with Transmitter for recording Flow Controller No. 1
Control valves carry the same designation as the instrument to which they are connected. Thermocouples carry the same designation as the recorder or indicator to which they are connected. Sequential point numbers are indicated thus (see Table 14.6):
| RTM-6-4, | Thermocouple connected to point No. 4 |
| RTM instrument No. 6. Also see Figure 14.9. |
Additional symbols include:
| PG-6, | Pressure Gage No. 6 connected in the field on some item of equipment. If panel board mounted, it becomes-6B. |
| LTA-1, | Low Temperature Alarm No. 1 |
| HTA-1, | High Temperature Alarm No. 1 |
| LPA-2, | Low Pressure Alarm No. 2 |
| HPA-2, | High Pressure Alarm No. 2 |
| LLA-6, | Low Level Alarm No. 6 |
| HLA-8, | High Level Alarm No. 8 |
| PG-, | Push Button |
Figure 14.22 Partial presentation of piping materials specifications for a specific process service. By permission, Borden Chemicals and Plastics, Operating Limited Partnership.
Process flowsheets do not normally show companion flanges for valves unless these serve as blinds or for orifice plates. This detail is sometimes shown on the piping flowsheet, but here again the use of detail, which does not contribute to the communication function of the sheets, is avoided. Such detail can be time consuming when considered over the entire set of sheets for a process. Figures 14.7 and 14.9 are typical of reasonably good presentation without unnecessary detail. Such specifications as heights of a seal leg, locked open valve, or other information not summarized elsewhere must be recorded on the flowsheets.
14.13 Working Schedules
As a direct companion of the completed flowsheet, the line schedule sheet transmits the process and mechanically necessary details for proper interpretation of the piping aspects of the flowsheet (see Figures 14.20a–d). These schedules are initiated by the process engineer to further explain the requirements of the process as shown on the flowsheets. They are often and perhaps usually cooperatively completed by other engineers, particularly the piping, mechanical and instrumentation groups.
Table 14.6 Instrumentation nomenclature--complete general identification.
| Modification of ISA Standards | |||||||||||||||
| First Letter | Second and Third Letters | ||||||||||||||
| Controlling Devices | Measuring Devices | Alarm Devices | |||||||||||||
| * Process Variable or Actuation | Recording | Indicating | Nonindicating (Blind) | Valves | Self-Actuated valve | Safety Valve | Recording | Indicating | Recording | Indicating | Nonindicating (Blind) | Primary Elements | Wells | Glass Devices for Visual Observation | |
| RC | IC | C | CV | V | SV | R | I | RA | IA | A | E | W | G | ||
| Flow | F | FRC | FIC | FV | FR | FI | FRA | FIA | FA | FE | FG | ||||
| Level | L | LRC |
LIC
| ||||||||||||
