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18-5/8" X-56 & K-55, 87.5 lb/ft, BTC Are compatible
28 February 2014
Dear Sir/Madam:

Are 18⅝" conductor, Grades  X-56 and K-55, 87.5 #/ft BTC; compatible to connect or do we need a crossover?

much thanks,
Boas
11 answer(s)
Punch
Managing director Punch Energy Services
Punch Energy Services
Total Posts: 18
Join Date: 24/06/20
Hi Boas,

These are interchangeable.
You will also see X56 pipe with K55 grade couplings for example.
Just bare in mind the pipe is manufactured in accordance with API 5L and the coupling API 5CT.

With this size you have to pay attention to the pipe body OD tolerance. Also premium manufacturers have other tolerance for this size, e.g. Vallourec has a 1.25% or 1.5% OD tolerance instead of the API standard 1%.

Can be an issue for elevators for example.


Augusto
Consultant [retired Shell staff]
SPREAD Associates
Total Posts: 279
Join Date: 02/09/05
Recommended reading: SPE/IADC 18697 New make-up methods for API connections - torque-to-position, Exxon.

Although that is primarily for API 8 Round connections, the practicalities of the paint-line are specially suited for inexperienced crews, allowing the desired 360º visibility for the Driller... Not all the Operators can afford a dedicated casing crew!

 

mullenmf
Technical Services Representative
Hunting PLC
Total Posts: 5
Join Date: 20/04/09
The API Triangle on the BTC connections is the mark where you make the joint upto. By API this is 4 13/16 from the pin nose.
The so called white paint is only an indication on were the Triangle has been marked.
Augusto
Consultant [retired Shell staff]
SPREAD Associates
Total Posts: 279
Join Date: 02/09/05
A simple comment on the API TRIANGLE.

I would encourage you to consider the "paint line", instead. This is the recommendation of Exxon ("Torque-to-Position").
JDDrouin
Project Quality
Myspread Users
Total Posts: 109
Join Date: 06/05/09

Michael,

With respect, you've made several incorrect statements and assumptions ...

To begin with, the buttress thread form is NOT made up to the base of the triangle, it's made to to a point between the base and the apex.  This may seem a minor difference, but it's critical to achieving proper interference fit between the coupling and pin which, among other issues, is critical to ensuring proper leak resistence and tensile capacity.

Additionally, within a given casing OD size, the API buttress thread form is identical, regardless of weight or grade (though from memory, small diameter casing in the 4½ range may have several thread forms).  Thus, relative to the question Boas asked, all 16" BTC connections are fully interchangeable with all 16" casing weights, or going slightly larger, all 20" BTC connections with all 20" BTC weights (see API Spec 5B).

If 18⅝" was offered in more than one weight, then they would all be interchangeable.

Further, conductor, i.e. line pipe, is not manufactured according to standard and limited ODs and weights as casing and tubing are.  In brief, a casing buyer specifies OD and casing weights according to a relatively short list in each API-recognised diameter.

Without digressing, end-users may order non-standard casing and tubing sizes in any dimension they wish, but the API-recognised sizes and weights are relatively limited.

Relative to Boas' question, with API casing, the ONLY weight available in 18⅝" is 87# with it's 0.435 wall thickness (API Spec 5CT, Table E1).

By comparison, a line pipe buyer specifies OD and wall thickness according to their requirements.

Again, relative to the question asked by Boas, line pipe OD and wall thickness may be ANY increment in either OD or thickness between 18" and 22" OD and 0.281" and 1.771" wall thickness (API Spec 5L, Table 9).

The issue, as I stated and Augusto amplified on, is the geometry of the finished product.  With 18⅝" casing, this is relatively simple because there is only one acceptable set of ranges; those for 18⅝" 87#.

With 18⅝" conductor, what has to be verified is whether or not the buyer actually specified (and the manufactured achieved) a product that would be dimensionally identical to 18⅝" x 87# casing.

I could have recommended that Boas review a relatively large dataset, however chose to recommend that he simply confirm the connections' finished geometry was / is identical for the reasons above.

The pitch diameter will confirm the 'z axis' of the two products (casing v conductor) connections is the same, and the thread form, thread height, taper, and lead will confirm the proper fit when made up.

James

mullenmf
Technical Services Representative
Hunting PLC
Total Posts: 5
Join Date: 20/04/09
James, You don't need thread inspection to check the grade of a connection.
mullenmf
Technical Services Representative
Hunting PLC
Total Posts: 5
Join Date: 20/04/09
There is no need for a x-over, the weight of the connection is the same, it's only the grade that is different,during make-up you make up to the base of the triangle, so the connection should be fine. You don't need gauges to check a grade of pipe, you only need these for the thread form.
attema
Drilling Superintendent
SPREAD Associates
Total Posts: 22
Join Date: 24/05/06
Sound like you need a crossover.
You can make the crossover from either K55 or X56.
Good luck.
minero
Drilling Engineer
Myspread Users
Total Posts: 1
Join Date: 08/07/09

Hi Boas,

If they are both BTC, there should be no issue of connecting them..

Cheers,

Fred

Augusto
Consultant [retired Shell staff]
SPREAD Associates
Total Posts: 279
Join Date: 02/09/05
Beware not of the thread interchangeability but on the geometry. This should be re.inspected in that light.

See quote below:
QUOTE
Line pipe used as Casing: The steel making and process of manufacturing should follow API Spec 5L but acceptance criteria - geometry mainly - should be in line with API Spec 5 CT. This is seldom the case. See case histories: 13⅜", 16",18⅝", 20" and 30" where pipe ovality and/or pipe 
maximum OD, created difficulties not only with threading but mainly with ancillary equipment - hoisting, centralisers/ stop collars and wellhead slips. UNQUOTE
JDDrouin
Project Quality
Myspread Users
Total Posts: 109
Join Date: 06/05/09

Boas,

The short answer is that they likely are.

The longer answer is that conductor and casing are not typically manufactured using the same processes, so interchangeability needs to be verified via thread inspection.  The TI should include thread form, thread height, taper, lead, and stand-off (the latter may be measured using a Pitch Diameter gauge, or ring and plug gauges).

Any competent machine shop that cuts or repairs connections must have those gauges (though maybe not 18⅝" ring and plug gauges but the PD gauge is perfectly acceptable).  The inspection should require no more than an hour or so from start to finish.

James

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