Liquid Transfer Automation - Part 4

In this post we look at the procedural side of transfers. Starting with Recipes
In S88 a General Recipe "expresses equipment and site independent processing requirements" As such it really has nothing to say about transfers, not least because it is possible that different plants may be able provide the equipment in different ways. For example one Unit in one plant may be able to do what 2 units are needed for in another

Much the same can apply to a Site Recipe

It is when we come to the Master Recipe that transfers become important because this level of recipe must address the actual equipment in the plant in its Procedures

So here's a transfer in a Master Recipe procedure, with Send (Transfer Out) And Receive (Transfer In) phases running simultaneously

PFC showing Transfer from one unit to the next

And it is the Control Recipe that must actually perform the transfer, by invoking transfer phases in the units between which the transfer is happening
You will note that the diagram shows a Synch line connecting the Source (transfer out) and destination (transfer in) phases. This represents the data flow between sender and receiver.
Please note that these communications should be directly between the two units and should work entirely in the equipment phases,
The next post will cover this in more detail.

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

What are all these Recipe Defer Functions for?

If you are programming a Batch Manager, such as DeltaV batch or RSBatch, you will find yourself having to define the Defer Levels of Recipe parameters.

What is all this about?

Well, you can see some explanation on the DeltaV Books Online web site. And by the way Emerson, thank you for that excellent resource. And the explanation of the paints project shows well how to build a recipe in DeltaV.  

The basic principle is that the value of a recipe formula parameter used in a phase can be set by a higher level, so that you can ultimately create a master recipe formula containing the settings and define a path through the procedural hierarchy that sets the required value in the phase and hence in the equipment control.
Now, there may be many, perhaps hundreds or more, parameters that are used in the entire collection of phases that are run for a batch, but the actual master recipe formula need only have a small portion of them.
A design rule might be to only defer parameters that have to change for different recipes.

Deferring a Recipe to the Recipe Procedure

Deferring a Recipe to the Unit Procedure

The actual process of defining the paths looks rather tedious, because (as I understand)  you have to go through each level of the hierarchy, bottom up, deciding whether a parameter must be deferred, and furthermore if a parameter has to pass though multiple levels, then each level needs to contain the parameter - shown as Pass Thru parameters in the above diagrams. I can't help thinking that there must be a better way.
ControlDraw by the way allows you to link the top level parameters to the bottom level ones and then automatically work out all these Pass Thru parameters. Whether DeltaV would allow you to import these I do not know.

Where is the Batch?

Continuous and discrete processes can be used to make batches of stuff or things. That is the key to using S88 outside of batch processes! There is always a batch!

Is this the most misunderstood aspect of S88? It is not hard to understand at all:

A Continuous process can make a batch by running for a period of time with a set of recipe parameters such an Flow, Pressure, Temperature etc

A Discrete process can also make a batch - in this case a quantity of the items it makes - by running for a period of time.