TM 1-1500-204-23-11
technical data exists, use a minimum of 20
the repair. When damage is through both
inches of mercury (Hg) vacuum. Leak rate
skins, a vacuum bag is required on both
of less than 1 in Hg per minute should be
sides of the part. Table 6-3 provides a con-
maintained; if not, air will be introduced to
version chart between inches of Hg and psi.
Vacuum Pressure Conversion Chart
Inches of Hg
PSI
10
4.9
12
5.9
14
6.9
16
7.9
18
8.8
20
9.8
22
10.8
Convert inches of Hg to psi by multiplying by 0.49116.
Convert psi to inches Hg by multiplying by 2.036.
c. Single Side Vacuum Bag Procedure. The fol-
(a) Before beginning a repair process, per-
lowing steps explain how to construct a vacuum bag
form a heat survey according to para-
on the repair side of the part. This is the most com-
graph 6-18g if required.
monly used vacuum-bagging procedure. The vacuum
bag should be prepared/set-up prior to mixing resin.
This procedure only addresses the bleed system. The
bleed system is used when excess resin is present
To achieve the desired resin-to iber ratio,
in the wet layup; the excess resin is bled off during
you must use the type of porous release ilm
the repair resulting in the correct resin-to-iber ratio
(size and spacing of perforations), type of
in the inished repair. Consult the system speciic
bleeders, and number of bleeders speciied
technical manual for procedures for a no bleed or net
in the system speciic technical manual or
resin system when the pre-preg contains the correct
repair disposition; these vary depending on
resin to iber ration desired in the inished repair.
the repair fabric, resin, and number of plies.
(1) Facilities, Equipment and Materials. The
(b) Connect thermocouples to the heat con-
following items are required to perform Single Side
troller and check for proper operation
Vacuum Bag procedures: Vacuum source (venturi
before placing on the part. Thermo-
or vacuum pump), Vacuum hoses, Vacuum port,
couple readings should approximate the
Vacuum gage, Self-vacuum ittings, Caul plate (if
ambient air temperature. If the thermo-
used), Temperature/Vacuum controller, Heat blanket
couple reading does not, replace ther-
(if used), Thermocouples, Scissors, Utility Knife, Peel
mocouple.
ply, Non-porous release ilm, Porous release ilm,
Bleeder plies, Breather cloth, Bagging ilm, Vacuum
bag sealant tape, Flash breaker tape
Failure to electrically insulate the thermocou-
(2) Procedures. After the repair plies are in
ples by placing lash break tape under them
place, use the following procedures. Minor variations
may result in a condition known as "cross-talk"
to these procedures are acceptable as long as the
and prevent the hot bonder-controller from
intent is met. To achieve the desired resin-to-iber
functioning properly.
ratio, you must use the type of porous release ilm (size
and spacing of perforations), type of bleeders, and
(c) Attach a minimum of three thermocou-
number of bleeders speciied in the system speciic
ples with lash breaker tape no further
technical manual or repair disposition; these vary
than inch from the patch border.
depending on the repair fabric, resin, and number of
Leave some slack in the wires inside
plies. Refer to igure 6-30.
the vacuum bag area as they have a
