3.2u Mixed papers 2 (old) Flashcards
HP water jet finishing on painted steel structure
(Question not clear, I dont have copies of this test paper anymore)
SA3
3.4u Manual
Paints
When paint is applied to a metal surface it presents a barrier to air, moisture and ions aggressive to the metal. However, paint cannot provide a complete barrier to oxygen or water. In time these will penetrate through to the surface of the metal. Any paint system used underwater must have a strong bond onto the metal surface and therefore high quality metal surface preparation is required such as SA3. The bonding between successive coats must also be strong and the topcoats must provide as impervious a barrier to the electrolyte as is possible.
Before CP survey, Bathycorrometer should be
Answer: All of the above
A. Tested in fresh seawater
B. Tested on zinc block and unprotected steel
C. Tested at Depth
D. All of the above
Answer is D
Prior to MPI inspection, checking a permanent magnet will lift 18kg serves what purpose?
Checking that it has sufficient power to induce the field strength and meets the required standard
Magnetising Equipment: BS EN 9934-1
1 Tesla magnetising force required
The efficiency of a cathodic protection system can be assessed by
Taking readings of the electrical potential
Over-protected structure : More negative than -1100mV Zinc: -1050 mV
Protected steel: -800 to -11—mV
Under protected steel: -640 to -800mV
Unprotected steel: -450 to-640mV
Monel: -50 to-150mV
If aluminium is connected to mild steel and immersed in seawater, the aluminium will be
The anode
Galvanic Series: think of it as a superhero team where some metals are strong and don’t get hurt (noble), and others are weaker and get damaged (corrode) when facing a villain (the liquid).
Galvanic Series in seawater.
Graphite
Gold
Platinum
Silver
Stainless steel
Monel
Copper
Niobium
Tungsten
Lead
Cast iron
Mild steel
Aluminium
Zinc
Magnesium
On the pH scale which of the following values would be described as acidic
pH2.5
Therefore, any value less than 7 would be described as acidic. The lower the pH value, the more acidic the substance is. Neutral substances have a pH of 7, while values above 7 are considered alkaline or basic.
An ion is atom that has a positive , negative or both?
Has a positive or negative charge
https://youtu.be/EIAaGHK5pjA?si=euKYfYEWKOLgpWD3
An ion is an atom or molecule that has gained or lost electrons, giving it a net positive or negative electric charge. If it has more protons than electrons, it’s a positive ion or cation. If it has more electrons than protons, it’s a negative ion or anion
The Pourbaix diagram displays 2 sets of data?
Electrode potential and pH value
There are numerous methods for preventing corrosion including, coatings, inhibitors (controlling the electrolyte), selective design, anodic protection and cathodic protection. Before considering these methods a brief examination of the way in which the corrosion process is influenced by the two main variables; the electrode potential and the pH value will assist in understanding the various protection methods.
A structure protected by an ICCP system identifies a shadow area….what could be done to improve that protection for that area
Install sacrificial anode
Offshore structures use impressed current systems in preference to sacrificial systems because they
Reduce overall weight loading
A calomel cell selected from a pair to be used for calibrating a CP meter, should give what reading on a voltmeter
+-2mv
3.4u manual: Calibration Checking between calomel cells. Acceptable readings between any pair of electrodes is +/- 2mV
ICCP systems use voltage/amperage values in which range?
30-80 volts DC / 300- 1000 amps
If a keeper plate was attached to a permanent magnet, which way would the flux lines run through the keeper plate
North to South
Here’s a simplified representation of the magnetic flux lines:
North Pole (N) → Keeper Plate → South Pole (S)
When lines of magnetic force jump the gap formed by a surface-breaking defect, it is called
Flux leakage
The symbol used for magnetizing force is?
H
At the coercive point on a B/H curve, the material would:
Have zero flux density
https://youtu.be/ZyVSMfSgOq0?si=Y4ZVd1J8rkAm7C5p
What can be used to protect a steel structure against corrosion in the splash zone
Protective coatings
If an atom loses one or more electrons, this will be called
An anodic reaction
https://youtu.be/ZyVSMfSgOq0?si=P1te2lJ1YiV0_RzC
In ultrasonics, frequency is measured in ?
Hertz
In regard to digital cameras, what do the initials CCD sand?
Charge Coupled Device
Before use; a Bathycorromter should be soaked for
30 minutes in fresh seawater
What is the formula to calculate the near zone?
NZ=D² / 4λ
lambda λ = wavelength of any wave.
Post-tensioning cables are used to put concrete under which sort of stress?
Compression
Post-tensioning cables are used to put concrete under compressive stress. This technique is employed to reinforce concrete structures by introducing compressive stress to counteract the tensile forces that the structure may experience during its lifespan1. The process involves applying controlled forces to prestressed cables or tendons, which are then anchored to the concrete, resulting in increased load-bearing capacity, improved resistance to cracking, and enhanced structural performance
In a single V butt weld the angle between the two prepare faces is called
The included angle