The separator may need to be modified for many reasons: de-bottlenecks, changing process conditions due to mature fields, increased production, connection of new subsea wells, poor performance of the original separator, etc. The separator designer usually initially focuses on the process aspect of modification. Essentially, it is to start computational fluid dynamics (CFD), determine which internal components need to be changed, and gradually solve the problem of how all these new components fit into the existing container. However, for vessels designed in accordance with the ASME Boiler and Pressure Vessel Code (BPVC) and registered with the National Boiler and Pressure Vessel Inspection Committee, much work remains to be done.
What is often left until later are comments on the impact of your modification on ship registration. The original design, manufacture and inspection of pressure vessels are subject to the ASME BPVC Section VIII, while the modification of the vessel is subject to the maintenance and modification of the National Committee Inspection Code (NBIC) NB-23.
In many cases, existing supports and nozzles can be used to retrofit the separation inners. In other cases, some welding is required on the container shell or the new nozzle.
This article focuses on some of the code and registration issues encountered by Savvy Separator engineers when modifying ships with internal parts, rather than as an engineering practice. Qualified and experienced engineers should always be involved in the work.
The discussion is limited to the changes made to the separator vessel that are intended to improve or restore the process performance of the separator. This may mean reconfiguring the internal structure, replacing the inlet or defogging equipment, adding baffles to change the internal flow pattern, or even adding and/or removing nozzles and similar types of changes. NBIC uses a specific language, so the terminology may be a bit confusing. In short, NB-23 is called “maintenance”, which refers to changes that restore the ship to a safe and satisfactory operating state without deviating from the original mechanical design. NB-23 states that “changes” are changes to any content listed in the ship’s original data report.
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Since the separator modification is a change in separator technology, it is intended to restore the separator to a satisfactory operating state, so even if there is no damage to the container, they are often regarded as repair work in the view of NBIC . Being refurbished. Only when the mechanical design of the vessel is affected, the changes made during the renovation are considered as changes.
Repair examples are detailed in NB-23 Part 3 Section 3. 3.3.3. Some of these examples may be considered as part of the divider transformation (as listed in the code):
Examples of changes are detailed in Section 3 of Part 3 of NB-23. 3.4.3. Although these situations are unlikely to occur in separator retrofits, some examples that may apply are:
The personnel responsible for ensuring that the requirements of NB-23 Part 3 are met are NBIC inspectors. This is an individual who holds a current National Committee Committee member who is valid and has an “AR” endorsement. The “AR” endorsement allows the inspection of new buildings in accordance with ASME BPVC and the inspection of repairs and changes in accordance with NBIC Part 3. This is an additional endorsement that allows inspection of repairs and changes. The difference between pressure vessels distinguishes the inspector who needs to modify the separator from the inspector who only inspects the new structure. Throughout the article, the term “inspector” refers to an inspector commissioned by NBIC with AR approval.
When dealing with separator retrofits, the changes usually made to separators fall into four basic categories.
Category 1 is a minor change that exceeds NBIC requirements. This means that such changes will not affect the registration of ships and are not subject to NB-23 requirements. These changes are not to weld any pressure holding parts. This includes internal components welded or bolted to existing internal support lugs/rings, internal components installed using expansion straps, and similar modifications that do not require welding to any pressure-holding components. The following should be noted when welding: Sometimes, other applicable standards and many owner specifications also limit the distance between the weld and the pressure holding part. This is done to keep the pressure holding part outside the heat affected zone of the weld. When dealing with Type 1 changes, it is still recommended to create a transformation plan, create an inspection and test plan (ITP), perform pre- and post-checks, and record the details of the transformation. For these types of changes, an inspector is not required, and the ship does not need to fill out an R stamp or R-1 form.
Figure 1 shows a simple schematic diagram of accessories suitable for this category, and Figure 2 shows a photo of a separator that uses existing supports that are trimmed and used to fix different internal parts. Figure 3 shows that existing supports can be used for multiple purposes, not just inside the separator.
