Chemical Engineering November 2013 - 36

Feature Report
Piping Design for
Potentially Lethal Chemicals
Source: BLS
Integrity and reliability
are critical for piping and
equipment that handle
chemicals with extreme
health hazards
Bill Huitt
W.M. Huitt Co.
W
orking in close proximity to
the high pressures and temperatures
commonly found
in the chemical process industries
(CPI) is cause enough for
concern over a person's wellbeing; but
working in close proximity to chemicals
that are considered toxic, hazardous
or reactive escalates that concern
to a higher degree (Figures 1 and 2).
The dangers of such chemicals underline
the paramount importance of integrity
and reliability in the design of
equipment and piping systems.
From a regulatory standpoint, the
requirements to which each chemical
processing facility in the U.S. must adhere
when manufacturing, handling or
storing chemicals are set forth within
the regulations of the U.S. Occupational
Safety and Health Administration's
(OSHA; Washington, D.C.; www.
osha.gov) " Process safety management
of highly hazardous chemicals " regulation
(part of 29 CFR 1910.119). OSHA
also provides guidance for the required
" Process Hazard Analysis " procedure.
From a piping engineering standpoint,
requirements for the design,
fabrication, inspection, examination,
testing and installation of piping used
to handle potentially lethal fluids are
stipulated in the American Society of
Mechanical Engineers (ASME; New
York; www.asme.org) B31.3 Process
Piping Code, Piping for Category M
Fires and
Exposure
to harmful
substances or
environments
7%
Falls, slips,
trips
15%
explosions 3%
Total = 4,383
Other
transportation
incidents 17%
Falls to lower level
12%
Struck by object
or equipment
12%
Contact with
objects and
equipment 16%
Roadway
incidents 24%
Transportation
incidents 41%
Homicides
11%
Violence and other injuries
by persons or animals 17%
Figure 1. Of the 4,383 work-related deaths overall for 2012, 7% were attributed to
exposure to harmful substances in the workplace
Fluid Service (Chapter VIII). This article
provides a deeper understanding
of existing regulations and code standards,
and guides engineers in determining
when a fluid should be considered
potentially lethal. And for those
cases involving lethal fluids, the article
provides information on what attributes
need to be considered in the design
of piping systems to handle them.
People working in CPI facilities
have every right to expect that they
will return home safely after completing
their shift. It is the job and responsibility
of every designer and engineer
of CPI facilities to ensure that this expectation
is achieved.
Piping integrity
When it comes to piping systems, integrity
is a relative term. In pursuit
of practicality, engineers should not
expect the same level of integrity to
be designed into a piping system for
cooling-tower water as that for a piping
system containing 30% sulfuric
36 ChemiCal engineering www.Che.Com november 2013
acid. Nor should they expect the same
level of integrity to be designed into a
system containing 30% sulfuric acid as
that for a piping system containing the
potentially deadly cyanogen bromide.
The degree of integrity assigned to the
design elements and components of a
piping system is therefore related not
only to the pressure and temperature
requirements, but also to the degree of
potential hazard (that is, volatility or
toxicity) that can be attributed to the
fluid itself.
Perceptions of chemicals and integrity
can be influenced by catastrophic
incidents that draw the attention of
the public and lawmakers (Figure 3).
Examples of such disasters include
the following: the 1984 Bhopal, India
incident that resulted in deaths in
the several thousands and injuries
in excess of 500,000; the October
1989 Phillips Petroleum Co., Pasadena,
Tex., incident that resulted in
23 deaths and 132 injuries; the May
1991 IMC, Sterlington, La., incident
http://www.osha.gov http://www.asme.org http://www.Che.Com
Chemical Engineering November 2013

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