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What is P&ID ?

P&ID (Piping and Instrument Diagram) is drawn the detail of plant control system and using material, which is including all equipment, piping and valves for consisting in the plant.

P&ID is making by based on PFD (Process Flow Diagram) , and basic document for the detail design of piping and instrument, plant operator is also using for plant operation, maintenance and safety training.

P&ID is sometimes called MFD (Mechanical Flow Diagram) or EFD (Engineering Flow Diagram), because P&ID is shown the mechanical requirement for piping and instrument and the result of engineering.

P&ID is consisted under writing drawings

1) Lead Sheets

Lead sheet is mainly using for explaining the symbols in the P&ID.

Each material and numbering for equipment, piping and instrument is indicated special symbol. When making P&ID, symbols is decided at first, and should attention to duplicate to same equipment, same material is basically one symbol only.

How to indicate the symbol is generally depend on client, which has not global standard, each company has special rule. P&ID originator need to confirm and decide the symbol with client at first. Specially instrument symbols is large difficult with each company.

Sample is attached, please see attachment-1.

2) Piping & Instrument Diagram = P&ID

Equipment, Piping and Instrument of Process unit, Utility facilities, Offsite facilities is made by in accordance with PFD, which is not considered actual equipment location.

3) Header Diagram

Utility piping (steam, water, air, nitrogen, fuel and etc) is blanched to each user from one large piping (this piping is called “Header”). This header and blanch pipings is depend on actual equipment location, which the method for making drawing is difference with P&ID. By this reason, P&ID and Header diagram can not draw in the same sheet.

4) Vendor P&ID

Vendor P&ID is making by manufacture vendor, which indicating material is supplied by manufacture vendor. Package system (like a compressor, boiler system and etc) is almost meat this case. Contractor reviews that these drawing is meat to project spec and contractor’s drawings.

1. How to read P&ID

P&ID is generally difficult for understanding by beginner, because P&ID is using many special symbols and necessary to read many documents.

This section will explain that what information is sending by each symbol.

1. Title block

Right corner in P&ID is shown Title block, which is indicating these informations,

・ Project Name

・ Client Name

・ Job Number

・ System Name

・ Drawing Number

・ Revision Number and description

2. Equipment on P&ID

Before writing piping and instrument, to decide layout for Equipment.

P&ID is basically separated 3 parts (upper , middle, under).

Upper part is mainly indicating vapor handling system, (like a Air Fin Cooler or Shell and Condenser)

Under part is mainly indicating liquid handling system, (like a pump)

Middle part is indicating vapor and liquid handling system,(like a Column or Drum)

Each equipment’s symbol is decided in the Lead sheet, but when draw column and drum, to need to indicate internal in accordance with equipment data sheet.

And each equipment name and data is indicated in equipment data box.

3. Piping on P&ID

Piping has variations for easy understand to engineer and plant operator,

Sample is as follows,

[pic]

And all piping have number for controlling construction and maintenance, which is including the information of piping size, what material using, what fluid, providing insulation or not. The detail is shown on attachment.

2.4 Instrument on P&ID

Instrument signal has variations, which is meaning that how to send signal to each instrument equipment.

Sample is as follows, (refer to ANSI/ISA-S5.1)

[pic]

And balloon symbol is showing Instrument function and equipment by using Instrument Tag Number.

Major balloon symbol is as follows

[pic]

Sample of Instrument tag numbering system is as follows,

Instrument tag number is generally including plant number, how to control, what instrument equipment is providing and loop number.

[pic]

5. Drawing connector on P&ID

Drawing connector is used when piping line or instrument signal is connected another drawing. Drawing connector symbol is as follows,

[pic]

Connection Number : same number input to Mater and Slave.

Drawing Number : Master is input Slave drawing number, Slave is input Mater drawing number.

Flow Direction : To indicate flow direction

Description : To indicate where come from or going to.

In the Process P&ID, Major process line is coming from left side of drawing and going to light side of drawing. (Utility and miner process line is not need to consider.)

2. Piping Symbol

1. Piping line numbering

All piping in the plant has line number individually for controlling construction material and easy operation.

Sample of line numbering system is as follows,

[pic]

Piping line number has many information, not only piping number.

1) Plant number

Plant is generally consisted some process units, utility units and offsite units. For easy operation, numbering to each unit.

2) Service Designation

Service Designation is meaning symbol for explaining what fluid in the piping. This symbol is actually decided by each project in considering process and client opinion.

