Original Date: 02/28/2000
Revision Date: 01/18/2007

Crane Army Ammunition Activity manufactured a small quantity of demolition line charges and experienced a 30% failure rate due to damaged explosive pellets. A review of the first production run revealed that excessive force was being exerted as the pellets were forced through the cylindrical hose used to encase the charges. The Activity now uses the existing clamping fixture to hold the hose in place, and then cap both ends and apply enough air pressure to expand the hose beyond its original dimensional size.

Crane Army Ammunition Activity (CAAA) manufactured a small quantity of demolition line charges and experienced a 30% failure rate due to damaged explosive pellets. A review of the first production run revealed that excessive force was being exerted as the pellets were forced through the 25-foot long cylindrical hose used to encase the charges. One of the fault factors was the method in which the hose was being received from the supplier. It came in long rolls and during the course of storage and transport, the hose had become either flattened or crimped. After being pressed, the pellets were then inserted by hydraulic ram into one end of the hose. With the charge requiring 236 pellets, which were only 0.008" smaller in diameter than the receptive hose and were inserted through only one end, the combination of crimped hose and friction developed by travel distance, minimum clearance, and minor cohesion created damage to the pellets.

The solution to the problem chosen by CAAA was to use the existing clamping fixture to hold the hose in place and then cap both ends and apply enough air pressure to expand the hose slightly beyond its original dimensional size. With the hose under pressure, the pellets were then inserted through both ends of the hose using two air-driven rams. Elimination of friction by pressurizing the hose reduced pellet breakage. Also, an additional pellet holding fixture was added at both ends of the clamping fixture to accommodate one-half of the required number of pellets, so that as one charge hose was being loaded, a second charge was being prepped with pellets for insertion (Figure 3-2).

By the end of production, this change to the production line added an additional 100 units (45 to 145) per 10-hour shift at a cost savings of $400,000. Similarly, it reduced the failure rate from 30% to 0.1% resulting in higher quality product through reduced pellet breakage.

For more information see the Point of Contact for this survey.