200 PId Development

200 P&ID Development

AbstractThis section is an introduction and comprehensive guide to the planning, layout, preparation, and review of piping and instrumentation diagrams (P&IDs). It follows the P&ID development process from start to finish and is applicable to drawings of any scale and complexity. Piping, equipment, and instrumentation aspects of the P&ID are given equal weight, and considerable attention is given to the inclusion of specific elements on the drawing. Particular emphasis is given to the P&ID as a major factor in determining the efficiency, operability, maintainability, and safety of a facility.

Note The foldout P&ID drawings referred to in this section are located at the end of this section.

Contents Page

210 The P&ID and Its Uses 200-3

220 Planning the P&ID 200-3

221 Developmental Stages

222 Layout Styles

223 Types of P&IDs

230 P&ID Symbol Standards 200-8

231 Symbol Standards—Piping and Equipment

232 Symbol Standards—Instrumentation and Controls

240 P&ID Content 200-11

241 Instrumentation

242 Piping and Equipment

250 Numbering Systems 200-16

260 Additional Information 200-19

270 P&ID Review 200-21

280 P&ID Drawings and Engineering Forms 200-24

281 P&ID Drawings

Chevron Corporation 200-1 July 1999

200 P&ID Development Instrumentation and Control Manual

282 Engineering Forms

290 References 200-25

July 1999 200-2 Chevron Corporation

Instrumentation and Control Manual 200 P&ID Development

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210 The P&ID and Its UsesPiping and instrumentation diagrams (P&IDs) are the graphic and symbolic summa-tion of the processing aspects of a facility. Although the piping, instrument and equipment information collected on a P&ID can be found elsewhere in a facilitydesign records, only the P&ID displays them in comprehensive, coherent relatioship to one another.

Activities in which P&IDs have a key role include the following:

• Design and design review. Defines piping, instrumentation and control systems

• Design and construction progress. Provides a graphic framework in which tomonitor design and construction

• Construction completion check. At plant completion, the construction agenc(either a contractor or Company) is responsible for delivering completed asbuilt P&IDs. This permits a piece-by-piece review of compliance with the design

• Startup. Provides critical information during startup of a new facility

• Operation. Provides the primary source of operating information and traininaid for a plant or facility

• New engineer training. Provides a sound example from which to design similar facilities

• Maintenance planning and safety. Provides a framework for planning and monitoring cleanup and isolation, inspection, and similar work prior to startuas well as future maintenance

• Governmental communications. Provides a vehicle for communication with regulatory and governing agencies

• Additions and modifications. Up-to-date P&IDs provide a basis for esti-mating, design and implementation of future additions and modifications

220 Planning the P&IDAll major P&ID decisions and approval should be secured early in the design process to avoid costly changes. Because this isn’t always practical, the P&ID musually accommodate some additions. Planning consists of determining the nuof P&IDs and their arrangement, content, and style. (For more on style see Section 222.)

Safe Design PracticesSafe design practices promote operating continuity, prevent upsets and alarm fures, and reduce unnecessary shutdowns. They are the foundation for employecommunity safety.



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Space AllocationTo prevent overcrowding and a confusing process flow, 25% to 50% of the space on drawings should be allowed for future equipment. Disorderly P&IDs may impede the design process, and can be a liability during plant upsets—when quick comhension is important.

D-size (22-inch by 34-inch) drawings are commonly used for P&IDs because thare a manageable desktop size; however, some systems would be seriously ovcrowded on a single D-size drawing. For a “grouped” P&ID (see Section 222) a longer R-size (28-inch-by-unlimited) drawing ensures that all closely related processing equipment is included on the same P&ID. The longer drawing may avoided by separating stand-alone process, utility, or package systems and plathem on their own major equipment or auxiliary P&IDs.

Arrangement of ElementsThe initial arrangement of each process P&ID is submitted for owner/operator approval. These P&IDs include equipment, piping and instrument manifolds, inment symbols (or reserved areas for them), piping runs (or reserved areas—hozontal and vertical), auxiliary systems and subsystems.

Arrangement of equipment and piping should follow a sequence that flows logi-cally across the sheet from left to right; for example, feed comes in on the left, pucts go out on the right. The main flow lines should be heavier than secondary process lines and utility lines, and should not double back. Lines should be spaevenly, with a minimum of lines crossing. In general, the P&ID should be kept readable.

221 Developmental StagesTo avoid the need for extensive rework and decrease the chance of error, P&IDusually revised and reissued several times during their development. This stagapproach also makes the job more manageable and allows critical path items tproceed before all aspects of the P&ID are firm. The stages might proceed as follows:

Preliminary stage (permits P&ID layout to proceed)

Stage 1 (permits facility layout and P&ID development to proceed)This revision affects the following critical path elements: site preparation, foundtions, underground features, structures and pipeways, piping, platforms, ladderwalkways, power and utility supply and distribution systems, etc. This revision itypically issued for design. P&ID elements necessary for this revision include thefollowing:

• Major process and utility systems equipment, including driver and numberinsystem selection. Though not entirely a P&ID function, the estimated size alocation of major equipment such as the air cooler, furnace, reactors, etc., ialso required



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• Estimated sizing and most major valving (with sizes) for major process lineand utility and relief headers (with major supply and return branches)

• Major piping and control valve manifolds

• Instrumentation, including the majority of field sensors, transmitters, recordand controllers

Stage 2 (permits major instrumentation purchase and equipment fabrication)The second P&ID issue follows closely upon the first. This issue permits major instrumentation purchase and equipment fabrication to proceed, and finalizes tplot plan. In addition, work starts on detailed piping design, and relief and utilityareas. P&ID elements necessary for this revision include the following:

