The purpose of the following list is to call
attention to a number of basic requirements associated with
the design and proper operation of a heat recovery system.
The list is not all-inclusive and is offered as a guide to
satisfactory heat recovery installation.
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The outer shell of the heat recovery unit must be
insulated to minimize loss of heat to the surroundings
and for personnel protection. Two inches of
calcium silicate insulation is a minimum. The
insulation can be supplied with the unit or applied at
the job site. Potential shipping and handling
damage favor application at the job site.
-
Flexible metal tubing should be used to connect the
exhaust gas piping to the heat recovery unit to minimize
forces and moments on the nozzle connections.
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Water treatment is of major importance in assuring long
life and minimum maintenance of a heat recovery system.
Due to the varying water conditions from one location to
another, it is not possible to give specific water
treatment procedures. It is recommended that a local,
reputable water treatment firm be contacted for
treatment recommendations.
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A safety valve must be installed to protect the heat
recovery unit from excessive pressure. The valve
must be sized to relieve the output of the unit when
operated at its maximum capacity.
-
A steam back pressure valve must always be installed on
an ebullient cooled engine system to protect the engine
from overheating.
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On natural circulation steam systems, the separator must
be installed above the heat recovery unit.
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A low point drain should be provided in the exhaust
piping near the engine to allow removal of water and
condensate before it can enter the engine. Installation
of a counterbalanced flapper type rain cap is also
recommended to aid in preventing the entrance of water
into the exhaust system.
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Locate the heat recovery unit as close to the engine as
possible to minimize heat loss and prevent shock waves
from developing in the exhaust pipe.
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Pipe the exhaust to a point where the exhaust gas can
discharge harmlessly.
-
Design the total exhaust system so that the pressure
drop is less than the back pressure allowed by the
engine manufacturer.
-
With a hot water system in which the engine jacket is in
series with the heat recovery unit, remove the engine
thermostat and bypass circuit. In its place, install a
temperature controlled valve and bypass circuit
downstream of the heat recovery unit. Make sure any
modification is acceptable to the engine manufacturer.
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Pneumatic controllers require a 20 psig dry air supply.
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Exhaust gas diverter actuators require a 100 psig
minimum air supply.
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Make sure equipment and materials are compatible with
the fluid and rated for the design pressure and
temperature.
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High point vents should be provided in the system to
allow removal of air.
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Support piping independently of the heat recovery unit.
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Insulation on piping and components handling combustible
heat transfer fluids can present a potential fire
hazard. Make provisions to prevent fluid from entering
the insulation in the event of leakage.
-
If an exhaust gas bypass valve is used for capacity
control, make provisions to prevent exhaust gas leakage
into an idle heat recovery unit.
