Fischer: Know your valve’s limitations 

Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer can be a part-time faculty professor. He is the principal reliability consultant for Fischer Technical Services. He could also be reached at
One of Dirty Harry’s well-known quotes was: “A man’s obtained to know his limitations.” This story illustrates why you have to know your management valve’s limitations.
A shopper just lately known as for help downsizing burners on a thermal oxidizer. Changes in the manufacturing course of had resulted in an excessive amount of heat from the existing burners. All attempts to lower temperatures had led to unstable flames, flameouts and shutdowns. The higher temperatures didn’t harm the product however the burners had been guzzling a hundred and ten gallons of propane every hour. Given the excessive value of propane at that plant, there have been, literally, tens of millions of incentives to conserve vitality and reduce costs.
pressure gauge digital ราคา . Operation of a cross related air/gas ratio regulator supplying a nozzle mix burner system. The North American Combustion Practical Pointers e-book may be found on-line at 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 referred to as for a value estimate to vary burner controls. As we mentioned their efforts to reduce gasoline usage, we realized smaller burners won’t be required to unravel 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 strain within the combustion air piping. Higher pressure forces more air via the burners. An “impulse line” transmits the air strain to 1 aspect of a diaphragm in the “gas management valve” actuator. As air strain on the diaphragm increases, the diaphragm moves to open the valve.
The fuel valve is mechanically “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 stable flame.
The plant was unable to hold up flame stability at significantly decrease gas flows because there is a limited vary over which any given diaphragm spring actuator can present accurate control of valve position. This usable control vary is called the “turndown ratio” of the valve.
In this case, the plant operators now not needed to completely open the gas valve. They needed finer resolution of valve position with a lot lower combustion air flows. The diaphragm actuator needed to have the power to crack open after which management the valve using significantly decrease pressures being delivered by the impulse line. Fortunately, altering the spring was all that was required to allow recalibration of the gas valve actuator — using 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 parts and minor rewiring were required to save heaps of “a fistful of dollars.”

Scroll to Top