To improve understanding of pipe and valves to help operating the plant better and safer.
Provide comprehensive information for specific piping systems including:
- Design Conditions
- Testing / Inspection / Qualifications
- Gaskets / Bolting
- Pipe Schedule / Materials of construction
What is a P&ID?
It is the most important mechanical description of the process operating facilities/units should have
- Combination of an instrument control diagram and a piping flow diagram
- Schematic drawings or a set of drawings that join pieces of equipment, instrumentation, and piping
- Enables one to see processes in a schematic format
- Contains the detailed pipe, insulation, painting mechanical design for the process
- Some of the information contained includes:
- Title Block
- Revision Block
- Equipment Tabulation
- Line Legend
- Line Numbering
P&ID Title Block
Contains several items to identify the drawing such as
- Drawing Number
- Revision Number
- Building, Project, Design Area, and Drawing Type
- Drawing Name
- Process Description
Border and Revision Block
- Provides a grid system to identify the location of items.
- Used to quickly locate information on the P&ID
- Documents and provides approvals for changes to the P&ID
- Provides grid information for locating revision on the drawing
The Equipment Tab denotes the common names and unique Identification Numbers of all equipment on the P&ID.
Equipment Numbering Example
Connected equipment such as a pump and motor will have the same Area and Unit ID, but different item and part number identifications.
- Pump #1 is 0805-0200-0400
- Pump #1 Motor is 0805-0200-0460
- Line legend indicates the types of lines and their respective uses on the drawing
- Not always complete, as is the case with this example drawing
Pipelines will have the following information:
- Description and/or number of equipment or line
- Reference drawing number the line originated from or continues on
- Nominal pipe size
- Line number
Comprehensive code providing information concerning the type, thickness, and options of the required insulation.
Protective Coating Specification
- Defines coating specification for the equipment or piping.
- Contains general information on the coating system as well as specifics on:
- Type of Coating System
- Surface Preparation
Many symbols are in use to represent different types of automatic valves.
Oval contains indicator for valve failure mode:
- A/O – Air pressure required to open valve
- A/C – Air pressure required to close valve
Pipe and Flange Leaks
A review of 800+ Process Incidents found:
- A large percentage of the incidents involved leaks (big surprise)
- The most common source of these leaks was flanges
- The most common source of leaks leading to incident is flanges. We should aim to change that.
- Flanges should not be expected to leak. Do not accept flange leaks! Investigate and Improve.
- Gasket selection is not just about chemical compatibility. Different gasket styles, materials, thicknesses have widely varying mechanical properties.
- Need have well-founded target bolt load for assembly based on engineering review of the entire flange assembly (including gasket and fasteners). It cannot be based on a rule-of-thumb regarding fastener stress level. Optimized assembly minimizes leakage and increases tolerance for relaxation.
- To achieve the specified Target Bolt Load you must:
- First understand the fastener specifications, fastener condition and lubrication to be used so that the nut factor (a measure of friction) can be estimated.
- Then specify a torque value that will develop the target bolt load based on the estimated nut factor.
- Torque and friction must always be considered together, and instructions pertinent to both issues provided. Just specifying a torque value isn’t good enough.
- For critical and problematic flanged joints special provisions are warranted to reduce variability in assembly and risk.
- Fastener tightening steps and patterns are geared towards bringing the flanges together squarely and resulting in evenly compressed gasket and evenly loaded fasteners.