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COMMERCIAL SAFETY PRODUCTS |
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Potential for Feed Water Pipes in Electrical Power Generation Facilities to Rupture Causing Hazardous Release of Stream and Hot Water.
- INFORMATION DATE : 19961031
- RECORD TYPE : Hazard Information Bulletin
- SUBJECT : Potential for Feed Water Pipes in Electrical Power Generation Facilities to Rupture Causing Hazardous Release of Stream and Hot Water.
October 31, 1996
MEMORANDUM FOR: REGIONAL ADMINISTRATORS
FROM: STEPHEN J. MALLINGER
Acting Director
Directorate of Technical Support
SUBJECT: Hazard Information Bulletin(1): Potential for
Feed Water Pipes in Electrical Power Generation
Facilities to Rupture Causing Hazardous Release of
Steam and Hot Water
________
FOOTNOTE(1) The Directorate of Technical Support issues Hazard
Information Bulletins (HIBs) in accordance with OSHA Instruction CPL
2.65 to provide relevant information regarding unrecognized or
misunderstood health hazards, inadequacies of materials, devices,
techniques, and safety engineering controls. HIBs are initiated based
on information provided by the field staff, studies, reports, and
concerns expressed by safety and health professionals, employers, and
the public. Bulletins are developed based on a thorough evaluation of
available facts in coordination with appropriate parties.
The Chicago Regional Office has brought to our attention the potential
for feed water pipes in electrical power generation facilities to
rupture causing hazardous release of steam and hot water. During an
investigation of a multiple fatality accident at an electrical power
generation facility in an industrial plant, the Appleton Area Office
uncovered at least three other feed water pipe failure incidents in
other power plants. In two of the three incidents, six additional
fatalities had occurred. In all cases, the feed water pipe failures
were attributed to wall thinning as a result of single-phase
erosion/corrosion, leading to rupture of the pipes under high working
pressures.
The rupture of feed water pipes due to wall thinning creates the
potential for serious burns, massive property damage, and power
outages in electrical power generation plants. These feed water pipe
failures could not be linked to any specific aspect of system designs,
materials, or operating histories to support a conclusion that
single-phase erosion/corrosion was distinctive to these particular
power plants. This suggests that these may not be isolated incidents
but a problem that may be widespread in the industry.
Several factors affect the rate of erosion/corrosion in piping. These
factors include material composition of carbon steel piping,
temperature, low water pH, low dissolved oxygen content, pipe
geometry, and fluid velocity. The flow path through elbows, bends,
tees, orifices, welds, valves, and backing rings creates turbulence in
flow which, with fluid velocity, has the potential to react with the
protective oxide layer of carbon steel piping, contributing to the
erosion/corrosion process.
Feed water pipes are addressed in the standard boiler inspection.
Generally only a visual inspection with the pipe insulation in place
is done or required. Since this will not reveal pipe thinning,
employers may not have actual knowledge of the pipe wall thinning that
could be occurring.
To minimize the potential for personal injury or loss of life,
property damage, and power interruptions resulting from feed water
pipe failure, it is recommended that employers of electrical power
generation facilities establish a flow-assisted corrosion (FAC)
program:
* to identify the most susceptible piping components/areas and
establish a sampling protocol consistent with engineering
principles and practices;
* use appropriate nondestructive testing (usually ultrasound) to
determine the extent of pipe thinning (if any); and,
* where thinning is identified, establish a preventative maintenance
program and replace piping in accordance with ASME
recommendations.
For additional information on FAC, the following documents are
suggested:
(1) ANSI B31.1-1995, American National Standards for Power
Piping.
(2) Recommendations for an Effective Flow-Accelerated Corrosion
Program, Electrical Power Research Institute, NSAC/202L.
(3) Yukawa, S, Guidelines for Pressure Vessel Safety Assessment,
NIST Special Publication 780.
Please distribute this bulletin to all Area Offices, State Plan
States, Consultation Project Offices, and appropriate labor and
industry groups.
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