Robert L. Fischer, P.E., is a physicist and electrical engineer who spent 25 years in chemical vegetation and refineries. Fischer can additionally be a part-time faculty professor. He is the principal reliability marketing consultant for Fischer Technical Services. He may be reached at
One of Dirty Harry’s well-known quotes was: “A man’s received to know his limitations.” This story illustrates why you have to know your control valve’s limitations.
A client just lately known as for assist downsizing burners on a thermal oxidizer. Changes within the manufacturing course of had resulted in an excessive amount of heat from the existing burners. All attempts to decrease temperatures had resulted in unstable flames, flameouts and shutdowns. The higher temperatures didn’t harm the product however the burners have been guzzling a hundred and ten gallons of propane each hour. Given the excessive value of propane at that plant, there were, literally, hundreds of thousands of incentives to preserve vitality and cut back prices.
เกจวัดแรงดันแก๊สหุงต้ม . Operation of a cross connected air/gas ratio regulator supplying a nozzle combine burner system. The North American Combustion Practical Pointers book can be discovered online at 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 referred to as for a value estimate to alter burner controls. As we discussed their efforts to scale back gas utilization, we realized smaller burners won’t be required to solve the issue.
Oxidizer temperature is basically determined by the position of a “combustion air” control valve. Figure 1 reveals how opening that valve increases strain in the combustion air piping. Higher stress forces more air via the burners. An “impulse line” transmits the air stress to a minimal of one side of a diaphragm in the “gas control valve” actuator. As air pressure on the diaphragm increases, the diaphragm moves to open the valve.
The gasoline valve is routinely “slaved” to the combustion air being equipped to the burner. Diaphragm spring tension 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 considerably lower fuel flows as a outcome of there is a limited vary over which any given diaphragm spring actuator can present accurate 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 totally open the fuel valve. They wanted finer decision of valve place with a lot decrease combustion air flows. The diaphragm actuator needed to have the power to crack open and then control the valve utilizing significantly decrease pressures being delivered by the impulse line. Fortunately, changing the spring was all that was required to permit recalibration of the fuel valve actuator — using the prevailing burners.
Dirty Harry would positively approve of this cost-effective change to the valve’s low-flow “limitations.” No capital venture. No burner replacements. No vital downtime. Only a few inexpensive elements and minor rewiring were required to keep away from wasting “a fistful of dollars.”