Category 2 is a minor change that belongs to NBIC requirements. Minor changes mean that these changes can be regarded as “routine maintenance” in accordance with NB-23 Part 3, Section 3. 3.3.2. This includes changes to the welding of pressure-holding components, but must meet the applicable requirements of NB-23.
The most commonly used part in section 3.3.2 for separator modification is section e-2: “Add or repair non-load-bearing accessories to pressure holding parts that do not require post-weld heat treatment.” The main advantage of this type of change is that it eliminates the need for additional stamping and/or testing of the container [NB-23, Part 3, Section 2. [5.7.2b], as determined by the inspector and the competent inspector. Although still considered repair by NBIC, stamping and other tests can be waived, greatly simplifying the transformation process. R-1 data reports and any non-destructive inspections (NDE) required by design specifications or inspectors are required. It is also a good habit to create a renovation plan, create an ITP and record the details of the renovation.
Figure 4 shows a photo of the entrance cyclone equipment of the workshop, which has been partially installed in the container. The inlet cyclone is bolted to the inner plate flange, which is connected to the sleeve and welded to the inlet nozzle of the vessel. In this case, it is necessary to use internal protrusions to meet the requirements of nozzle reinforcement, but the size and method of welding allow the inspector to abandon the re-hydraulic test of the container. Or, if other welding methods are required, the inspector may not give up on re-hydraulic testing. In the case of nozzles with internal protrusions, any excess protrusions (ie, protrusions larger than those required for nozzle reinforcement) can be considered as non-pressure holding parts. However, the inspector should be consulted before welding to excessive internal protrusions of the nozzle. Figs. 5 and 6 are photos of similar small brackets installed. These brackets can avoid re-stress testing and re-welding heat treatment (PWHT).
The third category is repricing. These are non-physical changes in vessel design conditions, such as design pressure, design temperature, including minimum design metal temperature, corrosion allowance or external load. The reassessment can be carried out in conjunction with other changes, but NBIC will treat it as a change and has nothing to do with other changes to the ship. Repricing requires new code calculations, new nameplates and R-2 data reports. In addition, depending on the new design conditions, it may be necessary to re-hydrostatically test the container.
Category 4 is the main physical change, or basically any change that does not fall into Category 1 or 2. These changes include the addition of large nozzles, housing cross-sections, load-bearing accessories or any changes that require extensive welding. These may be repairs or changes, depending on the type of change. They are not eligible to give up additional punching or testing. R-1 or R-2 data reports are required, as well as refurbishment plans, ITP, nameplates marked with R, and may also require new code calculations and NDEs required by the design code and checker.
Table 1 shows the requirements for each category of modification listed above. Where appropriate, please refer to the NB-23 section of NBIC.
Abbreviation: Insp-inspector; CH certificate holder; JA judicial inspector; NP nameplate; OU owner/user
In order to use the latest version of the design specifications, please comply with the provisions of NB-23 Part 3 Section 2. 3.4.2 Must be met. These include:
The location of the transformation is another factor that must be determined. Although extremely rare, in some cases it is necessary to unload the ship and return it to the store for refurbishment. The workshop provides a more convenient location to make required changes to the container when needed, perform all necessary NDE, refill the container and/or re-PWHT. The ability to easily handle and maneuver the vessel fundamentally eliminates most of the challenges faced by site modification. If you can send the separator back to the store for refurbishment, you feel lucky. You may also want to stop and pick up a lottery ticket on your way home from get off work, because this is your lucky day!
When you are forced to make changes on site, things become more challenging. A practice that is easy to complete in a store is almost impossible on site. Pay special attention to safety when performing on-site work to ensure that all safety requirements are met. In addition, stress testing and PWHT can be very challenging in this area. Article 5.2 of ASME PCC-2 describes changes that do not normally require stress testing; it also describes the use of certain NDE methods instead of stress testing. Similarly, NB-23, Part 3, Section 16. 4.4.1 Discussed pressure testing and other NDE methods for pressure vessels.
Although NB-23 allows inspectors to give up pressure testing on new or improved pressure-holding components, I believe that most inspectors would like to pressure-test the affected components when feasible. This can be difficult in the field.
