Page 231 - Shale Shakers Drilling Fluid Systems

ELECTRIC MOTORS 213

• Flame-proof enclosures SPECIFIC MOTOR APPLICATIONS
• Pressurized enclosures
• Increased safety protection, "e" With the exception of specialized motors for
centrifuge feed and high-speed shale shakers,
Common IEC symbols are: practically all electric motors encountered in drilling
fluid operations are integral-horsepower, across-
• Flame-proof—"d" or (Ex)d the-line start, horizontal squirrel-cage motors.
• Pressurized—"p" or (Ex)p Across-the-line, start-up motors are the simplest
• Increased Safety—"e" or (Ex)e and lowest cost. The motor is connected directly
to the input power through a starter switch. Full
Table 12-9 provides a detailed description of these current and torque are realized at startup. This
terms and symbols. is acceptable with solids control and processing

TABLE 12-9. IEC Nomenclature Applied to Motors for Hazardous Areas

Protection,
IEC or European
Standard Basic Principle Applications
Flame-proof Parts that can ignite an Switch gear, control and
enclosure, explosive atmosphere are indicating equipment, control
"d" enclosed to withstand boards, motors, transfor-
pressure developed during an mers, light fitting, and other
explosion and prevent trans- spark-producing parts
mission of the explosion to
explosive atmospheres around
the enclosure
Increased Additional measures against Terminal and connection
safety, internal or external arcs or boxes, control boxes and
"e" sparks, or excessive temperatures housing, squirrel cage
not produced in normal service motors, and light fittings
Pressurized Entry of surrounding atmosphere As above, usually for large
apparatus, is prevented by maintaining a equipment and contained
"p" protective gas at pressure higher rooms
than the surrounding atmosphere
Intrinsic Internal electric circuits are Measurement and
safety, incapable of causing explosions control equipment
"(" in the surrounding atmosphere
Oil Electric apparatus or its parts are Transformers
immersion, immersed in oil to prevent ignition (rarely used)
"o" of a surrounding or covering
atmosphere
Powder Enclosure is filled with a finely Transformers,
filling, granulated material so that an capacitors, heater
"q" internal arc will not ignite the strip connection boxes,
surrounding atmosphere; also, and electronic assemblies
ignition will not be caused by
flame or excessive temperature
of enclosure surfaces
Moulding, Parts that can ignite an explo- Only small capacity
"m" sion are enclosed (encapsulated) switch gear, control gear,
in a resin to prevent ignition of an indicating equipment, and
explosive atmosphere by internal sensors
sparking or heating