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SECTION 2 ITEM 1080
DATED NOVEMBER 2012
SUPERCEDES MAY 2010
(d) Removal of various scales and foreign material by
chemical cleaning is now being extensively practiced.
Certain qualified organizations will check the nature
of the deposits to be removed, furnish proper acid
solutions containing inhibitors, and provide equipment
and personnel for a complete apparatus and piping
cleaning job.
(e) If none of the above methods is effective for the removal
of a hard scale, coke, or other deposits, mechanical
means may be used for straight tube heat exchangers.
5. CLEANING PRECAUTIONS:
(a) Do not attempt to clean tubes by blowing steam through
individual tubes. This overheats the tube and results in
severe expansion strains and possible leaky tube joints.
(b) Do not blow out heat exchangers with air when fluids
normally handled are inflammable.
(c) In cleaning a tube bundle, the tubes should not be
hammered on to remove hard scale. In case it is
necessary to use scrapers, make sure that the scraper is
not sharp enough to cut the metal of the tubes.
(d) If scaling or other fouling were expected, provisions
in the piping could be made to allow connections for
flushing out or chemical circulation cleaning; these
openings, of course, would be normally plugged. In
large plants where there are a number of exchangers,
it may be profitable to have a tank of cleaning fluid
available for periodic flushing of shell and/or tubes.
Makers of commercial cleaning compounds would be
glad to advise in this respect. Then, there are qualified
organizations with experienced personnel who can
furnish a complete service of apparatus for the removal
of hard scale and sludge not easily removed otherwise.
Small exchangers that can be easily removed from the
line and small tube bundles can be sent to organizations
that do such cleaning on their premises.
6. TUBE ROLLING: To tighten a loose tube joint, use a
suitable roller type expander. Do not roll tubes that are not
leaking as this needlessly thins the tube wall, and work
hardens the metal which makes it brittle. Tubes are rolled
in at our factory by means of roller type expanders, and the
amount of expansion is controlled by means of a torquing
device for uniformity and positive sealing. Do not over-roll
the tubes as this would permanently damage the tube sheet.
7. GASKET REPLACEMENT: Gaskets and gasket
faces should be thoroughly clean and should be free of
scratches and other defects. Gaskets should be accurately
positioned before retightening bolts. It is recommended
that when a heat exchanger is dismantled for any reason,
it be reassembled with new gaskets. Composition gaskets
become dried out and brittle so that they do not always
provide an effective seal when reused. Metal or metal-
jacketed gaskets, when compressed initially, flow to match
their contact surfaces. In so doing, they are work-hardened,
and when reused, may provide an imperfect seal. Reused
metallic gaskets could result in deformation or damage to
the gasket contact faces of the exchanger.
1080 SERIES
8. SPARE AND REPLACEMENT PARTS:
or replacement parts may be obtained for Aurora heat
exchangers by reference to the part required and to the
serial number of the exchanger appearing on the nameplate.
Consideration should be given to stocking parts for
exchangers used in a process as inconvenient shutdowns
may be necessary until receipt of parts. Since some gaskets
are made to order with a long lead-time, it may be desirable
to have them on hand.
In situations where a shutdown for cleaning and/or
repairs could not be conveniently arranged, a standby heat
exchanger connected in parallel, or a complete replacement
tube bundle on hand for emergency, is recommended.
9. BOLTING: It is important that all bolted joints be
tightened uniformly and in a diametrically staggered pattern,
as illustrated in the diagram, except for special high pressure
closures when the instructions of the manufacturer should
be followed.
Nominal
Bolt Dia.
1/2
5/8
3/4
7/8
1
1-1/8
1-1/4
1-3/8
1-5/8
1-1/2
1-3/4
1-7/8
8
Torque required to tighten new flange ring bolts.
Parts of the above excerpts from the Standards of the Tubular
Exchanger Manufacturers Association.
6
9
14
4
7
12
4
Std. Machine Bolts
High Tensile Bolts
A-307
A-326 or A193-B7
Torque in ft./lbs.
Torque in ft./lbs.
15
40
30
75
50
125
80
200
125
310
200
450
276-5
650
–
850
–
1000
–
1400
–
1900
–
2500
–
2800
START
16
11
8
3
13
10
5
2
15
Spare
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