TH-750-IMI-REV-
5
11
22. Examine the heat exchanger coil for scale buildup and signs of leakage. If no leakage is
detected, carefully clean any excess scale from the coils and prepare the heat exchanger coil
for installation. If leakage is detected between the coils and water in the tank, either repair
the leaking coil(s) or replace the heat exchanger coil.
23. Remove the old gaskets and completely clean the mating surfaces. Install the two (2) new
gaskets: one (1) between the tube face of the coil and the flange welded to the tank, and one
(1) gasket with a divider to fit between the heat and the tube sheet.
24. Carefully insert the heat exchanger coil into the tank. The coil should be installed so that the
divider in the head lines up with the coil, and that the divider is parallel to the horizon.
25. After assuring that the heat exchanger unit is correctly aligned, clamp the flanges together
and proceed with the torque procedures detailed below.
Note: Bolts used to secure the heat exchanger unit in the TH-750V Heaters are rated
as B7. Grade B7 bolts are designated by B7 on the head.
a. Lubricate the bolt threads and the nut faces with a suitable lubricant.
b. Insert the bolts through the flanges, and then start and finger tighten the nuts.
c. Number all bolts so that torque requirements can be followed.
d. Apply torque in
three steps of 60%, 80% then 100%
of required final torque, loading all bolts at
each step before proceeding to the next step.
Note: Appendix A contains tables listing ANSI approved target torques for Grade B7
bolts. The correct target torque can be determined by the nominal pipe
size, number and grade of bolts used to secure the flange, and the size of the bolt
used. Be sure of the bolt grade used in the unit.
When replacing bolts, be sure to use the same type of bolt and corresponding nuts. Grade
B7 bolts can be used in all cases.
e. Tighten bolts in the applicable sequential order (0º- 180°, 90°- 270°, 45°- 225°, 135°-315°
etc.) at each step until final target torque is reached (see applicable diagram contained in
Appendix A).
f. Use rotational tightening until all bolts are stable at final torque level. Two (2) complete
times around is usually required.
Note: Appendix A contains drawings depicting the typical flange configurations
(number of bolts, location, tightening sequence, etc.) for the TH-750 Heater. Reference
the applicable drawing for the unit being serviced.
26. Reconnect the energy source inlet and outlet lines to the heat exchanger coil. If these lines
were broken at an additional location to allow for removal of the coil, be sure to also tighten
those connections. Follow recommendations contained in the manufacturer’s documentation,
