Water Leak Detectors.

摘要

1,184,603. Water-leak detecting coatings. ATOMIC ENERGY OF CANADA Ltd. 25 July, 1967 [29 July, 1966], No. 34058/67. Headings B2E and B2K. [Also in Divisions C3, C4 and Gl] An indicator for detecting water leaks comprises a strontium chromate/silver sulphate couple in a non-aqueous carrier. Water or steam causes a colour change from yellow to red as silver chromate forms. The indicator may be formulated as a flexible tape incorporating the couple, or as a paint for coating a non-porous substrate. The couple is compounded in a resin/solvent medium. Preferred tapes are of woven glass cloth. For use up to 250‹F a single tape is suitable, optionally with adhesive backing and a transparent cover of cellulose acetate or polyester, the resin/solvent medium being chosen from collodion, spar varnish, rosin and rosin esters, cellulose acetates or an alkyd, and a glycol ether, dioxane or mineral spirits; plasticisers such as camphor, dimethyl phthalate, ethyl acetate or triphenyl phosphate are preferably included, together with hydrogenated terphenyls, n-butanol or Carbitol to adjust the consistency. The "low temperature" tapes are alternatively made of linen, cotton, sisal, canvas, kraft paper, rayon, polyester, nylon, or foamed polyurethane. For use up to 550‹F double tapes having strontium chromate on one exterior face and silver sulphate on one interior face are suitable; the resin/solvent medium may be a silicone or polyfluorocarbon in dioxane or a glycol ether, containing consistency-improvers as before and the tapes may have adhesive tape attached at the ends or may incorporate embedded flexible metal wires to interlock the tapes. These "high temperature" tapes are alternatively of fibre glass, or woven or felted asbestos. The tapes are prepared by drawing through a tank of indicator composition between guide rollers, and drying. For use as a paint, the indicator is comnounded into compositions similar to those for tape use, and may be sprayed or painted on metal pining, cotton, fibre glass, paper, plastic or other metal substrates to detect the presence of water thereon. In Example (A) a glass fibre double tape for up to 550‹F use is treated on the outer tape with strontium chromate, a silicone resin and dioxane, and on the inner with silver sulphate and the same resin/solvent. In Example (B) a glass fibre tape for up to 250‹F use is treated with a composition containing strontium chromate, silver sulphate, collodion (4% solution of nitro-cellulose in ethanol and ethyl ether), camphor, dimethyl phthalate, nbutanol, ethyl acetate, and ethylene glycol monomethyl ether, and is given a transparent tape cover.