Tackling CIP Automation with S88

Clean-in-place (CIP) is a method of cleaning vessels and lines without disassembling them. It involves delivering solutions of chemical detergents and rinses at specifi ed flow rates and temperatures. Typically, a CIP skid creates the cleaning solutions and routes them to a user skid that requires cleaning.

CIP has grown over the last 50 years to be very important in the food and beverage, pharmaceutical, and cosmetics industries. Automating CIP effectively is a key factor in the plant running smoothly.

CIP is commonly used in the food and beverage, pharmaceutical, and cosmetics industries. Originating in the 1950s, early CIP systems were manually operated. Today, most CIP operations are automated. However, there are still some common challenges to automating a CIP system and these are:

• Finding an efficient way to automate similar actions
Making an alkaline wash solution may be very similar to making an acid wash solution, for example. Likewise, the routing of the alkaline wash though the skid being cleaned usually differs minimally from the routing of the acid wash through the skid — perhaps only in the flow rates or cycle times.

• Managing resources
Commonly, a single CIP skid will, at different times, clean several user skids. There is a need to supply solution to the different user skids and return to it. If the supply and return paths are not dedicated, there is a need to ensure that there is no confl ict among the paths.

• Minimizing time required for CIP cycle
Some of the operations can be performed simultaneously. Chemical wash solution can be prepared during rinsing, for example. There are two most common physical layouts for CIP systems:

• Fixed CIP systems connected to multiple user skids by transfer panels and/or distribution headers. (Fig. 1)
This is the most common approach. Cleaning solutions are routed through distribution headers or transfer panels to the skids requiring cleaning. The fixed skids with two vessels per CIP skid can handle high volumes of cleaning solutions. However, managing the complex distribution paths can be difficult.

Fig. 1: Each fi xed CIP skid can clean one of several user skids by transferring though a distribution header.

• Portable CIP system connected directly to a user skid (Fig. 2)
Portable CIP skids are small-capacity movable skids with a single vessel that is utilized for all rinses. Used mainly in multi-product facilities, this approach reduces the amount of CIP supply and return distribution piping required. A point-of-use (POU) connects the utilities and chemicals to the portable skid. Typically, the portable skid has a control panel mounted on it and has three or four connections to the user unit.

Fig. 2: Each portable CIP skid can clean one of several user skids connected directly to the skid.

ANSI/ISA-88 (S88) provides standards and terminology for batch control. S88 features a physical model that provides a way to organize the physical equipment. It also has a procedural model that defi nes the control required for the equipment to perform its tasks (Fig. 3). The S88 model can provide a framework to address these challenges for either CIP layout.

Fig. 3: A S88 physical and procedural model.

CIP Physical model
The first step to automating a CIP system is to define the S88 physical model. For fixed CIP systems, the S88 unit boundaries are drawn such that the CIP skid and the user skid are units (Fig. 4). Each unit consists of equipment modules (such as temperature control and level control) that are not shown in the figure.

Clean-in-place (CIP) is a method of cleaning vessels and lines without disassembling them.

The distribution headers and/or transfer panels that connect the CIP skid to one of several units can be made into equipment modules that are independent of either unit. While Fig. 4 provides a relatively simple diagram, the paths shown can be very complex in the plant. Having unique distribution path settings in equipment modules, which is separate from the unit, would accomplish two things:

Fig. 4: A physical model for fixed CIP.

• Allow resource management of the distribution path. Each CIP event can acquire the distribution path equipment modules it requires, leaving the ones it does not require to be acquired by other events.

• Allow every CIP skid in the plant to operate similarly. The distribution path from a CIP skid to a user skid is not part of the unit.

Fig. 5 shows the S88 physical boundaries for the portable CIP layout. When a user unit needs cleaning, it can acquire the portable CIP skid, which is an independent equipment module. This next section explains how this physical layout simplifies the procedural layout.

Fig. 5: A physical model for portable CIP.

