Figure 1 Gear pump with integral relief valve An example of good engineering but poor plant design. The relief valve prevents damage by pumping against excessive pressure heads, but since it is awkward to clean, and it is not obvious when the valve has operated, it tends to be "missed" and so provides a potential microbial breeding ground. : .'. i..::.-' •:....•ti•-:..-.•.' I' •.• •:..•.•:.'Z-:.-:•:: ..:i".:::.:t:•/7,. '.i"• •:•":' :. i.. •: .... , : ::: ":(_ ',.. : :•:-.:• : .:• :.:::::::::::::::::::::::::::::::::: ::'a?,•":::: '"':':'""•': ..... •-:.•. -.•., .•.•:.•½' ß .-.. :"•. 7'::::: '.-• • •,. ................ •.•.• • '•-:.::•. ?. :. • .':"(" :•,:..•½/.? .•(} ': s".:- •.•- ?•½..' :?'"'"• .... ' ...•::'"'•:.'½ ...... .•:•: • ..•½' •..•. '•" : "".• ß .5:-:-:.::':•J• • ... ½ ...::.::• . :::."•' :..:..• "..:.:.: '"' ... '. ' •'•'.:- .' :.'•%... •5 •' :: ....... :..3½'• •::. ?:, ?.,..' •%:, '• .... .• -m.: •::."• :. ..:' 4:.'•'.½#•T'• . ß .... : ß : .• .::::- -•......• •. .-•½.. • .-:-: ?'.:'.• •. •}. :'.. . ....... .... 1 • • •:-:'• :.•:•. :• :•-' ,., • '• '• '. '•: •:' : 4 "'½""'""7% • " .:.:•:. :• ½ ..... ..r,-•.....,•-• ....... ::•::•:. :. •. .-..::. •...• .?,.: .. Figure 2 6ood plant design spoilt by lack of attention to detail There are a number of easily dismantled and easily cleaned cocks and pipeworks, but the plant is spoilt by the use of glycehne filled U-tubes to pressure gauges, and the presence of plug valves, and pressure glands on the gear pump. There is also a lack of drain cocks on fixed items, and too many right-angled joints exist, all making adequate cleaning impossible. Facing page 398

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":•.?-'•?-•'-'*--- '• ?•-•":"- $•?f---.:'--,•* a•-:-½ a-.•:*:-**::•a' :'"• a.a*"'•*•a•'""'"" ß •F•..... -..:- ..... .,...•:•..••.-.--: ½•.,..•:,.- .... . ......................... , .. . ..._•...• ...... .................... ., ........... . ................. ....... . .......... ... Figure 3 Manifold to reduce number of u•ons The number of joints is reduced to a mi•mum by the use of a manifold. There are few right-angled internal corners dismantling, cleaning and sterilizing are therefore easy. l:aci•g page