• Selection of instruments and numbering system, and approval of all equipmand instrument connections

• Platform layout and specification of platform attachment clips so that vessesuppliers can begin fabrication

• All revisions to previously approved elements

• Columns, vessels, tanks, drums, and heat exchangers

• Connection sizes and types (flanged or stub welded), location, flange facinand ratings

• Relief valve settings

• Control valve failure mode: fail-OPEN (FO) or fail-CLOSE (FC)

• Setpoints of critical shutdown instruments

• All instrumentation. Control valve manifolds have been sized, all major instments numbered. Shared-display mounting, board mounting, or field mounhas been specified

• Piping. Final valving and sizing of all process lines (and major utility connections) their numbers, insulation requirements and heat tracing. All small pipand utility connections shown

Stage 3 (permits finished piping layout to be completed)P&ID elements necessary for this issue include the following:

• All revisions to previously approved elements

• Equipment, piping and instrumentation. All necessary additional detail. Siziand specifying of all relief, utility, and sample connections

• All small piping sizes, connections, and fittings, including startup, shutdownpumpout, steamout, washdown, etc.

• Plot limit block valves, fully detailed or on separate drawings, as warranted



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Stage 4 (receives approval for construction)P&ID elements necessary for this issue include the following:

• All revisions to previously approved elements• All operating elements• All maintenance elements• All safety elements

222 Layout Styles

Note Figures 200-3 through 200-10 are 11x17 foldouts at the end of this section.

The three primary P&ID layouts used by the Company are the grouped equipment layout, serial equipment layout, and geographical layout.

Grouped Equipment LayoutThis layout style emphasizes processing interrelationships between closely assated, often interactive equipment. It is used for plants where several feed/produstreams are processed concurrently, such as on-plot process facilities (the majomanufacturing areas of plants, as opposed to off-plot, or support, areas), utility generation facilities, water and waste treating facilities, etc. (see Figure 200-3). To keep drawing lengths manageable, the facility is divided into essentially indepedent functioning elements. For a large processing plant these elements might include furnaces, reactors, distillation columns (towers), compressors, etc., thabe conveniently grouped on separate drawings. On the separate drawings, linehandling lighter products are drawn along the top, lines handling the heavier pructs along the bottom.

Serial Equipment LayoutThis is a convenient layout for plants with a single major process stream that isacted upon sequentially at essentially independent stations, for instance, a pacaging plant or production facility (see Figure 200-4). The P&IDs for plants laid out in this style can be many feet long when on a roll or multifold paper. When properly laid out, these may be broken down into individual drawings to more easilydesktops or for inclusion in record books. Each segment holds usually one, somtimes two processing elements.

Serial-style P&IDs often have equipment information blocks along the top, procgas, relief, vent and flare headers just below, the equipment in the middle, internection lines just below the equipment, and pumps and compressors along the edge.

Geographical LayoutThis layout is used for collections of independent processing elements that arelinked by process relationships, such as tankfields, utility distribution systems, plimit manifolds, and interconnection diagrams. A roughly geographical layout isoften the most logical way to present them. (See Figure 200-5).



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223 Types of P&IDs

Main P&IDsThe main P&IDs show process flow, mechanical equipment, and instruments and controls. For small plants the main P&ID is all that is required.

Major Equipment P&IDsMajor processing equipment such as compressors, reactors, furnaces, treaters, and refrigeration systems are often placed on separate P&IDs (See Figure 200-6). This accomplishes the following:

• Provides the space to show the interrelationships of complex mechanical elements with their instrumentation and supporting supply systems

• Shows precise location details, particularly for critical temperature points

• Unclutters the main P&IDs

Auxiliary P&IDsEquipment not directly in the main processing stream is often referred to as auxil-iary equipment. Examples are seal, flush, and purge systems; lube oil, hot oil, aoil mist systems; and glycol heating systems (see Figure 200-7). These may be placed on separate P&IDs to reduce crowding on the main P&ID or when they sequipment on different P&IDs. When small, they may be combined on a single drawing with other auxiliary systems.

When auxiliary equipment is supplied assembled in a “package unit” from a venit should be depicted within a dashed-line box, with attention given to the followCompany/vendor interface areas:

• Equipment supplied at the boundaries. Otherwise, pickled pipe may arrive without mating flanges, the pipe material may be wrong, or both Company vendor may supply block valves

• Instruments. Otherwise, both parties may supply duplicate sets, or Compansupplied instruments may not fit vendor-provided connections

Plot Limit Block Valve Manifold P&IDsThis is a type of geographical layout (see Section 222). In major petroleum and petrochemical processing facilities individual plants or groupings of plants are sup as isolable entities. A single major assemblage of block valves at the end ofcentral pipeway, the plot limit block valve manifold (plot limit manifold), ties the individual plant headers into an interconnecting pipeway system serving other fities (see Figure 200-8). With a few exceptions (primarily underground lines) all lines in the plant pass through the plot limit manifold. This facilitates supervisorreview of plant isolation prior to a major planned shutdown. For small plants theplot limit block valves may be shown on the process P&IDs themselves. For larplants a plot limit manifold drawing is prepared.



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Interconnection DiagramsThese specialty drawings show, on one drawing, the relationship between control systems located in different plants.

Utility Distribution System P&IDsThese are usually laid out geographically to preserve the sequencing and relative locations of all elements (see Figure 200-5). In mid-sized plants, several utility systems (steam and condensate, all gases, water, etc.) may either be layered on a single drawing in separate well-defined strips or superimposed.

