Standard P&ID Symbol Legend | Industry Standardized P&ID Symbols
When this happens, it is usually noted. The same loop may have FT - which is the flow transmitter in the same loop. Since systems transform their inputs into their outputs, we use labelled arrows to represent specific interactions between systems:.
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We have filled all the back orders for the Fseries kits and are ready to accept your orders before Christmas! All kits contain all parts needed to complete the model for running on your HO railroad, including: Trucks, wheels, Kadee couplers, screws, weight, decals, brass castings stirrup steps, brake wheel, and roping staples and wire to make the brake rods, grab irons jig provided , and brake staff.
In this photo the Underframe plastic sprue is gray plastic, production kits will have this part in the same brown as the sides and detail sprues. The Deck will be in gray plastic as shown. Correct for prototype cars, built A number of these cars were assigned to SPMW service, at least by in many assignments. Correct for prototype cars, built for SP, in three number series.
A number of these cars were assigned to SPMW service, at least 36 by Totaling about assigned to MW service by , many lasting into the s and s in MW service. Totaling at least 36 cars by , many lasting into the s. After the Supreme Court break-up of the Harriman roads back into their individual identities in , the CS numbering system continued, but the SP and UP settled on a simpler classification system of car type: So F would be the first class of ton flatcars designed in this system.
Designs after for UP and SP diverged, but retained the Ftype series nomenclature for many years. The new production F and later designs used a built-up double beam centersill underframe. The car shows last being reweighing in Willits in July In later years NWP's lettering changed to be more like SP's standard freight lettering to comply with AAR's later recommended reporting mark practices.
Table 1 summarizes the F, -8 and -9 cars built during this era. The distinguishing feature of all these flatcars was the overhanging deck with wooden blocks and steel angle iron to support the overhang. This OwlMtModels series of kits replicates this deck block feature, unlike any other HO-scale flatcar on the market today.
The SP , an F class car made with Kit was one of the last group of surviving cars from PE group cars which were transferred to the SP in The second group joined the SP ranks in , and the last group in The cars in each of these groups were repainted as the car's next regular shopping and reweighing came due, which was every 48 months 4 years. The F, -5, -8, -9, and cars were the mainstay of the SP's fleet until after World War II, when the new Fseries cars were being built in large numbers.
Many earlier cars were renumbered as they continued in service Table 2. Some points of interest about this type of diagram:. An energy input split outside a system. Exercise for the reader: Take some time to study Figure 3, and try to identify as many shortcomings or ambiguities as possible. Discuss them in class. A sample system architecture diagram for a toaster. In this case, the product is a toaster and was created with a different software package than the preceding figures, which accounts for the stylistic differences.
In this case, there are far more annotations on the arrows and as such this constitutes a better diagram. Still, this diagram is not perfect. Take some time to study Figure 5, and try to identify as many shortcomings or ambiguities as possible. As the saying goes, a picture is worth a thousand words. A good diagram can capture a huge amount of information in a very small space. This makes diagrams a dense way to represent information. Diagrams can also represent non-linear information, such as the multi-dimensional relationships between systems.
Text is linear , which prevents it from representing non-linear information efficiently. One very important reason for creating a specification of a system is to record the decisions made during its design. Besides the legal requirements - being able to account for your actions as an engineer - documentation provides one with the means to remember what one did. It is not likely that one will remember everything one does, and why one did it. A record of decisions taken can work as a memory aid, so that one can work in the future knowing sufficiently well what one did in the past and why.
Diagrams, if properly constructed, are excellent mechanisms to communicate complex information to others, much like a well-made technical drawing. Designing is, among other things, an act of communication, so making sure one has an accurate and relatively easy to read account of design decisions is important for communicating that information to others. A system diagram captures the results of design activities. While it is possible to use other means to record one's work during designing and then generate the system diagram at the end of the systems design task, it is not recommended.
System diagrams can be used as thinking tools. By studying a system diagram, one can discover problems and shortcomings of the design it represents, and at the same time construct a final document that will capture the entire design. Thus, system diagrams should be constructed during systems design, and used as the basis for refining and specifying various aspects of the system. One may use pencil and paper, or software, to build a system diagram. Software-based diagrams are easier to maintain and to produce in a neat and concise form.
The final decision is, however, up to each design team. Salustri's recommendation is draw. It's free, works online, and has standalone versions also free for most platforms.
Also, it works very well. There are also some online web-services for diagramming, many of which have free trial periods - Creately , and Gliffy being the most popular. The development of a system diagram is often done at the same time as the identification of subsystems because the two tools complement each other. The PAS forces the designers to think in terms of the operation of the product, which can often bring to light shortcomings in the system identification chart.
Each box, or node , marks a subsystem. Generally, all boxes look the same, and contain the name of the subsystem. Every system has inputs and outputs by definition.
An interaction is shown as a transfer of mass, energy, or information between system elements. Each arrow interaction represents an interface between system elements. Be as specific as possible on the nature of that interface, without deciding how the interface will be implemented — unless you can justify your design decisions. Exercise for the reader Explain why the bad PAS is bad, and how the good one is better.
How could you improve the good PAS even more? User Tools Log In. Why use system diagrams? How does one construct a system diagram? Software for creating system diagrams. Summary of System Diagram Rules. System Diagram A system diagram is a visual model of a system , its components, and their interactions.
A system diagram is a visualization of a system as a flow-chart-like diagram. Since systems transform their inputs into their outputs, we use labelled arrows to represent specific interactions between systems: System design is a top-down or outside-in process: Air is distinguished from people and cargo: A flawed system diagram for the elevator.
If pursued literally, this design could result in the asphyxiation of the passengers. All three of these inputs outputs are treated as mass inputs outputs , but air is treated as a separate input output stream.
This is because of the intention of those inputs. This would be problematic at best. By making a separate interaction stream for air, we are embedding in our model the requirement that air must be treated entirely differently than people or cargo.
User commands and feedback are purely functional: