 Bonjour tout le monde, mon nom est Fulbert Baudouin. Nous avons vu les conséquences basées sur la compétition et pour contrôle et maintenant nous pouvons bouger à la présentation des symboles hautes et les lignes pour les connections d'équipement. Let's take a look at this figure again. Nous avons vu dans les parties précédentes que un level transmitter LT, L4 Level & T4 Transmitter Measures the level in the tank and transmits the signal associated with the level reading to a controller LIC with a display to indicate some data, I for indicator and C for controller. The controller compares this measurement with the desired value at which the controller variable should be maintained, the desired value or set point, and adjusts the manipulated variable which has a direct effect on the controller variable. The manipulated variable is, in this case, the flow rates with the control valve LV at the output of the tank, LV for valve in order to adjust the flow for level control. In these PNID diagrams, alarms are used to alert operator to series and potentially hazardous deviation in process conditions. Some question remains unanswered, like why LT and LV are surrounded by a circle, or why the controller is a square with a circle inside it? Where are these devices localized and what kind of controller is being used here? How are the PACs of equipment connected together? Which kind of signal transit inside? This third part aims to answer these questions. We are going to explain the various symbols and tag information to indicate the function of this device to show where the various devices are localized and how they are connected to one another. The what and where aspect can be determined from the symbol shape. The white part comes from text placed inside the symbol that is made up of two parts. This forms the tag number, C part 2 for further explanations. The symbol shapes are largely based on the accepted ISA 5.1 standard. This table shows the various symbols used to define the device and to locate it. Relative location is indicated via the presence of centered horizontal line or lack thereof, a dual centered horizontal line or a dashed centered horizontal line placed inside this symbol. The where part of a symbol is provided by the four columns of the various shapes, circle, square, square with circle, etc. Let's refer to the row D in this table. A circle symbol is quite simply an individual physical instrument or device in the field or on a panel. It doesn't matter if it is a level transmitter, a flowmeter, a pressure gauge or some other type of indicator. If it is a physical device that measure or display something, it will be illustrated by the use of the circle on a P and ID. Notice also how the tag number LT101 is placed inside this symbol. The common practice is to place the device function abbreviation on the top line with the loop number at the bottom. The next row in this table shows a hexagon. It means the computer is used for the process control. Have a look at row B on the table. A diamond within a square is used to define function within the programmable logic controller, a PLC. A programmable logic controller is an industrial computer control system that continuously monitors the state of input devices and makes decisions based on a custom program to control the state of output devices. This slide describes the main component of a PLC in more detail. The central processing unit, CPU, serves as a brand of the PLC. It is a 16 or 32-bit microprocessor consisting of a memory chip and integrated circuits for control logic, monitoring and communicating. The CPU directs the PLC to execute control instructions, communicate with other devices, carry out logic and arithmetic operations and perform internal diagnostics. The CPU runs memory routines, constantly checking the PLC to avoid programming errors and ensure the memory is undamaged. Memory provides permanent storage to the operating system for data used by the CPU. The system read only memory, ROM, stores data apparently for the operating system random access memory, ROM. It stores status information for input and output devices along with value for timer, counters and internal devices. PLC require a programming device, either a computer or console to upload data on to the CPU. PLC reads signals from different sensors and input devices. These input devices can be keyboards, switches or sensors. Input can either be in digital or analog form. Robots and visual systems are intelligent devices that can send signals to PLC input models. Output devices, such as motors or solenoid valves, complete the automated system. Now let's look at row A on the table, the ones that show a circle inside a square. This kind of symbol represents devices or functions that are part of a shared display and share control system, a distributed control system, DCS. A DCS combine one or more PLC with a human-machine interface. A distributed control system is a specially designed control system used to control complexe, large and geographically distributed applications in industrial processes for the chemical process industry. Avec these, controllers are distributed throughout the entire plant area. Controllers are distributed geographically in various sections of the control area. They are connected to operating and engineering stations which are used for data monitoring, data logging, alarming and controlling purposes via another high-speed communication bus. For instance, these symbols are used to represent a graphic on a computer screen or control panel that you can see and possibly interface via touch pad or mouse. It might be used to show the leveling tank or represent a hand switch that you can click on with the mouse to start a pump. The point is, if you can't see it on a control screen, it will be represented as a circle inside a square on a PNID. Now, we are going to focus on the various lines of this table. There are five lines. Concerning the first line, line number one, all shapes symbols have no horizontal or Dutch line inside. That means devices are located somewhere in the field, probably close to the general area shown on the PNID. Concerning the second line, all shapes symbols have a single horizontal line. That means devices are located on a main control panel near the control room or some computer screen in the main control room. The lines used have to be lighter than the associated process piping. Concerning the third line, all shapes symbols have a single Dutch horizontal line. When you see such a symbol that simply means that you can't normally see it or work with that device in the field, it might be installed behind or inside a panel so that is normally not in view, inaccessible to the operator. For instance, a circle with a Dutch line in the middle means it is an instrument or device that you can't normally see or get to. If you are an operator, it is probably something you do not need to get to, but it might still be vitally important to the plant control system. That is why we show it this way on a PNID. In a similar fashion, a graphic display symbols with a Dutch line in the middle simply means that this portion of the control system is password protected. Attentively, it could mean that it is hidden from normal view on a screen or operating panel so you can't get to it unless you know the secret access code. On the fourth and fifth line on this table, all shapes symbols have a double horizontal line or double Dutch horizontal line. On the wall, these kinds of symbols are infractedly used. A double line means the same things as a single line but devices are in this case located on the secondary control panel and not on the main control panel. The same goes for a double Dutch line. You will notice with these kinds of symbols, no specific location information is provided only that the device or graphic is associated with a relative general location. In many cases, it is not hard to figure out where something is, just from where the symbol is on the drawing but there are limits to what this symbol can convey. Now, we are going to explain the different line symbols that connect devices and equipment. The key line types are highlighted in the figure. By far, the most common line type is a solid line which is used to represent a pipe. Other common line types that you should be able to identify are first electrical signals, second instrument air to control valves or devices, and third software or data link which includes virtual communication such as what occurs inside a computer program or PLC leader logic. The software can include anything that happens inside a computer but you need a functional description to actually know what that is. Just note that when you see a software lines, it means computers are at work, linking the devices in some meaningful way that relates to the system controls. In this part, we have explained the different shape convention for the ISHA 5.1 standard in order to specify the location and the role of each device. You are now able to explain and understand every control loop shown in the P&ID diagrams. For each control loop, you know how to define the controller use and its locations, the values sensor put on the chemical processes, the values alarm in place, the different kinds of transits signals. The example shown at the beginning of this part can be analyzed again in detail. The shape surrounding the controller, LIC, the circle inside your square, shows that this controller is part of the shared displays like a distributed control system or just a control panel that you can see. The single horizontal line inside the shape indicates that it is probably located on the main control panel near the control room normally accessible to the operator. LT and LV are surrounded by a circle. As explained previously, the circle symbol is quite simply any physical instrument or device in the field or on a panel. In this case, it means a sensor transmitter for the level LT and a control valve at the output of the tank, LV. Concerning the different connections between devices, the solid line indicates that the sensor and valve are connected directly in the process. The Dutch line between the controller LIC and the valve indicates that the controller transmits an electrical signal to the valve. Perhaps in this case, the valve is an electric valve. The electrical signal is in general 4 to 20 mA current loop. In the same way, an electrical signal is used to link the transmitter with the controller. So, we are half way through this unit and the next part will cover final control system symbol and the different kinds of valves.