7
4610, 4620 edition 03
This chapter describes the specially approved mixer
versions 4610.490 and 4620.490. For identification,
see the mixer data plate and approval plate.
Specially approved mixers may
only be repaired and adjusted by
Flygt workshop and/or workshop
personnel authorized by Flygt.
General
In a specially approved product (explosion proof) the
gaps between different parts, for example the bearing
holder and the stator casing unit, shall prevent any
sparks from the interior of the machine from getting
out and igniting surrounding gases.
All joint widths and gaps shall be measured with
accurate and calibrated instruments. All joint surfaces
shall be inspected. No scratches, tool marks or the
like are permissible.
Failure to meet the above requirements may render
the special approval invalid. Note that the work
requires experienced and specially trained personnel.
To ensure that the product complies with the regula-
tions
and approval of the authorities, use only genuine
Flygt spare parts when carrying out repair work.
Always check the dimensions of vital parts before
assembly, see picture.
The assembled machine shall always be insulation-
tested
and test-run before delivery.
Workshop repair
The product must be thoroughly examined and a report
must be prepared on all findings. Any measurements,
dimensional checks, test regardings, details of mate-
rials,
parts of windings which are found require attention
should be carefully noted.
If the products have been modified and does not
comply with original approval, the owner must be
informed and further information on the application
must be requested.
If there are any doubts during the repair as to the
results of measurements, tests, the continued integrity
of parts or possible reclamation of damage parts,
reference must be made to your local Ex Coordinator.
Guidelines for repair
Dismantling
When dismantling Ex approved products, care must
be taken as damage to flameproof faces can easily
occur. For instance, if difficulties are found in separat-
ing
spigoted joints, draw studs should be used wher-ever
possible rather than trying to wedge the compo-nents
apart, as not only will damage occur at the point
of wedging, but the wedges are liable to be driven
through and damage the flamepath surface of the
spigot.
Similarly, care should be exercised when removing the
main bearing assembly and bearing holder to ensure
that damage does not occur on the parts that consti-
tute the flamepath.
Unless obviously damaged through either mechanical
injury or dry or wet burn out, the stator winding should
not be removed until preliminary testing has been done
to determine the condition of the stator winding and
monitoring devices, i.e. overtemperature thermal
switches.
The users instruction should be consulted to verify
whether the machine has been returned for repair
because of electrical problems, such as operation of
overload, short circuit or tripping out on an earth trip
leakage device.
Once the machine has been completely dismantled,
detailed examination of all parts should be made and
a concise record kept of all findings.
Assembling
Before assembling an Ex approved product, measure
the gaps and the joint widths. Inspect the joint surfaces
and smear them with grease to prevent corrosion.
If a part does not meet the requirements on dimen-
sional
accuracy or surface finish, it must be discarded
and a new specially approved part ordered. The new
part must also be inspected.
Observe caution during assembly to prevent damage
to the joint surfaces.
Flamepaths
Which parts require special examination can be
ascertained by refering to the Spare parts list and
dimensional checks.
The flamepaths should be examined for any corrosive
pitting or damage which may have occured.
All castings should be examined for blow holes or
hairline cracks. If there is evidence that there has
been an internal explosion of gases, this may be
confirmed by the user and will probably be evident by
smoke and debris tracking across the flamepaths.
SPECIALLYAPPROVED MIXER
