I'm not an expert on screw conveyors and feeders, but a few comments -

Screw conveyors convey a predetermined feed of material from inlets to outlets.

Screw feeders control material from a flood feed inlet and convey it to outlets.

To act as a feeder a U trough will normally have a shroud over a couple of flight pitches after the flooded inlet to effectively form a tube that controls the rate, this section being full.

It is not normal to convey at more than 45% filling so after the screw flighting is beyond the shroud the flight pitch is increased from the pitch through the inlet and shroud to reduce the casing fill.

So if your machine has been designed as a "feeder" I am surprised that the flight pitch is constant over the full length. I would think from your description that the machine is over full beyond the inlet.

At the final outlet it is common to stop the flights at the start of the outlet to aid free discharge of material. Commonly for safety a diaphragm pressure switch is mounted in the top cover over the outlet to sense any failure to discharge the full rate being conveyed.

If Lyn picks up on this thread I only hope he will agree with my non-expert comments. ■

Short of replacing the auger with a narrow width little giant grain paddle conveyor you will not be a happy person.

wood waste is no different that cottonwood tree seed spores etc., fluffy and with a mind of thier own.

lzaharis

their is enough surplus iron out there where you could buy a used elevator inexpensively and remove the monstrocity they sold you and eliminate any issues of transfer.

or ask your supplier to provide you with a small paddle chain conveyor to replace this one ■

Although the information on the installation is limited, I believe that the previous contributor has missed the main issue. There seems to be two separate problems. The first, indicated by the statement - ‘the bulk of the sawdust is not falling through the opening in the bottom of the hopper’, suggests that the dust is arching in the hopper. A small part of the problem may be the uniform pitch construction of the screw. It is suspected that from the length of screw described that there is a significant portion under a slot outlet of the hopper. A uniform screw flight construction would extract selectively from only a short section of the hopper outlet as, provided the sawdust flowed from the hopper, this would fill the initial pitch region so that product over the rest of the slot length would be unable to discharge and this 'dead' region would possibly deteriorate in flow condition.

However, the main difficulty is considered to be a question of inadequate hopper design for reliable flow. Sawdust is a poor flow material, particualrly if compacted by storage pressures, so will be reluctant the flow through the reatively narrow slot provided by a 9" diameter screw. Specialist retrofit action can probably be taken to improve this performance if the hopper construction is known. Removing flights can only make the situation worse.

The further comment that sawdust compacts to push up the end cover suggests that material is not clearing from the outlet, which again requires a proper investigation. My book, - ‘Guide to the design, selection and application of Screw Feeders, will offer some guidance, but is no substitution for an experienced assessment on consideration of the full details. Unless you have such a personal friend this is normally a professional service, complicated by the fact that the description – ‘Sawdust’ is far from sufficient to describe the flow properties of the material stored. If you care to send full details to lyn@ajax.co.uk, I will give provisional assessment. ■

Not wishing to be pedantic, but the statement is actually

The bulk of the saw dust is not falling through the opening in the bottom of the trough.

not

The bulk of the sawdust is not falling through the opening in the bottom of the hopper.

This led me to believe that the problem was at the ourlet NOT the inlet.

I must admit an inlet with a flood feed of sawdust only 9" wide is likely to be subject to arching, but the original post makes no reference to the length of the inlet or that any problem exists at the conveyor inlet/hopper outlet interface.

Maybe StephenB will provided us with more information after reading these posts. ■

A good point that I hope the user will clarify. I am so used to hopper problems that when sawdust was mentioned the mind immediately jumped to the potential problem rather than finely scrutinising the description. ■

Thanks for coming back to let us know how you are getting on.

Too often there is no feedback ■

There is just one feature of StephenB's post that I would comment on. As a general rule, the outlet of a screw feeder is located very soon after the shroud that is fitted over the screw at the exit from the hopper, so the screw cross section tends to be relatively full immediately prior to discharge. This allows the pitch construction to be varied more in the hopper section for progressive extraction.

Reducing the cross sectional loading on the screw after leaving the hopper is normally only an issue if the continuation length is relatively long. There are many factors to take into account when designing a screw feeder and whilst crude designs may work in a tolerable manner, they often do not give optimum performance over a long working life. ■