Document 9Lryv4LjDNpxp85rXLqBMav1L

TO H. Waltemate F.ELO POINT OR AKRON DEPARTMENT a BI.OO. NO. Cleveland DATE YOUR LETTER FROM M. M. 0'Mara SUBJECT nrtO POINT OR AKRON DEPARTMENT a 01.00. NO. Avon Lake Technical Center DATE THIS LETTER June 6, 1974 Samoline Rate and Testine of Welsh Cartridees: The Harvard ADDroach to Increased Efficiency One of the anomoLies in our testing program involving carbon cartridges has been the choice of rate of gas flow through the carbon bed. In one of my earlier reports I stated that we tested at 30 1/min. because this correlated so well to the Harvard studies which involved testing the entire mask at 32 1/min. (the OSHA standard). Since the entire mask contains two filters, the unidirectional gas velocity through each cartridge must be 16 1/min. The question that has remained unanswered is why we do correlate so well when the gas velocities are so different. This has finally been satis^ factorily resolved since I have seen an actual copy of the Harvard data and the OSHA requirement. The OSHA requirement calls for rates of 64 and 32 1/min. when testing the full mask. Under the more severe condition, the unidirectional gas flow is 32 1/min. through each of the two cartridges. Harvard (like us) has been testing one cartridge at a time at 32 1/min. to simulate the upper OSHA requirement. Jim Matheson of Welsh misinterpreted the Harvard data and this has been the source of the error. No problem exists with our program since we are in rough compliance with the OSHA requirement. Reversed Flow Engineering One other point that needs to be cleared up is the supposed break through made by Harvard in redesigning the Welsh mask so that expelled air travels back through the carbon bed. Matheson told me that in using this approach. Harvard was able to increase the life-time of the cartridge to about 40 hours (versus the 1-2 hour life-time which now exists). Jim Matheson has again misinterpreted the Harvard data. I believe Matheson meant 4 hours not 40 hours. A closer inspection of the Harvard data reveals that their claims of a "dramatic increase in life (of the cartridge)" are not justified. The Harvard data has been plotted for the 3" and 4" cartridges under continuous flow (unidirectional) and pulsating flow (reverse flow) in Figure 1. No data was available for unidirectional flow involving the 4" cartridge. In our meeting, Matheson implied that Harvard was comparing the 3" unidirectional curve with the 4" reverse flow curve in cpming to their conclusion of dramatic performance changes. Viewed iii this way, one must make the same conclusion. However, this is like comparing apples and oranges. In our unidirectional testing we have noted a 2.4X increase in. efficiency in going from the 3" cartridge to the 4" cartridge. So in view of this factor, one might find the 4" unidirectional curve somewhere around the 2 hour point (for 5 ppm). Thus, there is a change for both the 3" cartridge and the 4" cartridge when the flow is "pulsed". too8TSfrZ PO mu rev. ii/t* utmo. in u.s.a. BFG31579 ...fM ef ,H. Waltemate Page 2 June 6 1974 1 believe that In terms of the problem confronting us and the medical questions arising from this approach (i.e. high carbon dioxide concen trations in exhaled air) this is not a viable solution to the problem. ch Distribution: J. L. Nelson E. W. Harrington G. D. Schaaf B. A. DiLiddo E. G. Schwaegerle W. Wilcox B. M. G. Zwicker E. B. Katzenmeyer F. E. Krause R. M. Kreager J. Pausch P. Zakriski A. L. Schultz R. W. Strassburg H. N. Johnson L. B. Crider E. A. Collins R. J. Meyer C. Flynn D. L. Kent Plant Managers Plant Safety Engineers Attachment c'/yiaAA. M. H. O'Mara 24518002 BFG31580 NO. 34 0 -1 0 1 0 D X IE 1 T0 ZQPEERN GRAPH INCH PAPER EUGENE DICTZBEN CO. Ma OC tu U. a. a . BFG31581 ^ O O S itlS ^ f^ le change