Patent Publication Number: US-8540072-B2

Title: Packaging system for detonating cords for X-ray examination and safe shipping

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of application Ser. No. 10/554,245, filed Oct. 25, 2005, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to packaging for a detonating cord and a method of examining a detonating cord in its packaging. 
     Detonating cords are used to fire shaped charge perforators in perforating guns in the oil and natural gas industry. To ensure error-free initiation of charges, a defect-free detonating cord is needed. Incomplete detonation caused by inadequate filling of the detonating cord with explosive material may in particular lead to costly delays. 
     To enable these detonating cords to be shipped by sea, land or air, special packaging is required, the requirements for which are regulated by law. Packaging is described, for example in EP 0 382 615 BI, U.S. Pat. Nos. 4,586,602 or 4,817,787. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is to provide packaging for detonating cords which meets legal requirements and to provide a method with which the detonating cord may be examined in its packaging for defects. 
     The method according to the invention is distinguished in that the detonating cord is subjected to X-ray examination in its packaging prior to shipping. An X-ray examination makes it easy to detect defects caused for example by inadequate filling with explosive material. 
     Packaging according to the invention is characterised in that the detonating cord is wound in a single plane as a flat spiral. 
     In an advantageous embodiment, the individual laps of the spiral are spaced from one another. The space is preferably filled with air or material, e.g. by spacers or by a spacing cord extending in parallel, wherein the thickness of the spacing cord corresponds to the necessary space. 
     The space between the laps ensures that, in the event of misfiring of the detonating cord, the adjacent lap is destroyed without crossover firing. Crossover firing means that the adjacent lap is ignited and the ignition process passed on to the remaining laps. 
     Advantageously, the last lap is passed perpendicularly over the flat-wound spiral. 
     In a preferred embodiment, the base plate of the packing consists of paperboard, wood or polystyrene. 
     The detonating cord is preferably sealed in a vacuum bag, which is attached to the base plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below with reference to two Figures. 
         FIG. 1  shows an X-ray image of a spiral detonating cord in its packaging. 
         FIG. 2  shows a packaging system according to the invention for a detonating cord. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  shows a packaging system according to the invention for a detonating cord  1 . The detonating cord  1  is wound as a flat spiral, the two ends being provided with an end cap  4 . The base plate  2  of the packaging may consist, for example, of paperboard, wood or polystyrene. In the embodiment illustrated here, the detonating cord  1  is attached to the base plate  2  via a vacuum bag  3 . This means that the detonating cord  1  is sealed in a plastics bag, which is in turn attached to the base plate  2 . One lap of detonating cord  1  is passed perpendicularly over the flat-wound spiral. 
     Adhesive strips  5  adhering in the shape of a cross to  30  the detonating cord  1  serve to fix the detonating cord  1  prior to sealing in the vacuum bag  3 . The individual laps of the spirally wound detonating cord  1  are arranged at a given spacing from one another, so that, in the event of misfiring of the detonating cord  1 , the adjacent lap is destroyed without crossover firing taking place. Crossover firing means that the adjacent lap is ignited and the ignition process passed on to the remaining laps. In  FIG. 2 , the space is produced by a spacing cord  8  extending in parallel. 
     Reference numeral  6  indicates the image area of an X-ray installation, wherein the entire detonating cord  1  is advantageously X-rayed at once. The X-ray image is preferably taken at a right angle to the plane of the spiral detonating cord. If a booster is connected to the detonating cord  1 , the wad gaps between booster and detonating cord  1  may likewise be inspected by X-ray image. 
       FIG. 1  shows such an X-ray image of the spiral detonating cord  1  in its packaging. In this illustrated instance, the detonating cord  1  contains defects  7 , however, which would lead to failure of the detonating cord  1 . This defective detonating cord  1  would therefore not be shipped.