Document NNk257nmzvz7zY47aDQ271LdD

V/)C 6c6c^ <\pu^/ui^ fZ/Lcc/OS - SA^rov/fc Over twenty years ago industry began using PCB's as the working fluids in diffusion pumps and vapor booster pumps. Their reasons were simple but important. The fluids were not only fire resis tant. They were very stable under high temperatures. These properties gave users the ability to move large quantities of hot gas with safety from fire and explosion. rtJntil 1970 we did not segregate the sale of PCB's for vacuum -u-sc and wo du nut know how~much was used~I In 1970, however. to better control -applications T--PCB * s--for this- SarsJ Prq&uct San^vac "elate are as follows: ^ / 197i rT v'-p I'"' 92,610 lbs. t35v^/?/7( The major markets are vacuum melting and refining of metals; metallizing or coating plastics, glass and metal; welding or brazing metals; and chemical processing such as distillation and degassing. We have chosen to stay in this marfcfet because the danger of environmental contamination is small and bs^aas-e with drawing PCB& would work a major hardship on the users. Since vacuum systems (in addition to using only very small quantities) are generally closed or contain liquid traps, fhe only environmental hazards are spillage and disposal. The pump manufacturers in many cases have designed their pumps tc operate DSW 332124 STLCOPCB4078700 on PCB's and they do not recommend alternate fluids. The users have established manufacturing systems based on being able to handle specific large volumes of gas. To withdraw PCB's would create additional fire hazards and could force purchase of new pumps or, if possible, redesign of old pumps and reduced manu facturing capacity. . In summary, there is a long history of PCB's in^Vacuun/systems -- usecyboth for safety^and foy the specialhproperties of the fluid/itself. TJvdugh there /re other working flydds available, none' are dirjzrbt substituted for thp'' PCB's. Because of ease with which the user's can control the fluids, p]/s the increased danger and c/isruptaon to industry I shoulri we withdraw the fluids, we plan tlo continue selling Santovac. DSW 332125 STLCOPCB4078701