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BELL & GOSSETT
SERVICE MANUAL
HT-202A-SM
Installation, Operation and
Maintenance Manual for
Models CHX & CHXS
Fixed Tube Sheet Heat Exchangers
INSTALLER: PLEASE LEAVE THIS MANUAL FOR THE OWNER’S USE.
SAFETY
INSTRUCTION
This safety alert symbol will be used in this manual to draw
attention to safety related instructions. When used, the safety
alert symbol means ATTENTION! BECOME ALERT! YOUR
SAFETY IS INVOLVED! FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN A SAFETY HAZARD.
© COPYRIGHT 1989, 1995
Bell & Gossett
Morton Grove, IL, U.S.A.
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INSTALLATION
11. Before installing this equipment, environment and service
conditions should be checked for compatibility with materials
of construction. Contact your nearest Bell & Gossett
Representative if you are not sure what the actual materials of
construction are.
12. Provide valves and by-passes in the piping system so that
both the shell and tube sides may be by-passed to permit
inspection or repair.
13. Provide thermometer well and pressure gauge connections in
all piping to and from the unit and locate as near the unit as
possible.
14. Provide convenient means for frequently cleaning the unit as
suggested under “Maintenance.”
15. Provide necessary air vent cocks for units so they can be
purged to prevent or relieve vapor or gas binding of either the
tube or the shell sides.
16. Foundations must be adequate so that exchangers will not
settle and cause piping strains. Foundation bolts should be
set to allow for setting inaccuracies. In concrete footings, pipe
sleeves at least one size larger than bolt diameter slipped over
the bolt and cast in place are best for this purpose, as they
allow the bolt center to be adjusted after the foundation has
set.
17. Loosen foundation bolts at one end of unit to allow free
expansion of shells. Oval holes in foundation brackets are
provided for this purpose.
18. Set exchangers level and square so that pipe connections
may be made without forcing.
19. Inspect all openings in exchanger for foreign material. Re-
move all thread protectors and shipping pads just before
installing. Do not expose units to the elements with pads or
other covers removed from openings since rain water may
enter the unit and cause severe damage due to freezing.
10. Be sure the entire system is clean before starting operation to
prevent plugging of tubes with sand or refuse. The use of
strainers in settling tanks in pipe lines leading to the unit is
recommended.
11. Drain connections should not be piped to a common closed
manifold.
12. Location of the operating fluids in the heat exchanger can be
a function of the application. A few tips for the location of the
operating fluids are:
a. As a cooler, the preferred arrangement is with the hot medi-
um through the shell and the cooling medium through the
tubes. When the hot fluid is dirty or fouling, it is better to put
it through the tubes because they are easier to clean. With
single pass units be sure the shell inlet is on the same end
as the tube side outlet. In two pass units, the shell inlet
should be at the inlet-outlet bonnet end. It is customary for
the cooling medium to enter the lower bonnet connection,
although this can be reversed if necessary.
b. As a heater, the hot medium, usually steam or hot water,
must be in the shell. If it is steam, either of the shell connections, or both, can be used, dependent on the actual
entering velocities.
c. For the above applications and for temperatures above
150°F, the higher temperature fluid should be circulated
through the shell side of the exchanger and precaution
should
be taken to avoid shock from abrupt changes in
fluid circulation temperatures.
13. Steam hammer can cause serious damage to the tubes of any
heat exchanger. A careful consideration of the following points
before an installation is made can prevent costly repairs which
may be caused by steam hammer.
a. A vacuum breaker and/or vent, should be used in accord-
ance with the type of steam system installed.
b. The proper trap for the steam system installed should be
used.
c. The trap and the condensate return line to the trap should
be properly sized for the total capacity of the convertor.
d. The trap should be sized for the pressure at the trap, not
the inlet pressure to the steam controller.
e. The trap must drain into an unpressurized condensate re-
turn system. Condensate return lines must not be run at an
elevation above the bottom of the heat exchanger. To do so
may result in a buildup of the condensate level in the heat
exchanger, which could cause water hammer and damaged
tubes.
