Issue with Woven Mesh Braking on a Machine and Sensors

Agreed. Monitor the turbidity of the outgoing filtered water stream, and stop the machine if it exceeds some predetermined limit. GA.

A pressure sensor?

It would have to be sensitive enough to sense a sudden drop in water pressure inside the drum.

The drum is rotating inside the machine, we use pressure sensors for our external machines. In this machine the water comes in through a pipe ( whistle kind) and spreads across the surface. Drum is inclined, both ends are open, and there is a spiral inside to transport contamination up.

Hmm.

Without redesigning the drum to have a second wall of mesh as a backup; would it be possible to stretch a piece of the same mesh underneath the drum, and keep it stationary?

I'm thinking that it would prevent contamination in the event of a tear, and periodic visual inspections would show if the main drum was torn, and leaking contaminants.

Just to let you guys know of the maintenace subject, we recommanded the same thing, and here is the but. Last couple times they found out 3 weeks after the mesh has broken when all their pipes became clogged up with fibers. And that was with maintenance checking the machine daily.

Then that particular solution is the wrong one.

What recommendations did the equipment manufacturer make? Has their representative made a site visit at all? How long has the problem been going on?

He IS the equipment manufacturer.

Assuming the outflow of the filter is running through a single pipe, a sight tube or turb sensor, per Tornado, would work.

A downstream cartridge filter would do the job, too. Then a pressure sensor downstream of that would tell you when it becomes loaded.

_{Don't let your customer know you came here looking for solutions.}

My bill for consultation will be forthcoming, too.

Do feel free to send the bill directly to KrisDel™ Corporation, Etherville.

I was just trying to place a photo of the machine but it would not let me here. We manufacture this equipment, and this is something that my good friend and our customer approached me about.The main issue is here is that the mesh is opening is 80 micron, and when they place it on the drum it tends to bend and that's what breaks.

It's going to be difficult to help them if they are willing to lie to you.

Nothing will work.

I looked into running some kind of current over the surface of the mesh to have it pick up a breaks in the mesh, but then the issue is the rotating drum and water.

Any type of sensor will be useless if they ignore it.

GA

Like many customers, they don't use the equipment correctly, then they expect a re-design to match their incompetence (or they don't give a decent spec' in the first place)

(Kris made me say that... I was just thinking it)
Del

I wouldn't do well answering the customer service hotline...anywhere.

I would eliminate all problems by eliminating stupid customers.

Here's a clear filter with an available 80 micron washable nylon filter.

http://www.oilybits.com/filters/elements-housings/10-inch-polypropylene-filter-for-water-wvo-or-bio-diesel/prod_279.html

Woven mesh that would filter to 80 microns would be fine wire. Too fine to run a wiper (your spiral) against for any length on time. Also the velocity of the water maybe working the fine wire against the drum supporting it. How long does the mesh stay in tack before there is a tear?

I think that the mesh breaks because of wear. transported particles are quite hard and have sharp corners which makes them good cutting tools. The internal spiral has a clearance to the drum in which particles can clog and so the mesh is worn , it breaks due as well to the radial pressure between the clogged material and the mesh.

I think that although Tornado's suggestion is the best (GA) some steps could be done to increase mesh life time.

There are several possibilities. In order to obtain an 80 µm free passing mesh the wire is thin and thus has little material to withstand wear. Filtering can be done in 2 steps using the mesh and cyclones adapted to the dimensions to filter. A second action could be to put at the out side of the internal spiral a kind of compliant scraper to reduce the clog probability. It could be also possible to have at same edge some water jets to keep particles from entering the gap and build up a cutting tool. Does the mesh have any back support ? If yes it is may be too far and pressure breaks the worn mesh.

It is as well a concept/design problem not only a maintenance one.

Differential pressure switch, sensing inlet & outlet. Fit & watch closely, adjust so it switches pump 'off' (or alarm 'on') when diff pressure drops below 'normal running'.

Your best course of action will depend on how often the breakage occurs. If it is rare, then a pressure measurement/sensor might work well. If failure is frequent, you might consider a more robust technology such as used in electric shavers, or perhaps a stronger woven mesh.

Can you post a diagram or pictures or both of the process?

I do not have their diagram, but I am attaching our machine and rough information on it.

I am trying to attache a better quality diagram, hope this comes out better