Document NEa56rOb067Nd7KEv3g9erN3y

I I were agam encourages :c ciscontmue :ms crsettee. In April, 1975, ::e responded tc a notice in the March 19, 1975, and c a need recordkeeping retention twenty years. Aral _-.e tester dated rn.three years .to The Guideline allows the use of asbestos containing materials order carefully controlled conditions where acceptable substitutes are net available. Ey definition we did not have acceptable substitutes for Marinite cr A Cloth when the Guideline was issued and this office was charged with developing acceptable substitutes for these materials. Therefore, even though our goal has been not to use or work with asbestos ir. the future, we have had to accept these two materials. In September, 1576, you received a letter recommending the use of Marinate XI. a Johns Manviile developed product, which was asbestos free. This product had been tested by the Engineering Department and several of cur plants and was found to be fully acceptable as a replacement for asbestos containing .Marmite. Thus, the only asbestos containing material which we do net have an acceptable substitute for is A Cloth and the attached Guidelines are changed tc reflect this. Cur efforts to eliminate A Cloth have been direected a: replacing it with fiberglass. Two major problems must be dealt with in this approach: 1. The attack Of the ccmm.cn sodium silicate adhesives cr. :he fiber glass cloth at elevated temperatures. 2. The deterioration in structural strength and Increased friability of the calcium silicate Insulation due to the reels cement c: the asbestos binding fibers with nonasbestos fibers. The first of these two problems have been largely overcome by the use -- of a proprietary product originally called ''Tortaring", r.cw called "Cover rard1'.~*b in certain applications. This product is a fiberglass clcth with a rewettable ........ adhesive already applied to it. The adhesive is an inorganic proprietary substance. This material has been used and is recommended for use in locations net sub jected to moisture, elevated temperature, abuse or occasional removairi * j.-iY- Ih locations subject to moisture, elevated temperature, abuse or^ Ivj^. occasional removal, we consider calcium silicate with A Clcth severleg tk > t acceptable a: this time. In these locations, our etneidate for elimination of A. Cloth'is an -Insulation system (called soft blankets) consictltg cf a fiber class DUP 0903948 i i