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 bobfischer@fischertechnical.com.
One of Dirty Harry’s famous 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 assist downsizing burners on a thermal oxidizer. differential pressure gauge ราคา in the manufacturing course of had resulted in too much warmth from the present 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 had been guzzling a hundred and ten gallons of propane every hour. Given the excessive cost of propane at that plant, there were, actually, hundreds of thousands of incentives to conserve power and reduce costs.
Figure 1. Operation of a cross related air/gas ratio regulator supplying a nozzle combine burner system. The North American Combustion Practical Pointers guide could be found on-line 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 fuel usage, we realized smaller burners may not be required to resolve the problem.
Oxidizer temperature is principally determined by the position of a “combustion air” control valve. Figure 1 reveals how opening that valve increases pressure within the combustion air piping. Higher stress forces extra air by way of the burners. An “impulse line” transmits the air stress to one aspect of a diaphragm in the “gas control valve” actuator. As air stress on the diaphragm will increase, the diaphragm moves to open the valve.
The fuel valve 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 keep up flame stability at considerably decrease fuel flows as a result of there is a restricted range over which any given diaphragm spring actuator can provide correct control of valve place. This usable management vary is called the “turndown ratio” of the valve.
In this case, the plant operators not needed to totally open the gas valve. They needed finer decision of valve place with a lot lower combustion air flows. The diaphragm actuator needed to have the ability to crack open and then management the valve using 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 — utilizing the existing burners.
Dirty Harry would undoubtedly 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 inexpensive elements and minor rewiring have been required to save “a fistful of dollars.”
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