Dear Sinclasc,

In the previously discussed installation there was a feeder rotary lock.

Now it seems that the rotary valve is underneath a filter receiver vessel on top of a silo.

Which system are we discussing?

A feeder rotary valve is at the beginning of the pipeline.

A filter receiver rotary lock is at the end of the pipeline.

best regards

teus ■

Dear sinclasc,

The vacuum pump has to create 2 airflows.

1)conveying air mass flow through the suction pipe ( Qconv )

+

2)leakage air through the rotary lock into the filter receiver vessel ( Qleak )

At any moment : Qvacpump = Qconv + Qleak

or

Qconv = Qvacpump – Qleak

Qvacpump = PumpDispl * (1 – vacuum)

Qleak = factor * SQRT (vacuum)

Resulting in:

Qconv = PumpDispl * (1 – vacuum) - factor * SQRT (vacuum)

Increasing vacuum causes a decreasing air flow.

If the rotarylock is wearing out then the factor (leakage is the inverse of resistance) increases and the rotary lock leakage increases also.

A leaking rotary valve decreases the conveying air flow and thereby the air velocity in the pipeline.

At a moment, the convey air flow decreases to a level where pneumatic conveying stops.

First you will notice a decreasing capacity at the same vacuum.

best regards

teus ■

Dear Sinclasc,

A simple method to check rotary valve wear is by measuring rotary valve clearances by using a feeler gage. Well designed rotary valves have clearances of 0.004 to 0.006 but for very large size valves these can be up to 0.0010 inch.

My article on calculating rotary valve leakages was published in Chemical Enginering magazine in March 2005. This will help you in calculating the leakage.

Regards,

Amrit Agarwal

Pneuamtic Conveying Consulting

Email: polypcc@aol.com

Ph and fax: 304 346 5125 ■