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
The depth of a crack may be determined by (2)
NDE or by chipping or grinding until sound metal is reached
Whenever valves are removed from service for overhaul or refurbished for reuse, they should be inspected and tested to the requirements of API
598.
Flange joints can be inspected while in service by applying (2)
single-element or phased array UTs to the external surfaces to measure flange face corrosion and to detect ring groove cracking.
Cracks in alloy-steel welds are often associated with excessive hardness resulting from
improper control of preheat or PWHT.
leaking threaded joint should not be tightened
while the system is in service under pressure
misalignment is not apparent until the piping has
cooled and has moved to its cold position.
metal temperatures of about 800 °F (427 °C) and above—should be measured to check
for creep or deformation with time under stress.
Inspection of expansion joints involves examinations both at maintenance (2)
outages and during operation prior to shutdown and shortly after start-up
FRP - Joints with up to 85 % disbond have reportedly passed
pressure tests.
Many traditional NDE techniques and testing are used to assess nonmetallic piping. (6)
a) UT,
b) RT,
c) AE,
d) hardness testing,
e) thermographic imaging,
f) MW.
size of Tell-tale holes?
1/8”
There are three well-known methods of determining resistivity.
These are the Wenner Four-pin Method, the soil bar (AC bridge), and the soil box.
The Four-pin Method uses the formula:
resistivity (ohm-cm) = 191.5 x d xR
the Four-pin Method may not be applicable.
in cases of parallel pipes or in areas of intersecting pipelines,
The soil bar is typically inserted
to the depth in the soil where the resistivity is to be taken.
During the execution of repairs, the inspector should ensure that the work is executed per the scope and meets code requirements. Typical inspector activities include: (4)
a) ensuring NDE is performed at the hold points as stated in the inspection plan;
b) reviewing examination results to ensure that they meet code and specification requirements;
c) ensuring any heat treatment is performed per the work scope;
d) ensuring testing requirements, such as hardness and pressure testing, are performed and acceptable.
Additional thickness is often needed near _______connections.
branch
Metallic pipe for which t ≥ D/6 or P/SE > 0.385 requires
special consideration
ASME B31.3 contains a formula for determining the required thickness of
new, uncorroded, straight pipe subject to internal pressure
API 570 permits the use of the simple Barlow formula to determine the required wall thickness for
in-service piping
Additional consideration and allowances for structural thickness may be required for the following conditions (6)
b) Piping diameters greater than 24 in. (610 mm).
c) Temperatures exceeding 400 °F (205 °C) for carbon and low-alloy steel.
d) Higher alloys (other than carbon steel and Cr-Mo).
e) Spans in excess of 20 ft (6 m).
f) High external loads (e.g. refractory lined, pipe that is also used to support other pipe, rigging loads, and personnel support loading).
g) Excessive vibration.
Austenitic stainless steel piping often have lower minimum structural thickness requirements based
upon their typically higher strength, higher toughness and thinner initial thicknesses of piping components.
Valves and flanged fittings are subject to stress both from (3)
- internal pressure
- mechanical loadings and temperature changes.
- closing stresses and stress concentrations because of their shape.
Reduction of strength of the metal in a pipe, scaling, bulging, metal deterioration or complete failure are all
symptoms of:
excessive temp
Points of probable external corrosion of underground piping can be located by a series of
measurements of the
electrical (soil) resistance of surrounding soil or by measurement of pipe-to-soil electrical potential.
A weld is being made in carbon steel piping carrying Amine (MEA). What should the inspector check in
addition to insuring that the weld is proper and meets specifications
Amine can cause environmental cracking; the weld should be checked for hardness.
Welded joints in carbon steel and carbon-molybdenum steel exposed to elevated temperatures of 800degrees F or over may be subject to
graphitization.
_____of piping in high-temperature service—metal temperatures of about 800 °F (427 °C) and above—should be measured to check for creep or deformation with time under stress.
The OD
Special attention should be given to small connections such as vents, bleeders, any type of small nipple.
One method for successfully checking the condition and the thickness of nipples is the use of:
RT
A pressure test of piping, in most cases is a:
leak test
What should be considered when testing carbon steel piping during cold weather or if cold fluids are used in
the testing?
The transition temperature of the steel should be considered to prevent brittle failure.
