DPO Blueprint Reading & Interpretation 3 — Questions and Answers
Question 1: On a DP reference system blueprint, a DGPS antenna symbol connected to a junction box with multiple outputs most likely represents:
- A single GPS feeding one DP controller
- A shared GPS signal distributed to multiple DP computers (Correct answer)
- A backup GPS only activated during failures
- A GPS antenna used solely for AIS reporting
Correct answer: A shared GPS signal distributed to multiple DP computers
Junction boxes with multiple outputs on reference system drawings indicate signal splitting, allowing one physical sensor to feed several DP controllers for redundancy.
Question 2: In a DP hydraulic thruster blueprint, a relief valve symbol is positioned to:
- Increase pressure to the thruster motor
- Bypass flow when system pressure exceeds a set limit (Correct answer)
- Control thruster rotation direction
- Measure flow rate to the thruster
Correct answer: Bypass flow when system pressure exceeds a set limit
Relief valves open to divert fluid when pressure exceeds the design limit, protecting the hydraulic circuit from overpressure damage.
Question 3: A DP electrical drawing uses the abbreviation 'AMS' next to a switchboard. What does AMS stand for in this context?
- Automated Mooring System
- Alarm Monitoring System (Correct answer)
- Alternating Motor Starter
- Auxiliary Marine Switch
Correct answer: Alarm Monitoring System
AMS refers to the Alarm Monitoring System, which supervises vessel machinery and alerts operators to abnormal conditions.
Question 4: On a DP system P&ID, 'FT' adjacent to a flow line with a circle symbol stands for:
- Fault Trigger
- Flow Transmitter (Correct answer)
- Frequency Timer
- Feedback Terminal
Correct answer: Flow Transmitter
FT is the ISA standard tag for Flow Transmitter, a device that measures flow rate and sends a proportional signal to the control system.
Question 5: Which line weight convention is most commonly used in DP electrical blueprints to indicate a main power cable versus a control cable?
- Control cables are drawn thicker; power cables are thinner
- Power cables are drawn with a thicker or bolder line; control cables are thinner (Correct answer)
- Both use identical line weights but different colors only
- Main power cables are dashed; control cables are solid
Correct answer: Power cables are drawn with a thicker or bolder line; control cables are thinner
Standard electrical drawing practice uses heavier line weights for main power conductors to visually distinguish them from lighter control wiring.
Question 6: A DP blueprint revision block shows 'Rev C – Added thruster 5 isolation valve.' What is the correct action before using this drawing operationally?
- Discard earlier revisions and use Rev C as the sole reference
- Verify the physical installation matches Rev C before relying on it (Correct answer)
- Use the original drawing until management approves Rev C verbally
- Only update the computerized system; ignore the physical drawing
Correct answer: Verify the physical installation matches Rev C before relying on it
Before relying on any revised drawing operationally, the operator must confirm the physical equipment matches the updated revision to avoid acting on inaccurate information.
Question 7: In a DP system wiring diagram, terminal strip labels such as 'TB1-14' indicate:
- Terminal block 1, terminal number 14 (Correct answer)
- Transformer bus 1, tap position 14
- Test bench 1, circuit breaker 14
- Tachometer board 1, channel 14
Correct answer: Terminal block 1, terminal number 14
TB followed by a number identifies the terminal block, and the second number specifies the individual terminal position within that block.
DPO Blueprint Reading & Interpretation 3
On a DP reference system blueprint, a DGPS antenna symbol connected to a junction box with multiple outputs most likely represents: