W. G. Wright to J. D. Pennington of J. W. Roberts on the Health Hazard of the Limpet Asbestos Spray Process (1960)

A 16-page report dated October 17, 1960, to J. D. Pennington of J. W. Roberts Ltd., the Turner & Newall company that made and licensed the Limpet asbestos spray machine, on the airborne dust released when Limpet was sprayed. W. G. Wright and M. Edmondson did the work and S. Holmes approved it, using "the standard T.B.A. dust sampling apparatus" (a Casella thermal precipitator) from the routine dust surveys at Rochdale and Hindley Green. They measured about 5,000 particles per c.c. for the blue grade LB.3 and 2,000 for the white grade LW.25 in the spray booth at Horwich, 6,000 to 14,000 on board the liner "Empress of Canada" while she was on the stocks at the Vickers-Armstrong shipyard, Newcastle, and 140 to 520 for LW.25 at the new research laboratories of Pilkington Bros. at "Latham Park". The reduction from the spray machine's damping mechanism was "not statistically significant" and "disappointing", pre-damped fibre did no better, and the report doubted that its own sampler suited the work. Its tables label LW.25 "Amosite".

What it shows

The report sets out where the samples were taken, how they were counted and what the counts were:

• Horwich, J. W. Roberts' spray booth. Five samples on February 25, 1960, with LW.25, and five on the afternoon of August 10 with LB.3: spraying onto a wall and a ceiling or roof, five minutes after each, and spraying pre-damped fibre (Tables I and VII, pp. 6, 10).
• The "Empress of Canada". Twelve samples in duplicate on April 27, 1960, six of blue and six of white fibre, half with the machine's damping mechanism working and half without (Tables III and IV, pp. 7–8).
• Pilkington Bros.' new research laboratories at "Latham Park". Four samples in duplicate on the morning of August 10, two upstream and two downstream of the sprayer, in a strong draught (Tables V and VI, p. 9). Its tables head the LW.25 samples "Amosite (LW 25)".
• Portland cement. A size analysis of cement from a bag at the Rochdale works, for comparison (Table IX, p. 11).

Every sample was burned at 500°C to remove carbon and counted under a dark-ground microscope in six size bands from ½ to over 20 microns. Graphs of the size distributions follow on pp. 12–16. The report recommends trying settlement methods or the Hexhlet mass sampler before any further work (p. 2).

What the figures mean, set beside the dust limit of the day, is explained on the Sprayed Limpet Asbestos page.

About this copy

Plaintiff's Exhibit TN 3267, Bates AA00280–AA00295, with a court filing stamp on several pages. The report's reference list cites an earlier J. W. Roberts report, "'Limpet' Asbestos Spray Machines" by J. S. Evans, March 17, 1960, which is not in the Library. "Latham Park" is the report's spelling; Pilkington's research laboratories were at Lathom, Lancashire.

Related

• Armstrong Contracting and Supply Corporation: Sprayed "Limpet" Asbestos Machine Operating Instructions
• Union Carbide Chemicals Company: Thermal Insulation and Accessories Manual (1962), which lists the U.S. Limpet grades
• Label: "Limpet Mattresses" brass tag (J. W. Roberts Limited) (1944)
• Limpet (J. W. Roberts / Turner & Newall) in the products catalog