United States
Environmental Protection
Agency
Office of Enforcement
and Compliance
Assurance (2201A)
EPA 300-N-99-011
Enforcement Alert
Volume 2, Number 6
Office of Regulatory Enforcement
August 1999
Facilities Urged to Review Systems for Risk of
Check or Butterfly Valves Safety Hazards
On June 22, 1997, a serious chemi-
cal accident occurred at the Shell
Chemical Company in Deer Park,
Texas, 15 miles east of Houston. The
accident resulted in injuries to several
workers and extensive damage to the
Shell Plant, as well as minor damage
to nearby residential property. Damage
About
Enforcement Alert
"Enforcement Alert" \L
published periodically by the
Office of Regulatory
Enforcement to inform and
educate the public and regulated
community of important
environmental enforcement
issues, recent trends and
significant enforcement actions.
This information should helpthe
regulated community anticipate
and prevent violations of federal
environmental law that could
otherwise lead to enforcement
action.
See Page 3 for useful EPA
Websites and additional
resources.
Eric V. Schaeffer
Director, Office of
Regulatory Enforcement
Editor: Virginia Bueno
(202) 564-8684
bueno.virginia@epamail.epa.gov
Please email all address and
name changes
to the facility was estimated at $101
million and major transportation routes
were closed for several hours.
As a result of the Shell accident,
the U.S. Environmental Protection
Agency (EPA) and the Occupational
Safety and Health Administration
(OSHA) released ajoint accident inves-
tigation report, the "Shell Report" (June
19, 1998) to determine the root cause
and contributing factors of the accident,
and to make recommendations to pre-
vent similar accidents.
In their report, EPA and OSHA de-
termined that the immediate cause of
the accident was the internal structural
failure and drive shaft blow-out of a
3 6-inch diameter pneumatically-assisted
Clow Model GMZ check (non-return)
valve. Check and butterfly valves are
used in refineries, petrochemical plants,
chemical plants, and power generation
facilities to stop and control the flow
(e.g., prevent reversal of the flow's di-
rection) of process materials through
pipelines or apertures. According to the
Shell Report, the check valve's failure
resulted in a large flammable gas leak,
forming a vapor cloud that ignited.
This issue of Enforcement Alert
highlights key operational and design
factors that may result in failures to
check and butterfly valves as reported
in a Chemical Safety Alert issued by
EPA's Office of Chemical Emergency
Preparedness and Prevention Office in
September 1997, and as described in
the Shell Report. This issue also includes
recommendations contained in the Shell
~TTie Clean Air Act's
I 'General Duty
Clause'Requires
Owners and Operators
of Stationary Sources
to Identify, Prevent,
Minimize A ccidental
Releases of Hazardous
Substances.
Report to prevent similar accidents
from occurring.
In addition, this issue focuses on the
obligation that owners and operators of
stationary sources have to identify, pre-
vent and minimize accidental releases
of hazardous substances under the
Clean Air Act's "General Duty Clause."
Design Factors
Contributing to a Shaft
Blow-Out
The Chemical Safety Alert provides
an expansive and technical discussion
of factors that may contribute to a shaft
blow-out from check or butterfly
valves. These design factors include:
• The valve has a shaft or stem
piece that penetrates the pressure
boundary and ends inside the pressur-
Continued on page 2
his publication is found on the Internet at http://www.epa.gov/oeca/ore/enfalert
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Enforcement Alert
Continued from page 1
ized portion of the valve. This feature
results in an unbalanced axial thrust on
the shaft that tends to force it (if un-
constrained) out of the valve.
• The valve contains potential
internal failure points, such as shaft
dowel-pins, keys, or bolts such that
shaft-disk separation can occur inside
the valve.
• The dimensions and manufac-
turing tolerances of critical internal parts
(e.g., keys, keyways, pins, and pin
holes) as designed or as fabricated cause
these parts to carry abnormally high
loads.
• The valve stem or shaft is not
blow-out resistant. Nonblow-out
resistant design features may include
two-piece valve stems that penetrate the
pressure boundary (resulting in a
differential pressure and unbalanced
axial thrust), single diameter valve shafts
(i.e., a shaft not having an internal
diameter larger than the diameter of its
packing gland) or shafts without thrust
retaining devices, such as split-ring
annular thrust retainers.
Operational Factors
Leading to a Valve Failure
According to the Chemical Safety
Alert, operational factors that may lead
to potential check or butterfly valve fail-
ure include:
• The valve is subject to high
cyclic loads.
• The valve is subject to low or
unsteady flow conditions such that disk
flutter or chatter occur, resulting in in-
creased wear of keys, dowel pins or
other critical internal components.
