Installation, operation and maintenance instructions
High voltage flameproof motors for explosive atmosphere
AMD Rg 355-400-450-500
Coupling for cylindrical or conical shaft extensions with keyways
Fitting and dismantling instructions for horizontal machines having plain or
rolling contact bearings with axial shaft guidance
Issued by: MOLM
Sheet No.
3AAM101031 E
Rev. B
Page 1 of 2
01.2023
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Preliminary inspection
Inspection of all functional parts and components is
essential before fitting a coupling for the first time. The
hub bore and shaft extension should be checked
against the dimensions specified on the sketch or
drawing.
It should also be ensured that the keyways in the
coupling and shaft extension are truly parallel.
The machine rotor is balanced with a half-key.
Coupling components should be balanced on a
mandrel, with a half-key filling the keyway.
General information
The following are the most frequent causes of poorly
seated coupling hubs:
-
Damage on the shaft, coupling or keyway
(indentations, burrs or pressure marks).
- Non-parallelism of keyways causing jamming and
excessive lateral thrust on keys and keyways.
- Key too high causing it to bear top load.
-
A key fitted in a tapered shaft extension affects the
function of the tapered shrink seat and should
therefore be avoided. If a key is nevertheless fitted,
the coupling seat must be more accurate than
normal. This means not only maintaining all
tolerances but also that the exact contact between
shaft and hub mating surfaces must be verified with
blue oil, keyways in both shaft and hub must be
checked for absolute parallelism, and the slightest
imperfections such as burrs or pressure marks
must be absolutely avoided.
Fitting instructions
Thoroughly clean and dry all mating surfaces. Never
coat such surfaces with molybdenum disulphide
(Molykote) or similar products. A thin coating of oil on
the shaft extension and hub bore is to be
recommended.
In general, the coupling manufacturer’s instructions
are valid for mounting and removing the coupling hubs.
It is common practice to heat the coupling in order to
increase (or make) the clearance between the two
fitting parts. If the coupling is keyed there is a certain
clearance between the coupling and the shaft
extension, so heating the coupling up to 80°C (176°F)
will be sufficient for an easy fitting.
Cylindrical and conical couplings (without keyway) are
always fitted with interference and must be heated for
the assembling on the shaft end. Refer to the specific
instruction of the manufacturer.
IMPORTANT!
: the couplings assembled with
interference must be “enlarged” in case of
disassembling from the shaft end. The enlargement is
usually obtained by injection of oil under high pressure
in circumferential grooves connected to suitable small
oil injection channels.
It is very important to take care, during the coupling
assembling, to avoid any incision or axial scratch, that
would prevent the oil pressurisation. Remember that if
the oil can’t be pressurised, the coupling removal
become very difficult, and in some case impossible.
The weight of a coupling hub can be considerable,
therefore suitable lifting gear must be available.
Axial clearance
The values for permissible axial loading are given on
the machine dimension drawing. The axial clearance
in the coupling must be chosen large enough to
accept shaft displacement from the coupled machine.
Our machines are normally fitted with a guide bearing
at the drive end. Thermal expansion can therefore act
towards the non-drive end without loading the
coupling.
Disassembling instruction
Removal of couplings with keyway.
The removal of the coupling from the shaft end can be
easily obtained with a pulling tool of suitable
dimension. Remember to protect the shaft end, where
there is the contact with the pulling device centre pivot,
with suitable soft material (see point A).
Removal of couplings fitted with interference.
In this case a suitable device for injecting oil under high
pressure (in the order of 1000 bar and more) is
required, together with an hydraulic jack capable of
generating a force in the order of 100 ton.
