Possible health risk from beryllium oxide ceramic rectifiers of 1000 H.P. rail motor coaches.

Abstract

Beryllium oxide as a ceramic is much more stable than beryllium oxide powder and an unusual use in the form of cups in the rectifier part of the power supply for 1000 h.p. rail motor coaches is described. Its special properties for this particular use are high thermal conductivity and excellent electrical insulation. During trial runs a flashover occurred across one of the beryllia cups in which the temperature was probably in excess of 2000°C and 1·2 g of beryllium oxide was vapourised and lost from the lip of the cup. 18 hr after the incident the rectifier box was opened and although the smoky deposits had settled on the floor, sides and internal structures it is possible that the two engineers who opened and cleaned the box were subjected to an inhalation risk greater than the m.a.c. for beryllium (0·002 mg per m3). Serial clinical examinations, chest radiographs and respiratory function studies on these men have been normal. An experimental test rig was set up to simulate overload and arcing conditions; repeated beryllium air and smear samples on this and in rectifier boxes on trains after runs with peak loading have been taken. The box where the original flashover occurred has been particularly studied. The total amount of beryllium inhaled by either of the engineers most probably did not exceed a few µg but could have reached tens of µg. No harmful effects have been demonstrated.