• Valves in high-pressure service
lines may be more likely to undergo
shaft blow-out.
How to Obtain the Shell Report
and EPA's Chemical Safety Alert
The Shell Report can be found on the Internet at http://
www.epa.gov/ceppo/acc-his.html or a copy may be obtained
by calling 1-800-490-9198. EPA's Chemical Safety Alert is also
on the Internet at http://www.epa.gov/ceppo/pubs/shell.pdf.
• Valves used in hydrogen-rich
or hydrogen sulfide-containing environ-
ments may be more susceptible to
blow-out due to hydrogen embrittlement
of critical internal components, particu-
larly if these are made from hardened
steel.
Shell Report
Recommendations
The Shell Report includes recom-
mendations that are designed to prevent
a recurrence of an event similar to the
Shell accident.
One primary recommendation made
in the Shell Report is that companies
should review their process systems
to determine if installed valves may be
subject to a shaft blow-out hazard, and
modify or replace those valves as nec-
essary.
The report also recommends that
facilities should consult valve manu-
facturers or other appropriate design
authorities to ensure that any modifi-
cations made are safe.
Clean Air Act's 'General
Duty Clause'
As part of the 1990 Clean Air Act
Continued on page 3
Simplified cross-sectional view of check valve (flow's
direction is into page)
Valve Disc (flapper
shown in open position)
Valve Body
August 1999
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Enforcement Alert
Continued from page 2
Amendments (CAA), Congress di-
rected EPA to establish a program de-
signed to prevent accidental releases of
certain hazardous chemicals. Congress
also enacted Section 112(r)(l) of the
CAA (the "General Duty Clause"),
which places a statutory obligation on
owners and operators of stationary
sources. Specifically, the General Duty
Clause requires owners and operators
of stationary sources to anticipate, pre-
vent and minimize the effects of acci-
dental releases whenever extremely haz-
ardous substances are present (i.e.,
produced, processed, handled or
stored) at the facility.
Owners and operators can take
steps to reduce the likelihood of an ac-
cidental release and potential liability
under the General Duty Clause by:
• Identifying and managing haz-
ards associated with these check and
butterfly valves.
• Designing and maintaining a
safe facility to prevent accidental re-
leases by, among other things, imple-
menting a rigorous mechanical integ-
rity program for valves in extreme ser-
vice or with a known history of fail-
ure.
• Minimizing the consequences
of accidental releases from valves
which do occur.
The General Duty Clause aids EPA's
goal of increasing chemical safety and
preventing chemical accidents. Failure
to comply with the General Duty Clause
is a violation of the Clean Air Act.
EPA's Audit Policy and
Small Business Policy
EPA has adopted two policies de-
signed to encourage greater compliance
with environmental laws and regula-
Side View of a Common Check
Valve
Counterweight
Air Cylinder
Direction of flow
tions, including the General Duty Clause.
The "Incentives for Self-Policing, Dis-
covery, Disclosure, Correction and Pre-
vention of Violations" (Audit Policy) and
the "Policy on Compliance Incentives
for Small Businesses" (Small Business
Policy), provide incentives to conduct
environmental audits by substantially
reducing penalties for entities that vol-
untarily discover, disclose, and expe-
ditiously correct violations of environ-
mental law. More information about
the Audit Policy and Small Business
Policy can be obtained at http://
www.epa.gov/oeca/auditpol.html and
http://www.epa.gov/oeca/
smbusi.html, respectively.
Contact Leslie Oif, RCRA Enforce-
ment Division, Office of Regulatory En-
forcement, at (202) 564-2291 or Email
oif.leslie@epamail.epa.gov.
Useful Websites and Resources
RCRA Enforcement Division: http://www.epa.gov/oeca/ore/red/
Chemical Emergency Preparedness and Prevention Office:
http://www.epa.gov/swercepp/
Occupational Safety and Health Administration: http://www/osha.gov
EPA's Emergency Planning and Community Right-to-Know Hotline: (800) 424-
8346 or (703) 412-9810. (TDD (800)553-7672
EPA's Year 2000 website: http://www.epa.gov/year2000
EPA's Y2K Enforcement Policy: http://www.epa.gov/oeca/eptdd/ocy2k.html
or contact Gary Jonesi, Office of Regulatory Enforcement
(202) 564-4002 or E-mail: jonesi.gary@epa.gov
Y2K Home Page: http://www.y2k.com/
EPA's Small Business Gateway: http://www.epa.gov/smallbusiness
August 1999
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United States
Environmental Protection Agency
Office of Regulatory Enforcement
2201A
Washington, D.C. 20460
Official Business
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