Section 2 - Introduction to Materials for Subsea Systems Flashcards
What two categories (Broad) does Subsea Materials Fall into?
Drilling and Production
What are the common design factors for drilling casing? Name 5
Chemistry Collapse Burst Elongation Yield
What is the common per meter of pressure in subsea conditions?
Approx 1.50 psi meter from the ocean surface.
What Standard dictates the materials and design factors of Subsea casing?
API 5L
What does API 5L relate to?
API 5L relates to the Standards for designing Subsea Casing.
How are Steel batches tested for compliance?
They are stretched and pulled until breaking point.
When does a Steel batch get a Heat number?
The Melt or Steel Batch will get a Heat number after the test piece has passed its destructive testing. A certificate is also issued at this stage.
What else is issued with a Heat Number?
A test certificate is also issued, and the Heat reference number is stamped onto the Steel ignot.
What Heat Number will forgings, bar or other components from a Melt carry?
The same Heat number as the main batch or main melt.
What limits distortion in casing lengths?
A maximum of 5 joints high stack height.
What is the Low Pressure Wellhead housing?
This is made from low grade alloy steel and welded to a large casing size, usually 30”.
What is the High Pressure Housing?
This is rates to contain;
15,000 PSI
Carry Heavy Loads - 4000 Tons
High Temperatures - up to 240 Degrees
How is the High Pressure Housing installed?
This is welded to the next casing size that is 20” and is run, landed and locked into the inside of the previous housing, suspending the weight of the 20” Casing.
What part of the High Pressure Housing interacts with the BoP?
Either the Wellhead HUB or the Wellhead Mandrel
What is the MS-1 Seal Assembly?
A soft U-Ring and a wedge that is forced onto a much stronger wicker point, these dig into the softer seal and create 8 annular indents. They also create a lockdown mechanism.
What sort of weight is suspended on a High Pressure Insert Ring?
15,000 Psi test load (3500 Tones)
What are service conditions?
Flow, Temperature, Pressure, Composition of Fluids and Gases.
Why is H2S likely to cause cracking in untreated Steel?
It contains the smallest known Atom - Atomic Hydrogen, small enough to pass through untreated steel and cause cracking.
What is the Hardness Scale know as formally?
The Rockwell hardness scale.
Why are High Strength Carbon, Chrom and Molybednum used and treated to set levels in production wetted parts?
To provide resistant, when in tension, to attach from atomic hydrogen.
What standard is used for Production equipment materials subsea?
API 5CT and Nace
What is API 5CT related to?
The selection and specification of production materials designed to service hostile production environments.
What hardness is production materials in hostile environments usually engineered to?
22 on the Rockwell C Scale or
187-241 on the Brinnel Scale
At what temperature would you consider replacing rubber seals with metal sealing arrangements?
At temperatures greater than 250 Degrees or where more difficult sour services are expected.
What is meant by Static Seal?
Machined to a very accurate size and highly finished surfaces, forced together and put in a preload condition to avoid movement.
What is meant by Dynamic Seal?
A gold or platinum interface between the seal and the valve stem is used to achieve seal during operation of a valve or other component
What is Pulltrusion?
A die is made with injection points to allow resin to be pumped at high pressures whilst at the same time Kevlar and Carbon Fibre are fed into the correct position of the die and pulled slowly through.
What is Teflon typically used for?
As a bearing surface.
Why is Teflon a solid choice for subsea bearing surface?
Its inert in water, and has a low co-efficient of friction.
What other use (sealing) can Teflon be used for?
As a baked on coating for lubrication of piping seals.
What is Teflons thermal properties range?
-20 to 180 Degrees C
What are the most common mechanical properties of a material? Name 4.
Strength
Hardness
Ductility
Impact Resistance
What is meant by Hardness?
Can resist penetration by a sharp object
What is meant by Toughness?
Resist Failure by Impact/energy to fracture
What is meant by Ductile?
Can deform without breaking
What is meant by Brittle?
Fails at Maximum Load, in contrast to Ductile
What is meant by stiffness?
Resistance of an Elastic Body to deformation
What is meant by a strong material?
Requires Large force before rupture or deformation.
What is meant by Thermal Shock Resistance?
Resists Fractures from changes or gradients in Temperature.
