API 574 6-10 Flashcards
An inspection plan is often developed through the collaborative work of the
inspector, piping engineer, corrosion specialist, and operating personnel
For piping systems, inspection plans should address the following:
a) condition monitoring locations (CMLs) for specific damage mechanisms;
b) piping contact points at pipe support;
c) pipe supports and support appurtenances;
d) corrosion under insulation (CUI);
e) injection points;
f) process mixing points;
g) soil-to-air (concrete-to-air) interfaces (SAIs);
h) dead-leg sections of pipe;
i) PMI;
j) auxiliary piping;
k) critical utility piping as defined by owner/user;
l) vents/drains;
m) threaded pipe joints;
n) internal linings;
o) critical valves;
p) expansion joints
After an RBI assessment is conducted, the results may be used to establish the inspection plan and better define the following: (5)
a) the most appropriate inspection and NDE methods, tools, and techniques;
b) the extent of NDE (e.g. percentage of piping to examine);
c) the date for internal, external, and on-stream inspections;
d) the need for pressure testing after damage has occurred or after repairs/alterations have been completed;
e) the prevention and mitigation steps to reduce the probability and consequence of a piping failure (e.g. repairs, process changes, inhibitors, etc.).
single most frequent damage mechanism leading to pipe replacement is
corrosion.
factors to consider when establishing the corrosion-monitoring plan for process piping are: (5)
a) classifying the piping service in accordance with API 570 or risk ranking based on RBI analysis;
b) categorizing the piping systems into piping circuits of similar corrosion behavior
c) identifying susceptible locations where accelerated damage is expected
d) accessibility of the CMLs for monitoring when localized corrosion is not predicted;
e) RBI to identify high-risk piping circuits and/or specific piping locations
pros of establish circuits ?
By identifying like environments and damage mechanisms as circuits, the spread of calculated corrosion rates of the CMLs in each circuit is reduced.
mixing points concerns? (2)
corrosion or mechanical mechanisms (e.g. thermal fatigue)
Other intensive inspection chosen for the damage mechanism is usually required mixing points? (4)
- close grid thickness surveys,
- UT scanning techniques, and
- profile radiographic examination (RT) for corrosion. 4. Other NDE techniques (e.g. angle beam UT, PT, etc.) may be appropriate when inspecting for thermal fatigue cracking
If the temperature difference between two process streams exceeds a certain (delta T),
a thermal sleeve may be needed in order to prevent thermal fatigue.
why the quantity of water needs to be calculated carefully?
to ensure sufficient un-vaporized water remains to fulfill the function and not exacerbate corrosion.
why are dead legs a concern? (3 )
dew-point or ammonium-salt or water can collect in dead-legs
CUI is particularly aggressive where operating temperatures and what materials?
operating between 10 °F (–12 °C) and 350 °F (175 °C) / carbon steel and low-alloy piping systems,
IS carbon steel and low-alloy piping systems that normally operate in service above 350 °F (175 °C), but are in intermittent service susceptible to CUI?
YES
CUI concern for - austenitic stainless steel piping systems operating
between 140 °F (60 °C) and 350 °F (205 °C
What NDE can examine the refractory for volumetric flaws and for separation from the shell surface
Microwave examination technique (MW)
Preferred NDE methods of detecting fatigue cracking include
PT, MT, and angle beam UT when inspecting from the OD for ID cracking, and AE
Suggested locations for UT on elbows would include the 3 and 9 o’clock positions.
creep cracking has been experienced in the industry is in ____Material___ and above ____ temp
1 1/4 Cr steels above 900 °F (482 °C).
NDE methods of detecting creep cracking (5)
include PT, MT, UT, RT, and ET, and alternating current field measurement (ACFM), in-situ metallography, and dimensional verification (i.e. strapping pipe diameter) are other common practices for detection. and AE
What material is susceptible to brittle failure at or below ambient temperatures.
Carbon, low-alloy, and 400SS
NDE techniques that may allow inspection of touch points without lifting of the pipe or removal of the support (3)
- Long-range Ultrasonic Technique:
- Electromagnetic Acoustic Transducer (EMAT) Ultrasound
- Creeping Head Wave Method
What is Long-range Ultrasonic Technique pros (1) and cons (2)
pros
1. detection of internal and external corrosion from a single point of access on the pipe to a distance of about 30 m
cons
1. distance and effectiveness may be reduced by factors such as fittings, flanges, heavy external coatings and concrete, and heavy products inside the pipe
2. cannot differentiate between internal and external corrosion or may not locate the most severe localized corrosion
Electromagnetic Acoustic Transducer (EMAT) Ultrasound (3)
1 . can be used to inspect pipe support locations on live, on-stream process piping
2 . survey pipe diameters NPS (4 in. to 24 in. NPS)
3. Transducers housed in a scanner that moves along the pipe measure the mode and velocity changes of the Lamb waves and convert the output into readings of wall thickness
Creeping Head Wave Method
- able to detect corrosion of a pipe at a distance from the point of access
- can also be utilized to survey for corrosion between pipe and saddle supports.
