Regarding the requirement for periodic inspections proposed in the design of TSG21-2016
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TSG21-2016, Page P16, Clause 3.1.4.4.2, Sub-clause (3): “For pressure vessels that cannot undergo internal inspection due to structural reasons, indicate the calculated thickness and the requirements for regular inspections during use.” Which thickness is referred to by the calculated thickness here? How to write the requirements for regular inspections? I would appreciate some guidance from experienced teachers! !
Calculated thickness refers to the thickness obtained by applying the relevant formulas. If necessary, the thickness required for other loads should also be taken into account. The design thickness refers to the sum of the calculated thickness and the corrosion margin.
This post was last edited by cxd11888 on 2016-10-16 at 11:36. This is the explanation in GB150 regarding the calculation of thickness; so how should the thickness required for reinforcement at openings be determined? Is it included in the calculated thickness? How should the requirements for regular inspections be written?
Calculated thickness refers to the thickness obtained by applying the relevant formulas. If necessary, the thickness required for other loads should also be taken into account. The design thickness refers to the sum of the calculated thickness and the corrosion margin. :time::time::time:
The requirements for routine inspections can be considered from the following aspects: (1) Some stringent requirements that must be met during manufacturing, such as 100% RT and UT, as well as heat treatment and pressure testing, etc.; these requirements need to be thoroughly verified at the time of the first routine inspection； (2) The design specifies requirements for anti-corrosion measures in the process, such as strict control over the pH value, S, and Cl levels of the medium, as well as the types of corrosion inhibitors to be used; during regular inspections, it is necessary to verify the implementation of these anti-corrosion measures ； (3) The design should specify requirements regarding the rate of temperature and pressure changes during start-up, shutdown, etc.; it is necessary to verify whether these meet the design specifications during regular inspections ； (4) During routine inspections, verify conditions such as over-temperature, over-pressure, and over-load, as well as any changes in the medium used ； (5) Perform UT external wall testing on the butt welds at a certain proportion; the testing proportion for the final sealing ring welds should be increased appropriately ； (6) Thickness measurement: If there are concerns regarding the corrosive environment, it is possible to request that an ultrasonic flaw detector be used to conduct a thorough inspection of the cylinder’s steel plates ； (7) It is possible to request a pressure test after a certain period of operation ； (8) Requirements for acoustic emission testing can be increased at an appropriate time ； (9) System risk assessment can be conducted using the RBI method. Wait, wait—of course, all of this is based on the designer’s identification of the risks associated with the device. It’s not necessary to require everything; requirements should be established according to the specific risks identified, in other words, by taking appropriate actions based on those risks. Just my opinion, for discussion only!
Thank you all for your help! If there is an S30408 DN450 hydrogen storage tank (without nozzles larger than DN50), how should the inspection requirements be specified? !
Has no expert paid attention to reply? !
For the DN450 cylinder, it is possible to include a manhole in terms of size; I wonder why one wasn’t installed? If it is decided not to include inspection holes, consider how to perform non-destructive testing on the termination ring welds. UT is not very sensitive to stainless steel. Calculated thickness refers to the calculated thickness of the non-perforated area. Since all the openings are below DN50mm, there should be no issue with reinforcing those openings. The requirements for periodic inspection are to be determined by the design itself. If the medium is pure hydrogen, non-corrosive, and the temperature and pressure are not high, it is sufficient to perform a thickness measurement every 2 or 3 years; the component can continue to be used as long as the measured thickness is greater than the calculated thickness. Since accepting inspection holes is not an issue, there are likely no risks during use, so there is no need for overly strict regular inspection requirements; it is sufficient to mention them in the design documents.
It is the minimum thickness that the equipment should ensure