To reduce clutter, only the tie-in portions of utility systems should be shown on the main P&IDs. These should include all valving and instrumentation associated with the control or isolation of the processing equipment—checks, block valves, flowindicators, etc.; the utility P&IDs themselves show little valving. The tie-ins shoube labeled with the utility P&ID line and drawing numbers, and, if desired, their service.

Small, in-plant utility facilities are usually shown on their associated utility P&IDs—instrument air dryers, fuel gas knock-out drums (separators that removentrained water from the gas), condensate dryers, etc. Larger utility supply andprocessing systems are usually shown on separate process P&IDs—water treaplants, boiler plants, etc.

Relief System P&IDsFigure 200-9 shows a typical geographical layout for a relief system. Relief valveand bypasses are not shown here, but are included on the main process P&IDsusual practice for process operations information.

All calculated relief loads should be recorded on this drawing, since they are noalways found in the plant design records. Relief system P&IDs are very helpful determining relief system modifications when adding major equipment in the fu

230 P&ID Symbol StandardsThe following drawings show the P&ID symbols commonly used in newer plantThese symbols are derived from the nationwide Instrument Society of America (ISA) standards (see Standard Drawings and Forms):

• ICM-EF-824A, Standard Piping and Equipment Symbols• ICM-EF-824B, Standard Instrument Symbols• ICM-EF-824C, Standard Logic and Instrument Symbols• ICM-EF-824D, Guidelines for P&ID Presentation of Level Instrumentation

EF drawings may be adapted and condensed to a single sheet for a major facil



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231 Symbol Standards—Piping and EquipmentWhen making plant additions or modifications, it is sometimes best to continue using the existing symbology familiar to plant personnel. However, new facilities should use modern ISA symbology to ensure clear communications with installa-tion personnel.

An ISA symbol exists or can be adapted for almost any instrument. Equipment symbols are another matter. It is often necessary to elaborate on ICM-EF-824A for complex machinery such as compressors, multistage pumps, and materials handling equipment.

All project-specific symbols and other unusual symbology should be clearly recorded either on the project P&ID symbol drawings (if incorporated as project drawings) or in the notes column of the P&IDs themselves. Such symbols must also be used consistently throughout the project. This is vitally important because P&IDs may be the only drawings available to those unfamiliar with a particular project or facility, such as engineers involved in facility additions and modifications. Often what is regarded as a universal “standard” symbol by one organization is foundbe different elsewhere.

232 Symbol Standards—Instrumentation and ControlsThe following should be agreed upon before much work is done on the P&IDs for a project:

• A standard for continuous modulating controls• A standard for process safety and sequencing logic• How to document P&ID special symbols• The degree of details to be shown on the P&ID

Continuous Modulating ControlsModulating controls indicate and control variables that can change continuouslyover a range of values. ISA Standard S5.1 (see Appendices) is the preferred standard.

Process Safety and Sequencing LogicVariables for process safety and sequencing logic can normally assume only twstates; a pump is either on or off; a temperature either is or is not too high; a bueither is or is not lit; a filter is or is not ready to be backwashed.

The logic symbol standard used most often is ISA Standard S5.2, (see Volume Industry Codes and Practices). These symbols are most suitable for representibinary process logic, thus for documenting most safety systems. They do not erepresent sequencers such as drum programmers which have many output sta

In most cases the sequencing logic will be complex enough to require separatetional logic diagrams. The S5.1 symbols connect the individual instrument symbto a box labeled with the name of the logic system. For example, a boiler P&ID



show a box labeled BURNER MANAGEMENT SYSTEM. There may be more than one logic box shown on the P&ID to represent different logic systems (see ISA S5.2, Appendix A, Figure 1).

The box should direct the reader to a logic document that is recoverable by future users of the P&ID. This logic document might be a drawing, such as that shown in S5.2, Appendix A, Figure 2. Note that this drawing is tied to Figure 1 by the instrument balloons on the interlock system in Figure 1 and adjacent to the logic in Figure 2.

Word descriptions can supplement or replace logic drawings such as that provided in S5.2, Appendix A, Section 3.1.

Figure 200-1 is a type of word description called a control philosophy. This is a very effective way to communicate complex or simple process control schemes.

Fig. 200-1 Control Philosophy

Dirty Water Tank

EQUIPMENT: T-4

REFERENCES: P&ID F-40001

PROCESS DESCRIPTION: Tank T-4 is the dirty water surge tank for the produced water plant. It is 38 feet diameter and 24 feet high. It receives produced water from the FWKO vessels, coalescers, and other locations. This water may contain some oil that needs to be skimmed. From this tank the liquid goes to the flotation units which further separate the oil from the water.

PROCESS CONTROL

Level Control— Level control is very important in this tank. It is controlled by LIC-T4 at 18 plus or minus 2 feet. There needs to be a constant head in the tank so that relatively constant flow can be supplied out of the tank to the flotation units. (See the control philosophy of the flotation units.)

PROCESS UPSETS:

High Level—

Low Level—

Emergency S/D—

High level could occur if there is a block in the outlet line, the controller or control valve fails, or more water is coming into the system than can be handled. LAH-T4 will alarm at 22 feet in the control room if this happens. (The operator may then decide to manually control the flow out of the tank with the bypass valve to lower the level.) It will also close FV-T5 to keep from transferring to T-4.

The level may fall below the control range if there is a controller or control valve failure or there is a leak. In this case LAL-T4 will alarm at 7 feet in the control room.

