Wednesday, 23 May 2012

Liquid Transfer Automation - part 1

This is about moving liquids from one tank to another, a frequent activity in plants but one that has little guidance from the s88 standard.

Specifically it is about transferring via pipes rather than for example by intermediate containers such as bottles, barrels etc.  In other words, the situation when we want to transfer some liquid from a source tank to a destination tank. This could be when we want to move an entire batch, or it could be when one tank gets a quantity dosed from a supply tank

The issue is what control is needed during the transfer, and where and how to apply that control,.

This will cover the physical equipment, the procedures to carry out a transfer and the control logic involved. It will also suggest an S88 module structure for the task and touch on the resources handling of transfer systems

It is the intention is to define a single method that covers the various type of transfers in the same way.

This is in my opinion one of the areas where batch projects, S88 based or otherwise, have had the greatest problems, most especially in the time taken to define, and then program the solutions.

But first let’s look at the general requirements in terms of process flows and the mechanics, the pipes, valves and other equipment used to establish the flow route.

Single Source and Destination

Multiple Source and Destination via Single  line

Now, putting pipework in for each route is expensive and impractical so an alternative is to share the lines, so here for example any of three source tanks can feed any of three destinations via one pipe.
This type (often found in brewing and dairy for example) can be made automatic.

This type involves manually setting the route using Flow plates - this ensures that liquids cannot contaminate each other, typical of pharmaceutical plants

Of course in this case (and assuming the batches must not mix) only one transfer is possible at one time.
More to come, please check back.

Added 7 June 2012 - there is a very interesting discussion following this post in LinkedIn