Despatch S Type User Manual

Page 94

I-235 (9/03)

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LIFT DOOR TROUBLESHOOTING INFORMATION

Please Note: There can be a number of reasons or a combination of reasons for lift door and
oven front problems. They include: door not sealing, door or oven front warpage, and possibly
oven uniformity problems. One thing to keep in mind while you are investigating these potential
adjustments/fixes is to make sure that you only make one change at a time; both marking and
logging each change in case you have to go back to your original settings. If you make too many
changes at one time, you may find yourself not really knowing what fixed the problem, or worse
yet, only shifting or complicating the problem.

Following is a list of items to check out:

The first thing to check is the oven pressure. Many times you will find this is where the problem
originates, especially if you are having uniformity problems. It is easy to help your uniformity by
opening the fresh air in order to overcome outside air leakage, but this also pressurizes the oven
and, in some extreme cases, causes excessive outside oven skin temperatures and door
leakage, which can create door and oven front problems. To address this condition:

1.

Make sure the fresh air inlet(s) on the heating units/box(es) include a damper blade(s).

Fresh air damper should initially be closed. (Note: damper blade may be cutaway for
process requirements and/or safety requirements.)

Exhaust air damper should also initially be closed. (Note: damper blade may be cutaway for
process requirements and/or safety requirements.) Depending on the pressure drop in the
exhaust stack run, you may need to open the exhaust damper somewhat in order to create
a slight negative pressure in the oven. Positive/negative pressure can be realized/noted by
excessive outside oven skin temperatures, or air moving in or out around panel joints,
flashing joints or areas around the door perimeter. The simplest way to test oven pressure
is with a smoke test checking areas where leakage would be most evident. This can be
viewed on the outside of the oven watching the smoke being either pulled in or blown out
away from the areas tested.

Note: Oven should normally be set neutral to slightly negative for best door sealing
results.

Review door adjustment instructions, which are found in the "S" Oven Manual, provided
with the equipment. These instructions should have been followed prior to the initial heating
of the oven. Please review these Instructions before proceeding any further in order to
familiarize yourself with the door adjustment procedures.

Make sure door roller sleeves at each side of the door have been installed over each door
guide stub shaft that is welded on each side of the door.

Check door frame with a straight edge to make sure door frame is not crowned (full height
and width). Check both the right and left side and the top and bottom. Check the door in the
same fashion. Check when the oven is cold and also when oven is hot for comparison.