Safety Of Aluminium/Bronze Alloy In Hot Dunder


I want to build a simple low vessel which will take the hot waste from my continuous stripper still and as it fills up, a pump will switch on to pump the dunder into a larger vessel for storage & re-use in my next fermentation. I need this intermediate low vessel, because the dunder outlet is on a gravity feed circa 400mm from ground level and I have to pump into a tall storage vessel.

I've found a reliable industrial quality float switch, whose body is made from aluminium/bronze alloy. It's rated up to 210°C, although my dunder won't be hotter than 80 to 90°C, so it's not particularly demanding for it.


I've been trying to find data on aluminium/bronze alloys but from what I can tell, it should be safe i.e. will not leach anything into my dunder. They do make a stainless steel version but they are on 4 weeks back order and are considerably more expensive. The guy from Mobrey doesn't see I'll need stainless steel and I'm thinking he's probably right. This post is just in case someone thinks I'm being a nobber! ;-)

Appreciate thoughts. Cheers


  • edited May 18

    John what about the type of float switch that you have in the Genny?


    536 x 800 - 53K

    StillDragon North America - Your StillDragon® Distributor for North America

  • edited May 18

    Hi Larry,

    Yours would be better from a cost point of view, as Mobrey are crazy prices. The 2 handy things about the Mobrey switch is that:

    1. It can supply enough amps to drive a decent pump; and
    2. I read that I must be careful with float switches "bouncing" at the top / bottom if I drive a pump because the bouncing can burn out the pump. The Mobrey has some sort of damping built in so that there is just a definite click on / off etc.

    With a cheaper stainless switch, I could fit an SSR to solve (1) but my electronics isn't good enough to know how to solve (2). I guess it's a capacitor but I wouldn't know what size. My vessel is 650mm long x 530mm wide x 200mm high, so I wouldn't have thought I'd get much bounce if I put the switch on the opposite side to inlet / outlet ... Not sure though

  • If you use a VFD on the motor you should be able to program a "soft start" or time delay type feature that allows for that type of issue.

    StillDragon North America - Your StillDragon® Distributor for North America

  • Cheap solution is to use a single float switch at the top, with an off-delay timer.

    The float is normally closed, trips when the float rises, the off delay timer will run for a preset time after the float switch falls and trips off.

    Off-delay timers usually come with different time ranges - seconds/minutes - so you’ll need to adjust it based on the fill and flow rates.

    Either way, your float switches aren’t switching the pump directly, you’ll be using a relay or a contractor to turn the pump on or off.

  • edited May 18

    Hi Larry & @grim - Very grateful for the comments and suggestions. They have saved me quite a bit of cash! :-) I'm going to use a single switch version of Larry's stainless one and I've found this off-delay timer, which does what I need too. (The timer has a in-built relay, so I don't need to spend on the SSR - perfect).

  • you can also use the following type. This one is from Wika.

    I am using a similar one in an Ex configuration together with a safety barrier for intrinsically safe.


    696 x 344 - 16K
Sign In or Register to comment.