International and National Standards for Large Synthetic-Fiber Ropes

ABSTRACT Standards for large synthetic-fiber ropes are published by various national and international organizations. There are significant differences among these standards with respect to minimum breaking strengths, unit weights, and also test methods. With few exceptions, the strengths specified are considerably less than can be achieved in modern ropes of good quality. The rope purchaser may need to go beyond the standards to obtain top quality ropes with high strength and long service life. INTRODUCTION Large synthetic-fiber ropes are used for mooring tankers and other vessels, for towing, and for lifting operations. The safety of a vessel or the success of an operation frequently hangs on a rope. The engineer who specifies the rope or the buyer who purchases it may be assured by the rope manufacturer that "it is made to standards", but the critical question should be "made to what standards?" There are many national and international standards for ropes. Most standards specify only minimum dry breaking strength and unit weight forrope sizes. The methods of determining rope strength and weight are usually covered in separate test standards. There are differences among the various standards as to these strengths, weights, and test methods. Ropes which appear to be essentially identical can have significantly different performance characteristics. Purchasers who buy on price alone may receive substandard rope. Specifying and enforcing rope standards will assure ropes of at least a minimum quality. To obtain high performance ropes, the purchases must go beyond the ususal standards and comparing rope properties. The new OCIMF Hawser Guidelines provide standardized rope prototype test methods to permit comparisons, and also provide procedures to assure the quality of the rope product is the same as that of the test prototype. This paper will discuss the major rope standards and the major differences among them. BACKGROUND Table 1 lists the principal standards for large synthetic-fiber ropes and the types of ropes to which they apply. Also shown are the various standards covering test methods. Not shown in this table are the new OCIMF guidelines, which apply to all types of rope. Complete titles of the standards are given in the Bibliography at the end of this paper. Most standards for synthetic-fiber ropes were originally drafted in the 1960s and early 1970s, when the various man-made fibers were widely adopted for rope making, but before their full potential in rope making was realized. The specified strengths reflected the typical properties obtainable with the materials and production methods common at that time. Some standards specify rope-making details, such as lay length and arrangement of strands, which may not necessarily result in the best rope for a particular purpose today. Committees of the British Standards Institute, the West German Deutsche Institut fur Normung (DIN), and the International Standards Organization (ISO) worked in close cooperation as these rope standards were originally drafted in the late 1960s. Thus these standards are generally similar or identical. The West German Defense Ministry conducted a series of break tests on various types of ropes in the mid 1960s.