pressure gauge octa . Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical crops and refineries. เพรสเชอร์เกจ is also a part-time school 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 well-known quotes was: “A man’s received to know his limitations.” This story illustrates why you should know your control valve’s limitations.
A consumer just lately called for assist downsizing burners on a thermal oxidizer. Changes within the manufacturing process had resulted in an extreme quantity of warmth from the existing burners. All makes an attempt to decrease temperatures had resulted in unstable flames, flameouts and shutdowns. The higher temperatures didn’t harm the product but the burners were guzzling 110 gallons of propane every hour. Given the high price of propane at that plant, there were, actually, millions of incentives to conserve vitality and reduce costs.
Figure 1. Operation of a cross linked air/gas ratio regulator supplying a nozzle mix burner system. The North American Combustion Practical Pointers book 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 venture to retrofit smaller burners was being written. One of the plant’s engineers known as for a value estimate to alter burner controls. As we mentioned their efforts to scale back gas usage, we realized smaller burners might not be required to unravel the issue.
Oxidizer temperature is mainly determined by the place of a “combustion air” control valve. Figure 1 reveals how opening that valve increases strain in the combustion air piping. Higher strain forces extra air via the burners. An “impulse line” transmits the air strain to a minimal of one facet of a diaphragm in the “gas control valve” actuator. As air strain on the diaphragm increases, the diaphragm strikes to open the valve.
The fuel valve is automatically “slaved” to the combustion air being provided to the burner. ไดอะแฟรม is adjusted to deliver the 10-to-1 air-to-gas ratio required for steady flame.
The plant was unable to hold up flame stability at considerably lower fuel flows because there is a restricted vary over which any given diaphragm spring actuator can provide accurate control of valve place. This usable control vary is identified as the “turndown ratio” of the valve.
In this case, the plant operators now not wanted to fully open the gas valve. They wanted finer resolution of valve place with much decrease combustion air flows. The diaphragm actuator needed to be able to crack open and then management the valve utilizing significantly decrease pressures being delivered by the impulse line. Fortunately, altering 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 project. No burner replacements. No important downtime. Only a couple of inexpensive parts and minor rewiring were required to save heaps of “a fistful of dollars.”

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