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1. How to Read a P&ID
For
Risk
Analysis

2. P&ID is a Piping and
Instrumentation Diagram

3. To identify risk from a set of
P&ID you must have clear
understanding of three
things…

4. #1
Understand the
process

5. #2
Understand the
failures

6. #3
Understand the
consequence

7. Lines are used for showing
piping, equipment and
instrumentation
connections…

8. …so people can
communicate the process
sequence and the
relationship of different
equipment

9. Equipment and
instrumentation are
connected by lines
Here are some common
connections

10. Pipe
Common Failure Modes:
- Collapse
- Burst/Rupture
- Erosion
- Corrosion

11. Electrical Signal
Common Failure Modes:
- Open connection
- Electrical shorting
- Electromagnetic interference

12. Pneumatic Signal
Common Failure Modes:
- Leakage of internal fluid
- High components friction level
- Loss of pressure

13. Data Signal
Common Failure Modes:
- Radio interference
- Signal filtering
- Packets Loss
- Loss of signal

14. Flexible Pipe
Common Failure Modes:
- Compressive failure
- Tensile failure
- Over bending
- Rupture

15. Symbols are used to
simplify drawings
>>>
>>>
>>>
From this To this

16. Some equipment are
used to add or reduce
energy in the material

17. Blower
Common Failure Modes:
- Fail to operate on demand
- Loss of pressure

18. Furnace
Common Failure Modes:
- Flame out

19. Pump
Common Failure Modes:
- Fail to operate on demand
- Loss of pressure
- Over pressure

20. Compressor
Common Failure Modes:
- Fail to start
- Damage due to liquid
- Over pressure
- Excessive vibration

21. Heat exchanger
Common Failure Modes:
- Leakage
- Corrosion
- Plugged

22. Plate Heat Exchanger
Common Failure Modes:
- Leakage
- Corrosion
- Plugged

23. Aerial Fan
Common Failure Modes:
- Loss of air circulation

24. Some equipment are
used for material
storage

25. Floating Storage Tank
Common Failure Modes:
- Overflow
- Leakage

26. Sphere Tank
Common Failure Modes:
- Overpressure

27. Pressurized Vessel
Common Failure Modes:
- Overpressure

28. Some equipment are
used to separate
material

29. Horizontal Separator
Common Failure Modes:
- Overpressure

30. Vertical Separator
Common Failure Modes:
- Overpressure

31. Fluid Contacting Column
Common Failure Modes:
- Overpressure
- Corrosion
- Plugged

32. Tray Column
Common Failure Modes:
- Overpressure
- Contamination

33. Valves are used to
control the flow of
material

34. Manual Valve
Common Failure Modes:
- External leakage
- Internal leakage
- Inadvertent position

35. Control Valve
Common Failure Modes:
- Fail to close on demand
- Fail to open on demand
- Spurious operation
- Leakage

36. Solenoid
Valve
S
Common Failure Modes:
- Structural failure
- Seat Leakage
- Seal Leakage
- Loss of actuator

37. Motor-operated
Valve
M
Common Failure Modes:
- Motor failure
- Fail to stroke

38. Butterfly Valve
Common Failure Modes:
- Fail to close on demand
- Fail to open on demand
- Spurious operation

39. Globe Valve
Common Failure Modes:
- Fail to close on demand
- Fail to open on demand
- Spurious operation
- Leakage

40. Needle Valve
Common Failure Modes:
- Fail to close on demand
- Fail to open on demand
- Spurious operation
- Leakage

41. Ball Valve
Common Failure Modes:
- Fail to close on demand
- Fail to open on demand
- Spurious operation
- Leakage

42. Check valve
Common Failure Modes:
- Leakage
- Stuck at open position

43. Some equipment are
used to relief pressure
in the process

44. Relief Valve
Common Failure Modes:
- Fail to open

45. Curved Gas Vent
Common Failure Modes:
- Plugged

46. Rupture Disk
Common Failure Modes:
- Corrosion

47. Control system are used
to manage the behaviour
of the process

48. Programmable Logic
Control
Common Failure Modes:
- Software error
- Execution error

49. Shared display, shared
Control
Common Failure Modes:
- Software error
- Execution error

50. Sensors are used to
measure the physical
properties of the process
and convert it into a signal

51. Flow Transmitter
FT
Common Failure Modes:
- Spurious measurement
- Loss of measurement

52. Pressure Transmitter
PT
Common Failure Modes:
- Spurious measurement
- Loss of measurement

53. Level Transmitter
LT
Common Failure Modes:
- Spurious measurement
- Loss of measurement

54. Now lets identify the risk
of this process…

55. D-101 Re-boiler Condensate Pot
PSV Size ½
111 SET @ 700kPag
To atmosphere at safe
location
Steam
Drawing Ref. D-101
LT
3/4” 2” 253
3”
HLL=2550 mm
LG
253
NLL=1650 mm
LLL=250 mm LC
2”
3” 253
3/4”
6”
LY LV
253 253
Condensate
6” 6” 6”
Drawing Ref.
6”

56. Step 1: Understand the process
• There is low pressure steam
flowing into the vessel
• The steam cools and forms
condensate in the condensate pot
• The level of the condensate liquid is
controlled by a level control loop
• Condensate is drained out the
bottom of the vessel

57. Start D-101 Re-boiler Condensate Pot
PSV Size ½
111 SET @ 700kPag
To atmosphere at safe
location
Steam
Drawing Ref. D-101
LT
3/4” 2” 253
3”
HLL=2550 mm
LG
253
NLL=1650 mm
LLL=250 mm LC
2”
3” 253
3/4”
6”
LY LV
253 253
Condensate
6” 6” 6”
Drawing Ref.
6”

58. Step 2: Identify possible
failures
The control loop can
malfunction causing the
valve LV253 to fail in the
closed position

59. D-101 Re-boiler Condensate Pot
PSV Size ½
111 SET @ 700kPag
To atmosphere at safe
location
Steam
Drawing Ref. D-101
LT
3/4” 2” 253
3”
HLL=2550 mm
PG
253
NLL=1650 mm
LLL=250 mm LC
2”
3” 253
3/4”
6”
LY LV
253 253
Condensate
6” 6” 6”
Drawing Ref.
6”

60. Step 3: Assess the consequence
• The level control valve fails in the
closed position blocking the drain
line
• Hazard is high level and high
pressure in the tank
• Potential consequence of loss of
containment and equipment damage
with $$$$ losses

61. Now you have identified
the cause of the
overpressure hazard, can
you identify the
safeguard?

62. The pressure relief with
a set point of 700 kPa
will open and reduce but
not eliminate the risk of
rupture

63. D-101 Re-boiler Condensate Pot
PSV Size ½
111 SET @ 700kPag
To atmosphere at safe
location
Steam
Drawing Ref. D-101
LT
3/4” 2” 253
3”
HLL=2550 mm
LG
253
NLL=1650 mm
LLL=250 mm LC
2”
3” 253
3/4”
6”
LY LV
253 253
Condensate
6” 6” 6”
Drawing Ref.
6”

64. By understanding the P&ID
you can clearly assess
risk in your operation and
make good decisions

65. Any Questions?

66. Risk. Inspired.
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