LV-T4 closes during an ESD #1.



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Control philosophies (when used) are an integral part of the P&ID. They can be placed in an expanded note section of a P&ID or on separate P&IDs.

Simpler safety and sequencing logic can be shown entirely on the P&ID using the symbols of ISA Standard S5.1. For example, a low-level shutoff for a tank valve actuated by a level switch may be depicted without the need for a separate logic diagram.

Special SymbolsAny special symbols should follow the rules in ISA S5.1 and S5.2, and be defined on each drawing.

Degree of DetailISA S5.1 identifies three levels of detail, depending on user requirements, as follows:

• Simplified loop. See ISA S5.1, Section 6.12, Figure 1. Simplified symbolismand abbreviated identification identify the principal measurement and contrfunctions. Process control diagrams often use simplified loops

• Conceptual loop. See ISA S5.1, Section 6.12, Figure 2. Functionally orientesymbolism and abbreviated identification show the control function but not implementing hardware. Advanced process control diagrams and P&IDs intended primarily for the process operator normally use conceptual loops. Detailed loops are frequently shown on additional drawings

• Detailed loop. See ISA S5.1, Section 6.12, Figure 3. Detailed symbolism anmore complete identification show the type of hardware and kinds of signalDetailed loops are often needed by the plant control engineer and the desigcontrol engineering and maintenance staffs. For operator training, the conctual loops must frequently be shown on additional drawings

240 P&ID Content

241 InstrumentationThe development of process and equipment control schemes, and the placememinor instruments are discussed in this section and depicted in Figure 200-2.

Process Control SchemesProcess flow and control diagrams generally do not show equipment controls, scontrols, and miscellaneous minor instruments. When incorporating process controls on the P&ID, the plant designer makes hardware and software choiceswere unavailable to the process control designer. These choices can affect the tion of the process controls and should be reviewed with the process control ex



Equipment Control SchemesIf they are very simple, major equipment controls should be shown on the process P&ID. Otherwise, they should be shown in detail on a separate equipment P&ID and referenced on the process P&ID.

Equipment control schemes should be developed in coordination with equipment vendors, and Company and design agency equipment control specialists. The resulting P&IDs should be reviewed with an equipment control expert.

Review and approve equipment controls that are completely determined by the Vendor in packaged systems. With packaged systems, a Company instrumentation expert should be consulted before it is too late to make changes.

Minor InstrumentationThe P&ID designer is responsible for putting all minor instrumentation on the P&ID, including the following:

• Locally mounted pressure gages• Remote temperature indicators• Local temperature indicators• Local level indication• Remote flow indicators• Alarm and shutdown systems• Pressure sensors for automatic pump starters• Toxic and combustible gas monitors• Transmitter output indicators

Fig. 200-2 Development of the Instrumentation Portion of P&IDs



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The following paragraphs give guidance on the proper application of each of the minor instruments listed.

Locally Mounted Pressure GagesPressure gages should be installed on the following process equipment and piping locations to monitor operation and performance:

• Discharges of pumps and compressors

• Vessels and the bottom vapor space of columns

• Near the process connection for nonindicating pressure transmitting instruments

• Furnace fuel oil, fuel gas and atomizing steam branch headers

• Furnace draft. A single draft gage should be manifolded to the inlet of the convection section and to a position below the stack damper on each furna

Pressure test points consisting of a process connection with a plugged valve arlocated in process equipment and piping, as follows:

• Near the inlet and outlet of all packed vessels and columns• At all indicating pressure transmitter instruments• Inlets and outlets (both shell and tube side) of each heat exchanger and re• Inlet and outlet of each air cooler

Remote Temperature Indicators (Thermocouples and ResistanceTemperature Devices [RTDs])Remote temperature indication should be provided, as follows, on most procesequipment and piping:

• Columns. All inlet and outlet lines

• Vessels. All inlet and outlet lines expected to have different temperatures

• Fired heaters. Inlet line and outlets from each pass, header pass points fromthe convection to the radiant section, on the tube wall as recommended byfurnace supplier (a minimum of three per pass), and on the stack just aheathe damper

• Process stream junctions. Downstream of the junction point of all important process streams

• Coolers. All liquid product inlets and outlets

• Temperature controllers and transmitters. These instruments should have aadditional thermocouple and thermowell separate from the controller or tranmitter. Instruments on high pressure piping and reactors may use a commothermowell

• Orifice flow meters. For heavy hydrocarbons. Used to estimate viscosity anmake flow corrections from fluid temperature changes



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• Parallel piping lines. Temperature transmitter thermowells should be installein both lines, and the sensing bulb for the transmitter in one line. The instaltion should permit transfer of the sensing bulb to the other well

• Process compressors or blowers. Inlet and outlet lines. One point is required on the combined inlet and one on the combined outlet of compressors or blowers in parallel on the same service

Local Temperature Indicators (Dial Thermometers)Local temperature indication should be provided for process equipment and pipwhere required for manual field control. Such temperature indicators should measure outlet water temperature from all condensers or coolers, discharge of blowers, discharge of each compressor cylinder, and lube oil and water for pumturbines, compressors and similar mechanical equipment.

• Heat exchanger thermowells. Thermowells should be located at the inlets anoutlets of heat exchangers (shell side and tube side) that don’t have remotetemperature indicators. If a thermocouple point or dial thermometer is prestemperature test points are not needed

• Compressor temperature alarms and shutdowns. High discharge tempera-ture alarms are necessary on each cylinder of a main reciprocating compreand, frequently, on other compressors as well. Thermocouples and thermismay be used for this service; filled thermal systems should not be. Becausehigh temperatures must be detected at very low or zero flow, the sensing pshould be either in the compressor nozzle or immediately downstream of it

Local Level IndicationLocal level indication should be provided for all columns, vessels and drums todetermine total and interface (if any) level.