CIP procedural model
To a large extent, the physical model drives the procedural model. The following sequences are typically required for the CIP skid: drain CIP skid, circulate pre-rinse, acid preparation, circulate acid wash, circulate post acid wash, alkali preparation, circulate alkali wash, circulate post alkali wash, circulate final water-for-injection (WFI) rinse, air blow, and drain CIP skid. The following sequences are common for the user skid: set up, pre-rinse (circulate routes 1-x), acid wash (circulate routes 1-x), post acid wash (circulate routes 1-x), alkali wash (circulate routes 1-x), post alkali wash (circulate routes 1- x), fi nal WFI rinse (circulate routes 1-x), and air blow (through routes 1-x). The sequences that operate the CIP skid equipment become phases on the CIP skid unit, and the sequences that operate on the user skid become phases on the user skid unit. Similar sequences can be modularized or made into reusable, flexible phases. The differences are handled with recipe parameters.

For example, acid and alkali preparation may be combined into a single phase called solution preparation (Fig.8). Pre-rinse and final rinse circulation can be combined into a single phase called circulate rinse. Acid and alkali circulation can be combined into a single phase called circulate wash.

Fig. 8: Acid and alkali preparation may be combined into a single phase called solution preparation.

Similarly, on the user skid, all of the sequences that circulate the different solutions through routes of the user skid can be combined into a single phase circulate route 1-X, using recipe parameters to handle the differences. This modular approach helps to ensure consistency and also decreases software development and maintenance costs. The phases on the two units would coordinate with each other when the CIP skid and the user vessel need to interact with each other. The user vessel acquires and sets required equipment modules on the distribution path.

This approach allows a generic CIP skid. The CIP skid phase does not require unique logic to handle the differences between cleaning the different user skids and can operate exactly the same regardless of which user it is cleaning.

The S88 procedural model for the fixed CIP skid can also be optimized by running phases in parallel to reduce CIP cycle time. For example, while circulating the pre-rinse solution from one of the vessels on the CIP skid to the user, the other vessel on the CIP skid can prepare the acid rinse solution (Fig.9).

Fig. 9: Minimize CIP cycle time through parallel operations.

Likewise, if one of the two CIP vessels is draining, the other vessel can position the valves for re-circulation or for receiving water for the next wash or rinse. By taking advantage of phases executing in parallel, the CIP procedure can run more quickly and the user skid has more time available for making product.

For the procedural model for the portable CIP system, each phase addresses the sequencing requirements for both the CIP skid and the user skid. When it requires cleaning, the user skid unit acquires the portable CIP skid equipment module (EM). Since the user skid unit acquires and drives the CIP skid EM directly, there is no coordination between phases on two different units.

Similar to the fixed CIP skid, phases can be modularized in order to increase consistency and decrease the cost of software development and maintenance. For example, the pre-rinse, acid wash, post-acid rinse, alkali wash, post-alkali rinse, final rinse, and air blow can be modularized into one phase with recipe parameters to handle the differences. This modular approach helps to ensure consistency and also decreases software development and maintenance costs.

Conclusion
CIP has grown over the last 50 years to be very important in the food and beverage, pharmaceutical, and cosmetics industries.Automating CIP effectively is a key factor in the plant running smoothly.

Using an S88 approach helps to effectively address the challenges of CIP automation by driving modularity, which is the key to making batch logic work efficiently and consistently.

The two most common equipment architectures are fi xed CIP skids that use distribution headers and portable CIP skids. Although the S88 physical and procedural models are different for each, applying the S88 modular approach helps tackle the challenges for either architecture:

• Modularizing software
Using a modular approach makes automation more efficient and more consistent. Drawing unit and equipment module boundaries can make it possible to create classes of equipment modules and units. It can also help to combine sequences into a smaller number of more modular phases. This approach increases consistency and decreases development and maintenance costs.

• Managing resources
Drawing unit and equipment module boundaries appropriately makes it possible to better manage the resources in the plant. CIP distribution headers can be defined and managed as independent equipment modules in order to avoid resource conflicts. In the case of the portable CIP skid, the entire CIP system can be managed as an independent equipment module.

• Minimizing time required for CIP cycle
If the physical equipment supports it, as in the case of the fixed CIP system, the procedural model can be defined so that different phases can run in parallel. This approach can minimize cleaning time and allow the user skid more time for making product.

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