Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer can also be a part-time faculty professor. He is the principal reliability marketing consultant for Fischer Technical Services. He could additionally be reached at bobfischer@fischertechnical.com.
One of Dirty Harry’s well-known quotes was: “A man’s obtained to know his limitations.” This story illustrates why you should know your control valve’s limitations.
A consumer recently referred to as for assist downsizing burners on a thermal oxidizer. Changes within the manufacturing process had resulted in too much warmth from the present burners. All makes an attempt to decrease temperatures had ended in unstable flames, flameouts and shutdowns. The greater temperatures didn’t hurt the product but the burners were guzzling one hundred ten gallons of propane every hour. Given the excessive cost of propane at that plant, there were, actually, hundreds of thousands of incentives to preserve power and cut back 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 can be discovered online at https://online.flippingbook.com/view/852569. Fives North American Combustion, Inc. 4455 East 71st Street, Cleveland, OH 44015. เกจวัดแรงดันแก๊สหุงต้ม of Fives North American Combustion, Inc.
A capital project to retrofit smaller burners was being written. One of the plant’s engineers called for a value estimate to vary burner controls. As we discussed their efforts to scale back gas usage, we realized smaller burners might not be required to solve the issue.
Oxidizer temperature is mainly decided by the place of a “combustion air” control valve. Figure 1 reveals how opening that valve will increase pressure within the combustion air piping. Higher pressure forces extra air via the burners. An “impulse line” transmits the air strain to a minimum of one side of a diaphragm in the “gas management valve” actuator. As air pressure 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 rigidity 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 considerably lower fuel flows as a result of there’s a limited range over which any given diaphragm spring actuator can present correct control of valve position. This usable management vary is called the “turndown ratio” of the valve.
In this case, the plant operators not wanted to completely open the fuel valve. They needed finer decision of valve place with a lot lower combustion air flows. The diaphragm actuator wanted to have the ability to crack open and then management the valve utilizing considerably decrease 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 definitely 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 cheap parts and minor rewiring were required to save “a fistful of dollars.”
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