World Leaders in Ultra-Pure Heating
Revision 10
www.heateflex.com
01/17/13
405 E. Santa Clara St.
Arcadia, CA 91006-7218
Tel: (626) 599-8566 Fax: (626) 599-9567
At this point the manual inlet/outlet valves can be reopened and D.I. water flushed through the
unit until the effluent water quality meets the user‟s qualification specifications. Note that
there is also a zero dead leg valve on the right side of the unit, which can be used to direct the
water passing through the unit to drain rather than through the normal outlet of the unit.
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6.2 Initial Heat-Up
Before introducing steam and heating up the unit, make sure that the unit will always "see" a
minimum of 20 psig in D.I. water supply line pressure at all flows which are to be used. This
requirement is based on two factors. First, since the shellside pressure in the exchanger is
approximately 15 psig there would never be reverse flow of "dirty" or contaminated steam into
the process if a tube in the exchanger develops a leak. Second, since the temperature of the
water in the exchanger can reach 120°C the D.I. water will begin to boil if a minimum D.I.
water pressure of 15 psig is not present. This means any throttling valves to control flow
through the unit should be downstream of the unit rather than upstream. The maximum D.I.
water pressure should be limited to 60 psig which is based on the working pressure rating of
the PVDF piping.
Please note that a loss of D.I. water supply line pressure will not harm the unit in any way, and
in fact, the unit can be run dry with no effect. For example, if a unit is to be taken out of
service for time, the process side of the unit can be "drained and dried" by simply draining the
external piping and boiling out all of the water in the exchanger. This can be followed by a
CDA or nitrogen purge. The CDA or nitrogen will also be heated as it passes through the
exchanger to evaporate the last residual water left in the external piping. Also, note that the
Auto-Isolation System will attempt to close the isolation valves when the D.I. water pressure
falls below the Low Process Pressure alarm set point, so the isolation valves will have to be set
to “Flow” or opened manually.
Once the unit is fully facilitated as described in the previous section, return the pneumatic
isolation valves and the cold bypass valve to their normal, non-energized position, closed for
the isolation valves and open for the cold bypass valve. Again, check that the manual isolation
valves on the heads are fully open, and that the manual inlet/outlet valves are fully open. The
manual outlet valve can be throttled down to minimize the flow of D.I. water through the unit,
or alternatively the outlet valve can be closed and the zero-dead leg valve on the right side of
the unit can be opened if flow is to be directed to other than the process distribution piping at
this time.
Check the pressure gauge on the small air regulator on the inside of the electrical enclosure to
see that there is a minimum of 60 psig and adjust as necessary to a range of 60 to 70 psig. This
air is used to activate the pneumatic valves on the unit.
At this point remember that almost any unplanned event during the next steps can be
immediately remedied by depressing the EMO switch, which will close the pneumatic steam
