Past Paper Questions - Jan 2016

Question 1

Identify this form of corrosion related cracking and describe the cracking mechanism.

Answer 1

Hydrogen Induced Cracking. Sour corrosion occurs at H2S > 0.0035 Bar, it is associated with non-metallic inclusions.

Question 2

Why is production of the steel using the TMCP route better for preventing this type of cracking?

Answer 2

TMCP - Themo Mechanical Control Process.

It maximises a uniform microstructure by minimising carbon, manganese and phosphorus.

Question 3

Obtain a general relation for estimating the heat loss from the pipeline fluid through the pipe.

Answer 3

Write this out

Question 4

For multi-phase pipe flow, what is the Flow Regime Map? With an increasing of gas flow rate, for a horizontal pipe, write down the main flow regimes and describe their features. What are the main parameters affecting the multi-phase flow regime map?

Answer 4

The flow regime map depends on a number of parameters:

• Pipe diameter
• Pipeline pressure
• Liquid velocity
• Gas velocity
• Water Cut
• Pipeline Inclination

For increasing gas flow rate in a horizontal pipe, the main flow regimes are:

• Bubbly - high gas flow rate
• Slug - frothy waves
• Annular - ringed flow
• Wavy - ripple flow
• Stratified - layered flow

Question 5

List down two main flow analysis methods for multi-phase flow, and describe their pros and cons.

Answer 5

• Large scale modelling which includes the use of transient and steady-state two fluid models using empirical and semi-empirical correlations.
• Small scale modelling which relies on the direct solution of fluid dynamic equations. A limitation is it reduces the scope, however greatly reduces the need for empiricism.

Question 6

In the first iteration for sizing the pipe diameter, the pressure loss in a 12 inch pipe is greater than the pressure difference between upstream & downstream. What would be your next choice for pipeline diameter and why?

Answer 6

Next choice would be greater than 12 inch, so say 13, as the larger the pipe the smaller the pressure difference.

Question 7

What are the considerations of route selection for connecting a pipe to a floating platform?

Answer 7

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

Question 8

Name at least six other users of seabed that should be considered in route selection of pipeline?

Answer 8

• Fishermen
• Cruise Ships
• Renewable companies
• Oil and Gas companies
• Marine Environment
• Governments

Question 9

State the Hall-Petch equation, defining each of the terms in this equation. With reference to the Hall-Petch equation, indicate how the following treatments can be used to increase the strength of plain carbon steel.

i) The addition of silicon to the steel.
ii) The addition of aluminium to the steel.
iii) Controlled Rolling or Thermo Mechanically Controlled Processing (TMCP) and Accelerated Cooling

Answer 9

σy = σi + Ky d^-1/2

σy = yield strength
σi = lattice friction stress
Ky = constant
d = ferrite grain size

i) Introducing different sized atoms disturbs the smooth sliding of atom planes. σi increases, σy increases.
ii) Particles pin the austenite grain boundaries and transform to fine grained ferrite and dislocations are prevented from moving. d decreases, σy increases.
iii) Control rolled breaks down the austenite grains and transforms them to fine grained ferrite. Accelerated cooling enhances grain refinement by preventing pearlite formation. d decreases, σy increases.

Question 10

How would you find the thickness of the insulation knowing all the temperatures (Tin, Tout, Ts1 and Ts2)

Answer 10

ln(r2/r1) = (Ts1-Ts2) * 2piL*k / Q

Q given, Ts1 from Tin-Tout/2

Rearrange so r2 = exp (number) * r1

thickness of the insulation = r2-r1