Rotary Valve Problems
You might want to consider setting up two properly modified slide gates in a "double dump" configuration. There are, of course, some other factors to consider. However, you might look into this option. ■
Potato Starch
The leakage of conveying gas from high pressure to low pressure is a key factor in valve performance, and especially so in powder service. Clearances that are too large make purging ineffective and allow product to be carried, with the leakage gas, into non-product areas. This can result in build-up and degradation of the product, even binding of the valve, or accelerated valve wear which further opens the clearances, exacerbating the problem.
Reputable manufacturers will publish, even certify rotary valve leakage rates. Obtain this data, if possible, for your valve. If it is determined that replacement of the valve is necessary, select a valve with a high differential pressure design, even 3.5 bar. This will insure that a mininmal purge will effectively solve your problem.
Dennis Hauch ■
Rotary Valve & Starch
Hello Peter
Send us more information please, about the installation situation and maybe a sketch about these. Further we need more detailed information, e.g. about the capacity, the diameter of the rotary valve, rpm, different pressure. We need this information in order to assess the situation and to search for a solution. You can visit our homepage, www.schaeffer-vt.de , for advance information about our company.
regards
Christoph ■
Re: Rotary Valve & Starch
It appears to me that the product is being smeared onto the valve endplates. This build up closes the clearances between rotor and body causing the valve to stall.
A simple answer may be to fit a new rotor with flexible blades.
This allows the rotor blades to flex rather than stall.
We have used this method on many Rotary Valves handling products which smear.
Regards
Patrick Rowley ■
Re: Rotary Valve & Starch
This is a familiar problem. We have developed a rotor spec that will drastically reduce this 'smearing' of the product. It is a well tried and tested solution.
You can visit www.dmn.info for company information and to contact me at DMN UK for further information.
Best regards
Simon Pantall ■
Re: Rotary Valve & Starch
Dear Guy,
I received your case and question.
Well, I do not have this kind of process, but how ever I have interesting proposal, which you should consider.
Please visit our web pages: www.larox.fi, where you can see our valves, which could be a perfect solution for you. This kind of valve is never jamming or leaking and in many pneumatic conveying processes it is optimal solution.
If I can get clloser details of your process including:medium( now dry potatio starch), temperature, conveying pressure, valve cycles(hour or day), valve DN, actuator type, I can give you our recommnedation of valve selection for you and also some reference experiences.
Dear Guy, this is my idea, how you could develop your process situation.
Please let me know if you want to know more.
I'm gladly at your service.
Best Regards,
Raimo Lavikainen
Vice President, Sales and Marketing
Larox Flowsys Oy ■
Re: Rotary Valve & Starch
Thanks for all your advice regarding the starch problem.
Just to clarify things a bit the valve seizing does not appear to be caused by a buildup on the rotor tips and end plates due to smearing. When I stripped the valve down it was actually a buildup of starch around the shaft as it passed through the end plate of the rotary valve that was causing the seizing of the valve.
I think I need to keep the starch out of the bores of the endplate, but as the clearance is about 0.25mm on each side I can't really use air purge as the volume of air required is too great.
The Rotary Valve is performing approximately 7, 1 hour deliveries a week, and delivers approximately 25 tonnes per delivery. The blowing air is at around 50ºC and up to 1 bar.
Regards
Guy ■
Re: Rotary Valve & Starch
Perhaps an open rotor with secondary seals on the end of the vanes, together with air purge seals, will prove more effective.
Attachments
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Af Feeder
kindly refer to web site www.acsvalves.com for information on the Aero-Flow feeder valve with features intended to solve the problems you are encountering. ■
Rotaval Rotary Valves Seizing Using Starch
we are currently using Rotaval HD 300 type, Model 1D300 stainless steel atex approved, round flange rotary valves and like guy martin,ours seized up very quickly one with 9Hrs of service. also the same around the shaft between the blade root and end casing. even with the air purge on the reverse jets seem to eventually overcome and push product up the airline and fill up the regulator ,then seizing up the rotary. when the starch plant is in use it probably runs at a rate of 1 tonne/hour.
any ideas greatly appreciated..
Martin ■
Rotaval Rotary Valves Seizing Using Starch
Hi Guy,
Could you go into more detail in regards of the valve size? If the valve is to small, then one cause could be overfilling the valve and causing the valve to seize.
Another option would be to use a deflector plate to direct the flow of material more towards the centre of the pocket. Adding rubber tips may also prove useful.
If you like, you can send me more information and I can see which the best solution would be for your problem.
Best Regards
Tilo Springer
Anval Valves ■
Re: Rotary Valve & Starch
Good morning Martin,
Per Tom Thompson's reply to Guy below, we can work on a solution for you. I will need some more information, so I will contact you to discuss a solution.
Thank you!
Sarah
ACS Valves ■
Re: Rotary Valve & Starch
Many thanks Sarah. looking forward to a successful solution ■
Still Looking For Help In Uk
Any mechanical seal manufacturers advice would be brilliant!. ■
Rotary Valve & Starch
I have a problem with a blow through rotary valve seizing up while pneumatically conveying potato starch.
When we have stripped the valve down, the starch has got into the clearance between the end plates of the valve and the rotor and obviously run hot and solidified.
Has anyone else experienced this problem before? And if so any suggestions as to modifications to the valve to eliminate the problem?
We have tried to air purge the seal area but the clearances mean that the volume of air required is not feasible.
Thanks
Guy Martin ■