Blind nuts

Where thin sheets are to be joined and access is availabie from only one side, rivet bushes or rivet nuts are used. These provide an adequate length and strength of thread which is fixed and therefore allows ease of assembly, Fig. 12.5(c). Available in thread sizes up to 12 mm for lighter applications, blind nuts of the type shown in Fig. 12.5(d) can also be used. The nut is enclosed in a plastics body which is pressed into a predrilled hole. A screw inserted into the nut pulls it up and, in so doing, expands and traps the plastics body. 

The ultimate proof that the EPR method is useful for the identification of irradiated food is its performance in blind trials. A number of studies have already been completed (Table 5), and the results have been very encouraging. In the majority of cases it has been possible to identify foods treated with irradiation at doses well below those likely to be used commercially. In trials reported by Desrosiers etal., 1990, Scotter etal., 1990, Desrosiers, 1992 and Schreiber etal., 1993 all irradiated and non-irradiated samples were correctly identified. In the more extensive trial reported by Raffi etal., 1992, the numbers of correct identifications depended on the foods examined and the doses applied. In this trial the results for meat bones, dried papaya and dried grape were good but those obtained with fish bones and pistachio nuts were not as conclusive as the results from the trial reported by Schreiber etal., 1993. However further development of the protocols involved with these products has been undertaken and the results from future trials on these products should be more acceptable. 

In people whose thiamin intake is marginal, colonization of the gastrointestinal tract with thiaminolytic microorganisms may be a factor in the development of beriberi. The thiaminases present in raw fish can result in so-called Chastek paralysis of foxes and mink, as a result of destruction of thiamin, and may be important in parts of the world where much of the apparent thiamin intake is from fish that is eaten raw or fermented. The polyphenols and thiami-nase in bracken fern can cause thiamin deficiency (blind staggers) in horses, and tannic acid in tea and betel nut have been associated with human thiamin deficiency. 

Lever LR. Peanut and nut allergy creams and ointments containing peanut oil may lead to sensitisation. Br Med 1996 313 299. Wistow S, Bassan S. Peanut allergy. Pharm J 1999 262 709—710. Hourihane JO, Bedwani SJ, Dean TP, Warner JO. Randomized, double blind, crossover challenge study of allergenicity of peanut oils in subjects allergic to peanuts. Br Med J 1997 314 1084— 1088. 

The screw-on flanges, as the name implies, are screwed on to the body of the electrolyzer (pipe nipple). The blind flanges are bolted to the screw-on flanges, with a Teflon gasket placed in between each blind and screw-on flange. When the bolts and nuts are tightened, the pair of flanges are sealed. 

Figure 12.5. Types of nut (a) wing (b) dome or acorn (c) rivet bush or nut(d) blind (e) flat spring steel fastener and (f) J type fastener...

Whenever possible, remove flange bolts on the side away from the workers, leaving a minimum of two, then loosen these bolts and without completely removing the nuts spread the flanges to install the blind. 

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