»
SINGLE-USE
» • • • •
The traditional approach: Purchase components and make connections. Steam-sterilize the assemblies.
The lean-thinking and process optimization approach: Purchase multi-component assemblies, connect as needed, and sterilize.
The reasonable approach for single-product facilities: Purchase process-specifi c assemblies that are irradiated and ready to use.
The “modular” approach to provide operational fl exibility and reduce support costs: Purchase ready-to-use subassemblies and connect as needed with closed system connectors. Figure 1 illustrates an “expand to fi t” modular approach for a liquid fi ltration operation.
2. Select junctions to meet requirements, and minimize the number of junctions. Minimizing the number of junctions must be weighed against increases in module size. One way to reduce connections inside modules is to use the highest possible degree of fl ow splitting (furcation) in a single molded component. As shown in Figure 2, the number of connections or molded junctions is reduced by using 4-way rather than 3-way connection points. The principle applies for higher order connectivity. As single piece connectivity increases, the chance of leaks decreases.
Figure 1. Schematic of a simple modular process to fi lter liquid into a set of containers. Generic connectors are represented by the “U” and orange dot. Closed system connectors or tube welding could be used to make these connections downstream of the fi lters. The system can be extended using the connection point on the right, or this point can be sealed to terminate the chain.
Figure 2. Increasing junction complexity decreases the number of mechanical connections in fl uid transport networks. The left side of this fi gure shows two networks, one with 4 inlet/outlets and one with 5. Using 4-way junctions leads to the simplifi ed designs on the right. They have the same number of inlet/outlets, but fewer potential leak points.
The internal standard for assemblies should defi ne: • Decision-making methodology for “make vs. buy” decisions
• Design principles for making connections and building assemblies
• •
• Specifi cations for qualifi ed subassemblies (modules)
A selection guide to match module connectors with process requirements
Approved disconnection methods and supplies
Standard connections/disconnections need to cover a design space that spans the majority of anticipated applications.
The following heuristics are off ered to start discussion about best practices in SUS design. Best practices will vary with organization size, number of products and product types supported, and local regulatory requirements.
1. Minimize material types in each assembly and in the collection to reduce engineering support, validation, and change management eff orts.
20 | | November/December 2013
3. Separate “furcation” from “translation”: Take advantage of fl exible single-use tubing and split fl uid paths in one location. Imitating “hard piped” systems as shown in Figure 1 makes assembly more complicated and provides more points of failure. A high degree of connectivity that might be enabled by fl exible tubing and a high complexity molded fl ow splitter is illustrated in Figure 3. Note that “simple and standard” may look diff erent than “hard piped” or custom- designed single-use systems.
4.
Balance complexity across modules: Avoid creating assemblies that are diffi cult to build and handle by distributing parts among modules. The less complicated assemblies should include the tubing needed to transport fl uids to adjacent, more complicated, assemblies. It is a good idea to break up modules into those with a transformative function (fi lters, for example) and those with only fl uid transport functions. The transport modules should contain the majority of the tubing required for the fully assembled, end-to-end process.
5. Employ a “design once – use many” strategy for modular design to simplify management of SUS. Most of the work
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92