Frequently Asked Questions
Why are TPI’s used to represent the client, on-site during inspection service
Whilst the client’s own staff engineer’s core skills are usually strongest with the technology related to using the products, they do not always have the same detailed technical knowledge on the latest inspection methods and acceptance criteria and/or have the staff freely available to go on-site and witness for themselves, whether or not the inspection contractors are in compliance.
The advantage of having an independent TPI representing the client on-site during inspection service, is to provide that additional layer of assurance that the inspection contractor has the proper capabilities to perform the scope of work and that they adhere to the current best practices.
Why are TPI’s used to represent the client on-site during manufacturing
This service is not required for monitoring the manufacture of everyday basic components with well-established and credible manufacturing vendors, but more so used for the rarer high criticality items, where there are significant complexities in the manufacture processes or where a client has recently experienced some concerning quality issues and feels the need for some additional oversight and a need to manage any NCR dispositions closely.
Using an independent TPI to monitor precision manufacturing/fabrication also aides in providing regular and timely updates on manufacture progress and/or resolution of any obstructing issues, especially when there are tight deadlines to be met.
What types of 3rd party testing services do TPI’s witness for clients?
• Hydrostatic pressure testing
• Load testing
• Mechanical function testing
• Mock-up assembly testing
• Drift and ring clearance testing
What does 'OCTG' stand for?
OCTG is the standard industry acronym for 'Oil Country Tubular Goods', and usually refers to all sizes, grades, poundage, length of ‘casing and tubing’ (including accessories) used in both onshore and offshore wells.
Typically API 5CT and API 5B are the main industry standards for OCTG manufacture compliance, however there are a number of custom proprietary material grades, and thread designs which fall under the relevant OEM specifications.
What is an OCTG accessory?
Basically OCTG accessories (or sometimes called jewellery) are anything connected to the casing or tubing string, which are not defined as either casing or tubing.
Casing and tubing come in 3 length ranges (i.e. Casing - Range 1 ~ 16’ to 25’; Range 2 ~ 25’ to 34’; Range 3 ~ 34’ to 48’), so essentially any casing pup joint shorter than 16’ and/or crossover, landing collar, float collar, float shoe, reamer shoe, drill shoe, etc. would be considered an accessory.
Avoiding the pitfalls in welding of Large Casing & Conductors
Unqualified welds on Large Casing & Conductors performed by cheaper 3rd party vendors (or using general structural welding facilities) can be a significant risk management issue for major operators, especially where there is a weld separation failure in the field, with costly environmental consequences (which can lead to a loss of social license) and when the NCR identifies the root cause as being the use of general structural welding fabricators to weld on conductors without a WPS (Welding Procedures Specification) in place, instead of using suitably qualified coded welding facilities with the appropriate WPS in place.
This is NOT just like welding two bits of steel pipe together down at the farm … this area of welding sorts out the men from the boys and is significantly more complex than general fabrication welding on structural steels.
Having been repeatedly asked to advise on this subject, and notwithstanding the obvious reason of why companies will not publicly publish their actual intellectual knowhow, as in their WPS’s for coded welding, I will attempt to detail some of the more general aspects of welding of large casing and/or conductors, which are rather important for all the operators ‘contracts and procurement’ managers and their staff to be very aware of, especially when they are selecting OEM’s and quality vendors for high criticality items like large casing and conductors.
Firstly, there is a lot of technical evolution is going on in this area, to ensure OEM connection designs are able to withstand the test of time with regards to ocean currents and/or tidal fatigue in high stress applications, this is on the back of some actual fatigue failures in the field, and for this reason the leading OEM’s have been undertaking both desktop theoretical engineering analysis and actual mechanical testing to prove their designs will not fail in the clients particular application (noting not all wells are over 1km deep or subjected to >7metres of tidal pull, so fit for purpose provides a market for all products with some level of scrutiny).
That said, even if the conductor body and the connectors are both proven to be theoretically and mechanically suitable for the clients application, there is still the potential for a weld to fail, IF either the OEM (Original Equipment Manufacturer) or any 3rd party vendor perform a faulty or unqualified weld.
