Some equipment code systems number all items on first process flowsheet with 100 series, as C-101, C-102, P-106 to represent compressors number 101 and 102 in different services and pump 106 as the sixth pump on the sheet. The second sheet uses the 200 series, etc. This has some engineering convenience but is not always clear from the process view.
To keep process continuity clear, it is usually best to number all like items sequentially throughout the process, with no concern for which flowsheet they appear on. Also, another popular numbering arrangement is to identify a system such as reaction, drying, separation, purification, incineration, vent, and cooling tower waters and number all like process items within that system for example:
Table 14.5 Typical identification for flowsheet process functions.
| AS | - Air Supply |
| BD | - Blowdown |
| BF | - Blind Flange |
| CBD | - Continuous Blowdown |
| CD | - Closed Drain |
| CH-O | - Chained Operated |
| CSO | - Car Seal Open |
| CSC | - Car Seal Closed |
| DC | - Drain Connection |
| EBD | - Emerg. Blowdown Valve |
| ESD | - Emerg. Shutdown |
| FC | - Fail Closed |
| FO | - Fail Open |
| HC | - Hose Connection |
| IBD | - Intermittent Blowdown |
| LO | - Lock Open |
| ML | - Manual Loading |
| NC | - Normally Closed |
| NO | - Normally Open |
| OD | - Open Drain |
| P | - Personnel Protection |
| QO | - Quick Opening |
| SC | - Sample Protection |
| SO | - Steam Out |
| TSO | - Tight Shut Off |
| VB | - Vacuum Breaker |
| Reactor System, R: | Reactor is RD-1 |
| Reactor vent cooler is RE-1 | |
| Reactor vent condenser is RE-2 | |
| Reactor recycle pump is RP-1 | |
| Level control valve is RLC-1 | |
| Relief valve is RSV-1 |
Then, establish the same concept for all other unit or block processing systems. This is often helpful for large projects, such as refinery or grass roots chemical processes. Valve identification codes are usually used in preference to placing each valve specification on the flowsheet. This latter method is feasible for small systems, and is most workable when a given manufacturer (not necessarily the same manufacturer for all valves) can be selected and his valve catalog figure number used on the flowsheet. For large jobs, or where many projects are in progress at one time, it is common practice to establish valve specifications for the various process and utility services (see Figures 14.21 and 14.22) by manufacturers’ catalog figure numbers. These are coded as V-11, V-12, V-13, etc., and such code numbers are used on the flowsheets whenever these valves are required (also see Figures 14.8 and 14.9). By completely defining the valve specification in a separate specification book the various valves—gate, globe, butterfly, plug, flanged end, screwed end, welding end—can be identified for all persons involved on a project, including piping engineers and field erection contractors.
Figure 14.17c summarizes a system for representing components on the flowsheets. The instrument symbols of Table 14.6 and Figures 14.18a and b are representative of the types developed by the Instrument Society of America and some companies.
Figure 14.21 Typical valve codes and specifications. By permission, Borden Chemicals and Plastics Operating Ltd. Partnership.
Some other designation systems indicate the recording or indicating function in front of rather than behind the instrument function. For example:
| RTC-1, | Recording Temperature Controller No. 1 |
| VRTC-1, | Control Valve for Recording Temperature Controller No. 1 |
| RFM-6, | Recording Flow Meter No. 6 |
| ORFM-6, | Orifice flanges and plate for Recording Flow Meter No. 6 |
| OTrRFC-1, |
Orifice flanges and plate used
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