Más contenido relacionado Batch Control According to S88 Standards1. Batching
Advanced Batch Control
Batch production is one of three main types of manufacturing processes, used to turn raw
materials into finished goods. It can be defined as:
• Starting with input materials
• Subjecting them to an ordered set of processing activities
• Creating a new output material
Contents
1 The need for dedicated batch control
2 Batch control system selection considerations
3 Implementing dedicated batch control
4 Summary
5 Additional resources
An accurate, reliable weighing system that measures
ingredients and transfers them into the batch is a criti-
cal part of the process. This process can be auto-
mated, manual, or a blend of both.
Realistically, automated transfer and batch control can
be managed at the weigh terminal instead of a full-
scale PLC or DCS control system. The right weigh ter-
minal/system can also guide manual batching. A
stand-alone batch control system may be of particular
benefit in smaller-scale operations because it elimi-
nates the processing time and cost associated with
PLC programming.
This paper will explore benefits of stand-alone batch
control and discuss ways they help:
• Achieve consistent results
• Increase efficiency
• Lower costs
Ultimately, consistent results increase customer satis-
faction and make it easier to meet processing or prod-
uct certification standards. The right solution will give
rise to process transparency while simultaneously
improving a company’s bottom line.
2. 2 METTLER TOLEDO - White Paper - Batching
Batching
2011©Mettler-Toledo AG
An example of batch control most people can relate
to is baking bread. Raw recipe materials are lined up
then combined in an ordered fashion. Tools such mea-
suring spoons, mixers, and heat transform the raw
materials into a new output material – a fresh, deli-
cious loaf of bread.
This example is simplified, but it translates to the
manufacturing environment. Only now, imagine hun-
dreds or even thousands of bread loaves being baked
every day. There may even be variations in forms and
flavors.
The batch control scenario has changed significantly.
A batch control solution to manage batch-to-batch
consistency is critical to ensure high product quality.
Investment in a well-designed batch control system to
manage this larger-scale manufacturing scenario can
also help:
• Increase throughput
• Reduce raw materials waste
• Eliminate end product variations
• Maximize overall efficiency
1 The need for dedicated batch control
When faced with selecting the right batch control
system for a particular process, the task may seem
daunting: How can it be established that the selected
system will improve production efficiency, eliminate
raw material losses, and improve output consistency?
The overall solution must manage the various types
of material transfer onto the weigh platform and weigh
each ingredient. A weigh terminal that can manage
both activities lends itself to batching applications and
can help a control engineer simplify processes, since
ingredient weighing and material transfer are essen-
tially two parts of a single action.
A PLC system can be applied effectively, particularly in
instances when the batch process is fixed – producing
the same end product – and does not see a great deal
of switching between ingredients and recipes. How-
ever, this may not be the best solution for the small to
mid-size operation that requires flexibility in their pro-
cess because of limited resources.
The Instrument Society of America (ISA) S88 Batch
Control (Part 1-4) provides a consistent batch stan-
dard that can help manage the batch application, no
matter what kind of solution is chosen. Having a con-
troller that has the S88 guidelines built in allows the
user to have a modular system that will provide a con-
sistent application of the control system across mul-
tiple locations, which can minimize training require-
ments, simplify user interface and allow multi-plant in-
stallations to share recipes and information about their
process in the same data structure. With a PLC solu-
tion careful programming and implementation would
be required to ensure that a consistent approach was
followed, especially in multi-plant installations.
A dedicated batch control solution, on the other hand,
will combine batch management and material trans-
fer technology into one, full-featured batch controller.
This eliminates the need for PLC code writing, reduces
start-up time and allows the customer to focus on their
areas of expertise: their unique, palatable recipe.
2 Batch control system selection considerations
3. 3 METTLER TOLEDO - White Paper - Batching
Batching
2011©Mettler-Toledo AG
Example of a multi-material, 2 speed feed automatic material transfer Batch installation
Selection of a dedicated system that follows a docu-
mented structure for equipment handling, I/O control,
and material paths/recipes in the production process
can produce immediate and measurable benefits.
The ISA S88 batch standard provides a helpful guide
to this selection by:
• Defining a useful batch control model
• Communicating common batch control requirements
• Offering helpful configuration information
• Guiding vendor solution integration
The high-level objective of S88 is helping batch pro-
ducers make consistent, repeatable batches. The
standard provides common terminology for batch
manufacturing as well as guidelines on how to recover
from upsets during batch processes.
Batch Control/Reliable Weighing
Having consistent guidelines at the center of a batch
process can help lower production costs, increase
throughput, improve yield, reduce material loss, and
increase batch equipment utilization.
Following the S88 standard separates the physical
equipment from the recipe. This allows flexibility in
system configuration and makes switchover time from
recipe to recipe much shorter, which helps increase
throughput. The standard also provides an operator
with a consistent interface, which helps increase
familiarity with and utilization of the equipment.
Material loss is minimized because the operator is
prompted through each ingredient addition. A user
interface allows each material to be added within an
allowable tolerance range.
Ideally, a batch controller will take the S88 batch stan-
dard into account out of the box to simplify batch con-
trol implementation. A reliable weigh terminal such as
IND780batch will also be integrated into the solution.
