Bell & Gossett HT 205B SM Models ACA Straight Tube, Removable Bundle Heat Exchangers - Manual (Page 3)

3. Provide convenient means for frequently cleaning heat
exchangers as suggested below:
a. Circulating hot wash oil or light distillate through tubes or
shell at good velocity will effectually remove sludge or
other similar soft deposits.
b. Soft salt deposits may be washed out by circulating hot
fresh water.
c. Some cleaning compounds on the market, such as
“Oakite” may be used to advantage for removing sludge or
coke, provided hot wash oil or water, as described above,
does not give satisfactory results.
d. If none of the above described methods are effective for
the removal of hard scale or coke a mechanical means
may be used. The interior of the tubes may be rodded.
WARNING: Care must be exercised when handling
certain fluids. Follow manufacturers instructions. Use
eye and skin protection. Wear a respirator when required.
4. To clean or inspect inside of tubes, remove channel cover and
rear head. On exchangers having bonnet type heads (without
channel cover), piping must be disconnected and both heads
removed.
5. Do not attempt to clean tubes by blowing steam through indi-
vidual tubes. This overheats the tube and results in tube
expansion strains and sometimes leaking tubes.
6. Frequently and at regular intervals, observe interior and exte-
rior condition of all tubes and keep them clean. Frequency of
cleaning should be according to scale build-up.
CAUTION: Neglect in keeping all tubes clean may
result in complete stoppage of flow through some
tubes with consequent overheating of these tubes, resulting
in severe expansion strains, leaking tube joints, and damage
to the heat exchanger.
7. Exchangers subject to fouling or scaling should be cleaned
periodically. A light sludge or scale coating on the tube greatly
reduces its effectiveness. A marked increase in pressure drop
and/or reduction in performance usually indicates cleaning is
necessary, if the unit has been checked for air or vapor bind-
ing and this has been found not to be the cause. Since the dif-
ficulty of cleaning increases rapidly as the scale thickens or
deposits increases, the interval between cleanings should not
be excessive.
8. Tube bundle removal:
a. During bundle removal, the dead weight of bundle should
never be supported on individual tubes since the tubes are
small and of relatively thin metal. Rest the bundle on the
tube sheet, support plates, or wood blocks cut to fit
periphery of the bundle.
b. Be sure there is a soft wood filler between ends of tubes
and steel bearing plate when pushing bundle out. On
smaller bundles of 12" diameter and under, it is permis-
sible to use hard wood block in place of wood filler and
steel bearing plates. See Illustration No. 1.
c. Tube bundles may be raised using slings formed by bend-
ing light plates into a “U” form and attaching lifting lugs to
the ends of the sheets. Baffles can be easily bent and dam-
aged if dragged over rough surfaces.
OPERATION
1. When placing a unit in operation, open the vent connections
and start to circulate the cold medium only. Be sure that the
passages in the exchanger are entirely filled with the cold fluid
before closing the vents. The hot medium should then be intro-
duced gradually until all passages are filled with liquid, close
vents and slowly bring the unit up to temperature.
2. Start operation gradually. Do not admit hot fluid to the unit
suddenly when empty or cold. Do not shock unit with cold fluid
when unit is hot.
CAUTION: Fluids must be gradually introduced to the
unit. Failure to do so can cause damage to the heat
exchanger.
3. In shutting down, flow of hot medium should be shut off first.
If it is necessary to stop circulation of cooling medium the cir-
culation of hot medium should also be stopped by by-passing
or otherwise.
4. Do not operate equipment under conditions in excess of those
specified on nameplate.
WARNING: Failure to operate the heat exchanger
within the design pressure and temperature on the
nameplate may result in damage to the heat exchanger and
potential injury to adjacent personnel.
5. Drain all fluids when shutting down to eliminate possibility of
freezing and corrosion. To guard against water hammer, con-
densate should be drained from steam heaters and similar
apparatus both when starting up and when shutting down.
6. In all installations there should be no pulsation of fluids since
this causes vibration and strain with resulting leaks.
7. All gasketed joints should be checked after starting for leaks
and tightened if necessary.
MAINTENANCE
1. Do not open heads until all pressure is off equipment and the
unit is drained.
2. Do not blow out heat exchangers with air when operating
fluids are of a flammable or otherwise hazardous nature.
WARNING: Proper precautions must be taken (special
clothing, equipment, etc.) to protect personnel from
injury due to escaping fluids.
3
Illustration No. 1 – The method employed to push tube bundle out
of shell.