CAUSE AND CONTRIBUTING FACTORS OF HEATING BOILER FAILURE
It is this time of the year again when the thousands of heating boilers in North America will be utilized to provide heat for our homes, businesses, institutions, schools and many other facilities. Perhaps you have heard of the old stories of the beginning of the industrial revolution of boilers exploding and killings thousands of people every year around the world. These days are long gone thanks to the mandatory boiler inspection and maintenance programs instituted in the early 1900s. What the engineers found then was that boilers that were inspected regularly and were maintained and operated properly did not explode; only the ones that were not. These observations led to a “revolution” in the thinking of the role of insurance: it became a loss prevention industry.
The leading cause of heating boiler failures is the non-functioning low water fuel cutout
Based on the thousands of boiler maintenance, repairs and failure investigations we conducted over the years, we can tell you with certainty that the leading cause of heating boiler failure is low water. Most of the time, the low water fuel cutout safety switch has failed and this led to the overheating and failure of the boilers. There are always early sign of boiler failure, if you know where to look and how to interpret them. For example, small leaks could appear in the boiler vessel or the piping. These water leaks may not look serious, but they should never be ignored as they will most certainly lead into greater problems. Most of the time, some low cost items, such as a pressure relief valve, are defective or are old and need replacement. If they are not replaced, significant losses could occur.
If an insurer has refused to insurer your boiler, then this should be a good clue that it is time to replace it or repair it. Insurers, like The Hartford Steam Boiler Inspection and Insurance Company, Travelers, and others have a very good handle on boiler safety. When they stay away from a piece of equipment, please take the hint.
Here is a photo of a valve that was installed incorrectly. In fact, the inlet and outlet were stamped on the valve, so there is no excuse for such error. Mistakes are more frequent than you think. It is that our inspections help caught them prior to any damage occurring.
Why Boiler Failures can be Dangerous
Water boils at atmospheric pressure at 100 C (212 F). When placed under pressure, the water can be heated to extremes without flashing to steam. The typical expansion rate for 1 cubic foot of water is 1,700 cubic feet of steam. This amazing expansion rate is the reason that the boiler explosions are so powerful. Imagine this amount of steam to exit from a small pipe break under tremendous pressures: The routinely inspected water heater holds 119 gallons (16 cubic feet) of water. It is really a small bomb due to this massive energy release and in the past thousands of people died from such explosions. See below the results from a failed relief valve.
Boiler Inspection and Maintenance
The following provide important recommendations for heating boiler inspection, maintenance, and operation prior to the heating season. Low pressure boilers are inspected annually while in operation and internally every 3 years, if construction permits:
1. Perform an external exam for leaks. Many times we find that the leakage is caused by failure to remove hardness from inside the boiler; then the hardness expands during boiler heating, pushing apart the boiler sections and causing leakage.
2. Perform an evaluation of all safety device function.
3. Test all high temperature and high pressure switches.
4. Insulate water lines that are exposed to freezing temperatures to avoid pipe freeze-ups. Quite a few of these freeze ups occurred this past winter and another round of equally severe winter is forecast. We have our fingers crossed.
5. The safety relief valves or devices are crucial devices that must be tested very frequently, ideally every month. A malfunctioning safety valve will cause the boiler fail. If the relief valve does not properly function, then the temperature control will fail to properly control temperature. The water heater will heat unchecked until catastrophic failure occurs.
6. All other valves, gauges, pressure and temperature control instruments must be inspected for proper functioning.
7. Due to constituents found in the water, we get sediment built up pretty much everywhere in the boiler, including the sight (or gage) glass used to observe the water level. The water level sight glass should be cleaned from the accumulated water impurities and scale.
8. Disassemble the low water fuel cutoff and make-up water feeding devices. All parts should be thoroughly flushed, cleaned and reconditioned as required, then tested and evaluated before the boiler is put into regular service. While in service the devices should be tested once a week for steam boilers and once a month for hot water boilers.
9. All leaking pipes, valves, connections, etc. must be repaired or replaced to prevent water loss and property damage.
10. The boiler burner should be cleaned and adjusted to provide maximum burning efficiency.
11. All the internal surfaces of the boiler should be cleaned of all the water impurities that accumulate over time. These impurities inside the boiler are the cause of corrosion, cracking, deterioration and even explosion of the boiler.
12. A chemical water treatment should be used to minimize built-up of scale and other deposits and to slow down or minimize corrosion.
13. Ensure that all other equipment associated with the boiling system work properly.
14. Maintain a record book of boiler operation, maintenance or repairs. Some boilers have failed because technicians did not know what another tech had done to the boiler.
Regarding pressure vessels, most mechanical codes require that are inspected once every three years. This inspection requires a test of:
· Safety relief devices
· Temperature and pressure controls
· External exam to check for leaks
· Testing to verify thickness of the vessel body
We commonly see leaking and corroded boilers during many of our inspections, especially for older boilers. Unfortunately, even with a regular inspection program, people just ignore proper maintenance and operation. Just like our cars, some people are good at maintaining and some people are simply bad. We also observe leaking steam from the spindle, and many steam and water connections are also found leaking. The mud drums are another area where we observe corrosion and leakage. See figure below.
We have seen situations where there is very little monitoring of boilers in schools and municipalities on a regular basis, other than the inspector doing his annual inspection. This has led to leaks and other problems with the boiler efficiency and operation. As we wrote in the beginning, the most frequently found deficiencies are associated with the low water fuel cut offs, safety and relief valves are stuck, and high pressure and temperature switches are not often installed. It appears that the boiler owners believe that the service technician who may maintain their boiler will also test for the operation of the safety devices. We have found that this is not true, as the technician will only perform the service of the combustion and burner fuel systems, change the fuel filters, clean the fuel pumps and nozzles, check the igniter, vacuum the gas passes of the boiler, perform an efficiency test of the unit, etc.
METROPOLITAN ENGINEERING, CONSULTING & FORENSICS (MECF)
Providing Competent, Expert and Objective Investigative Engineering and Consulting Services
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