Document zbzbXkO0NyqRn91QYzg1x8Nbm

VN(2)/229 17th March, 1950 J.'/l. Roberts Limited "Limpet" Asbestos Spray Machines The object of this series of du3t estimations was to determine the health hazard arising from the use of the asbestos cement 3pray and to estimate the improvement obtained by the present modifications introduced by the firm. The work was carried out on the 4th of October, 1949. A room, in which no other process except the spraying of asbestos was carried out, was put at our disposal. This resulted in very clean slides from the thermal precipitator, only particles of asbestos and cement were obtained on the samples. The same area of ceiling was sprayed for each sample in the series. The operator stood on a working platform supported by trestles. For each run the sampling head of one thermal precipitator was strapped on the chest of the man operating the spray gun. For. each run except one a sample was taken at floor'level just below the working platform in order to get an idea of the-'risk to which other workers in the vicinity might be exposed. In' the;case of sample TP 102/744 the second sampling head was strapped on the chest.of the man who fed the dry asbestos to the pre-damping machine and'then fed the opening machine. : Of ... Each sample was incinerated for half an hour.before counting in order to destroy any carbonaceous dust which'might have been present. The sample was then counted on- the Vickers projection microscope using a 2 mm. apo. objective/and. xlO"compensating eye piece. Each sample showed a low concentration'of asbestos fibre relative to the amount of cement dust. The asbegtos. fibres could readily be distinguished from the cement dust, and in the stable of results attached, the count of asbestos fibres in particles per'cubic centimeter is given separately from the particles of cement per cubii centimet'er. ..A photograph of a typical sample is attached, this illustrates^hhe low'proportion of fibrous asbestos particles. Three main sets of conditions were tested: 1. The spraying of (dry asbestos cement. In this case the asbestos cement was opened by brushes and spiked roller in an opening machine and fed by compressed air to the gun. Round the circumference of the gun were four water sprays which impinged with the asbestos cement on the area of ceiling sprayed by asbestos. 2. The spraying of asbestos cement fed dry to the opening madhine . but damped during opening. In this case five sprays of water were applied to the asbestos"cement in the opening machine itself. This damped asbestos cement was fed to the gun and the four water sprays applied from the circumference as under (1). 3. Pre-damped asbestos was fed to the opening machine. The asbestos mixture was fed into a horizontal drum which was rotated and the asbestos was damped during rotation. This predamped asbestos was then fed into the opening machine and thence to the gun provided with four-spray nozzles. ,/^002-77 -2- RE5ULT3 1. Spraying dry asbestos cement Sample No. Position Dust Count Asbestos Cement Alter Incineration at 500C. TP.101/745 On Chest of man operating spray 483 11,866. TP.102/746 On Floor below scaffold 234 3,324 TP.101/747 On chest of man .. operating spray >- .364 6,602 Repeat of 101/745'? . after cleaning room yy . `''J/* { ' with fans, r'ty `"-V ' Median Site Asbestos 3.3/vi Cement 0.57/u. Asbestos 4.0/u Cement 0.64/u Asbestos 4i0/u Cement 0.56/u . ' . flit-: 2. Spraying asbestos cement damped during opening Sample iJo. //' ' .. Position \ ,v Dust Count Median Size . v5 ->/ . . . Asbestos Cement ' ' Alter Incineration - . at 500UC. TP. 101/739 On chest of man operating spray an 7 2,489 Asbestos 3.2/i Cement 0.6/u TP.102/740 On floor below scaffold 102 2,330 Asbestos 4.O/1 Cement 0.7/u TP. 101/741 Repeat of 101/739 after clearing air for 10 minutes with fan 123 3,464 Asbestos 3.2/Cement1' 0.7/u TP.102/742 Repeat of TP.102/740 Asbestos 3.0/ 264 3,453 Cement 0.8/u 3. Sorav ing with asbestos predamoed in thet drum ' : before feeding to the opening machine Sample Mo. Position Dust Count Median Siae Asbestos Cement After Incineration at 500C. TP.101/743 On chest of man operating spray 49 1,085 Asbestos 4.0/ Cement 0.6/u TP.102/744 On chest of man feeding drum and opening machine 54 982 Asbestos 3.0/ Cement 0.65/v /1A0027J The sampling in each case was done over a period of half an hour, spray was carried on continuously during this period. In the case of TP.101/739 and TP.102/710 there were a number of short stoppages for blockages in the gun and this probably accounted for the results being lower, than TF.101/711 and TP.102/71-2. In order to assess the health hazard the results should be considered in conjunction with those obtained in the spinning room of J.W. Roberts Ltd. on July 20th, 1933 with the thermal precipitator. In the "Report on Conference between Employers and Inspectors concerning Methods of Suppressing Dust in AsbestosThxtile Factories'1 published in 1931, the Committee agreed that for practical purposes the conditions arising from flyer spinning carried on without exhaust under good general conditions should be taken as the "dust datum". ^ ?'.-y h^ ^ /, - /, * / .v . In Mr. Cbodall1 s peport on samples ..taken in 1938 he obtained counts of asbestos fibre between''410 particles per c.c. and 165 . particles per c.c. in a good flyer `spinning ^room. . I Therefore it can be said that for the ..latest machine with predamping in the opening machine,the.exposure to asbestos fibre is about that of a good flyer spinning room and for asbestos predamped in a cylinder the exposure to asbestos'is substantially below that I in a flyer spinning room. 1 vkv ", cp ' It must be emphasised that the object of the measurements was to compare the throe methods of spraying and the measurements show conclusively that the predamped method exposes the workers to the lowest concentration of dust. . The measurements were carried out in a room in which no ventilation wa3 provided during spraying. At the end of each period of sampling the dust was cleared by means of fans before the next determination was carried out. In actual 'practice higher concentrations would be found 'an confined spaces and in similar rooms where spraying was carried on for a longer period. ' (Sgd) J.3. EVANS. M00279