Whilst an OEM may offer their product already welded as a completed assembly (with well-established in-house welding procedures), some have been known to offer just the connectors lose and the clients can order the casing blanks from trading houses and use a local welding vendor to weld on the connectors (also applies for local connector repairs), which if unmanaged is a high risk practice, because in many cases both the clients ‘contracts and procurement’ staff and the 3rd party welding vendors are often not fully aware of the correct processes and procedures for this type of welding and what can potentially go wrong should the weld fail in the field.
It is usually the client who makes the decision on the minimum inspection acceptance criteria they will accept for the welds to suit their application (requiring input from the well design engineers), and this is usually choice of either ASMI IX or API 1104, both standards are rather similar, however ASMI IX is considered much tighter when it comes to rejection criteria for say inclusion detected on x-ray (from memory ASMI IX is 6mm [for pressure vessels] and API 1104 is 50mm [for API pipeline] for say a 36” x 1.5”WT conductor).
Obviously the tightness of the acceptance criteria affects the price of the weld, so as a general guideline ASMI IX for deep offshore, and API 1104 for JU - onshore would be one way of deciding on a standard to use, but ultimately each client must decide for themselves.
In brief, a WPS is a document which includes a lot of very specific details on 'exactly what materials it is used for welding' and in very detailed steps 'how a weld is to be performed', some of the details would include:
•the inspection standard to be used (ASMI IX vs API 1104);
•both base material types (including grade/grouping/class/size/thickness);
•weld position (1G - horizontal rotating);
•joint design (single vee butt weld, welded both sides)
•weld method (both root & filler);
•weld medium (wire type, material & thickness);
•flux used (SAW or Submerged Arc);
•gas used (for GMAW or MIG);
•preheat & post heat as well as inter-pass max temp instructions;
•‘travel speed, amps & volts’ (all varied at different stages of the weld); and
•many more criteria to suit specific weld types.
All new WPS are required to undertake some basic steps to become validated and before they can be performed on actual products:
•first a suitably qualified or experienced person (in-house or external consultant) will need to design the WPS to suit the specific base materials and other relevant parameters (the author of the WPS);
•then a suitably trained/qualified welder will use calibrated welding equipment and measuring devices to perform the draft WPS “under surveillance” (meaning with a QA/QC monitoring every minute step in the procedure is strictly adhered to and documented);
•the specimen weld must pass local NDT inspection MPI (Magnetic Particle Inspection) and RT (Radiographic Testing) before sending the specimen to undergo further destructive mechanical testing.
•then the sample specimen is sent to an appropriately capable laboratory for numerous destructive mechanical testing, including macro-photographic examination;
•if the specimen fails … the WPS is deemed unsuitable for the application and a new WPS is designed and the previous four steps are repeated until a specimen is passed;
•if the specimen passes … then the laboratory will issue a document usually called the PQR (Procedure Qualification Record);
•the PQR essentially validates that the WPS is now valid for that specific application and can now be used on actual product; and
•the welder will also have a WPQR (Welder Performance Qualification Record) for this WPS, which qualifies them to perform this WPS on actual products.
NB: The validated WPS cannot be used for other applications outside its documented parameters, including different material grades & thicknesses.
NB: Any other welders working at the same facility cannot automatically use the WPS, as they are still deemed unqualified, until they have also successfully performed a first article under QA/QC surveillance and NDT results are conforming and a WPQR created.
NB: One common oversight is the importance of using calibrated welding equipment and measuring devices to perform the WPS. This is crucial in order to maintain the high degree of repeatability in welds which can be prone to high stresses over a considerable period. This would include such instruments as the welder voltage & amp gages and thermal measuring devices.
Any WPS without a matching PQR is deemed invalid (so auditors, check vendors for plagiarised WPS's without supporting PQR's).
All production welds are required to be 100% inspected using NDT methods as stipulated by the governing standard (ASMI IX or API 1104) and will include MPI and RT and these test results must be fully traceable to the specific weld, also identifying on which end of the pipe and also a copy of the NDT report should be included in the CoC (Certificate of Conformance) along with other quality documents.
