not sufficient that a piece of equipment fulfils the functional
requirements assigned to it. It also has to be protected against
possible adverse external influences, and likewise to ensure that it is
not harmful to the user or to the environment.
can be used alone or combined to comply with this last requirement. All
of them derive from one of the following methods:
last method has the advantage of providing an easy solution to the
other requirement that is the protection of equipment against certain
influences such as:
The IP Code
- The ingress of
foreign bodies which could disturb the mechanical or electrical
operation. They comprise not only sand and dust but also small animals
and flying or creeping insects,
- Water and other liquids which
could alter the insulation and generate degradation, mechanical impacts
that might deform or break brittle parts,
- Corrosive gas from the environment,
- Radiated electromagnetic fields,
- Various radiations including light.
The IP code is described in Publication 529 of the International Electrotechnical Commission.
IP Means: International Protection.
code allows for the description of the degrees of protection provided
by enclosures against access to hazardous parts, ingress of solid
foreign bodies and against harmful effects of water, by means of the
numerals and letters described hereunder.
This standardised code
is intended to be used in product standards. It can also be used to
describe an empty enclosure, but then some difficulties can appear as to
- Where to locate harmful parts to keep them at «adequate distance?
- Where may water or dust deposit without disturbing the correct operation of the equipment?
In fact, degrees of protection will only be required when the enclosure is in service with equipment inside.
assembler is therefore responsible for the final product complying with
it's standard. But the manufacturer of the enclosure must state in the
documents where equipment has to be installed inside the enclosure to
maintain the degrees of protection he has assessed.
people in charge of the installation who will connect the equipment
(cable pass), fix it and in some cases adapt auxiliaries (pushbuttons,
meters) must ensure that the specified degree of protection is
Letters IP of the code are followed by two
independent numerals and sometimes by letters. When the degree of
protection corresponding to one of the numerals is not stated (be it
unnecessary or unknown) it is, replaced by an X.First Numeral
a result of decisions made for previous editions of the standard,
decisions, which cannot to be reconsidered, the first numeral indicates
- Protection of persons against access to harmful parts and
- Protection of equipment against ingress of foreign bodies.
check compliance with the first numeral, two probes must therefore be
used (an access-probe and an object probe) with the application forces
specified in the standard, or the same probe is used with two acceptance
The various degrees correspond to the following meanings:
|IP 1X|| ||it
can be a wire-mesh or an enclosure, the largest opening of which does
not allows a ball of 50 mm diameter to ingress. This corresponds
approximately to the ingress of a hand (see fig. 3).|
|IP 2X|| || the
protective wire-mesh has smaller holes and the diameter of the
object-probe is 12.5 mm. In addition, the jointed test-finger must stay
at adequate distance from harmful parts. |
|IP 3X|| ||the
enclosure must not allow ingress of foreign bodies 2.5 mm of diameter.
The test is performed with a steel wire with edges free from burrs,
because the use of a 2.5 mm diameter ball would not be convenient.|
|IP 4X|| ||as for the previous degree but with 1 mm instead of 2.5.|
|IP 5X and IP 6X|| ||these
two degrees correspond to protection against ingress of dust. IP 5X
allows penetration of some dust in places where it is not harmful. IP 6X
accepts no ingress of dust at all. The test is performed in a test room
where talcum powder is sustained floating by means of an airflow. In
addition, the enclosure is de-pressurised internally except if the
relevant equipment standard specifies that it be of category 2: that is,
the normal operation of the enclosed assembly cannot generate
significant internal pressure reduction. Although the test is performed
with talcum powder, the effects that might give any other type of dust
must be taken into account here.|
second characteristic numeral of the IP code indicates the degree of
protection against harmful effects of water penetration. It is specified
that the tests are performed with fresh water (see fig. 4) with no
The interpretation of tests for this numeral may be
difficult since water penetration into the enclosure is permitted,
provided it does not generate harmful effects.
The various degrees of the second numeral correspond to the following situations:
enclosures complying with these degrees must have double marking if
they also comply with a lower degree, for instance IP X5/X7 (a bucket
immersed upside down is IP X8, but not IP X4).
Water-tests of the IP code have been recently incorporated into IEC 68-2-18 with the following correspondence Additional Letter
some cases, the protection provided by an enclosure against access to
harmful parts is better than indicated by the first numeral (which also
indicates the protection against ingress of foreign bodies). For
instance it is frequently the case of an opening of the enclosure
blinded by a staggered joint or a sheet bent.
This protection can
be characterised, by an additional letter added after the two numerals.
It allows openings useful for thermal dissipation when keeping the
degree of protection required for the protection of persons.
It has one of the following meanings:
|IP XXA ||has no practical application since the test for the letter A is the same as for the first numeral 1 (see fig. 3). |
that foreign bodies of diameter larger than 12.5 mm can ingress into
the enclosure, but that the test-finger does not penetrate more than 80
mm, i.e. not beyond its 50 x 20 mm guard and stays at an adequate
distance from harmful parts (see fig. 5). |
penetration of foreign bodies of diameter larger than 2.5 mm, but a
straight steel wire of this diameter and 100 mm long stays at an
adequate distance from harmful parts. |
situation is similar to the previous degree, but for a diameter of 1
mm. The additional letter is also used when only the protection of
persons is aimed at. |