Low Consistency Pulp Stock Suction Design

[imspeller]

Longtime lurker, first time poster.

Artisi had a response to a post almost fifteen years ago regarding stock pump suction design. I was wondering whether Artisi (or anyone else) has come across any technical literature that suggests a similar design to what was described in that post (see below). If not, general discussion on LC stock pump suction design would also be greatly appreciated.

Thanks in advance,
imspeller

A normal end suction process pump can usually pump paper stock upto around 3-4%, although this is dependent on the stock type and a number of other factors such as the amount of entrained air in the stock etc etc.
For stock of 3-6 % you need to use paper stock pumps for trouble-free pumping.
One factor that needs careful consideration is the approach pipe work to the pump inlet and the pipe/pump connection, for 3-6% stocks the greatest problem is bought about by using good hydraulic principles - the fitting of tapered pipe reducers is usually the greatest cause of inlet pumping problems as the stock tends to "jam" in reducer and can be very quickly become dewatered completely blocking the reducer. For stock pumping the best way to reduce from the suction pipe (usually a much larger diameter than the pump flange size) is against all good hydraulic principles, this is an eccentric square entry - that is a flat plate welded to the approach pipe with short piece of pipe(pump inlet size) welded to the top side of the flat plate, the stock cannot "jam" in this type of reducer because of the highly tubelent flow at this point and therefore cannot dewater.

The standard "paper stock" pumps manufactured by Allis Chalmers, Alhstrom, Sulzer, Worthington etc etc, are capable,under ideal suction conditions of pumping stock upto and including 6% consistency - it is possible to exceed this in the field but I would caution against ever designing for anything above 6%. To exceed 6% you need to look at fitting suction agitators or feeders or using thick-stock pumps.

To put in perspective what 6% paper stock is like - wearing snow shoes, you can walk on it.