What’s Your Boiler Maintenance Plan?
EP Editorial Staff | August 9, 2016
Boilers are critical components in many manufacturing systems. Poorly maintained boilers are energy wasters. Here are maintenance factors to consider.
Even facility-maintenance professionals can be willing to “let the boiler slide” for months or even years without a proper checkup. In many cases—especially with early generations of atmospheric gas boilers—this happened because the equipment was designed to go a long time without maintenance.
Today, the National Boiler Codes specify that all commercial boilers must be checked by a licensed boiler contractor at least annually. This is a good start, but the truth is that, as the market has pushed the need for higher-efficiency equipment—such as condensing, fully modulating systems (mod-con)—boilers and burners may require two or more maintenance checks each year. Here are some insights to help you.
Before starting the evaluation, carefully record baseline conditions. Keep a detailed record of all conditions and the work you do. The trail of information is too often neglected, lengthening the time it takes to perform system diagnostics.
Many boiler problems stem from mistakes made during installation–so the first order of business in establishing a preventive-maintenance schedule is to assess the overall picture. Look closely and record what you see with regard to the system piping, venting, gas or oil supply, and all other key facets of the mechanical room. Completion of a check-sheet not only documents the basic situation as you see it today, but sets a baseline for later maintenance.
Key evaluation factors include venting, combustion air, fuel-supply piping and filtration, water quality and piping, electrical wiring and diagnostics, and controls.
Venting. Check all venting under Category I venting (non-condensing, negative pressure) for white chalky substance on the outside of the vent. This substance often indicates condensation inside the flue. If signs of condensation are present, verify that the boiler is piped properly and operating at the prescribed temperature.
“One common remedy is to increase boiler operating temperatures,” said Nate Warren, hydronic sales manager at Bradford White Corp., Ambler, PA. “Also, if the vent material shows signs of condensation, it may be necessary to check the flue or the boiler for damage.”
Category III and IV appliances require sealed venting with stainless-steel or specific plastic vent material to withstand the corrosive effects of condensation.
Combustion. For atmospheric systems, check for any blockage of combustion-air openings. “Think how easy it would be for a janitor to unknowingly tape cardboard or stuff insulation into combustion-air entry points to prevent cold air in the boiler room! That’s sure to cause problems in a hurry,” said Joan Mishou, customer service manager for Laars Heating Systems Co., Rochester, NH. “Also, clean and check filters every six months, or at least once a year.”
Check gas pressures while at peak load or on the coldest day of the year if possible to determine if there is a measurable reduction during peak operation. Inadequate gas pressure can cause rough light-off and lock-outs. Also, it’s often misdiagnosed as faulty ignitors, ignition controls, or gas valves.
Fuel-supply piping, filtration. Clean or replace fuel-line filters on oil boilers at least once a year, or every six months if the tanks are older and likely to contain sediment or sludge that’s sure to drift into the line.
Water quality and piping. Any evidence of corrosive activity on piping should be addressed immediately. It could be evidence of air infiltration. All visible piping should be checked for signs of deterioration. If stainless steel or aluminum is used in the heat exchanger, the manufacturer may have water-quality requirements.
Electrical. Check all wiring in the system for overheating. Insulation hardening or melting can incapacitate or otherwise influence diagnostic systems, disabling safety (boiler-off) checks that would turn off the boiler in the event of problems.
Verify that the boiler shuts down on high-limit and at low-water cutoff. Check operation of the aquastat to be sure that the boiler shuts down at the set-point temperature. Also check the flow switch to assure that the boiler shuts off under no-flow conditions. Test the igniter to confirm that the Ohm resistance or micro-amp signal is within acceptable guidelines.
Ignition. If an igniter fails, probable causes include condensation, venting, or lack of proper combustion air.
Mike Haigh, a well-respected 27-yr. hydronics expert in Oklahoma City, adds that when he discusses boiler maintenance, the conversation often drifts toward the “neediest” of units: modern-day modulating-condensing
“It’s often a four-pronged approach in order to keep up with condensing boilers,” said Haigh. “First, boilers must be inspected routinely—every few months isn’t overkill. That doesn’t mean they’ll require maintenance, but it’s good to know when they will before an issue expands. At the top of this list is the boiler’s refractory. Some mod-con designs have very small combustion chambers that really take a beating. The refractory material may need to be replaced more often than expected.”
Igniters are number two on Haigh’s list. Mod-con boilers can operate with wet combustion chambers and, as such, they’re susceptible to moisture damage. Oxidation on the flame rod/igniter can cause nuisance shutdowns. He suggests changing the igniter at least annually.
Fireside cleaning is next. With mod-cons, water vapor mixes with fuel and air impurities to form “mouse turds” or “coffee grounds” inside the combustion chamber. These must be removed, lest they impede condensate drainage.
Haigh reminds of the old hydronics rule of thumb: “Scale the thickness of an eggshell can reduce efficiency by 10%, or more.”
“And that’s not to be ignored with condensing systems,” concluded Haigh. “Condensate can have a pH level as low as two or two-and-a-half—very acidic stuff. It needs to be drained out and neutralized. The systems are amazing in their ability to produce heat efficiently, but they must be maintained.”
Whatever the boiler’s application, the key to preventing maintenance problems starts with a careful and deliberate startup of the equipment, routine monitoring and logging, and six-month scheduled maintenance to promptly address little problems before they become big ones. MT
Technology Links Boiler to Pumps
New technology has entered the process-heat industry. Its roots are tied to commercial-comfort systems, but now have applicability in plant operations.
“Many process-heat systems today that use boilers require flat-out, full-fire operation, but that’s changing as plant managers consider new ways to reduce fuel and electrical use, said Chuck O’Donnell, marketing manager for Rochester, NH-based Laars Heating Systems Co., a subsidiary of Bradford White Corp.
An outgrowth of refinements to a boiler’s intelligent link to variable-speed pumps that control heat distribution
are controls that enhance the “total installed efficiency” of process boilers
used in a wide range of applications, including dehumidification, drying, the curing of paint or coatings, cooking, and fermentation.
“The new technology is especially applicable where two or more boilers are linked for staged operation to meet the need for variable-heat output which, by design, is a smart way to save energy,” added O’Donnell.
This technology permits the boilers and pumps to “talk to each other” in ways that match a boiler’s variable firing rate with flow—optimizing heat output to exactly match the need for process heat. No more heat than is needed, and no less—perfect for precise repeatability of manufacturing operations and energy efficiency.