Crossovers — Where the String Changes Size or Thread

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What a crossover does

A crossover — also called a crossover sub or conversion joint — connects two components that do not directly match: different outside diameters, different thread forms, or a pin that must meet another pin through a box-to-box sub. A tubing string may step down in size above a pump; a premium-thread section may have to join an API-thread section; test tools and completion accessories arrive with their own connection and must be adapted to the string. Each of those junctions is a crossover, specified end by end.

The company's catalogue lists ten crossover entries under titles such as tubing crossover, crossover joint and conversion joint, and its coupling pages add that conversion joints and crossover couplings can be customised to customer requirements. The company also lists drill pipe conversion joints among the products named on its coupling detail page — noted here as a catalogue reference; drill pipe itself is an empty family in the current catalogue and is not offered on this site. Crossovers are therefore quoted as made-to-specification items: the two ends define the part, and everything else — overall length, material grade, pressure duty — follows from the string it will serve.

Specifying a crossover, end by end

The table is the whole discipline: describe each end completely before discussing price. Pin or box, size, thread form, grade and hand — a crossover with an un-stated hand or an assumed thread form is scrap with good machining. If the crossover joins a premium connection to an API connection, name the premium pattern exactly as it appears on your string tally; the pattern families the factory machines include BGT and TPJC types named in the catalogue. A dimensioned sketch, even a photographed hand sketch, is worth more than a paragraph at this stage.

Grades, testing and marking

Crossovers are made to order for the conversion named in the enquiry. State if the crossover will see pressure testing as part of a test string, or sour service, or repeated make-and-break as part of a workover tool string. No finished-marking layout for crossovers is stated in the catalogue material behind this page. If your tally needs the joint identified on the rack — for example by the two sizes, the two thread forms and the grade — state the marking you need in the enquiry, and the quotation will confirm whether it can be accepted and in what scope.

Crossovers can be ordered together with pup joints on one RFQ, where a size change also changes the spacing calculation. Send the full string diagram with the crossover position marked; the quotation answers line by line — the lengths and the crossover — confirming which lines can be accepted for the order.

Is a crossover sub the same as a conversion joint?

On this site, yes — the catalogue uses crossover, crossover sub and conversion joint for the same function: joining mismatched ends. What matters is not the name but the end-by-end specification.

Can a crossover change thread form as well as size?

Yes. Size change, thread-form change and pin/box change are the three standard reasons for a crossover, and one part can combine them. Each change must be stated for both ends in the enquiry.

Do you need a drawing to quote?

For premium-pattern crossovers, name the pattern and both ends in the enquiry — by component drawing or thread data sheet where you have one — and the quotation confirms whether that work can be accepted for the joint. For standard API thread crossovers, state both ends in full on the enquiry line, from the table above; the quotation confirms the work for that line.