Which of the following piping should NOT be hammer tested? (material and what service)
cast iron and stress-relieved lines in caustic and corrosive service.
Important points for consideration when using a soil box include: (3)
a) avoiding contamination during soil sample removal, handling, and storing;
b) avoiding adding or subtracting water;
c) having to compact the soil sample to the same density in the soil box as it was prior to removal from the ground.
The following conditions should be considered in four-pin soil resistivity measurements: (4)
a) all underground structures should be excluded from the measurement,
b) all of the pins should be in a straight line and equally spaced,
c) the depth of the pins inserted into the ground should be less than 4 % of the spacing,
d) the soil resistivity meter should be designed to exclude any effect of extraneous AC or DC currents.
Suggestions for use of the soil bar include: (3)
a) use of a standard prod bar to provide the initial hole;
b) avoiding addition of water during, or after opening the hole;
c) applying pressure on the soil bar after insertion into the open hole
Wenner Four-pin Method
resistivity (ohm-cm) = 191.5 x d x R
d= feet
at what temp does sulfidation on CS occurs
500 F
Special attention should be given to low-alloy steels (especially 21/4 Cr-1 Mo material), because they can be
prone to temper embrittlement, and to ferritic stainless steels.
creep cracking has been experienced in the industry is in 1 1/4 Cr steels above
900 °F (482 °C).
Special delay-line materials and water-cooled transducers are available that permit the use of pulse-echo instruments at temperatures up
to 1100 °F
A close-interval pipe-to-soil potential survey measures the potential of the pipe to the soil directly over the pipe, at predetermined intervals between measurements, usually at
2.5 ft, 5 ft, 10 ft, or 20 ft
Creep is dependent on
time, temperature, and stress.
NDE for environmental cracking? (4)
- PT
- WFMT
- UT
- eddy current (ET).
bulges or staining of the insulation or jacketing system or missing bands is what damage mechanism?
CUI
Gate valves should be measured for thickness _________, since turbulence can cause serious deterioration
between the seats
bulges at insulation can indicate
corrosion product buildup
Gate valves - Reduced port valves should not be used as block valves associated (3)
with pressure-relief devices (PRDs) or in erosive applications, such as slurries, or lines that are to be “pigged.”
injection point examination
12 feet upstream , and 10 pipe diameters downstream
one quarter turn valve?
- plug
- ball
- butteryfly
For services with high potential consequences if a failure were to occur, the piping engineer should consider increasing the
minimum allowed thickness
if buried piping has CP, when is excavation required?
when evidence of wrap or coating has failed
FRP piping include service
water, process water, cooling medium, potable water, sewage/gray water, nonhazardous waste, nonhazardous drains, nonhazardous vents, chemicals, firewater ring mains, firewater deluge systems, and produced and ballast water.
gates valve another name is
block valve
gate valve are not used for
regulating flow
globe valve are used for
regulating flow
For fine-throttling service, a very steep tapered seat can be used; this particular type of globe valve is referred
to as a needle valve.
Plug valves can be operated by a . ____. What other valve like this too?
gear-operated device or by turning a wrench on the stem /
ball valve
Plug valves are either
lubricated or nonlubricated;
Plug valves usually function as ____. What other valves are like this?
block valves to close off flow (like gate valves and ball valves)
the slide valve is a specialized gate valve generally used in
erosive or high-temperature service. I
Periodic temperature monitoring via visual, infrared, temperature indicating paints should be undertaken on these types of lines to confirm the integrity of the
refractory
injection point NDE
RT/ UT
what valve would make it impossible to pig a line
globe valve
type of valve should not be used if pig a line (4)
- reduce port gate valve
- plug valve
- butterfly valve
- globe
what type of valves to use with pigging (2)
gate valves / ball / slide
generally piping is replaced or repaired when it reached
min thickness requirement
schedule 40s , S =?
stainless steel
The corrosion rate in _______ can vary significantly from adjacent active piping
dead-legs
buried piping uncoated should consider excavating
6-12 inches
secondary piping is isolated from
main process lines
The external condition of buried piping that is not cathodically protected should be determined by either
pigging, or excavating
lengths greater than 100 ft (30 m) and not cathodically protected, evaluations of soil corrosivity
should be performed at appropriate intervals
based on likelihood of change
leak test for burried piping
8 hours