When defects are found in the waterproof coating of insulation, either (2)
- enough insulation should be removed o
2. the affected area should be radiographed to determine the extent and severity of the corrosion.
Tightening flange bolts in a pressurized line is only recommended when special steps are taken to avoid three potential problems:
a) bolt interactions—when a bolt is tightened the adjacent bolts are loosened,
b) a bolt can yield or fail due to overloading,
c) tightening one side of a flange can cause deflections in the areas opposite and adjacent to it.
injection points concerns
corrosion and erosion
what type of issue with pipe containing anime?
Stress corrosion cracking
Piping leaks where should be giving most attention?
flanged joints, packing glands, bonnets of valves, and expansion joints on piping
Spring hanger loads should be checked under
both cold and hot conditions,
Improper spring support settings can cause excessive
pipe loads on rotating equipment that can result in misalignment.
how do you inspect non-destructively for loose or broken foundation bolts ?
Lightly rap the bolts sideways with a hammer while holding a finger against the opposite side.
pipe line that is vibrating and swaying. What is one of the most important things you would you check for and where would you check?
Welds should be inspected for cracks, particularly at points of restraint.
primary means (NDE) for thickness measurement? (2)
- primary UT
2. RT
UT devices should have training on the proper use of this equipment, including
ultrasonic theory, high-temperature thickness measurements, corrosion evaluation, midwall anomalies, potential for “doubling,” and equipment operations.
Numeric Thickness Readout (3)
- dual-element pitch-catch transducers
- probe zero and a velocity setting for calibration
- range on for these instruments usually ranges from 0.040 in. to 20.000 in
A-scan with Numeric Thickness Readout (3)
- incorporate a numeric display and an electronic display for viewing an A-scan presentation
- The advantage to an A-scan display over a numeric display is that it allows the examiner to view the ultrasonic waveform to verify the proper signal is being measured by the instrument. to avoid doubling and for evaluating a laminar indication vs. corrosion damage
- these instruments primarily use a 0.250-in. to 0.500-in. diameter, 2.0 MHz to 5.0 MHz, dual-element pitch-catch search unit, but some instruments have options to use single-element delay or even EMATs.
Doubling occurs when measuring
wall thickness below the instrument/transducers ability to separate the signals adequately for proper measurement gate function. This problem can occur on thin wall below approximately <0.1 in. thickness and for evaluating a laminar indication vs. corrosion damage.
Ultrasonic Flaw Detectors with a Numeric Display
- similar to a-scan
2. a lot more options and features, including the capability for angle beam examinations
Ultrasonic velocities are different in
different materials
The best search units for conducting corrosion evaluation are
dual-element transducers
UT high-temperature search units are designed to withstand temperatures up to
1000 °F (538 °C)
As the test specimen temperature increases above ambient temperature, the velocity of the material _____ and increasing the as- measured ultrasonic thickness by a factor % / F
decreases, / 1 %/100 °F (1 %/55 °C)
RT primary functions of this method are to detect (2)
metal loss and check weld quality
Radiography has the following advantages:
a) pipe insulation can remain intact;
b) the metal temperature of the line has little bearing on the quality of the radiograph
c) radiographs of small pipe connections, such as nipples and couplings, can be examined for thread contact, corrosion, and weld quality;
d) film provides a permanent visual record of the condition of the piping at the time of the radiograph;
e) the position of internal parts of valves (dropped gates) can be observed;
f) radiographic equipment is easily maneuverable in the refinery or chemical plant;
g) isotope radiography is not an ignition source in the presence of hydrocarbons;
h) pitting and other nonuniform corrosion can be identified;
i) provides a view of a large area.
RT thickness measurement accuracy relies on (2)
exposing the films and the person reviewing them
The locations most susceptible to cracking are (2)
welds and the heat-affected zones
Other areas prone to cracking are locations that contain crevices, such as
socket-welded piping, flange surfaces, or threaded joints.
MT PT and UT can be used on what type of materials.
MT = magnetic PT/UT = both nonmagnetic and magnetic materials