• Gage glasses. Gage glasses are preferred for local level indication, with the following exceptions:

– At pressures above 900 psig, except for steam or water service– Where they are unsuitable for the process fluid (dirty stocks that will co

the glass, etc.)– Determine if a gage glass for an elevated vessel will be readable from

grade and, if not, include an additional indicator at grade

• Displacer-type level transmitters. When level glasses cannot be used, includa displacer-type level transmitter with a local receiver gage. Usually, any lealarm should be taken from this transmitted signal. This transmitter should separate from the level controller loop

• Differential pressure level transmitters. Use with a flange-mounted diaphragm capsule when neither a gage glass nor a torque-tube displacemtype instrument is suitable



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• Pyrometer-type level sensors (ram’s horns). Use for heavy oil columns (e.g., atmospheric and vacuum columns) if approved by the operations representa-tive. No fewer than five should be used

• Automatic tank gages. Tanks used for inventory control should have auto-matic tank gages readable from the ground, and level transmitters that dispin the central control house (if there is one). Heated tanks and tanks storingproduct at above-ambient temperature should have remote readout of spottemperatures. If there is an existing tank gaging system, a project decisionshould determine whether automatic tank gages should read out on it

Remote Flow IndicatorsAll feed, product and utility lines should have remote flow indication.

Alarms and Shutdown Systems• Shutdowns and interlocks. Automatic shutdown and interlock systems (see

Section 1200) prevent the startup of equipment or portions of the plant whenoperation would be a serious hazard. Alarms may be anticipatory or activatthe time of shutdown, and are displayed on the central control room alarm system

• Alarm and safety setpoints. Setpoints for alarms and safety trips should be recorded on the P&ID if they require setting in the field

• Low flow shutdowns in high energy systems. When a centrifugal pump is injecting liquid into a high energy system, shutdown of the pump can causedisastrous reverse rotation if the check valve fails to hold. In such cases, a flow reading on the feed meter should close a control valve to prevent the backflow

• Computer communication. The process computer (if used) should monitor alarm and shutdown status

Pressure Sensors for Automatic Pump StartersIn services where continuous flow is critical, drivers for spare pumps should aumatically start on loss of flow from the prime unit.

Toxic and Combustible Gas MonitorsToxic and combustible materials require special attention. Facilities handling hydrogen sulfide (H2S) require an ambient H2S monitoring system. Monitoring stations should be judiciously located around equipment handling high H2S concentrations.

Transmitter Output IndicationBlind transmitters (except level) should have at least one indicating gage on thetransmitted signal. If a control valve is associated with several transmitted varia(directly or indirectly as with flow and level indicators on the same stream) the gages should be readable from the manual bypass valve. Gages for split rangeinstruments should be readable from each valve. A gage is not required for leve



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transmitters if the gage glass can be read from the control valve. The same applies to any indicating transmitter that can be read from the control valve.

242 Piping and Equipment

Physical Size and Mechanical Design InformationThe physical size and mechanical design information almost universally found on P&IDs for all major processing and production facilities is as follows:

• Piping elements. Nominal pipe diameters and sizes of valves, flanges, reducers, connections and miscellaneous and special fittings

• Columns, vessels, tanks. Internal diameter(s) (“ID”), seam-to-seam height(s)or length(s) and equivalent boot and dome dimensions

• Relief valve setpoints

Additional Mechanical and Process InformationMajor processing plants usually control operating conditions by varying feed strcomposition, throughput, heat input, etc. As a result, relief valve setpoints are usually the only mechanical design information shown on the P&IDs. By contraadditional mechanical design and (sometimes) process information (such as detemperatures and pressures, duties, horsepowers, speeds, capacities, and throare shown on production facility P&IDs, because actual conditions can be quitedifferent than anticipated.

Some operators of major processing facilities now request expanded equipmeninformation on their P&IDs. This information can be of considerable help in opetions, and in estimating and designing additions and modifications.

250 Numbering Systems

Plant, Equipment, and Piping Numbering SystemsThere are so many systems in use throughout the Company that it would servepurpose to discuss more than a few general principles here. API RP 14C, Table“Component Identification” is another system of line numbering and equipmentidentification.

Facility Names and Plant Numbering SystemsMajor facilities (both upstream and downstream) are generally named for their tion. Small facilities such as small producing gas plants and small stand-alone asphalt plants are not further subdivided. Larger processing facilities are brokeinto distinct plants. These plants are generally named for their function (crude ugas dehydration, boiler plant, effluent treating plant, etc.). They are usually alsoassigned a number. During construction and later, during maintenance, this proa rough-cut way of segregating, by construction area, the hundreds (and some



thousands) of items of delivered equipment. Local management should be consulted in determining plant numbers for a new project.

Operations approval should be obtained for numbering systems (plant, piping, equipment, and instruments) at the beginning of a new project. Once drawings and specifications are issued for quotation, the cost of changing numbering systems is surprisingly high. A confirming letter or memorandum emphasizing the importance of this decision is helpful.

Equipment Numbering SystemsWhere plant numbers are used, they should be incorporated into equipment numbers, and, often, into the instrument numbers. Where plant numbers are not used (such as for offshore platforms) many prefer that the instrument numbers relate to uniquely numbered equipment. This method is used on platforms built to API RP 14C to associate safety devices with the equipment they protect. Some facilities incorporate a plant number into the equipment number and associate instruments with equipment.

