MIL-DTL-17124F
ends. Record the distance between the timing start and end points (D). Secure a commercial
Number 6 blasting cap to the samples. For Type I samples, secure the blasting cap
approximately six (6) inches from the end using adhesive tape, so that it is almost completely
covered with tape except for the ends. For Type II samples, secure the blasting cap to the
detonating cord's square cut dry end using a butt joint; the end of the blasting cap shall be in
immediate contact with the detonating cord's explosive core. Initiate the blasting cap. Measure
μ
,
and record the detonation time in microseconds (T). Calculate the velocity of detonation as
,
,
follows:
Repeat for the remaining samples. The samples and lot shall be rejected if any of the detonating
cords do not exceed the minimum velocity of detonation requirement.
4.13 Propagation of detonation test (Type I). From each of the five (5) spools, cut a
sample approximately three (3) feet in length to be used as branch lines. From any one of the
spools, cut an additional twenty (20) foot length to be used as the main line. Starting
approximately six (6) inches from one end of the main line, attach each of the five branch lines
to the main line using a girth hitch, see Figure 1, at approximate three foot intervals. Ensure the
main line is straight and that the branch lines are at right angles to the main line. Secure a
commercial Number 6 blasting cap approximately six (6) inches from the end using adhesive
tape, so it is almost completely covered with tape except for the ends. Initiate the blasting cap.
The samples and lot shall be rejected if any of samples do not detonate completely.
FIGURE 1. Girth hitch.
4.14 Cut-off test (Type Ip). From each of the five (5) spools, cut at least twelve (12)
inches of detonating cord to be used as witness lines and at least twelve (12) feet of detonating
cord to be used as a donor. On a flat board, at least three (3) feet long and one (1) foot wide,
place a cardboard sheet to be used as a witness plate. Obtain the five (5) witness lines and
position them on parallel and at least six (6) inches from the neighboring line. Secure the
witness lines in position using adhesive tape. Wrap the donor around the board so the angles
between the donor and witness lines are no greater than fifteen (15) degrees. See Figure 2 for an
illustration of a test setup. Ensure there is intimate contact between the donor and acceptor at
each detonating cord intersection. Secure a commercial Number 6 blasting cap six (6) inches
from an end of the donor using adhesive tape, so it is almost completely covered with tape except
for the ends. Initiate the blasting cap. Verify complete detonation of the donor and that no
9
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