134 



THE INDIA RUBBER WORLD 



[December 1, 1918. 



U. S. NAVY DEPARTMENT SPECIFICATIONS 



FOR INSPECTION OF RUBBER MATERIAL. 



GENERAL SPECIFICATIONS. 



1. "General Specifications for Inspection of Material," issued 

 by the Navy Department, in efYect at date of opening of bids, 

 shall form part of these specifications. 



TEMPERATURE OF TESTING ROOM. 



2. All tests of the rubber parts shall be made in a room, 

 the temperature of which is not below 65 degrees F., nor above 

 90 degrees F. No tests shall be made until 48 hours after vul- 

 canization. 



APPARATUS FOR TESTS. 



3. A standard testing table suitable for the purpose shall be 

 used. 



TESTS OF ADHESION OF RUBBER PARTS TO COTTON OR 



FABRIC PARTS. 



PKEPARATIOK OF TEST PIECE. 



4. In making the test, a section of the article shall be cut 

 as follows : 



(a) In testing hose the section shall be cut transversely, 

 unless the diameter of the hose is too small to be practical for 

 this test, in which case it shall be cut longitudinally. 



(b) When testing belting, packing, or gasket material, it 

 may be cut in any direction. 



(c) When testing rubber-lined cotton hose the test piece 

 shall be prepared by cutting directly through the section, so as 

 to lay out upon the table a piece measuring the full length of 

 the circumference of the hose and 2 inches in width. On this 

 piece two parallel cuts V/z inches apart shall be made by cutting 

 through the lining only and not injuring the cotton cover. This 

 strip shall be started at one end to the extent of about VA 

 inches. The cotton cover only shall be fastened in the clamps. 



(d) When testing a fabric-plied hose the section shall be 

 one inch in width. The piece shall be separated until the part 

 next to the rubber cover shall be loosened. The section shall 

 then be placed on a mandrel whose diameter is the same as 

 that of the inside of the hose to be tested. 



(e) When testing packing the piece shall be prepared as in 

 the case of rubber-lined cotton hose, unless the thickness of 

 rubber is greater than Vs inch, in which case the piece shall be 

 prepared in such a way that the rubber part may be clamped 

 at the top and held immovable while the weight, as described 

 below, is clamped to the fabric. 



(f) When testing belting the test strip shall consist of two 

 plies of fabric only, one ply being held in the stationary grip, 

 with weight suspended freely from the other ply. 



(g) Square Tuck's packing shall be tested in the same man- 

 ner as is specified for testing the friction between the plies of 

 a belt. 



(h) The friction in round Tuck's packing shall be tested 

 by the same method as is used in fabric-plied hose, the core 

 being drilled out to permit the insertion of a mandrel. When- 

 ever the core is 3/16 inch or less in diameter it shall be tested 

 in its original shape. When it is over 3/16 inch in diameter a 

 piece six inches long shall be separated from the fabric and cut 

 and buffed on four opposite sides to form a square section Ys 

 by H inch in the center of the test piece. The i/^-inch square 

 shall be at least one inch in length. 



(i) In testing the friction of belting the load should be ap- 

 plied at right angles to the plane of separation, or the test strip 

 should consist of only two plies of fabric, one ply being held in 

 the stationary grip with the weight suspended freely from the 

 other ply. By this means the efifect of the thickness of the belt 

 may be eliminated. 



PERFORMANCE OF TESTS. 



5. Having thus fastened the test piece, the clamp ring shall 

 be slipped upon the mandrel, or, in the case of fabric-plied hose. 



the test piece shall be slipped upon the mandrel. The free- 

 moving clamp shall be tightly fastened to the free end and the 

 weight supported upon a movable table hooked over tlie hook 

 in the clamp. Tlie weight and the clamp together shall be 

 exactly equal to the weight called for in the spccilications. 



The weight then supported by the movable table of the test- 

 ing machine shall be lowered until the clamp and free end of 

 the hose are just taut. An indelible pencil mark shall be placed 

 upon the separating layers of the test piece, and by quickly 

 loosening the thumb screw supporting the table it shall 4)e al- 

 lowed to fall, leaving the weight freely suspended. In every 

 case this shall be done without a jerk. The time sliall be read 

 at the moment of freeing the weight and at the moment of re- 

 marking. The weight shall be allowed to act upon the test 

 piece for ten minutes, at the end of which time an indelible 

 pencil mark shall be placed again upon the separating layers 

 of the test piece. The movable table shall then be brought 

 up to hold the weight, the test piece removed and hiid upon the 

 table, and the distance between the pencil marks shall be meas- 

 ured by means of a certified rule accurately graduated in deci- 

 mals of an inch. The distance between the marks shall be 

 recorded as the number of inches of separation in ten miiuUes. 

 from which shall be computed the rate in inches per niiiuite. 



TESTS OF RUBBER PARTS. 

 PREPAEATION OF TEST PIECE. 



6. (a) For hose, a section one inch in width shall he cut. Toi 

 belting, packing, and sheet gaskets a piece one inch in widtli and 

 six inches in length shall be cut in any direction. The rubber 

 parts shall be carefully separated from the fabric of this piece, 

 using benzine in small amount if necessary. The benzine used 

 in this case shall always be 76 degrees Baume, free from oil. 



(b) In case of articles to be tested, such as washers, fer- 

 rules, and molded gaskets, which are of such peculiar shape 

 that the above methods do not apply, small sample pieces shall 

 be sent with each delivery. These sample pieces shall be eighl 

 inches in length, IH inches in width, and % inch in thickness. 

 unless otherwise specified. These sample pieces shall be guar- 

 anteed by the manufacturer to represent truly the average com- 

 position and cure of the article delivered. Test pieces shall 

 be cut from these samples as described below. 



(c) From these one-inch sections, or from sample pieces thus 

 prepared, a test piece shall be cut by a die. The dimensions 

 of the test piece shall be indicated in each specification. It is 

 tlie intention to have the cross-section area at the constricted 

 part approximately 1/32 square inch. The backing or cloth 

 impression shall be removed from the test piece by buffing for 

 determining the cross-section area. The test specimen shall be 

 buffed on a machine such as is made by the Emerson Machine 

 Co., of Boston, or its equivalent. 



(d) No test shall be performed until the piece has been al- 

 lowed to stand for one hour after removal from the article, if 

 it has in any way been in contact with benzine. 



TESTING MACHINE. 



7. (a) The jaws shall tighten automatically and exert a 

 pressure proportionate to the applied tension. The rate of 

 speed of separation of the jaws shall be uniformly 20 inches 

 per minute. The jaw shall exert a uniform pressure across the 

 width of the test piece, regardless of any variation in the thick- 

 ness of the rubber. 



(b) The test machine shall be suitable to carry out the 

 necessary tests, and shall be standardized in accordance with 

 the latest approved designs so far as practicable. 

 MAKING THE MEASUREMENTS. 



8. (a) Taking of Time. — All measurements of time shall 

 be taken by means of a stop watch. The fundamental methods 

 of testing are so made throughout the entire rubber specifica- 

 tions that the following procedure shall be uniform: After 



