Just like the engine in your car, boilers have need of a certain fuel-to-air ratio for proper
combustion. Too little air results in incomplete combustion, but too much creates wastefully heated air
that gets exhausted through the flue. Since changing factors such as ambient temperature, pressure,
and humidity can cause variations in air quality, it is prudent to add an excess amount of air to account
for these variations. To add the proper amount of air to mix with the fuel, controls are used to introduce
air to the system at the burner. Of the boilers currently in use in the United States, many older models
utilize a simple control called a mechanical jackshaft for their modulating burner control. These are also
known as single-point controls due to their use of only one mechanical linkage assembly to control the
flow of both air and fuel for the burner.
The whole point of utilizing these controls is to ðÌðtuneðÌð the boiler in order to achieve complete
combustion. With that in mind, anything that prevents mechanical controls from operating to their full
range limits the amount of air that can enter the burner, thereby jeopardizing the combustion and
efficiency of the boiler. One of the most common mistakes made that impairs the controls is painting
the linkage or failing to keep it clean; this leads to what is known as ðÌðsloppy linkage.ðÌð Paint or grime
covering the linkage will prevent the controls from allowing fine adjustments, hindering an operatorðÌðs
ability to regulate the air being added. During the inefficient operation that inevitably results, expensive
fuel can be wasted, and the rated steam output of the boiler is harder to deliver.
There are also significant long-term consequences to sloppy linkage; for example, depending on
how filthy or covered the linkage is, the valves can eventually stick or bind, which is going to require
otherwise unnecessary maintenance to repair. If the valves are out of position and air is improperly
mixed with fuel, excess soot may build up in the boiler and flue, which may necessitate a premature
shutdown of the system for cleaning or repair. WareðÌðs own Gary Seltz notes that ðÌðone of the most
common issues we see is bent linkage that people have accidentally kicked.ðÌð Care should be taken
around the jackshaft, as not all equipment in a boiler room is as robust as the boiler itself. It is estimated
that damaged linkage can be replaced in about four hours, so depending on when that changeover must
be performed, it could mean more downtime and less steam generation for your company.
When a boiler is not being operated properly, you may be liable for any repairs due to
negligence. By taking some simple steps to ensure that equipment is properly maintained, you can avoid
costly and time-consuming repairs. It is recommended that the controls be checked at least twice per
year (though quarterly would be ideal) to see if seasonal adjustment or tuning is needed. Make no
mistake, linkage can be marked upon, but fully covering the assembly with paint or allowing it to get
filthy only serves to create long-term problems that are easily avoidable. Maintaining efficiency with
your boiler prolongs its life, avoids down-time for repairs, and reduces operation and maintenance
costs. So remember: keep your linkage cleanðÌðitðÌðs easy and will save time and money!
**WARE Grime Newsletter. Pentad Associates does not take any credit for what has been stated above.