Fischer: Know your valve’s limitations 

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 college professor. He is the principal reliability advisor for Fischer Technical Services. He may be reached at
One of Dirty Harry’s well-known quotes was: “A man’s received to know his limitations.” This story illustrates why you have to know your management valve’s limitations.
A client recently known as for help downsizing burners on a thermal oxidizer. Changes within the manufacturing process had resulted in an excessive quantity of heat from the existing burners. All makes an attempt to lower temperatures had led to unstable flames, flameouts and shutdowns. The higher temperatures didn’t hurt the product however the burners have been guzzling a hundred and ten gallons of propane each hour. Given the excessive value of propane at that plant, there have been, actually, hundreds of thousands of incentives to conserve vitality and reduce costs.
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 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. compound gauge ราคา of the plant’s engineers referred to as for a price estimate to alter burner controls. As we mentioned their efforts to reduce back gasoline utilization, we realized smaller burners may not be required to unravel the problem.
Oxidizer temperature is mainly decided by the position of a “combustion air” management valve. Figure 1 reveals how opening that valve increases pressure in the combustion air piping. Higher strain forces extra air through the burners. An “impulse line” transmits the air stress to 1 aspect of a diaphragm within the “gas management valve” actuator. As air strain on the diaphragm increases, the diaphragm moves to open the valve.
เกจ์อาร์กอนsumo is mechanically “slaved” to the combustion air being supplied to the burner. Diaphragm spring rigidity is adjusted to ship the 10-to-1 air-to-gas ratio required for secure flame.
The plant was unable to take care of flame stability at considerably lower gas flows as a outcome of there is a limited range over which any given diaphragm spring actuator can provide accurate 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 gas valve. They needed finer decision of valve position with much lower combustion air flows. The diaphragm actuator needed to have the ability to crack open after which control the valve utilizing significantly lower pressures being delivered by the impulse line. Fortunately, altering the spring was all that was required to allow recalibration of the gas valve actuator — utilizing the present burners.
Dirty Harry would undoubtedly approve of this cost-effective change to the valve’s low-flow “limitations.” No capital project. No burner replacements. No important downtime. Only a couple of cheap components and minor rewiring have been required to keep away from wasting “a fistful of dollars.”

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