Coupler technology is generally applicable to straight runs of pipe, thereby restricting
repairs at junctions where a change in direction occurs. However, valves, fittings, etc., may
be bypassed or replaced using coupler technology. When replacing fittings such as Tees or
Elbows using couplers, thrust blocks must be installed on all comers and intersections to prevent
the coupler from pulling apart from the pipe, or the fitting from pulling apart from the coupler,
due to the internal pressure of the system. Figure 2-4 shows valve repair using couplers.
Couplers can be used as the sole repair material for pipe punctures; but, hardwall pipe
is required as a replacement for complete breaks. Replacement sections must also be hardwall
pipe, although the type of material used for replacement may vary. Pipe sections can be heavy
and cumbersome, particularly in the larger sixes. Generally, couplers only work for a given size
pipe, thereby requiring a stockpile of different sixes of couplers, and also a stockpile of different
sizes of replacement piping.
d. Design Criteria. Table 2-l lists temperature and pressure requirements used in the
selection of couplers. The amount of pressure that a coupler can contain will vary, based upon
the size of the coupler, the type and extent of damage, environmental conditions, and installation
workmanship. The temperature range of the couplers will vary, based upon the type of gasket
material used. Couplers specified in this publication, with the exception of steam applications,
provide a minimum pressure rating of 150 psi at a minimum temperature range of 0F to 150F.
Couplers specified for steam applications provide a minimum pressure rating of 150 psi at a
minimum temperature range of 0F to 600F.
TABLE 2-1. Temperature and Pressure Requirements
0 - 125
0 - 125
0 - 125
360 - 500
e. Desirability Criteria. The following criteria, used to define the desired features of
couplers, are based primarily on input from military personnel experienced in NCF utility
(1) The coupler should be of the "full circle" open-side type vs rigid slide-/push-
(2) The coupler should have no detached bolts; bolts should be part of coupler.
(3) The coupler gaskets should have a 5-year shelf life.
(4) the bolts on the coupler should use an adjustable wrench for tightening; Allen
wrenches are not required.