I designed a system that conveyed polymer chips basically we had a veined blower running at 40 horse power blowing air into a flexible steel pipe .we had a mixer Y valve that let polymer chips be sucked in by vacuum and gravity and blown down the pipe to a holding hopper. We used a Taylor programmable controlled, the process input variable was a pressure transmitter monitoring the static pressure at the valve inlet and controlling the proportional valve .is that sort of what you have ?

Ray at (http://www.rs-controls.com) ■

In theory, yes this can be done...but in practice, the on-line pressure measurements will be unreliable (after some time). Auto unblocking technology was developed at Uni of Wollongong several of years ago (and avoids the need for such methods). In industry, I would measure pressure only upstream of feed point (this can be used to indicate a blockage)

regards

wypych@uow.edu.au

http://www.uow.edu.au/eng/bmh/ ■

When you are runing a very long or inaccesible pneumatic conveyor, or as in my case a hot 750` C line with Iron, Hidrogen and Co and you want to do as little as possible after a blockage occurs , yes you measure pressure in different points as after and before bends, if you have emergency vent lines you might want to clear the lines before trying to unplugg the system.

Be carefull, if your vent line is in right angle (and a length before the plugg) with your line you might end up plugging youl line worst. or digging a hole in the vent line.

Your valves should be capable of venting with large differential pressure and dust. Not an easy task.

Bottom discharge traps work fine if you have a sealed container where to deposit the product.

The pressure sensor lines can plugg themseves and be worthless, see Molhamm and Marcus work in the Presidents Mine in south africa.

It will be worth while

Marco ■