Past Paper Questions - Dec 2016

Question 1

What are the three main material requirements to be considered when designing a pipeline using a stress based design criteria?

Answer 1

• Strength
• Toughness
• Weldability

Question 2

Describe the round bar tensile test method for determining the mechanical strength of pipeline steel.

Answer 2

An instantaneous measure of applied load and resulting extension. Finds the yield strength, defined as maximum stress material can withstand before plastic flow

Draw the graph.

Question 3

What are the main areas of application of the round bar tensile test and the advantages and disadvantages of this method?

Answer 3

Preferred for high strength grades. Can find important material properties such as the yield strength, elastic modulus and ultimate tensile strength.

Does not account for the bauschinger effect , added as a safety factor later on.

Question 4

What is strain based design and what additional property requirements are placed on the material when using a strain based design approach?

Answer 4

Strain-based design sets strain limits in the design limits rather than stress based. Traditional stress limit design use the yield stress as the limit state where as strain based design uses the ultimate tensile limit.

It allows utilisation of longitudinal strain capacity, important parameters are the Yield/Tensile ratio, the strain hardening capacity and tensile strain capacity.

Question 5

For designing multiphase flow pipeline, what are the main concerns different from the single phase pipeline?

Answer 5

• Flow regime
• Flow pattern
• Pressure loss estimation
• Heat loss estimation
• Physical properties
• Thermodynamic properties
• Hydrate formation management
• Wax formation management

Question 6

What are the main parameters affecting the multi-phase flow regime map?

Answer 6

The flow regime map depends on a number of parameters:

• Pipe diameter
• Pressure
• Velocity
• Water Cut
• Pipeline Inclination

Question 7

What is multiphase homogeneous model for calculating frictional pressure gradient dp/dx? What is its limitation?

Answer 7

dp/dx = 𝑓 * (ρu^2/2D)

It assumes no slippage between the liquid and the gas.
applicable for ρl/ρg < 10 or G > 2000 kg/m^2s

Question 8

What are the considerations of route selection for connecting a marine pipe to a land terminal (shore approach)?

Answer 8

• Seabed Terrain
• Shore Approach
• Other Users
• Construction Limitations
• Local environment and politics

Question 9

Name five different types of measures to enhance pipeline on-bottom stability

Answer 9

• Burial
• Concrete coating
• Mechanical protection
• Covering (rocks, sand, gravel mattress)
• Increase the wall thickness