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ARTICLE KF-9SPECIAL FABRICATION REQUIREMENTS FOR

WIRE-WOUND VESSELS AND FRAMES

KF-900 SCOPE

The requirements of this Article apply specificallyto pressure vessels consisting of an inner cylindricalshell (or a number of concentric shells) prestressed bya surrounding winding. The end load is not carried bythe cylinder(s) or the winding. The winding consistsof a wire helically wound in pretension in a numberof turns and layers around the outside of the cylinder.These requirements also apply to additional frames usedto carry the load from the closures.

The rules of this Article shall be used as a supplementto or in lieu of applicable requirements given in ArticlesKF-1 through KF-7. When requirements of this Articlediffer from those of Articles KF-1 through KF-7, theyare specifically delineated.

KF-910 FABRICATION REQUIREMENTS

The general and special requirements stated in Arti-cles KF-1, KF-6, KF-7, and KF-8 shall be valid whenapplicable. The welding fabrication requirements statedin Articles KF-2 through KF-8 shall be replaced bythe requirements in KF-911.

KF-911 Welding Fabrication Requirements

Welds and repair welds are not permitted in partsthat are prestressed by wire winding and carry pressureloads. However, an exception is made for the weldedjoints that are necessary to lengthen the wire in orderto get an uninterrupted winding. The requirements forthese welded wire joints are stated in KF-912.

KF-912 Welded Wire Joints

When it is necessary to get a winding consisting ofan uninterrupted length of wire, butt welded joints maybe used to join wire lengths. The minimum distancebetween these joints shall not be less than 6,500 ft

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(1 982 m), and the average distance not less than 12,000ft (3 660 m). Welded joints are not permitted in theoutermost winding layer. The welded joint shall becarefully ground in order to get a smooth surface andthereby reestablish the original cross-section shape.

The Manufacturer shall measure the reduction instrength of welded wire joints obtained by his weldingprocedure. The wire force shall be reduced to a corres-ponding lower level for a minimum of two turns beforeand after the welded joint.

After welding and before proceeding with fabrication,each joint shall be subjected to a tensile stress levelof not less than two-thirds of the specified minimumtensile strength of the nonwelded wire. If the jointbreaks, the welding shall be repeated until the strengthrequirement specified above is fulfilled.

KF-913 Winding Procedure Requirements

Each wire-wound vessel shall be wound in accordancewith a detailed wire winding procedure. This procedureshall provide all details relevant to winding, includinga description of the winding machine and how tensileforce in the wire is applied, controlled, and measured.All winding shall be carried out in accordance withthis procedure.

The application of the winding onto the cylinder orthe frame shall be carried out in a special windingmachine equipped with devices that make it possibleto control and measure the tensile force used forapplying the wire. This force shall also be recordedon a diagram that shall be filed by the Manufacturer.The measuring devices shall be calibrated at least every6 months, or at any time there is reason to believethat the measuring devices are erroneous.

The winding procedure shall include a calculatedwire force (see KD-912) that shall be used for eachwinding layer. Measurements shall be made of thecompression at intervals specified in the program andthe results compared with the calculations. The measure-

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KF-913 PART KF — FABRICATION REQUIREMENTS KF-913

ments shall be made using methods that guarantee aresult with adequate accuracy. If differences are notedbetween specified and measured compression at thesecheckpoints and there is reason to presume that thespecified final compression will not be reached if theoriginal program is followed, a change may be madein the remaining program by increasing the specifiedwire force by not more than 10%. The final differencebetween originally specified and measured compressionshall not exceed 5%.

The wire end shall be properly locked to preventunwrapping.

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