Most facilities also use alphanumeric systems with a letter prefix that indicates the type of equipment involved. For instance, the prefix MAF designates a 7-tray glycol contactor for an offshore platform (see API RP 14C). The same equipment in a downstream major processing plant would be denoted by a C for column.

The prefix system allows the number series to be restarted for each type of equip-ment, so that numbers can usually be limited to two digits. Equipment is numbered serially or in decade steps for major equipment. Thus, for plant 20, three sequential columns might be numbered 2010, 2020, 2030. P-2021 might be the reflux pumps for column C-2020. Skipped numbers are acceptable in a system such as this.

Instrument Numbering SystemsAssignment of instrument numbers must be coordinated with all design agencies that are developing P&IDs or subsections of P&IDs. A unique identification for each instrument is assigned in accordance with ISA Standard S5.1 (see Appen-dices), as follows:

70-FIC-101

Reading left to right, the first element of the code is the plant number. This is normally omitted on the P&IDs, but it is included in the instrument number for other purposes such as ordering, I. D. tags, etc. The letters that follow represent the instrument type according to ISA Standard S5.1. The final element is the loop iden-tification common to all instruments and components in a loop. If possible, loop identifiers should be in order of their positions upstream in the process flow; that is, feed loops have the lowest numbers, and product and final effluent loops the highest.



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Loop Identification SystemsFor additions, the existing instrument numbering system is usually extended to include new instruments. For new construction, the following methods are avail-able:

• Functional orientation. This system was developed for large distributed control systems. Its restricted identifier size accommodates electronic databases. It is organized as follows:

– 100 to 899. Except for safety relief devices, major instrument loops taketheir identifiers from this block. An alphabetical suffix is added where more than one of the same component is present in a loop, as with sprange control valves. Temperature points that are part of the control display system use this block

– 900-999. Safety relief devices, relief valves and bursting disks have 3-dgroups from this block

– Four-digit groups. Minor instruments have 4-digit identifiers

• Hardware orientation. This system was developed when individual control-lers were mounted in control panels. Seven blocks of numbers are used:

– 100 to 399. Loops monitored or controlled from the control center– 400 to 499. Field controlling, recording and indicating loops, including

dial thermometers– 500 to 599. Field contacts for alarms– 600 to 699. Pressure gages– 700 to 799. Level gages– 800 to 899. Board temperature points, including test wells– 900 to 999. Relief valves and bursting disks

• Major equipment orientation. This system provides much information to theplant operator. However, it is unwieldy and is not recommended except whealready used

Line Labeling SystemsLines generally require four to seven identifying elements. Symbology dependsthe facility and organization involved. These elements are as follows:

• Plant number

• Service. Also called a “line identification letter” (i.e., process, instrument air,caustic)

• Line number. Often (and best) a separate unbroken series restarting with eservice designation (critical for large jobs to keep number length reasonabl

• Nominal line size

• Piping classification. Service classification, service, etc. Specifies pipe, valvand fittings



t

vi-

• Insulation

• Heat tracing

See Standard Drawing ICM-EF-824A. For major processing plants in which many additions and changes are anticipated during the design phase and later, sequential line numbering that follows process and utility flow is recommended.

Processing FacilitiesTo minimize line numbers and better indicate process relationships, line numbers at processing facilities usually run unchanged from one piece of equipment to the next, including branches to multiple or similar pieces of equipment such as a pump and its spare. Also, the number is not changed for a change in pressure or materials.

Producing FacilitiesCOPI and some producing organizations change line numbers when the pressure classification (piping classification) changes, on branches to multiple or similar equipment, and when a materials change is required. Their requirements differ from major processing plants. They have many fewer piping classifications and much larger pressure changes that need to be clearly indicated. COPI assigns a different series of sequential numbers for each service, and has a very organized numbering procedure.

Line SchedulesIn larger plants (particularly those constructed by large contractors) it is necessary to keep track of assigned line numbers using line schedules. Otherwise, accidental re-use of the same number would surely occur. In addition, line schedules are required by some governmental agencies for permitting.

A line schedule often becomes a valuable control document summarizing all piping design criteria, including the following:

• Design/process information critical to line design and specification (serviceflow, pressures, temperatures, viscosity, density, pour point, etc.)

• Resulting design information (pipe size, piping classification, insulation, heatracing specifications, etc.)

• Line connection points (to/from)

260 Additional Information

Miscellaneous ElementsA variety of components, details, and descriptions are shown on typical P&IDs,including the following:

• P&ID revisions. Changes should be clearly identified by sequentially numbered symbols, such as “diamonds,” to pinpoint the location of each resion on the drawing. These changes are listed in the revision block or on a



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separate sheet issued and filed with the P&ID. Avoid the use of vague terms such as “general revision”

• Line classification changes. Line classification changes may occur where different streams join, for instance:

– Where utility piping ties into process lines with a higher corrosion rate, temperature or pressure

– Lines entering and leaving a vessel where processing changes occur trequire additional valves of a higher class than dictated by conditions within the line

P&IDs should be carefully reviewed to ensure that all line classification chasymbols are shown. This is particularly important when the plant is modelebecause there are no piping layout drawings (plans and elevations). The mpiping isometrics (spool drawings) and P&IDs are then the only records of lclassifications.