3 Implementing dedicated batch control
Material 3
Material 2
Material 1
Fast Feed
Fine Feed
Fast Feed
Fine Feed
Fast Feed
Fine Feed
Fast Feed
Fine Feed
Fast Feed
Fine Feed
Material 5
Material 4
Hand Add
Operator
IND780batch
TerminalMixer
Scale
Discharge Material
To storage tank
4. 4 METTLER TOLEDO - White Paper - Batching
Batching
2011©Mettler-Toledo AG
Achieving Automated Targets
The S88 standard outlines a modular, flexible process
that allows a user to simplify a batch process. An inte-
grated, stand-alone solution supports this flexibility by
pre-defining the process equipment and letting the op-
erator select from several different recipes, shortening
the time to switch from batch to batch. It also provides
central control of material transfer using machinery
such as feed valves, gates, and screw conveyors while
simultaneously monitoring weight to ensure accurate
target cutoff of each transferred material. This can
dramatically improve batch throughput and reduce
material waste.
Manual Processes & Batch Control
If the process is manual – with an operator selecting
and adding ingredients – typically no discrete I/O is
associated with control. This method is highly flexible
since there is no associated I/O and several different
materials can be batched without preconditions.
In a manual process, the operator typically manages
batching. However, adding a batch control system to
guide the operator can eliminate problems with over-
and under-filling and ensure that unnecessary ingredi-
ents are not added or necessary ones missed.
Generally, the operator will use a bar code scanner to
identify an ingredient, add it, and move on to the next.
Material validation alerts the operator when an incor-
rect material is chosen and provides a prompt to scan
for the correct ingredient to ensure batch consistency.
In a blended approach, the operator may start a batch.
Then, the rest of the process runs without user inter-
vention unless additional hand-added ingredients are
needed.
If the process includes automatic material transfers,
then a batch controller that allows assigning I/O to
manage the material feeds is required. Usually, there
are also auxiliary equipment pieces that require man-
agement.
Barcode Scanner
facilitates tracking and
traceability
IND780batch
Terminal
guides operator
through recipe with
on-screen prompts
Hand Add
up to 999 materials
per recipe
Bench Scale
Example of a multi-material, manual formulation Batch installation
5. 5 METTLER TOLEDO - White Paper - Batching
Batching
2011©Mettler-Toledo AG
Auxiliary Equipment Management
Control of auxiliary equipment may require certain
criteria to operate properly. For example, if a mixer is
required, the batch controller may need to be able to:
• Turn on the mixer at a specific recipe step
• Pulse the mixer for a certain amount of time
• Delay starting the mixer until an add-by-hand ingre-
dient is placed on the scale before the mix starts
No matter the type of batch control being used, a
controller that accurately handles material transfers,
provides accurate target cutoffs, minimizes overfeed/
underfeed scenarios, and manages the batch process
is required for batch-to-batch consistency.
Track and Trace/Data Collection
Another desirable element for a batch controller is the
ability to track and trace phases in the batch process
to identify:
• When a product was made
• What and how much material was used
• Which operator ran the particular batch
This allows investigation into potential performance
problems. Managers can check for evidence of pro-
duction changes. This helps with easy batch and raw
material identification and can help:
• Determine why a batch may have been “off,”
• Pinpoint the ingredient that caused the problem
• Minimize number and extent of recalls
• Allow users to approach vendors who supplied the
ingredient
A stand-alone batch control processor should be able
to incorporate track-and-trace functionality, as well as
handle recipe creation and storage, backup terminal
settings and collect data. These actions are to:
• Implement a defined recipe-creation sequence
• Edit ingredients or amounts
• Re-scale the entire batch
Using a dedicated, stand-alone batch control solution
that accommodates the above functionalities can sig-
nificantly improve batch repeatability and productivity
while controlling costs. METTLER TOLEDO offers this
type of robust functionality in various stand-alone and
easy to integrate batch controllers.
PC configuration tool for Batch application
allows off-line recipe creation and system
configuration.
6. 6 METTLER TOLEDO - White Paper - Batching
Batching
2011©Mettler-Toledo AG
Implementing batch control management capabilities
can help achieve advanced material transfer and pro-
cess control goals. Using an out-of-the-box solution
that integrates weighing and material transfer can pro-
vide powerful cost and time savings for smaller-scale
producers who may not have the resources to imple-
ment a PLC with its requisite programming expertise
and time.
Ideally, any chosen solution will:
• Provide dedicated batch control for both manual and
automatic batching
• Contain control logic in the measurement instrument
for faster I/O
• Adhere to the S88 batch standard for process flex-
ibility and quality maintenance
• Increase material transfer throughput and improve
feed accuracy
• Provide track and trace/data collection to manage
risk and minimize waste
The right stand-alone solution can run multiple batch
processes while eliminating complex PLC reconfigura-
tion when a customer’s needs change. The resulting
tighter control can make products more consistent. This
can increase customer satisfaction and loyalty while si-
multaneously improving productivity and enhancing the
bottom line.
4 Summary
The following links and papers can provide more information on industrial weighing solutions and how effective
batch control can enhance quality, improve materials use rates, and lower production costs.
• METTER TOLEDO Material Transfer Control
www.mt.com/qi
• Instrument Society of America
www.isa.org
• Applying S88, Batch Control from a User’s perspective;
Jim Parshall and Larry Lamb – ISBN #1-55617-703-8
• Batch Control Systems, Design, Application, and Implementation 2nd Edition;
William Hawkins and Thomas Fisher – ISBN # 1-55617-967-7
• Control Global
www.controlglobal.com
• Functions that need to be considered in for Material Feed (Transfer) Batch Controls;
Charlie Fu Ph.D, Technology Leader, Procter & Gamble
• World Batch Forum
www.wbf.org
• ARC Advisory Group
www.arcweb.com
5 Additional resources