Maintaining boilers for safety

June 1, 2000
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Since the beginning of this year, there have been several deadly accidents related to boilers, including explosions at a Ford Motor Co. plant in Michigan and at Kansas City Power and Light Co. in Missouri.

These accidents are not uncommon. In fact, since 1990, there have been more than 21,000 boiler and pressure vessel accidents in the United States.

In light of these accidents, it has never been more important to point out the necessity of frequent safety inspections, and of implementing a regular routine of preventive maintenance for boilers in any industrial setting, large or small.

Causes of accidents

According to the National Board of Boiler and Pressure Vessel Inspectors, the most common causes of accidents relating to boilers include:

  • Failure of the fuel cutoff system when the water level inside the unit becomes too low for proper operation;

  • Operator error, poor maintenance, and/or improper maintenance;

  • Failure of any primary safety control or failure of the safety relief valve, which should relieve the excess pressure of excessively high-temperature water or steam from inside the vessel; and

  • The addition of cold water to an extremely overheated boiler.

For most manufacturers who use boilers, it is company policy to have annual and biannual equipment inspections by certified boiler technicians. But during the rest of the year, keeping a watchful eye on the boiler can be the best preventive maintenance.

Boiler checks

The National Board of Boiler and Pressure Vessel Inspectors, which certifies all qualified repair organizations (including Aircond) recommends that technicians check the following on a regular/monthly basis:

  •  Exterior shell and insulation — These are the first places to look for indications of overheating.

  •  Leaks — Check for water on the floor and water or steam escaping from any part of a pressurized system, including the boiler, valves, or piping.

  •  Flue gas leaks — Look for black dust or soot around sheet metal joints. Check any part of the boiler enclosure and breaching, especially the connection to the stack.

  •  Controls — Look for open panels and covers, and signs of rewiring on the floor or bottom of control panels. Check for jumper wires and locked shutoffs.

  •  Electrical — Ensure that covers are installed on over-limit switches, temperature sensors, and controls.

  •  The burner — Analyze the combustion and make sure the mixture is not running too rich or emitting unsafe levels of carbon monoxide.

  •  Chemicals — Monitor the boiler’s chemical mixtures to make sure there is no build-up of scale on the tubes.

  •  Safety valves — Ensure that a safety valve is installed with full-sized discharge piping, properly supported and directed to a point of safe discharge. Safety valve set pressure must be equal to or less than boiler maximum allowable working pressure. Safety valve relieving capacity must be equal to or greater than boiler output.

  •  Fuel sources — Check for the ability to shut off the fuel source to the boiler.

  •  Gauges — Make sure the temperature and pressure gauges are operational and located for proper monitoring.

  •  Operating certificate — Note the last date of inspection and expiration date.


Certification

State and federal governments now require that all companies who install, maintain, or service boilers have a certificate of authority for the service provided, and that the certificate be renewed annually.

The certification requirements include five years’ experience in boiler service or maintenance, a certification of training from a technical school, a license to operate boilers, and a license that is issued by the Secretary of State’s office.

State laws also require that a company using a contractor ensure that the firm holds all required licenses and certification.

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