Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical plants and refineries. Fischer can be a part-time college professor. He is the principal reliability marketing consultant for Fischer Technical Services. He could also be reached at bobfischer@fischertechnical.com.
One of Dirty Harry’s famous quotes was: “A man’s got to know his limitations.” This story illustrates why you need to know your management valve’s limitations.
A client recently called for assist downsizing burners on a thermal oxidizer. Changes within the manufacturing course of had resulted in an excessive quantity of heat from the present burners. All makes an attempt to decrease temperatures had ended in unstable flames, flameouts and shutdowns. The greater temperatures didn’t harm the product but the burners have been guzzling a hundred and ten gallons of propane each hour. Given the high price of propane at that plant, there were, literally, hundreds of thousands of incentives to preserve power and scale back costs.
Figure 1. Operation of a cross related air/gas ratio regulator supplying a nozzle mix 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 project to retrofit smaller burners was being written. One of the plant’s engineers known as for a worth estimate to change burner controls. As we discussed their efforts to reduce gasoline utilization, we realized smaller burners may not be required to solve the problem.
Oxidizer temperature is mainly decided by the position of a “combustion air” control valve. Figure 1 exhibits how opening that valve will increase stress within the combustion air piping. Higher pressure forces more air by way of the burners. An “impulse line” transmits the air strain to one aspect of a diaphragm in the “gas management valve” actuator. As air stress on the diaphragm will increase, the diaphragm moves to open the valve.
The gas valve is routinely “slaved” to the combustion air being provided to the burner. Diaphragm spring pressure is adjusted to deliver the 10-to-1 air-to-gas ratio required for steady flame.
The plant was unable to take care of flame stability at significantly lower gasoline flows as a result of there is a limited range over which any given diaphragm spring actuator can provide accurate control of valve place. This usable management range is named the “turndown ratio” of the valve.
In pressure gauge หลักการ ทํา งาน , the plant operators not needed to totally open the fuel valve. They wanted finer decision of valve position with a lot decrease combustion air flows. The diaphragm actuator wanted to have the ability to crack open and then management the valve using considerably 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 prevailing 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 components and minor rewiring have been required to save lots of “a fistful of dollars.”
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