Level switch alarm setting for silo

[knapee]

Dear

First time to post in this control forum.

Please bear with my poor knowledge.

I need to design a high/low level alarm for silos I am currently

building. The silos once finished will contain Si in granules.

Height of the silo is 5 m and diameter is approx 1.5 m.

I need to set two levels switch with high/low alarm"

I have been searching the different manufacturers and obviously

every and each one makes the best system.

It looks to me as if tilt switches might be my best bet used as

dry material high/low level detector, but as this is the first

time I am doing this I would like anyone can kindly help to

guide me how to choose the proper number for this high/low alarm.

Please give me some help. Thank you very much.

Knapee

 

[controlnovice]

We use vibrating fork on our silos with powder. Sometimes these get coated and create a false signal.

We switched to a capacitance type level switch with a 'shield' to prevent coating, and it seems to work better.

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This is normally the space where people post something insightful.

 

[knapee]

Dear Sir

Thank you for your kindly reply.

Process and I&C should decide the high/low level for the silo.

Could any I&C or process members please tell me how to choose a good safety factor for this high level and low level alarm setting point?


Thank you so much.

 

[danw2]

The article at the link is an excellent discussion of high limits in tanks, as related to safety evaluations.

http://www.chemicalprocessing.com/articles/2010/143.html?page=print

I don't work with silicon, so I'm not sure what the safety considerations are, but you can apply your knowledge with the principles in the article to make a determination (it might not even be a safety issue as much as an operational issue).

With regards to low level, isn't it just a back-up in case the continuous LT gets dementia - indication that you're running out?

 

[ScottyUK]

Silicon is hard and in granule form likely to be very abrasive. I would avoid anything with moving parts in such an environment. It has a dielectric constant significantly higher than air, so it would likely be a good application for a capacitive probe. Ultrasonic might be worth a look. Microwave / radar would also work although it would also be an expensive overkill for what you're doing.


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