10. In emergencies, the liquid in the piping system
also may be used as an artificial cooling medium 15
minutes after kick-over. This is done by circulating the
liquid at very low pressure (not above 10 psi) through
the system for approximately 5 minutes. This procedure
generally reduces the time before full pressure can be
restored to the system by about 15 minutes.
The sketch shown in figure 2-25 illustrates the
relative positions of patch materials to one another.
This buildup in the patch during application must be
considered in initially determining the length of patch
to be applied.
Elbow Patch. The elbow patch shown in fig-
ure 2-27 is applied, using the same basic procedures
as the simple patch. However, note the following
1. The edges of the void cover are slit 2 to 3 inches
at each end to conform to the contour of the pipe. See
view B of figure 2-27.
2. After the impregnated woven roving cloth has
been wrapped around the pipe, use the gloved hand to
shape the cloth to the contour of the pipe.
3. Then apply the PVC film and tie it with the chalk
line as described for the simple pipe patch.
Severed Pipe Patch. The severed pipe patch
shown in figure 2-28 is also applied with the same
basic procedures as the simple pipe patch, but this
procedure too has some exceptions:
1. Where the gap exceeds 4-inches, thin sheet met-
al or other suitable materials may be used as a substitute
for the void cover in bridging the gap. The substitute
Figure 2-27.Elbow pipe patch.
Figure 2-28.Severed pipe patch.