How can powder be sampled under vacuum in a flowing pipe?

[katchum]

Good day

I'm wondering how to sample powder that is flowing through a pipe under vacuum.
Which systems can be used for this?

I have a DN300 pipe under slight vacuum (ranging -500 mbarg to -100 mbarg). The sampler should be connected to the pipe.

These are the process conditions of our installation.

- Product flow : 180 kg/hr powder = 0.1125 m^3/hr
- Particle diameter 40-200 micron
- DN300mm pipe
- Air Flow = 7000 m^3/hr
- Powder concentration = 16 ppm = +/- product flow / air flow
- Velocity of air = 100000m/hr = 27 m/s


I found out on line samplers also use vacuum to retract the sample, but this vacuum is too small to overcome the -500 mbar of our installation. Other samplers with a retractible arm are of no use because of the high velocity of air in the pipe. I can only imagine a sampler that has a huge ventilator that can suck the powder out from the pipe wall. The problem with this kind of sampler is that large particles and small particles will be separated which gives an unrepresentative sample. Another solution would be to cut the pipe in two pieces and build a cyclone + rotary valve in the intersection.

Any ideas?

Thanks for all the hints.

 

[Navin A S]

For this particular application, I would recommend a vacuum rotary valve sampler. This system uses a rotating valve to draw the sample from the pipe, and then a vacuum system to suck the sample into a container. The advantage of this setup is that it samples at a constant rate, and is able to handle particles of any size. The disadvantage is that it requires a large vacuum system to pull the sample from the pipe.