Elbow Patch

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 exceptions: 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. 2-19 Figure 2-28.—Severed pipe patch.