Typically the lower grades of base material of the casing body are rather easy to weld to themselves, like X-52 to X-52 and X56 to X56, etc. (similar alloys), however usually the forging used for manufacturing connectors, landing collars, float collars, float shoes, etc. are made of other more complex alloy steels, often AISI 4130 or something very similar and these can become very troublesome to weld together as in say AISI 4130 (connector) to X60 (casing blank), and this is usually referred to as ‘welding dissimilar alloys’, which requires skilled welding engineers with sound knowledge in metallurgy to design the appropriate WPS.
When welding dissimilar alloys, a lot of focus is placed on: on managing of the pre-heat, inter-pass max temp, post-weld heat treatment (tempering or normalising) as well as the constant micro changes to ‘travel speed, amps & volts’ between each rotation during the weld.
Improper management of these key parameters often leads to embrittlement and stresses in the welds, which in turn can lead to premature weld failure, where often poorly managed welds can simply crack and separate when sitting on the rack, without any force applied.
Welds which have a minor non-compliance inclusion issue detected during NDT, can have a special remedial WPS designed to say gouge out a localised area and manually weld to fill back and MPI performed again, however any such remedial WPS must have all the same details and rigors and also a PQR as does the main WPS.
In addition to the connector welds, there are also sometimes lift lugs welded to the casing body, and these also require a WPS and are usually welded to comply with DNV (Det Norske Veritas) specifications and include NDT inspection of MPI & a localised pull test, with much of the same WPS & PQR compliance as detailed on the welding of connectors.
Usually the welder who has been successfully monitored performing a WPS is deemed to be ‘qualified’ for that specific WPS and will remain so, unless they do not repeat that WPS within a 6 month interval, in which case it will automatically lapse and just like any other welders who will be required to perform the weld for the first time, they too will be required to be given a refresher training on the WPS and a QA/QC surveillance on the first article, which must include documenting a WPQR (Welder Performance Qualification Record) and successfully pass the NDT testing (MPI & RT).
Ongoing maintenance of skilled welder training records, which includes their WPQR, and identifies which WPS’s they are qualified to weld and when they last performed that WPS, are all part of a well-managed and compliant facility.
A suitably qualified facility will require many separate WPS’s (and thus PQR’s) for each base material combination they weld (it's not unusual to have 20-50 ea. WPS’s), and have suitably trained & qualified welders with regular exposure to the WPS’s, calibrated welding equipment and measuring devices, access to a 3rd party NDT inspection company with MPI and RT capability and familiar with interpreting the relevant standards … so the cost of maintaining proper facilities is fairly significant, and thus it is understandable that reputable companies who have invested much in building up these high skilled capabilities will not willingly divulge their IP, and have sensitivities when asked to disclose WPS for auditing and conducting desktop reviews (NDA's with strict guidelines are a must).
Hopefully this helps to better understand more on some of what is involved in welding on large casing and conductors and avoiding the many of the pitfalls of using unqualified general welding facilities and selecting vendors based on price alone.
I have personally witnessed a 30" x 1"WT connector being welded whilst laying on a static laydown rack, using a portable diesel powered welder (unstable amp & volts), no constant rotation (no travel speed, plus risk of exceeding inter-pass temp), no temperature measuring devices, no WPS, non-tradesman foreign visa welder, the company performing the work was core business in mine maintenance (basically they didn't know what a conductor was). The price I was told they charged for the weld was approx. 1/6th the usual price to do it right, but what would be the cost if the weld failed in the field?
It would be a very interesting exercise for major operators to do some detailed compliance auditing on where they have been getting their Large Casing & Conductors welded more recently, and as to whether their 3rd party vendors are in compliance to the above requirements.
There are very significant consequences in the form of loss of ‘social license’ to explore and/or develop whenever there is a real or perceived threat to the environment, and as Large Casing & Conductors often form the main isolation barrier to the environment, cutting corners in this area is putting the operators future business at significant risk.
If you have any concerns in this area and would like some assistance, Oilfield Connect can assist you to audit your existing quality records and or your vendors’ capabilities, and going forward Oilfield Connect can provide you with professional on-site TPI monitoring of criticality processes like welding of Large Casing & Conductors.