners won’t be required to unravel the problem.
Oxidizer temperature is mainly decided by the position of a “combustion air” management valve. Figure 1 shows how opening that valve will increase stress in the combustion air piping. Higher stress forces extra air by way of the burners. An “impulse line” transmits the air pressure to at least one aspect of a diaphragm in the “gas control valve” actuator. As air stress on the diaphragm increases, the diaphragm moves to open the valve.
The gas valve is automatically “slaved” to the combustion air being equipped to the burner. Diaphragm spring pressure is adjusted to deliver the 10-to-1 air-to-gas ratio required for stable flame.
The plant was unable to hold up flame stability at considerably lower gasoline flows as a end result of there is a restricted vary 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 no longer wanted to completely open the gasoline valve. They needed finer resolution of valve place with a lot lower combustion air flows. The diaphragm actuator wanted to find a way to crack open and then control the valve utilizing significantly decrease pressures being delivered by the impulse line. Fortunately, changing the spring was all that was required to permit recalibration of the fuel valve actuator — utilizing 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 important downtime. Only a quantity of inexpensive parts and minor rewiring have been required to save “a fistful of dollars.”
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