Chapter 7 Flashcards
What is point to point method?
CR (LT) and CR(ST)
What are the 2 method to determine corrosion rates?
- point to point
2. statistical analysis
What is the statistical analysis?
probability plots or related tools to establish a representative corrosion, remaining life estimate and/or re-inspection date
Statistical analysis employing point measurements is NOT applicable to piping circuits with
significant localized unpredictable corrosion mechanisms
What is required to be done if newly pipe or change of service? (3)
- use CR of similar service
- use CR of owner/user experience or published data if #1 is not available
- initial thickness measure shall be made no more than 3 months. Corrosion monitoring devices, such as corrosion coupons or corrosion probes, may be useful in establishing the timing of these thickness measurements. Subsequent measurements shall be made after appropriate intervals until the corrosion rate is established
What method to be done for existing pipe?(2)
use point to point or statistical analysis
The MAWP for the continued use of piping systems shall be established using ________code
using the applicable code
MAWP computations may be made for known materials if all the following essential details are known (5)
a) upper and/or lower temperature limits for specific materials,
b) quality of materials and workmanship,
c) inspection requirements,
d) reinforcement of openings,
e) any cyclical service requirements.
For unknown materials, MAWP computations may be made assuming (2)
the lowest grade material and joint efficiency
When the MAWP is recalculated, the wall thickness used in these computations shall be ….
Estimated actual thickness minus twice the estimated corrosion loss
MAWP formula
2SEt/D , t = Estimated actual thickness minus twice the estimated corrosion loss
The required thickness of a pipe shall be the greater(2)
- of the pressure design thickness
2. the structural minimum thickness.
For services with high risk, the piping engineer should consider increasing the required thickness to
provide for …..
unanticipated or unknown loadings, or undiscovered metal loss
Piping shall be supported and guided so that: (4)
a) its weight is carried safely,
b) it has sufficient flexibility for thermal expansion or contraction, and
c) it does not vibrate excessively, and
d) accounts for other loads (e.g. those included in the original code of construction).
Piping flexibility is of increasing concern (2) for what kind of specs on pipe
- the larger the diameter of the piping
2. the greater the difference between ambient and operating temperature conditions
Piping stress analysis can identify the …? (3)
- highly stressed components in a piping system
- predict the thermal movement of the system when it is placed in operation.
- vibration
When is a piping stress analysis performed?
When unexpected movement of a piping system is observed, such as during an external visual inspection
What does a Piping stress analysis to assess? (2)
system flexibility and support adequacy
What records should be maintained and what duration? and who?
- piping systems/PRD
- throughout the service life of each piping system
- owners/users
Piping system and pressure-relieving device records shall contain four types of information pertinent to mechanical integrity as follows.
- Fabrication, Construction and Design Information to the Extent Available
- Inspection History
- Repair, Alteration, and Re-rating Information
- Fitness-for-Service assessment documentation requirements
Site operating and maintenance records, such as operating conditions, including process upsets that may affect mechanical integrity, changes in service, mechanical damage from maintenance should also be available to the
inspector.
The primary purpose of inspection ISOs is to
identify the location of CMLs and to identify the location of any recommended maintenance
when documenting inspection results A combination of (2)
checklist and narrative record keeping is recommended
A deferral procedure shall be in place that defines a risk-based deferral process, including a (3)
corrective action plan and deferral date, plus necessary approvals
If inspection of a piping circuit is to be deferred beyond the established interval. that procedure should include: (4)
a) concurrence with the appropriate piping personnel including the inspector and appropriate owner/user
management representative;
b) any required operating controls needed to make the extended run;
c) need for appropriate nonintrusive inspection with NDE, if any, as needed to justify the temporary extension; and
d) proper documentation of the deferral in the piping or PRD records.
an inspection or pressure relieving device servicing interval may be deferred by the
inspector, without other approvals, based
on a satisfactory review of the equipment history and appropriate risk analysis, when the period of time for which the item is to be deferred does not exceed 10 % of the inspection/servicing interval or six months, whichever is less
initial thickness measure shall be made no more than
3 months
