|Description / Abstract
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|This document applies to the classification of locations for
both temporarily and permanently installed electrical equipment. It
is intended to be applied where there may be a risk of ignition due
to the presence of flammable gases, flammable liquid-produced
vapors, or combustible liquid-produced vapors, mixed with air,
under normal atmospheric conditions (identified throughout this
document as "gases and vapors"). Normal atmospheric conditions are
defined as conditions that vary above and below reference levels of
101.3 kPa (14.7 psia) and 20 °C (68 °F) provided that the
variations have a negligible effect on the explosion properties of
the flammable materials.
The following items are beyond the scope of this document.
a) Piping systems used for odorized natural gas used as fuel for
cooking, heating, air conditioning, laundry, and similar
b) Catastrophes such as well blowouts or process vessel
ruptures. Such extreme conditions require emergency measures at the
time of occurrence.
c) The suitability of locations for the placement of
non-electrical incendiary equipment.
d) Classification of locations containing combustible dust,
ignitable fibers, or flyings.
Recommendations for determining the degree and extent of
classified locations for specific examples of situations commonly
encountered in petroleum facilities are given in Section 8 through
Section 14. While it is important for area classifications at
refineries, production and drilling facilities, and pipeline
facilities to agree to some extent, there are differences in
production, drilling, transportation, and refining facilities. Some
differences include the process conditions, types, and quantities
of products handled, the physical size of typical facilities, and
varying housing and sheltering practices.
Section 8 includes applications that are common to several of
the facility types described in Section 9 through Section 14.
Section 9 is applicable to locations in which flammable
petroleum gases and vapors and volatile flammable liquids are
processed, stored, loaded, unloaded, or otherwise handled in
Section 10 is applicable to locations surrounding oil and gas
drilling and workover rigs and production facilities on land and on
marine fixed (bottom-founded, non-floating) platforms where
flammable petroleum gas and volatile liquids are produced,
processed (e.g. compressed), stored, transferred (e.g. pumped), or
otherwise handled prior to entering the transportation
Section 11 is applicable to locations on Mobile Offshore
Drilling Units (MODUs).
Section 12 is applicable to locations surrounding oil and gas
drilling and workover rigs and production facilities on floating
production units (FPUs) such as, but not limited to, tension leg
platforms (TLPs), floating production systems (FPSs), floating
production systems with off-loading (FPSOs), single anchor leg
mooring buoys (SALMs), caisson structures, spars, and other
floating structures where flammable petroleum gas and volatile
liquids are produced, processed (e.g. compressed), stored,
transferred (e.g. pumped) or otherwise handled prior to entering
the transportation facilities.
Section 13 is reserved for future use.
Section 14 is applicable to onshore and offshore facilities
handling the delivery of flammable or combustible petroleum liquids
or flammable gases. Pipeline facilities may include pump and
compressor stations, storage facilities, manifold areas, valve
sites, and pipeline right-of-way areas.
The purpose of this recommended practice is to provide
guidelines for classifying locations Class I, Division 1 and Class
I, Division 2 at petroleum facilities for the selection and
installation of electrical equipment. Basic definitions given in
the 2011 Edition of NFPA 70, National Electrical Code
(NEC), have been followed in developing this recommended practice.
This publication is only a guide and requires the application of
sound engineering judgment.
NOTE Recommendations for determining the degree and extent of
locations classified Class I, Zone 0, Zone 1, and Zone 2 are
addressed in API 505, Recommended Practice for Classification
of Locations for Electrical Installations at Petroleum Facilities
Classified as Class I, Zone 0, Zone 1, and Zone 2.
Electrical installations in areas where flammable liquids,
flammable gases or vapors, or combustible liquids are produced,
processed, stored or otherwise handled can be suitably designed if
the locations of potential sources of release and accumulation are
clearly defined. Once a location has been classified, requirements
for electrical equipment and associated wiring should be determined
from applicable publications. Applicable publications may include
NFPA 70 and API 14F. Reference Section 2 for publications for other
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