INSTRUMENTASI DAN KONTROL (MS312) – MINGGU KE 3 & 4III, 2011/2012

Liman Hartawan

Materi Pembelajaran/Pokok Bahasan

Standar-standar Instrumentasi

Sub kompetensi

Mahasiswa mengetahui standar-standar & simbol-simbol Instrumentasi

Referensi Utama

4. Michael D. Whitt. 2004. Successful Instrumentation and Control Systems Design. The Instruments Systems and Automation Society (ISA).

Piping and InstrumentationDiagrams (P&IDs)

P&IDs are foundation of I&C engineering package of deliverables.

P&ID is multidiscipline drawing Piping department Process department I&C department systems integration department electrical department.

P&ID – developed & provides

The P&ID developed from : process flow diagram (PFD), a mechanical

department product. heat and material balance (HMB) sheet, a

process engineering department product. PFDs and HMBs are purely conceptual

documents. P&ID provides the link between the

conceptual and the actual.

P&ID is the road map for the engineering design team

It is graphical index of all process equipment, all major sections of pipe, and all instruments.

Pneumatic tubing is shown where information is important to communicate controls,

and electrical wiring information is presented in the form of

dashed lines to communicate functional intent to the electrical and instrumentation departments.

Pipe specifications, tag numbers, and sizes are shown. Heat tracing requirements are indicated, as are all

safety devices. Computer logic is shown to a degree, as are alarms

and process-control elements.

Instrumentation diagrams

Types : Process Flow Diagrams (PFDs) Process and Instrument diagrams

(P&IDs) Loop diagrams (“loop sheets”) SAMA diagrams (Scientific Apparatus

Makers Association)

Process Flow Diagrams

Exp. level transmitter (LT) send the signal that controls level valve (LV) Temperature transmitter (TT) part of temperature control, lets steam into the

heating jacket of that vessel.

Process and Instrument Diagrams

differential pressure transmitter (PDT) flow indicating controller (FIC) and a “recycle” control valve that allows some of the vapor coming out of the

compressor’s discharge line to go back around into the compressor’s suction line

Loop diagrams

SAMA diagrams(Scientific Apparatus Makers Association)

Focus on the flow of information within a control system.

Exp. flow transmitter (FT) sending a process variable signal to a PID controller, which then sends a manipulated variable signal to a flow control valve (FCV)

Engineering disciplines provide input to P&ID

Process engineering: drawing content, process data, vendor equipment

depiction Mechanical:

pipe ID numbers, equipment numbers

and labels, graphical depiction of

equipment and piping

Instrumentation: instrument numbers, graphical presentation

of instruments and instrument

wiring/tubing Controls/systems:

control logic depiction Electrical:

motor ratings, motor wiring depiction

P&I tag, Distance

PFD and HMB as guide, instrumentation P&ID designer places flow transmitters at places in process that need flow information, level transmitters on tanks, and so on.

Each item shown on P&ID is given unique identification (ID) number called P&I tag, which allows item to be tracked throughout design.

Size and distance have only minimal effect on process, so P&ID has only minimal relationship to physical area.

Standards

ISA - The Instrumentation, Systems, and Automation Society ISA-5.1-1984 (R1992)– Instrumentation

Symbols and Identification.1

ISA-5.3-1983–Graphic Symbols for Distributed Control/Shared Display Instrumentation, Logic, and Computer Systems,2 (applies to the depiction of items for computer display)

Typical P&ID symbology

Ex. : Flow element FE-10 is shown upstream of flow-control valve FV-10. Flow element is orifice plate that forces flow of liquid through beveled hole that

specially sized to achieve a certain pressure drop across it for a given flow rate. Flow transmitter (FT-10) samples pressure drop and generates an electrical output

proportional to flow (dashed lines indicate the electrical signal). Signal is fed to a panel-mounted meter (FI-10a) and then on to analog input point in

computer (FI-10b), which is presented as display to operator. After signal is in computer, it is processed and a control signal is generated to force a

flow-rate correction. This correction signal is routed to flow-control analog output point (FC-10), where

signal is converted back to electrical signal and fed to a current-to-pneumatic (I/P) transducer that converts the 4–20 mA electrical analog signal to a 3–15 psi pneumatic analog signal.

This signal is then fed to the control valve to force it to open or close as needed to achieve desired correction.

Typical P&ID symbology showing combined computer functions

In practice, two computer symbols are usually combined into one that represents both computer functions.

Signal lines are differentiated to indicate the medium of the signal. For example, dashed lines indicate electrical signal, while the solid

line with two cross-hatches indicates a pneumatic signal.

Instrument and process equipment symbols - ISA (Instrumentation and Safety Association) 5.1 standard

Line types Process/Instrument line connections Instrument bubbles Process valve types Valve actuator types Valve failure mode Flow measurement devices (flowing left-

to-right) Process equipment SAMA diagram symbols

Line types

Process/Instrument line connections

Instrument bubbles

Process valve types

Valve actuator types

Valve failure mode

Flow measurement devices(flowing left-to-right)

Process equipment

SAMA diagram symbols

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