However, an important fact that cannot be ignored is that the components need to be hydrostatically tested, which does not mean that the entire container needs to be retested. For example, if a new nozzle is added to the container, only the nozzle and the welding seam of the nozzle to the shell need to be tested. There may be an easy way to accomplish this. If the design specification permits, the nozzle (especially the coupling) can be installed as an “installation” type nozzle. The nozzle on the fixed or boss is actually a nozzle fixed on the outside of the housing and welded in place. In this application, it is possible to install and test before cutting the hole into the housing. In some cases, additional testing of the housing may be required before the installation nozzle can be used. For larger nozzles, it is possible to cover the nozzle with a temporary head, which allows testing the welding of the nozzle to the housing without testing the entire container (Figure 7). Of course, if required, both methods must be approved by the inspector and judicial inspector. After testing the nozzle, cut the hole or remove the temporary head, clean the area, and perform all necessary NDE to ensure that the housing is not affected.
Similarly, when you are forced to weld to a container that has been PWHT, you will face other challenges. PWHT of the container can be very difficult on site. It is often beneficial to find a replacement for the complete PWHT when needed in the field modification. NB-23, Part 3, Part. 2.5.3 and ASME PCC-2 Article 2.9 both propose alternative methods for post-weld heat treatment of modified vessels. These methods include specific welding methods that can weld the container without negatively affecting the original PWHT cycle. In addition, when a special welding method is not acceptable, partial PWHT can be performed. When necessary, these all depend on the approval of the inspector and judicial inspector.
Hydraulic testing and heat treatment are usually not feasible in this field, and in some cases may damage the container, related pipes or supports and surrounding structures. In these applications, the Inspector must be allowed to supervise the transformation as early as possible in the planning phase.
Another area that may appear during the reformation of the separator is the modification of the inlet or outlet pipes of the separator. Sometimes piping needs to be changed to ensure that the separator’s performance goals are met. The changes to the pipeline exceed NBIC’s requirements. However, these changes should at least meet the requirements of the building code version built by the original components. [Refer to NB-23, Part 3, Section. 1.2.6].
Although it is not within the scope of this article, it should be noted that although NB-23 is not applicable in addition to the above, other codes may also be applicable, such as API 570 or other similar codes. Engineers should also carefully consider changes to piping and vessel accessories, as these external changes may affect vessel nozzle loads. The impact of changes in nozzle load on the mechanical design of the container must be evaluated.
Inspector involves almost all types of separator modifications. They play an important role in determining what can and cannot be done. This is especially true when defining what can be used as a regular repair, stamping and inspection can be avoided, when NDE can be used instead of rewatering, and when can alternative welding methods be used instead of rewatering. PWHT, etc. Therefore, it is essential to involve inspectors in the early stages of most renovations.
In some cases, judicial inspectors need to be reformed. In Texas, there are no other jurisdictional rules that apply when installing separators, but this is not the case everywhere. In addition to applicable design codes and NBIC requirements, certain states in the United States and Canadian provinces have other requirements. This is also true in some international locations. In those cases, the involvement of judicial inspectors will be required.
For offshore installations, the situation may be a bit confusing. If the separator is located within state waters (usually extending 3 nautical miles from the low water level of the coastline, but in Texas and western Florida, the distance is 3 maritime unions or 8.7 nautical miles), then the state has jurisdiction. However, in one of most states in the United States (California is an exception), the state is subject to inspection and enforcement by federal regulatory agencies. In the US territorial waters (12 nautical miles from the low water mark), the responsibility for inspection and enforcement rests with the US federal authorities. Outside the regional boundary, but within the Exclusive Economic Zone (EEZ) (extending from the regional boundary to 200 nautical miles beyond the low water mark), the responsibility lies with the country/region that allows the use of the facility. The federal authority overseeing pressure vessels on offshore platforms appears to be the US Agency for Security and Environmental Enforcement, and the US Coast Guard may have jurisdiction in some cases.
A common idea in dealing with the judiciary is that certificate holders and inspectors can advise on the measures to be taken and the personnel involved in all separator renovation projects.
