Substitution of Cotton and Hemp for Linen Yarns in Unlined Hose
Manufacturers of fire-protective appliances, like those engaged in almost every other industry, are feeling the need of substitutes for materials which were formerly supplied through such well-regulated channels that the possibility of an interruption of the supply was given little, if any, thought. Among the materials the supply of which is now restricted, which were supposed to be necessary in the manufacture of fire protection appliances, linen yarn is included. Statistics compiled by the raw materials section of the British War Office show that Russia produced 80 per cent, France and Belgium 10 per cent, Germany and Austria 6 per cent, Ireland 2 per cent and Holland 2 per cent of the flax required for the manufacture of yarn, from which it will be seen that the recent refusal of Great Britain to export any of this material to this country cuts off the entire supply. The stock at present in possession of Great Britain is being held for essential war purposes, such as the manufacture of fabrics for aeroplanes. Tests and investigations have recently been conducted at Underwriters’ Laboratories to determine to what extent, if at all, cotton and hemp yarn and tow may be substituted for linen yarn in the manufacture of unlined fire hose with a view to increasing the quantity of hose obtainable from such stocks of linen yarn as may be available. Hydrostatic pressure in tests in accordance with the established standards were made on samples of 1 1/2-inch, 2-inch and 2 1/2-inch hose supplied by different manufacturers. An examination of the samples showed that the filler strands were manufactured from cotton yarn and that these strands composed approximately 30 to 40 per cent of the weight of the completed hose, the percentage varying in samples of different manufacture. The test data indicated that, so far as the bursting strength values were concerned, cotton yarn could be substituted for linen yarn for the filler or woof strands of the circular woven construction. Micro-photographs were taken of the fibers of yarn for identification purposes. The leakage tests showed a leakage slightly in excess of that prescribed for the best quality linen yarn, but this was not considered to be of enough importance to constitute an objection to the intended use of the material, the amount of leakage not being sufficient to cause undue loss in the working pressure of a fire hose stream. Careful examination of fabrics built up of cotton filler threads and linen yarn warp threads disclosed no ground for believing that water friction losses will materially differ from those regularly obtained with unlined linen hose. Subsequent to the above-mentioned investigations, samples composed of various percentages of cotton, ranging from 54 to 100 per cent of the total weight of the hose, were tested, and the conclusion was reached that, owing to excessive leakage, certain constructions could not be considered as acceptable substitutes for unlined linen hose. The following are the constructions which were deemed unacceptable on the ground that working pressures would be seriously reduced by leakage if they were used:—
- A construction employing 100 per cent cotton yarn substituted for linen yarn.
- A construction employing any percentage of mixture of cotton or linen yarn in the twisted strands for warp or woof members.
- A construction employing cotton yarn for the warp members.
Hydrostatic tests have also been made on unlined hose made exclusively of hemp yarn, and it appears from the investigations so far made on hose of this character that if hemp yarn in necessary quantities and of suitable quality can be secured from spinners, without drawing upon supplies of this material necessary for other essential uses, it may be possible to accept, for the period of the present emergency at least, unlined hose made of hemp yarn in lieu of the unlined linen hose previously specified for use at standpipes and elsewhere in buildings.