Tapflo Sanitry Double Diaphragm pump failing?

[beattsmjk]

Hi,

Hopefully someone can assist me with a problem we have a basic pump system installed in a bakery, pumping (when required) milk at 2 degrees celsius (Tapflo T80 pump is installed in the fridge with the milk containers) operating at around 5-6 bar.

The suction / discharge lines are 35mm and we have this system in numerous places without any hitch.

This one bakery however is giving us a lot of problems with the pump failing to start on demand. We have the pump linked to a dosing valve (Gemu). Most of the time the pump functions ok and then others not at all. I have serviced the pump with a new set of internals i.e air valve, diaphragsm, balls etc but still no joy.

The pump is less than a year old and is probably used to pump around 100 litres of milk per day in 1.5 litre doses, so is used relatively little.

It is kept clean and the air supply is fitted with a dryer but occasionally the pump just fails to operate. After ten mins or so the pump normally functions again.

The pump is kept pressurised at all times to allow for accurate dosing through a meter.

Any ideas what the problem may be??

Like I say we have these systems elsewhere more or less identical running problem free.

thanks in advance

 

[JoeySoap]

Of course, 2 Celsius is close to freezing. If the milk is a little over chilled, could the pump partly freeze?

 

[mechsealhelp]

1, is it the pump..? Could it be the motor..?
2, possibly 'air' trapped inside the pump chamber, is the pump fitted with a vent-off..?
3, re-prime the pump and vent any trapped air.

 

[TenPenny]

Freezing...good point. Is the compressed air wet? Is it possible that it's freezing?

 

[beattsmjk]

Hi Thanks for the replies,

in response to your points,

firstly the setup is exactly the same as we have in approx 10 sites (no problems in these sites),

The compressor has a dryer attached to it, its not a particularly big compressor but it doesnt really need to be for the job at hand, I cant see any water coming from the airline at all, (thats not to say it is dry though but how would I tell?)

The pump has no motor, is a pneumatically operated double diaphragm pump made by Tapflo

The fridge has been raised to five degrees to overcome any possible freezing issues but the problem still arises

the pump is a self priming pump, and it is kept under pressure at all times so there should be no trapped air theoretically anyway.

The pump is less than a year old, just and we have just changed everything inside of it for new but still no success.

Am getting baffled now!

thanks

 

[Compositepro]

It is probably water in the compressed air freezing. Even pumps that operate at room temperature can freeze due to the air expansion when the exhaust valve opens. If the pump starts spontaneously after 10 minutes, the ice is probably melting. Some pump valves can stall and require the air to be turned off and then on again. What kind of drier is used?

 

[beattsmjk]

Thanks compositepro,

I agree it probably is freezing although I'd love to know if there was a way I could determine if the drier was doing its job.

I really dont know the type of drier, but I am pretty sure it is the refrigeration type

 

[Compositepro]

Use as low an air pressure as you can to minimize expansion cooling. You could also try an air line lubricator with non-toxic propylene glycol or glycerin antifreeze. The pump really should be lubricated, in any case.

 

[JoeySoap]

To eliminate freezing as a possible cause of trouble, I suggest that you hire a bottle bank of 12 Nitrogen bottles. These will be full of compressed N2 (~200 Bar) at a dew point of better than -80 Celsius and in fact probably much drier than that. Use a regulator and a PRV set to no more than the normal air supply pressure for safety. Hook the N2 supply up to the diaphragm pump and see how you go. HTH.

 

[CH5OH]

keep in mind memmbrane pump is a positive displacement pump
eg it doesnt like to be throttled fully (a closed discharge)
does the discharge line has a over pressure valve installed?
first thing I can think of would be jammed suction /discharge ports (ball type of valves,with ball getting stuck into its port)