Some owners/users also made other requests. Although for many applications, these are covered by company regulations, there are other requirements that need to be met when the U.S. government is the owner, such as 10 CFR 851, Worker Safety and Health Program, Part 851 Appendix A of Section 4. meet. Likewise, if applicable, certificate holders may be familiar with these requirements.
Safety is the main concern of all activities, especially the modification of separators. The separator in use can be filled with residues from the process. In this case, it is not only necessary to comply with the site safety regulations, including all appropriate personal protective equipment and work regulations, but also to thoroughly clean the ship before performing any modification activities. Another thing to consider is to safely and correctly dispose of the waste and waste separated from the refurbished machine.
Figure 8 is an example of a typical separator at the beginning of a retrofit project. If welding is required, not only the partitions need to be cleaned to provide a safe environment for workers, but also the surface needs to be cleaned for welding.
In addition, when estimating the time of the renovation project, some secondary activities can be ignored. Don’t forget to clean the partitions before work; erect scaffolds inside the vessel; dry/curing time of the internal paint; remove the scaffolding; clean the partitions after finishing the work. When creating a project schedule, these activities and other similar activities are often ignored, leading to unexpected and costly delays. In short, the easiest way to implement a retrofit plan with little or no problems is to plan well, invite certificate holders to participate and inspectors early in the process, and jointly develop a plan to achieve the process goal that has the least impact on ship registration.
Transformation. Changes to the items described in the original manufacturer’s data report will affect the stress tolerance of the stress retention item. (Refer to NB-23 Part 3, Section 3.4.3, change example) Non-physical changes, such as increase in maximum allowable working pressure (internal or external), increase in design temperature or decrease in pressure minimum temperature-retention items should be considered For change.
b) An entity recognized by an authorized inspection agency to perform in-service inspection activities approved by the National Committee NB-369 meeting; NB-371, an owner-user inspection organization certification (OUIO); or NB-390, an entity that performs in-service inspection activities Qualifications and responsibilities of the Federal Inspection Agency (FIA).
Certificate holder. An organization with a valid “R” authorization certificate issued by the National Committee.
field. Temporary location under the control of the certificate holder, used for repairing and/or changing pressure-holding items, and its address is different from the address shown on the certificate holder’s authorization certificate.
an examination. The review process to ensure that the engineering design, materials, assembly, inspection and testing requirements are met and conform to the specifications.
jurisdiction. A government entity that has the power to interpret and enforce laws, regulations or regulations related to boilers, pressure vessels, or other pressure-keeping articles. It includes national committee member jurisdictions defined as “jurisdictions.”
Judiciary. Member of the National Committee as defined by the Constitution of the National Committee.
Judicial inspector. Inspectors certified by the judiciary to verify compliance with the requirements of all jurisdictions.
Nameplate. Identification plate installed on the container. This can include original design nameplates, repairs, re-rated or modified “R” nameplates.
NBIC. National Committee inspection rules issued by the National Boiler and Pressure Vessel Inspectors Committee.
Owner/user. The lowercase letters refer to any individual, company or legal person who is legally responsible for the safe operation of any pressure-holding article.
repair. The work required to restore the pressure-holding article to a safe and satisfactory working condition.
shop. Permanent location, that is, the address shown on the authorization certificate, from which the certificate holder can control the repair and/or modification of the pressure-holding articles.
The author would like to thank Russ Scinta, chief mechanical engineer of Schultz Process Services, and Keith Gilmore, authorized inspector of TÜVRheinland, for their valuable assistance in this article.
Thanks to current and past officials and directors of the Separation Technology Section for their contributions. The list of current members can be found here.
Jay Stell is the Vice President of Engineering at Schultz Process Services, Inc. (SPS). He holds a bachelor’s and master’s degree in mechanical engineering from the University of Texas at Arlington, and a PhD in mechanical engineering from Purdue University. Stell has been in the separation industry since the early 1990s, in Burgess-Manning, Peerless Mfg. Co. and SPS have more than 25 years of experience. Most of his career has been spent on product development, separator design, laboratory and field testing, and troubleshooting. You can contact him at email@example.com.
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Post time: Feb-04-2021