Chief Boiler Inspector, State of Hawaii
Summary: The following article is a part of National Board
Classic Series and it was published in the National Board BULLETIN. (3 printed pages)
No one wants to experience the effects of a boiler or pressure vessel-related
incident. With this in mind, one goal is apparent to every inspector: find a
way to prevent the destruction of property, and more importantly, the loss of
Unfortunately a variety of injuries, and even deaths, continue to encumber the
boiler and pressure vessel industry, not only in Hawaii but around the world.
For instance, eight years ago a steam kettle exploded in a Hawaii school
cafeteria kitchen, injuring one cook. The incident occurred at a time when the
cafeteria was not filled with school children.
The investigation revealed that the cook had turned the kettle on and was
standing on a step next to the unit, when 10 minutes later, its lid blew off
and struck her face. The entire kettle was blown 30 to 40 inches above its
footing before falling to the floor. Steam and debris blew about in the
immediate vicinity following the accident. No other employees, nor any
children, were injured.
It was discovered that the jacketed steam kettle had been losing water for some
time and that the water had to be replenished on a regular basis. The school
administration had ordered a replacement, but prior to its arrival, the
original kettle failed. Surprisingly, the kettle had been in service for only
Following the incident, the remaining four kettles were inspected for
corrosion. Serious corrosion was found and the kettles were immediately taken
out of service.
After some investigation, it was found that the failed vessel had suffered
excessive corrosion in the skirt area and the lower head, therefore causing the
failure at a very low pressure. In addition, the vessel failed at the
circumference of the head skirt.
Upon this conclusion, the investigation team suggested that the failure may
have occurred because of the presence of a silicone-like substance between the
decorative vessel skirt and the lower head. The substance may have caused
cleansing agents and moisture to collect between the head and skirt. This
possibly led to localized corrosion of the carbon steel head, resulting in the
The National Board issued an alert after the incident and suggested the
following inspection guidelines to help prevent further incidents.
Jacketed Steam Kettle Inspection Guidelines:
Obviously, no pressure-retaining item is immune from the possibilities and
dangers of a failure. However, the guidelines mentioned above are designed to
greatly reduce the chance of another jacketed steam kettle failure.
If the lower head and all pressure parts are fully exposed, external inspection
should reveal any apparent problems.
If the lower head is concealed by a skirt and is fabricated of carbon steel,
inspect for corrosion in the following manner:
Check the bottom of the unit. If there is a splash shield covering the lower
end, have the shield removed.
Examine the lower head. If there is evidence of staining or moisture, there is
an excellent chance of corrosion in the skirt area.
If there appears to be a seal between the skirt and head, remove a portion and
determine if corrosion or debris exists. (This area is very tight and will be
difficult to observe. A strong light and mirror are necessary.)
If water is added to the jacket manually, check with maintenance to find out
how much water is being added and determine the path the liquid follows inside
Editor's note: Some ASME Boiler and Pressure Vessel Code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition and addenda of the ASME Boiler and Pressure Vessel Code for current requirements.