Document x1Yagz8ge9KJvyr3n8a7K2Jm6

i 23 m Bgf Kwal m mi few n i Assignment Jto. HU.1010 Physics Ref. FH.19J2/J Work by* R. Clayton, C. Roberta Written by* I. Harness Approrea ujt 9 Date: 29th Deoeaber, 1962. Wr. J. S. Campbell, J. W. Roberts Ltd., HOOTICK. THIRD INTERIM RRPQRf OTBJBCT An assessment of the concentration of airborne duet produced by the [depot* Asbestoa-Ceaent Spray Prooees. OBJECT 1. To oarry out testa in tbe experimental tunnel at J. W. Roberts Ltd., la order to measure the dust levels arising fron the use of various damping techniques and employment of additives to the 1M.25/1U spray Material. 2. To compere the dust concentrations resulting froa the application of various asbestos-cement spray alxtures. IRTRODUCTIOW The current series of tests assessing the dust hasard associated with *Liapet* spraying have all bees carried out in tbe experimental tunnel erected at J. W. Roberts Ltd. The initial tests (Referenoe La) were principally coneermi with the aeasureaent of tbe rate of decay of tbe dust level, after spraying had ceased. Tests vers carried out at various positions along the tunnel under both nonventilated and ventilated conditions. The next visit (Referenoe Lb) ni United to the comparison of airborne dust arising froa spraying L*.25/U* aateriala containing different additives and damped by various techniques. Tests were confined to sampling in positions adjacent to the spray operator during the application of the aaterlal, with the tunnel ventilation systes running. for tbe first time, dust concentrations approaching the order of those experienced In the textile industry vere obtained. It was therefore decided to repeat continued* o -4 Qie* -*. mw- '*** '***/ J Tjhl P"1--'* t <$$'"I - - *a*liL?Lxn.**x-. ( n i !i -3 - a'WlBT further dust tests here been carried out durian the application of "Mapet* asbestos-cesent spray in the experimental tunnel et J. *. Roberts Malted. These ere largely confirmatory teste assessing the affect of various deeping techniques and the use of additives to the spray Material. Sanplea have been taJcen by Beans of two 'Ottwav* instruments positioned adjaoont to the spray-gun operator. The results are very encouraging sad dust concentrations a1*liar to those found for textile processes have been obtained. This Is considered to bo due to pro-damping the spray aaterlal with a \% Calgoa solution. There is also some indication that doubling the oil content also results in lower dust levels, but a combination of the two daeping techniques does not appear to produea lower results than pre-daaping with Calgoa solution alone. It has also been confined that leaping at the spray-gun with a \% Calgoa solution Instead of water has little effeot on the resultant dust concentrations. DETAILED RSPOST . 1 Test Procedure (a) Spray Application The tunnel, spraying procedure and spraying equipment used were as described in reports referenoe PH.1932 and PH.1$}2/2, With regard to the ventilation tbo only dlfferenoe adopted for the current tests was that a length of trunking leading out of the garage windows was connected to the outlet of the extraction unit thereby preventing re-elroulation of the dust-laden air. Three control mu were carried out or each of the two latest visits as recommended (Referenoe 4b). The introduction of trunking appears to have little effect of the resultant lust level of the control runs, although a ohange in the sise distributions is notioeable. (b) Saapllng Procedure As desorlbed in Report reference FT!.1932/2 (Referenoe 4b). () Counting Technique As described In Report referenoe HI. 1932 (Referenoe 4a). 2, Results (a) Results for the latest series of testa are tabulated la App-nlix 1, Tables 1 and 2 give details of dust con centrations and sise distributions obtained during the two latest visits, aade on 3/7/62 and 24/10/62 respectively. (b) Dust concentrations for all test tuna (covering the last four visits to J.Y. Roberts Malted) using 1% Calgoa at the spray-gun together with the eorrespoadJ/ig control runs are sunnarised in Table 3, oontinuedt \O tfiil - i*T ( O - 5- (*i) n- p-w-lieptog/Supplying the spray-gun with *at*r/011 content doubled. Igain, the LW.25/14 containing double oil produced dust concentrations lover than those obtained with the nerval oil Mixture. When the ventilation draught was approximately tOO ft. per minute the reduction was quite considerable. The decrease was not so marked however when the extraction rate was less than ^0 ft. per minute. (vli) Wo ore-dagpin^SuppiyHrm the spray-run with water/Otl content Quadrupled. The results obtained indioate that further increasing the oil does not lead to *ny appreciable decrease in . dust level. (ill) Wo pre-damping/Supplring the aprav-wun with water/ Pureaor oil r-placed by Shell oil. It is difficult to cospare the te additives as the Shell oil mixture was sprayed early in the day on both occasions. This scans that the previous control runs were the first of the day and as usual produced the highest concentrations. However, comparing the Shell oil mixture with the second control run indicates that there is no great difference between the two additives. (b) Comparison of Hlndler Green and Horwich Spray Materials TI57237TU and fcKH 7037 Grade. ~~ The results of the two comparisons between Hindley Creen and Harwich material showed that there is no appreciable difference between the two grades. The new spray mixture EHN 7057 however, produced a relatively high dust level when sprayed, resultant concentrations being <650 fibres per eo. downwind and 856 fibres per oo, upwind. (o) Site distribution The site ditribut low for the equivalent test runs on the recent two visits bear little or no relation to one another or to earlier evaluations* Therefore section *B* of the oonoluslons of the Seeond Interim Report (Reference 4b) cannot bo confirmed. The most prtbable explanation for this variation is the different conditions existing on each of the visits to 3. W. Roberts Limited made to date. For example although the same ventilation system was used OS the two recent occasions, the extraction draught was approximately 100 ft. per minute on 5/7/62 ai*4 loss than 50 ft. per minute on 24/10/62, On the first of these dates there was a natural draught assisting the extraction unit bvt cn the second visit this condition tculd not be repeated. Also, it should be noted that the site distributions of the 1# Calgon solution pr"-daped runs arm somewhat tentative because of the small number of fibres courted. It would be an advantage to have a variable vertiiatlon system available 90 that the extraction drmught could be kept constant, and also it would be possible to " investigate the effeet of the air velooity on the resulting site distribution and dust levels. continued! *"V V. P' . &*? *"?* ( 2^ in mufiturn TriiiiiniMa 4 i { 1 A \j I O { I .0 i if r- IA eo o KoV I Sa ft P*% NA.i ir> ga oo a 4. 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Water Dust Conoen"rations (yibreg/co.) 30.11.61 Off 473 340 706 669 14.3.62 Ob 615 447 474 397 3.7.62 Ob 286 283 247 199 24.10.62 Ob 635 681 218 227 iresrest Control Ban* r i j /. * -* / * '*