• Level, alarm, and shutdown setpoints and operating ranges. Although often shown on other drawings, such as vessel drawings (see Section 134) and tlevel instrument piping drawings, these should be shown on the process P&when they are critical to the safe or proper operation of the process

• Flanges. Most often, all 2-inch and larger equipment connections and valveare flanged, but there are some which are not, such as welded stub nozzlewelded line-to-equipment connection often used on high, hard-to-reach vesconnections and between stacked exchanger pairs) and weld-in valves ushigher pressure services

To distinguish welded from flanged connections, either show all the flangesstipulate that all 2-inch and larger connections are flanged except where a symbol (sometimes “WE” for weld-end) is placed adjacent to the connectioThe P&IDs may then be used as a blinding control drawing during shutdowand to indicate flanged connections to the design draftsman. When differenfrom the piping classification, flange sizes and rating are also shown on theP&IDs.

• Entering and leaving line designations. Careful labeling of lines as they enteand leave the P&ID allows good continuity from one P&ID to another. Labeling includes the reference P&ID drawing number, the line identificatio(noted along the line or enclosed in a rectangular “tag” or “balloon”), the to/from equipment number, and a service description

• Equipment internals. P&IDs should include a graphic representation of vesinternals whose function (or lack of it) may impact the operation of the facilExamples include column and vessel internals, gas and liquid distribution asegregation mechanisms, internal level floats, heat exchanger overflow weand tubes, furnace tubes and dampers, and many more. For complicated ement such as reactors, a separate major equipment P&ID is often prepareddocument critical bed temperature points, process gas flow path, quench fepoints, etc.



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• Detail reduction. Level, pressure, and flow instrument piping details on process P&IDs (e.g., testing and maintenance isolation valving and connections) can be greatly reduced by using auxiliary instrumentation draings (see Figure 200-10). Repetitive (and sometimes complicated) vent, drainand sample system details may also be included on a separate schedule

• Reference Drawings. A reference drawing block is often incorporated along the lower edge of the P&ID. It lists major associated drawings—plot plans, piping layout, electrical, etc., with type of drawing, item or area covered, andrawing number. This can help locate associated drawings that may be scatered among hundreds of project drawings. When modifying a facility it is equally important to add new reference drawings to the drawing reference blocks

• Drawing Titles. Many styles are used throughout the Company for drawingtitles. Titles may contain helpful information on the type of drawing (P&ID, instrument, piping, etc.) the item or area covered, the project title or plant name, and the name of the facility or division. Depending on the organizatititle blocks may be sequenced differently or omit some items

Information Not Shown on P&IDsThe following information is usually not shown on P&IDs:

• Pipefitting details are not shown, except for reducers. These details include hydrotest high- and low-point vents and drains, elbows, tee’s, other joints, a(sometimes) unions

• Pipe supports are not shown. These supports include hangers, anchors, guand pipe expansion loops

• Structural information is usually not shown. This information includes mostsupport structures, platforming, ladders, etc.

• Electrical information is not shown, except for special controls such as threeway switches

• Instrument piping/tubing is not shown, except for level instrumentation piping. In major processing facilities, level piping valves and details are plaon auxiliary P&IDs or piping drawings, leaving only a skeletal piping outlineon the main process P&IDs. By contrast, producing organizations usually revalving and level piping details on the main P&IDs

270 P&ID ReviewVarious P&ID review techniques may be used to ensure full consideration of facdesign, including safety, operability, maintainability, reliability, etc. These tech-niques include the following:

• Parallel element review. A comparative analysis of all occurrences of a singldetail to verify design consistency. The types of review should be discussedagreed upon



ity

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• Line-by-line review. A stepwise review of small related groupings of design elements (such as all the elements associated with a single line). It is usedprimarily to obtain owner/operator approval of the design

• Design practices review. Focuses on all features ensuring operating continu(the foundation for employee and community safety). Covers piping, equip-ment, and instrumentation and control systems that protect against upsets failures

• Hazard Assessment, Mitigation, and Hazard Abatement. An evolving set of lengthy, formal techniques (both qualitative and quantitative) being adopteda national scale. Primarily intended for the analysis of new or untried proceor facilities (or elements thereof) where there is a potentially significant hazto employees or the community.

Parallel Elements ReviewThis technique involves the comparative analysis of all occurrences of a single design element on all P&IDs. These elements are easily located even on compP&IDs by the design engineers or an individual familiar with the type of facility. Parallel element review is fast, thorough, and very revealing of errors and omissions. It works well with groups and for individual review.

Optimally, only one element at a time is selected for analysis, because several aspects of each element may need examination simultaneously, such as use, naptness, and engineering rationale. One might take several passes through theP&IDs to review the following equipment connections: vessel drain size for eacvessel, flanged versus stub weld connections, all flanged thermocouple locationpiping classification changes for lines tying into vessels in corrosive service, etc

Line-by-Line Review (Operational and Maintenance Review)Conducted by the design/operations team, line-by-line review is the stepwise reof related groupings of design elements. Groupings may comprise an individuapiece of equipment or a line with its valving, drains, sample connections, pipingclassification, insulation, heat tracing, etc. The review follows the general path process flow.