-Sample of service designation-

PL : Process Liquid

PG : Process Gas

SH : High pressure Steam

SL : Low Pressure Steam

BFW : Boiler Feed Water

CW : Cooling Water

3) Line number

Line number is to provide each line individually from upstream to downstream.

4) Line size

Piping size is that almost company is using “inch” (for example 8”), but some European company is using “mm” (for example 50mm). 1” = 25.4 mm

5) Piping material service class

Piping material service class is to consist of P-T rating, material and corrosion allowance information.

Sample of piping material service class is as follows,

[pic]

1). Pipe Material

A : Carbon Steel

B : Killed Carbon Steel for Low Temperature Service

C : Stainless Steel Type 304L

D : Stainless Steel Type 316L

E : Galvanized Carbon Steel

2). Corrosion Allowance

0 : 0 mm

1 : 1.6 mm

2 : 3.2 mm

3). Pressure Rating

A : Class 150

B : Class 300

C : Class 600

Pressure rating is selected in considering design pressure and temperature.

6) Insulation type

When need to keep fluid temperature in the piping, insulation is providing outside of piping. And when fluid temperature is high, possible to damage to plant operator by touching piping, this case also provide insulation for protection of plant operator.

Generally piping line number is shown insulation type by using alphabet symbol.

Sample is as follows,

H : Hot insulation

C : Cold insulation

PP : Personal protection

ST : Steam trace

2. Requirement for piping

1) Valve selection

The purpose of valve installation is mainly two reasons, one is isolation of system by closing valve (it called “block valve”), another is controlling flow (it called “control valve”).

Block valve is generally using Gate valve, Ball valve and butterfly valve.

Control valve is generally using Globe valve.

And check valve is using for protection of back flow, which valve has not operating handle, simply supported by spring and etc.

Valve selection has impact to construction cost, which is generally specified in contract specification.

Major valve is summarized as follows,

[pic]

2) Auxiliary piping equipment

Major auxiliary piping equipment is summarized as follows,

[pic]

These equipment is also to install on P&ID in accordance with project specification.

3) Fitting

In piping design, actually many type fitting is using for connection of pipings. P&ID is also need to show the fitting, however P&ID is not 3D, which is limited for requirement of piping design, not all indicated on P&ID.

Major fitting is summarized as follows,

[pic]

1) Flange

Flange is using for connection to equipment nozzle, piping, valve, instrument equipment and etc, which will be used that don’t like to connect by welding.

When consider to disconnecting piping for maintenance or blind installation, it should be used.

2) Blind Flange

Blind Flange is using for end of piping or valve for protection of leaking to atmospheric.

3) Welded End Cap

Welded End Cap is using for end of piping for protection of leaking to atmospheric. When not consider to disconnecting piping for maintenance or blind installation, it should be used.

4) Reducer

Reducer is using for connection with difference size piping by welded.

Reducer has 2 type, Concentric Reducer and Eccentric Reducer, which selection is depend on piping 3D design, and selected by piping engineer.

5) Screwed Cap and Screwed Plug

Screwed Cap and Screwed Plug is using for end of piping for protection of leaking to atmospheric. When consider many time disconnecting for maintenance, which is mainly using at vent, drain and utility hose connection.

6) Blind

Blind is using for separating tow system, which is installed to flanges.

Blind thickness is designed for considering design pressure and design temperature at installation point.

When not use blind, spacer is installing instead of blind for keeping space.

[pic]

7) Gravity Flow

Requirement of Gravity flow is that upstream is higher elevation than downstream.

Making low pocket at on the way is no problem.

[pic]

8) No Pocket

Requirement of No pocket is no providing “High pocket” and “Low pocket”.

[pic]

9) No Liquid Pockets (No Low Pockets)

Requirement of No liquid pockets is no providing low pockets.

Making high pocket is no problem.

When condense liquid from vapor, the liquid possible to be storage in low pocket and blocking vapor flow.

[pic]

10) No Vapor Pockets

Requirement of No Vapor pockets is no providing high pockets.

Making low pocket is no problem.

When vaporize from liquid, the vapor possible to be storage in high pocket and blocking liquid flow.

[pic]

11) Free Drain

Requirement of free drain is that piping design automatically drain out without no storage in the piping.

[pic]

12) Slope

Slope is more easily drain out than free drain. Piping is constructed continues sloping.

How many slope is to need indicating on P&ID.

[pic]

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