AWS F1.1M pdf free download
AWS F1.1M pdf free download.Methods for Sampling Fumes and Gases Generated by Welding and Allied Processes.
6. Sampling Considerations
6. 1 When an eiIit—hour. time—weighted average (TWA ) concenlration is required. sampling should he pertormed br a sutticiciit period ot time to provide al 1(1 results. Generally, the only method of assuring (he validity of the test is to sample br eight hours. Icept br highly repeliti e and continuous operations, shorter sampling limes cannot reliably provide a valid eight—hour. TWA result.
6.2 (‘onsideranon should he given to laLing addi fional samples to confirm the validity of initial results.
6.3 A suliicieiu quantity of sample should be collected for the required analytical methods. Samples should not have total weights in excess of’ the N l( )Sl I Method 05(M) ( N\1AM recommended maimuin %amplc eight of 2 iii ill igrams lug). Smaller sample sites are acceptable. based on the requirements of the specitic analytical methods used and the requirement for accurate weight measurements. A in iiii mum sample site of 0.5 mg should he obtained for accurate weight and Iti me concentral I n determ i nat i n. I)i.iri ug suiiipl I ng. filters should he replaced w itli ne sample filters it’ any loose l)articuIlL(e is noted on the filter.
7. Sampling Equipment
7.1 A calibrated air sampling system. which includes ihe pump and tiller system. should be used for sampling. The pump
should he capable ol operation (or aL least an S—hour period. v liii an adjustment device to permit a constant sampling rate ±5.’ within the range of 1.5 urn (02.5 lJni.
7.2 A hydrophobic (e.g.. poly viny I chloride—PVC) filter or a Ii her system which is capable ol’ repeated weighing to within 0.05 mg tinder di lien ng him midily conditions should he used hen eight determination for total fume concentration is to be made. A cassette with a 25 mm or 37 mm diameter filter and a filter pore site within the 0.45 microns (rim) to 5.0 pm range is acceptable. The most popular pore site used is 0.5 pm.
7.3 high—purity membrane bikers of 0.45 pm to 5.() pm pore site or other types of hygroscopic e.g.. mixed cellulose ester—M(’E) filters may be used with specific analytical methods. Niatched—weight MCE tillers oiler the advantage of determining both toul particulate and individual metal concentrations t’roni a single air sample. This sampling rnethodol— ogy emplo’s a filter cassette containing Iwo filters that are matched in eight. The top filter collects the fume sample and the hack filter serves as a control. After sampling. both tillers are removed and weighed individually : the difference between weights is the sample weight.
7.4 1 lexa alent chromium ((‘r\’ I ) samples are collected on a hydrophobic (e.g.. pohv my I chloride PVC billet system which is capable of repeated weighing to within 0.05 nig tinder differing huiiiidity conditions. OSIIA Method 2 1 5 specifies (lie sample he shipped to the lahoralory within 24 hours ob sampling and he analyted within S days ob sampling. A cassette ith a 25 mm or 37 mm diameter filter and a filter pore site within (he 0.45 pm to 5.0 pmii range is acceptable.
8. Sample Conditioning
8.1 t’pomi completion of’ sampling, the moisture level retained by the fume sample should be considered. Vacuum drying or desiccator drying to a constant weight hetre weighing the sample is necessary with limited exceptions (such as with matched-weight filter systems).
8.2 Ilecause moisture pickup is almost immediate. the tiller sample should he weighed itliin 20 seconds after drying.
8.3 An analytical balance with a sensiti ilv of’ at least 0,01 mg should he used br eighing the ti Iter elemiieni.
8.4 i’he filter element should he weighed after removal from the cassette. i’he filler should he handled only with nonniagilelic. unserrated flrceps. and should he exposed to ionizing radiation prior to each eighing to eliminate static charge.AWS F1.1M pdf download.
