Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer is also a part-time college 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 have to know your management valve’s limitations.
A shopper just lately called for help downsizing burners on a thermal oxidizer. Changes in the manufacturing process had resulted in an extreme quantity of warmth from the prevailing burners. All makes an attempt to decrease temperatures had resulted in unstable flames, flameouts and shutdowns. The larger temperatures didn’t harm the product but the burners had been guzzling a hundred and ten gallons of propane each hour. Given the excessive price of propane at that plant, there were, literally, hundreds of thousands of incentives to preserve vitality and cut back costs.
Figure 1. Operation of a cross connected 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 called for a value estimate to alter burner controls. As we discussed their efforts to reduce fuel usage, we realized smaller burners may not be required to solve the issue.
Oxidizer temperature is principally determined by the position of a “combustion air” management valve. Figure 1 reveals how opening that valve increases stress within the combustion air piping. Higher stress forces more air through the burners. An “impulse line” transmits the air stress to 1 side of a diaphragm within the “gas management valve” actuator. As air pressure on the diaphragm will increase, the diaphragm strikes to open the valve.
The gas valve is mechanically “slaved” to the combustion air being equipped 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 maintain up flame stability at significantly decrease fuel flows as a end result of there’s a limited range 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 เกจวัดแรงดันแก๊ส , the plant operators not wanted to fully open the gas valve. They needed finer resolution of valve place with a lot lower combustion air flows. The diaphragm actuator needed to have the flexibility to crack open after which control the valve using 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 — utilizing the present burners.
Dirty Harry would undoubtedly approve of this cost-effective change to the valve’s low-flow “limitations.” No capital challenge. No burner replacements. No vital downtime. Only a couple of inexpensive elements and minor rewiring were required to save “a fistful of dollars.”
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