CAUTION:
expansion can occur. We recommend the installation
of a properly sized relief valve on both sides of the heat
exchanger.
During times of shutdown, volumetric
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 introduced 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:
unit. Failure to do so can cause damage to the heat
exchanger.
Fluids must be gradually introduced to the
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3. In shutting down, flow of hot medium should be shut off first.
If it is necessary to stop circulation of cooling medium the circulation 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.
5. 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.
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, condensate 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.
WARNING: The CHX and CHXS exchangers are suit
able for use as heaters using steam as the heating
medium. These exchangers are, however, fixed tubesheet
units and, therefore, not designed to absorb thermal shock
inherent in the intermittant service of on and off heating
with frequent short intervals of demand. Their recommended use is where service is continuous or steady, with
relatively long periods between shutdown and start-up.
Heat exchanger failure due to thermal shock may result in
potential personal injury.
MAINTENANCE
1. Do not open heads until all pressure is off equipment and the
unit is drained.
6. 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.
e. The exterior or shell side of the tubes of a fixed sheet heat
exchanger can only be cleaned chemically by using a
chemical dissolved in water solution. We suggest that the
user contact the manufacturer of the cleaning chemical for
instructions.
WARNING:
Care must be exercised when handling
certain fluids. Follow manufacturers instructions. Use
eye and skin protection. Wear a respirator when required.
2. Remove the bonnets. Inspect all tubes carefully for possible
erosion, corrosion, or foreign material.
3. Inspect all anodes to be sure they are neither excessively corroded nor insulated with scale. Scrape to a bright surface.
4. Inspect filters in the system to prevent foreign matter from
entering the exchanger.
7. When replacing heads, use a torque wrench.* Tighten 1/4"
diameter bolts (2” diameter units) to 6 ft-lbs.,
bolts (3" & 4" diameter units) to 16 ft-lbs., and
5
/16" diameter
3
/8" diameter
bolts (5", 6", & 8" diameter units) to 24 ft-lbs. If the gasket joint
still leaks, tighten in 2 ft-lb. increments until leak stops.
*The above torque values apply to well lubricated nut bearing
*surfaces.
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8. All bolted joints should be tightened uniformly and in a diametrically staggered pattern as illustrated below:
START
1
6
9
14
16
11
8
3
10. Exchangers subject to fouling or scaling should be cleaned
periodically. A light sludge or scale coating on the tube greatly
reduces its effectiveness. Therefore, low-fouling fluids should
be used in the shell side of all heat exchangers with nonremovable tube bundles. A marked increase in pressure drop
and/or reduction in performance usually indicates cleaning is
necessary, especially if the unit has been checked for air or
vapor binding and this has been found not to be the cause.
Since the difficulty of cleaning increases rapidly as the scale
thickens or deposits increase, the interval between cleanings
should not be excessive.
4
7
12
2
15
13
10
5
9. Frequently and at regular intervals, observe interior and exterior 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.
FRONT HEAD GASKET
FRONT HEAD
(BUNDLE&SHELL ASSEMBLY)
ANODES
1. Some exchangers may be equipped with renewable anodes.
The purpose of the anodes is to inhibit electrolytic corrosion.
In order to remain active the anodes must be kept free of scale
or other surfaces coatings.
2. On some applications where electrolytic corrosion is not a
problem, pipe plugs may be substituted for the anode. The
pipe plug material selected should be softer than the base
part to avoid pipe thread damage.
CORE
REAR HEAD
RENEWABLE ANODES
(ZINC)
For further information, contact Bell & Gossett Heat Transfer Products, 175 Standard Parkway, Cheektowaga, NY 14227,
Phone (716) 862-4171 — Facsimile (716) 862-4176.
PRINTED IN U.S.A. 6-95
REAR HEAD GASKET
MOUNTING LEGS
Bell & Gossett
Morton Grove, IL, U.S.A.
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