Originally Posted by Michael Reid

Is the bagfilter design one where the filter bags are fitted to the venturi with a worm-drive clamp? (There will be a felt gasket under the venturi flange). If that is the case, you will need the venturi to be able to assemble the filter bag and support cage and seal it to the tube plate.

If it is of a design where the filter bag is fitted to the tube plate indpendently of the cage and venturi then you can probably do without the venturies (but not the cages) at the expense of a bit more pulse cleaning compressed air.

Many bagfilter designs do not use a venturi.

Can you post a photo?

Michael Reid

This is an American Process Systems bag dump hopper that originally came with a built in pulse jet filter system. That was maybe a dozen or so plants ago, and the unit eventually ended up with my client. As it has been around the world, various plant engineers have remover/modified/altered the filtration. When it ended up with my client, the filters and associated items had been removed and the last plant it was in saw it fitted with fogging water spray nozzles to try and suppress the dust. We cannot use water as the powder has to be dry as it goes into a milling circuit. At the moment, the attempt made by the last person to try something saw it hooked up to one of the dust collectors in the plant.

At the moment, around 20% of the contents of a bulk bag (1,000 kg) ends up in the dust collector and has to be brought back in drums where it is put back into the unit. 20% of that ends up in the dust collector and so it goes on until the amounts are small and discarded.

I was called in, and my recommendation is to reinstate the built in filter. The local dust collector suppliers are not interested as it is just 4 or 5 bags, 600 mm long. One has come back with a price that would be about the price of a new dump station complete with filter! During discussions with the filter supplier, their conclusion was exactly what I had suggested anyway, only they are not willing to provide even basic dimensions of the venturis. We can't get the original filters in Australia as APS has no presence here and even if we import the components, replacements will also have to be imported at a high cost.

Yes, it is the venturi that goes through a tube plate, with the bags on cages clamped to the venturi body with a worm drive clip. This is what the current filter that collects the dust from the station has. Unfortunately it is under a massive dome and is not due to be lifted for a couple of months. We are trying to use the components that exist in the current filter that collects the dust laden air as we know they work.

We are not concerned how much of the product is collected by the filters as the dust will be discharged back into the unit anyway.

The truly unfortunate thing is that there is another dump station on another process line that will also need to be done in this plant and then this will need to be done on a couple of other plants. Despite this, the dust collector suppliers are unwilling to assist. When concern was raised over the price, I got the strangest e-mail that a supplier has ever sent me. As a customer, I was basically "told off" for even daring to raise the issue of price, as they believed that this would have been a highly competitive quotation process. They went on to suggest that because I had contacted them again, we were considered desperate and so we should not be questioning the price but be grateful that they were actually considering supplying the items!

I am going to be talking to an engineering workshop this week and will probably just buy some hardware to get the dimensions we need. As I told the GM, "if it does not work, we will be no worse off and have some spare parts to boot". By the way, he was stunned with the response from the dust collector supplier and does not want to use them. ■