Chemical Equipment Update
this, the burner ignites and is generally quickly given the signal to move to the highest load level. In extreme low-load phases, it is very often switched off again while it is still starting up and then – often too quickly afterwards – preventilated and ignited again. The stress caused by the constant temperature changes during heating up and ventilation causes differences in the rate of expansion between the furnace and the boiler casing, which can lead to material fatigue over the course of time. In addition to increasing the system’s susceptibility to damage, this operating system also has a negative effect on economic efficiency, since every preventilation process causes a considerable loss of heat.
ATI TUBING
®
SOLUTIONS
SUPERIOR CORROSION PERFORMANCE
· Greater application longevity · Lower replacement costs · Lower operating costs through less down time
Some of the world’s most important endeavors require the most highly corrosion-resistant, high-temperature tubing solutions.
The companies of Allegheny Techhnologies (ATI) offer the most complete range of corrosion-resistant tubing and tubing materials in the specialty metals industry.
Fig. 2. The consequences of faulty hardness monitoring.
For this reason, burner switching cycles of ≤4 per hour should be the aim. To achieve this, the following steps are recommended:
❒ The installation of low-load controls which delay the immediate adjusting up after the burner start.
❒ The use of performance regulators which enable the burner to be left in the low-load position for an unlimited period of time.
❒ The use of burners with a high regulating range. ❒ The modification of the burner capacity to actual requirements (ie, burner modification or the provision of a burner with a smaller output range).
As is already known, the performance of the steam boiler is
regulated via the steam pressure measured in the boiler. If the level falls below the adjustable steam pressure PBurner.on the burner is switched on – if PBurner.off is exceeded, the burner is switched off. If the spread between PBurner.on and PBurner. off is set too low, the consequences will be as follows: frequent switching on and off caused by overshooting of the pressure and thus to the temperature change stresses described above, with their negative consequences. Of necessity, strict regulation parameters in the performance regulator in order to keep the setpoint value in a tight regulation range. The result, in addition to excessive wear on the control elements in the burner, is premature material fatigue of the heated walls. Experience has shown that with a set spread of 10 to
15 per cent between PBurner.on and PBurner.off (depending on the burner regulation and burner operating pressure) in relation
Our titanium, zirconium and patented OmegaBond® seamless tubing products are ideal for the harshest chemical processing and nuclear energy applications.
Our specialty stainless, titanium and nickel alloys are integral in the manufacture of corrosion-resistant tubing for the oil, gas, nuclear and alternative energy industries.
Wherever you find the toughest corrosion challenges, you’ll find ATI.
Contact
tubing@ATImetals.com for more information.
www.ATImetals.com
© 2010 ATI. All rights reserved.
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