Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical plants and refineries. Fischer can additionally be a part-time school professor. ร้านซ่อมเครื่องวัดความดัน is the principal reliability consultant for Fischer Technical Services. He may be reached at bobfischer@fischertechnical.com.
One of Dirty Harry’s famous quotes was: “A man’s obtained to know his limitations.” This story illustrates why you have to know your management valve’s limitations.
A client just lately called for help downsizing burners on a thermal oxidizer. Changes within the manufacturing process had resulted in too much warmth from the prevailing burners. All makes an attempt to lower temperatures had led to unstable flames, flameouts and shutdowns. The larger temperatures didn’t harm the product but the burners were guzzling a hundred and ten gallons of propane each hour. Given the high value of propane at that plant, there were, actually, hundreds of thousands of incentives to conserve vitality and scale 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 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 called for a price estimate to vary burner controls. As we discussed their efforts to reduce gasoline utilization, we realized smaller burners may not be required to unravel the problem.
Oxidizer temperature is principally decided by the place of a “combustion air” management valve. Figure 1 exhibits how opening that valve increases pressure within the combustion air piping. Higher stress forces more air via the burners. An “impulse line” transmits the air strain to one facet of a diaphragm in the “gas management valve” actuator. As air strain on the diaphragm will increase, the diaphragm strikes to open the valve.
The fuel valve is mechanically “slaved” to the combustion air being supplied to the burner. Diaphragm spring pressure is adjusted to deliver the 10-to-1 air-to-gas ratio required for secure flame.
The plant was unable to take care of flame stability at significantly lower gasoline flows as a result of there’s a limited range over which any given diaphragm spring actuator can provide accurate management of valve place. This usable management range is named the “turndown ratio” of the valve.
In this case, the plant operators no longer wanted to completely open the gas valve. They wanted finer resolution of valve position with much decrease combustion air flows. The diaphragm actuator needed to have the power to crack open and then control the valve utilizing considerably lower pressures being delivered by the impulse line. Fortunately, altering the spring was all that was required to allow recalibration of the fuel valve actuator — using the present burners.
Dirty Harry would positively approve of this cost-effective change to the valve’s low-flow “limitations.” No capital challenge. No burner replacements. No vital downtime. Only a few inexpensive components and minor rewiring have been required to save “a fistful of dollars.”
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