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Pressure Transmitter Design and Protection from Moisture and
Particulate Ingress
Technical
Comparisons
Moisture and particle entry can have a major impact on the function and longevity of pressure transmitters.
Environments can range from "condensing" moisture to w ash-dow n w ith w ater under pressure, to total,
permanent submersion. WIKA manufactures a w ide range of pressure transmitters to meet specific
protection requirements.
The degree of protection of an enclosure from environmental elements is defined by tw o types of enclosure
classification rating systems. One is the NEMA rating (National Electronic Manufacturers Association). The
other is the IP system (Ingress Protection), w hich is commonly used in Europe and increasingly used in the
U.S. These systems define protection from solids and liquids entering an enclosure. The tw o systems use
different test parameters, therefore they are not directly comparable.
NEMA & IP Ratings
NEMA (National Electrical Manufacturers Association) Ratings
NEMA 1: General Purpose – Indoors
Intended for general purpose indoor use, primarily to provide a degree of protection against contact w ith
the enclosed equipment or locations w here unusual service conditions do not exist
NEMA 2: Drip Proof – Indoors
Intended for general purpose indoor use, primarily to provide a degree of protection against limited
amounts of falling w ater and dirt.
NEMA 3: Dust Tight, Rain Tight & Ice/Sleet Resistant – Indoors/Outdoors
Intended for general purpose outdoor use, primarily to provide a degree of protection against w indblow n
dust, rain and sleet
Will be undamaged by the formation of ice on the enclosure
NEMA 3R: Rain Proof & Ice/Sleet Proof – Indoors/Outdoors
Intended for general purpose outdoor use, primarily to provide a degree of protection against falling rain
Will be undamaged by the formation of ice on the enclosure
NEMA 3S: Dust Tight, Rain Tight & Ice/Sleet Proof – Outdoors
NEMA 4: Water Tight & Dust Tight – Indoors/Outdoors
Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel
against incidental contact w ith the enclosed equipment
Provide a degree of protection against falling dirt, rain, sleet, snow , w indblow n dust, splashing w ater
and hose-directed w ater
Will be undamaged by the external formation of ice on the enclosure
NEMA 4X: Water Tight, Dust Tight & Corrosion Resistant – Indoors/Outdoors
Same as NEMA 4, w ith the addition of corrosion resistance
Enclosures and external parts attached to these enclosures shall be manufactured of American Iron and
Steel Institute (AISI) Type 304 Stainless Steel, polymerics, or materials w ith equivalent corrosion
resistance. If material other than Type 304 Stainless Steel is used, it shall be tested in accordance w ith
5.9 and 5.10.
NEMA 5: General Purpose Dust-Tight
Intended for use indoors or outdoors w ith protection from dust provided by gaskets
NEMA 6: Submersible, Water Tight, Dust Tight & Ice/Sleet Resistant – Indoors/Outdoors
Intended for general purpose indoor and outdoor use primarily to provide a degree of protection against
the entry of w ater during temporary submersion at a limited depth
Will be undamaged by the formation of ice on the enclosure
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NEMA 7: Underw riters Lab Class 1 – Groups C & D – Explosion Proof – Indoors
Intended for indoor use in locations classified as Class I, Groups A, B, C or D, as defined in the National
Electrical Code
Capable of w ithstanding the pressures resulting from an internal explosion of specified gases and
contain such an explosion sufficiently that an explosive gas-air mixture existing in the atmosphere
surrounding the enclosure w ill not be ignited.
