in this video we're going to answer the question what are the different classes of steel conduit
this question relates to the video that I made on the conlok clean room range of conduit and
fittings from Metpro where we took a dive into the pernicious problem of zinc whiskers so please go
and check that video out after watching this one classes of conduit can be found in the BSEN61386
series of British standards which replaced earlier standards there is also table 5.1 in
the IET Guidance note one which you may find useful and we'll have a look at a little bit
later in the video the classification relates to a few different qualities of the conduit the main
ones being compression and temperature ranges but we're going to look at the quality that visually
sets it apart which is the surface corrosion protection the classes of conduit in this
context are Class 1 light which consists of low protection both inside and out for example using
something like priming paint Class 2 is medium which consists of medium protection inside and
out for example in this case we might use stove enamel or air drying paint or electroplating
Class 3 is medium heavy and this is an interesting one because it's a combination of classes two and
four so stoved enamel or electroplating offering medium protection on the inside of the conduit
and perhaps something like sherardised offering high protection on the outside
Class 4 is then heavy protection which consists of high protection both inside and out for example
by the use of hot dipped zinc coating or maybe sherardised again now if you're wondering what
that word sherardising means it's one method of galvanizing or adding zinc to the surface layer
of the material in this case conduit sherardising is the hardest and most wear resisting method
of galvanizing making it perfect for heavy duty protection so interestingly there's only really
three classes of protection but two of them are combined to give a fourth it's pretty rare to
come across Class 1 conduit in installation work and then perhaps the slightly longer in the tooth
electricians among us will remember installing black enamel conduit and accessories which would
conform for Class 2 conduit we probably also remember painting the scratches and marks caused
by the hand tools on the tube during installation and that awful gut-wrenching moment when you bend
a piece and one dodgy patch of paint would peel away like the skin of an orange of course we'd
use this type of conduit in areas that are dry and non-corrosive and then in areas where there's
a chance of damp or corrosion then Class 3 or Class 4 conduit would be considered in addition
to these requirements there are various tests that the different classes of conduit need to go
through to meet the British Standard for example these tests would include the durability of the
markings on the conduit a test of the mechanical properties of the conduit resistance to corrosion
and of course electrical continuity there's also information available in table 5.1 in the IET's
Guidance note one which you may find useful when you're selecting the class of conduit for
a particular project the table lists the relevant ranges of impact that the conduits are tested to
as well as temperature range IP rating corrosion protection tensile strength and suspended load
in addition to this there are other installations that may require the use of specialised finishes
on conduit and accessories such as clean rooms like Laboratories and data centers in environments
like this there is a possibility that traditional galvanized finishes containing zinc can actually
start to produce use tiny contaminants that if they get into sensitive equipment or
materials being produced can cause them to fail catastrophically these are the zinc whiskers that
we mentioned earlier and they can be seriously damaging one solution is that conlok clean room
system from Metpro which has a surface treatment that helps to eliminate the source of these zinc
whiskers now we've created a whole video on this subject so check that out and there's also more
information on the manufacturer's website one thing that I found really interesting about this
range is that each length of conlok steel conduit for clean rooms is supplied with one threaded
end so that it can be connected to traditional conduit systems as well as conlok accessories
so that might be useful if you're looking to add to an existing installation and if you'd like to
see the con lock system in action please check out this video here thank you very much for watching