Technical Information on IP, NEMA and ATEX Ratings

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IP & NEMA Ratings :: ATEX - Protection Concepts & Standards
ATEX Gas & Device Grouping :: ATEX - Substance & Apparatus Info

IP (Ingress Protection) & NEMA Protection Rating Information
(helpful information only, detailed reference should be taken from an appropriate agency)

An IP number contains two numbers (i.e. IP65) in most instances which relate to the
level of protection provided by an enclosure or housing.

The first number relates to protection from solids as follows:

0: No Special Protection
1: Protected against solid objects up to 50 mm in diameter
2: Protected against solid objects up to 12 mm in diameter
3: Protected against solid objects up to 2.5 mm in diameter
4: Protected against solid objects up to 1 mm in diameter
5: Dust protected
6: Dust tight

The second number relates to protection from liquids as follows:

0: No special protection
1: Protected against dripping water
2: Protected against dripping water when tilted up to 15^o from normal position
3: Protected against spraying water
4: Protected against splashing water
5: Protected against water jet spray
6: Protected against heavy jet spray
7: Protected against the effects of immersion
8: Protected against submersion

Example: IP66 = Dust tight and protected against heavy water jet spray

NEMA (National Electrical Manufacturers Association) ratings can be approximately compared to those of the IP system as shown below.
Other factors such as corrosion protection are also involved in the NEMA system, please refer to official documentation for details.

NEMA 1 = IP10
NEMA 2 = IP11
NEMA 3 = IP54
NEMA 4 = IP56
NEMA 4X = IP66
NEMA 6 = IP67
NEMA 12 = IP52
NEMA 13 = IP54

ATEX & Intrinsic Safety Information - Explosive Atmospheres
(helpful information only, detailed reference should be taken from an appropriate agency)

Protection Concepts
ZONE	HAZARD	PROTECTION CONCEPTS
0	In which an explosive gas/air mixture is continuously present for long periods	Exia or Exs
1	In which an explosive gas/air mixture is likely to occur in normal operation.	Exd. Exe, Exib, Exp, Exia, Exs
2	In which an explosive gas/air mixture is not likely to occur in normal operation.	All concepts suitable for Zone 0 & 1, ExN, ExO and Exq

Standards For Methods Of Protection
METHOD OF PROTECTION	PERMITTED ZONE OF USE IN UK	CODE LETTER IEC, EX.., CENELEC, EEX
General requirement	-	-
Oil immersion	2	o
Pressurisation	1 or 2	p
Powder filling	2	q
Flameproof	1 or 2	d
Increased safety	1 or 2	e
Intrinsic safety	* 0, 1 or 2	ia or ib
Non-incendive	2	n #
Encapsulation	1 or 2	m
Special	1 or 2	s
* ia: Zone 0,1,2. ib: Zone 1,2. not Zone 0. # n: used locally in UK.

Gas Grouping		Temperature Classification
GAS # GROUP CENELEC EN 50 014, IEC	REPRESENTATIVE GAS	T Class / IEC 79-7	Max. surface temp ° C
I * (mining)	Methane	T1	450 ° C
IIA	Propane	T2	300 ° C
IIB	Ethylene	T3	200 ° C
IIC	Hydrogen	T4	135 ° C
		T5	100 ° C
		T6	85 ° C

Certification Code (CENELEC marking information - example [EEx ia] IIC T4)
[	E	Ex	ia	]	IIC	T4
Associated apparatus*	Certified to the CENELEC standard	Explosion protected	Protection concept (IS)	Associated apparatus*	Apparatus group (gas group)	Temperature classification (not Gp I)
* (located in safe area and may be connected to hazardous area)

Device Group & Category
DEVICE GROUP	DEVICE CATEGORY	ZONE
I	M = mining	–
Mining	M 1	–
Pit gas &/or flammable dusts	M 2	–
II	G = gas
Other areas	1 G	0, 1, 2
Explosive atmosphere	2 G	1, 2
	3 G	2
D is added after G in the certification class number	D = dust
(i.e. GD) if device is dust category approved also	1 D	20, 21, 22
	2 D	21, 22
BACK TO TOP	3 D	22
Explanation of the categories: 1 - Very high safety = device safety must be guaranteed even in case of rare device failures, e.g. simultaneous failure of two components. 2 - High safety = device safety must be guaranteed if frequent failures can be expected, e.g. failure of one component. 3 – Safe in normal operation = device safety must be guaranteed in normal operation. Note: A number in brackets before device category designation signifies that the device meets the requirements of an additional category to the main one that is specified. Example: II (1) 2G signifies that the device meets requirements for both 1 G and 2 G categories

Flashpoint

This is the lowest temperature at which a liquid generates sufficient
vapour to support ignition. This vapour can be ignited in many ways
including temperature or energy (i.e. a spark)

Ignition Temperature

This is the lowest temperature at which the vapour will be ignited.
This defines the temperature class.

Classification of maximum surface temperatures of electrical apparatus (CENELEC)

Temp. Class	Max. Surface Temp.
T1	<450ºC
T2	<300ºC
T3	<200ºC
T4	<135ºC
T5	<100ºC
T6	<85ºC

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Apparatus Group (energy ignition)
All surface industry gases/vapours are classed as Group II gases.
Group II is divided into 3 sub groups:

IIA – High energy is required to ignite. Less intense explosion. (Propane)

IIB – Less energy is required to ignite. More intense explosion. (Ethylene)

IIC – Little energy is required to ignite. Most intense explosion. (Hydrogen)

Characteristics of some common flammable materials

Gas/Vapour	Flashpoint	Gas Group	Ignition Temp.	Temp. Class
Acetone	19ºC	IIA	535ºC	T1
Butane	-60ºC	IIA	365ºC	T2
Heptane	-4C	IIA	215ºC	T3
Ethyl Methyl Ether	37ºC	IIB	190ºC	T4

Note: There is no connection between ignition energy and ignition temperature

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Conversion Program

'Convert!' is a small program that allows you to convert one set of engineering units to another quickly, easily and exactly with up to 10 decimal place precision possible!

Click on the arrows below to download your copy

Convert consists of a single file named convert.exe that is only 548KB in size. When you click on the image opposite to download, simply choose 'save' when prompted and select a directory to put the file into. Once download is complete, locate the file and double-click the icon and the program will open.

To put a shortcut on the
desktop for easy access, right-click the icon,then left-click 'Send To' followed by 'Desktop (create shortcut)'...and that's it!

ZONE

I

II

Example: II (1) 2G signifies that the device meets requirements for both 1 G and 2 G categories

Example: II (1) 2G signifies that the device meets requirements for both
1 G and 2 G categories