Enclosed heat generating devices shall not cause external surfaces to reach temperatures capable of
igniting explosive gas-air mixtures in the surrounding atmosphere
Enclosures shall meet explosion, hydro-static and temperature design tests
NEMA 8: Underw riters Lab Class I – Groups C & D – Explosion Proof – Indoors
Same as NEMA 7, except the unit is oil-immersed
NEMA 9: Underw riters Lab Class II – Groups E, F, G – Indoors
Intended for special-purpose indoor use in locations classified as hazardous (Class II, Groups E, F and
G, as defined in the National Electric Code)
Capable of preventing the entrance of dust
Enclosed heat generating devices shall not cause external surfaces to reach temperatures capable of
igniting or discoloring dust on the enclosure or igniting dust-air mixtures in the surrounding atmosphere
Enclosures shall meet dust penetration and temperature design tests and aging of gaskets (if used)
NEMA 11: Corrosion Resistant & Drip Proof – Oil Immersed – Indoors
NEMA 12: Industrial Use – Dust Tight & Drip Tight – Indoors
Constructed (w ithout knockouts) to provide a degree of protection to personnel against incidental
contact w ith the enclosed equipment
Intended for industrial indoor use, primarily to provide a degree of protection against dust, falling dirt and
dripping noncorrosive liquids.
NEMA 13: Oil Tight & Dust Tight – Indoors
Intended for industrial indoor use, primarily to provide a degree of protection against dust, spraying of
w ater, oil and noncorrosive coolant)
* The comparison of NEMA and IP enclosure ratings is only approximate. It is the responsibility of the user to
verify the enclosure rating necessary for the given application.
IP Ratings
Ingress Protection
The IP rating system provides a means of classifying the degrees of protection from solid objects and liquids
afforded by electrical equipment and enclosures. The system is recognized in most European countries and is
set out in a number of British and European standards. These include: Classification of Degrees of Protection
Provided by Enclosures, BS (British Standards) 5490:1977; IEC (International Electrotechnical Commission)
529:1976.
The first number defines the level of protection against penetration of solid objects into the housing. The
second number defines the level of protection against penetration of liquids into the housing.
Num ber
(1st Digit)
Degree of Protection (Solid)
Num ber
(2nd Digit)
Degree of Protection (Liquid)
0
No protection against contact or entry
of solids
0
No protection
1
Protection against accidental contact by 1
hane, but not deliberate contact.
Protection against large objects.
(greater than 50 mm)
Protection against drops of
condensed w ater. Condensed w ater
falling on housing shall have no effect.
2
Protection against contact by tools,
Protection against drops of liquid.
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w ire, etc. Protection against small
foreign objects. (greater than 12 mm)
Drops of falling liquid shall have no
effect w hen housing is tilted to 15°
from vertical.
3
Protection against contact by tools,
w ire, etc. Protection against small
foreign objects. (greater than 2.5 mm)
3
Protection againts rain. No harmful
effect from rain at angle less than 60°
from vertical.
4
Protection against contact by tools,
w ire, etc. Protection against small
foreign objects. (greater than 1 mm)
4
Protections against splashing from
any direction.
5
Complete protection against contact
w ith live or moving parts. Protection
against harmful deposits of dust.
5
Protection against w ater jets from any
direction.
6
Complete protection of live or moving
6
parts. Protection against penetration of
dust.
Protection against condition on ship
decks. Water from heavy seas w ill not
enter.
7
Protection against immersion in w ater.
Water w ill not enter under stated
conditions of pressure and time.
8
Protection against indefinite immersion
in w ater under a specified pressure.
Examples
Umbrella: IP-01 or IP-02 (depending on umbrella)
Chain link fence: IP-02
Chicken w ire: IP-20
Screen: IP-30
Kevlar cloth: IP-40
Tent (camping): IP-42
Saran w rap: IP-51
Bottle of w ine: IP-67
Submarine: IP-68
NEMA Ratings vs. IP Ratings
It is not possible to state that an IP rating is equivalent to a NEMA Type designation. An IP rating only considers
protection against ingress of solid foreign objects and ingress of w ater. The NEMA types consider these but
also consider other items such as corrosions and construction details. For this reason, it is possible to say
that a NEMA type is equivalent to an IP rating but it is not possible to state that an IP rating is equivalent to a
NEMA Type.
There is no direct conversion betw een NEMA Types and IP Codes.
This Application Note first appeared in the March 2009 issue of the WIKA e-New s. To receive the
m onthly WIKA e-New s, click here to subscribe.
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