This review is often used to obtain acceptance or approval by operations. It is logical and sequential (often a yellow marking pencil shows progress, a red penadditions or changes). However, since the elements in each grouping usually hdifferent functions, the immediate impact of a parallel element review is lost. Further, the process can be tedious, particularly when involving many lines withrepeating features. Suggestions for conducting a line-by-line review:

• Break up sessions with parallel element review to dispose of the most repetive elements

• Use interactive role playing, in which the operator walks through all steps needed to start up, run and shut down the plant. Design engineers, procesrepresentatives, etc., point out erroneous or missing piping, equipment andinstrument elements



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Design Practices ReviewThis is employed, particularly in larger, more complex facilities, to confirm that good design practices have been used. It is best conducted using finished P&IDs. Its objectives are as follows:

• Identify elements whose failure could, through malfunction or human error,endanger operating continuity, employees, or equipment

• Confirm that good design practices have been incorporated, including safesystems, mitigating systems, alarms and shutdowns, etc., to eliminate or rethe consequences of failure to acceptable levels

• Estimate the potential for alternate failure modes

• Determine whether the consequences of failures constitute an acceptable r

• Modify (or provide additional) design features or safeguards to reduce consquences to acceptable levels

Design practices review focuses on the active elements of the facility—instrumand controls, pumps and drivers, furnaces, compressors, utility supply systemsThese elements are examined in “brainstorming” sessions that consider both hiand unusual equipment and control system failure modes. Techniques of inquirinclude the “what if” method and the related, more powerful Hazard and Opera-bility Study Method (see the American Institute of Chemical Engineering (AIChE“Hazard Evaluation Procedures” and, in this manual subsection, Hazard Assesment). Usually an abbreviated, verbal run-through of these techniques resolvesconcerns or identifies problem areas for later evaluation.

Hazard AssessmentWhen used in the early design phase, hazard assessment review techniques unecessary changes that can be made at minimum cost. Later, errors may be extremely costly to correct.

Almost without exception a representative of the owner/operator/client must bepresent at every review meeting. Other interested organizations include procesdesigns, maintenance, operations, safety, reservoir engineering, plant or drillingforemen, area superintendent, other management, etc.

Hazard assessment may also include mitigation and abatement techniques sucthe Hazard and Operability Study, Failure Mode and Effects Study, Fault Tree Aysis, SAFE charts, Blast Effect Analysis, Atmospheric Dispersion Study, RadianHeat Study, etc. These can be quite costly, particularly when full documentationrequired. They are used when mandated by federal, state or local laws and regtions or as judged appropriate by the responsible manager.

California and New Jersey have passed legislation requiring the application of ttechniques to plant processes and equipment for stipulated toxic or flammable rials whose catastrophic release could impact the general population (see API 14C, Analysis, Design, Installation, and Testing of Basic Surface Safety SystemOffshore Production Platforms). AIChE has published “Vapor Cloud Dispersion



d by s-

roce-und

a o a mits. fer- to nt

“Vapor Release Mitigation,” “Guideline for Safe Storage and Handling of High Toxic Hazard Materials,” and “Hazard Evaluation Procedures.” The Hazard andOperability Study covered in “Hazard Evaluation Procedures” has been acceptethe EPA as definitive. Future publications planned are: “Quantitative Risk Assesment” and “Guidelines for Process Control.”

Because of the many safe design practices built into Company standards and pdures, these AIChE Procedures—and their reporting requirements—may be foto be unnecessarily formal and lengthy. Modification and shortening should be considered if the full procedure is not legally mandated.

The AIChE guidelines do not define what level of risk is acceptable, and this is complex subject affected by conditions peculiar to a facility such as closeness tpopulation, amounts and types of materials involved, and regulatory emission liA guideline recommending “applicable projects, techniques, sources of help, reences, suitable consultants, waiver procedures, and other appropriate guidanceoperating company personnel” is under consideration by the Hazard AssessmeSteering Committee. Contact HE&LP for an update.

280 P&ID Drawings and Engineering Forms

281 P&ID DrawingsThe end of this section contains the following figures referred to in the text of Section 200:

282 Engineering Forms

Figure 200-3 P&ID—Grouped Equipment Layout

Figure 200-4 P&ID—Serial Equipment Layout

Figure 200-5 P&ID—Geographical Layout

Figure 200-6 Major Equipment P&ID—Furnace

Figure 200-7 Auxiliary P&ID—Tempered Oil

Figure 200-8 P&ID—Plot Limit Manifold

Figure 200-9 P&ID—Relief System

Figure 200-10 Auxiliary Instrumentation Drawing

ICM-EF-824A Standard Piping and Equipment Symbols

ICM-EF-824B Standard Instrument Symbols

ICM-EF-824C Standard Logic and Instrument Symbols

ICM-EF-824D Guidelines for P&ID Presentation of Level Instrumentation



290 References

Instrument Society of America (ISA)

• ISA Standard S5.1, Instrument Symbols and Identification• ISA Standard S5.2, Binary Logic Diagrams for Process Operations

American Petroleum Institute (API)

• API RP 14C, Analysis, Design, Installation, and Testing of Basic Surface Safety Systems for Offshore Production Platforms, Table 2.2, “Component Identification”

American Institute of Chemical Engineering (AIChE)

• “Guideline for Safe Storage and Handling of High Toxic Hazard Materials”• “Hazard Evaluation Procedures”• “Vapor Cloud Dispersion”• “Vapor Release Mitigation”




Fig. 200-3 P&ID—Grouped Equipment Layout



Fig. 200-4 P&ID—Serial Equipment Layout



Fig. 200-5 P&ID—Geographical Layout



Fig. 200-6 Major Equipment P&ID—Furnace



Fig. 200-7 Auxiliary P&ID—Tempered Oil



Fig. 200-8 P&ID—Plot Limit Manifold



Fig. 200-9 P&ID—Relief System



Fig. 200-10 Auxiliary Instrumentation Drawing

Documents

200 PId Development