How to Specify API 5CT Casing and Tubing in an RFQ

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Why RFQs stall

An enquiry that carries only a size and a request for the best price leaves the specification unstated. Casing and tubing are not catalogue commodities with a single price per size; they are specification products whose cost is built from size, weight, grade and variant, thread and coupling, length range, inspection level and quantity, on top of a mother pipe position that changes with the market.

The eight fields, in order

• 1. Product and construction — casing, tubing, coupling, pup joint or crossover; seamless stated explicitly where the design requires it.
• 2. Size — outside diameter, from the casing sizes chart or the tubing list; metric dimensions are accepted as written.
• 3. Weight or wall — lb/ft or millimetres; this sets ID, drift and ratings, and two joints of one OD with different weights are different products.
• 4. Grade and variant — J55, K55, N80-1 or N80Q, L80-1, P110, or the chromium grades; variant letters are part of the grade, not decoration.
• 5. Thread and coupling — STC, LTC, BTC, premium pattern by exact name, EUE or NUE; coupling grade and any special clearance or finish.
• 6. Length range — Range 1, 2 or 3 for pipe; measured lengths and convention for pup joints.
• 7. PSL and documentation — PSL1, PSL2 or PSL3 where applicable, certificates required, third-party inspection if any.
• 8. Quantity and destination — joints or tonnage, plus port or site and delivery terms, so MOQ, packing and lead time are quoted on the real basis.

None of these fields is bureaucratic. Weight changes the steel in the joint. The Q in N80Q changes the heat treatment. PSL changes the inspection scope and therefore the price. Destination changes the packing that will actually protect the threads across an ocean. A quotation desk that guesses any of them is transferring risk to the buyer, silently.

Two worked examples

A complete casing line reads like this: Seamless casing pipe, 9-5/8 in, 47 lb/ft, N80Q, BTC, Range 3, PSL2, 240 joints, thread protectors steel, destination Dammam, CIF. Twelve facts, zero ambiguity. A complete accessory line reads: Tubing couplings, 2-7/8 in, L80, EUE, phosphated, PSL1, 800 pieces, cartons on pallets, same destination. Note what both examples share: every field the product family needs, and nothing the desk must invent.

Accessories: the lines to add to the enquiry

Accessory lines are where an RFQ can go wrong on paper — a coupling or pup joint line written loosely fails the order even when the pipe line is perfect. Three habits follow. First, order couplings on their own lines with their own full specification — size, grade, thread form, finish, PSL — never as couplings to match above, because above changes during negotiation and the coupling line must not change silently with it. Second, order pup joints with lengths, set logic and the length convention stated. Third, specify crossovers end by end — each end's size, form, hand and grade. For a premium section, name its pattern exactly as on the string tally. The published coupling stock sizes run 1.315, 1.66, 1.9, 2-3/8, 2-7/8, 3-1/2, 4 and 4-1/2 in, and the published casing sizes run from 4-1/2 in to 20 in in fourteen sizes.

What a good quotation looks like in return

Judge the reply by the standard of the enquiry. If a quotation arrives without restating the specification, ask for the restatement; if it prices a variant you did not name, ask why. API 5CT exists so that a specification written in one country is manufactured correctly in another — the RFQ is where that promise is either kept or lost.

Common RFQ mistakes — the ones that stall quotations

Four mistakes stall quotations. The first is the naked size: casing 9-5/8 with no weight, grade or thread, which is not a specification but the first word of one. The second is the inherited line — as per our last order — sent to a new supplier who has no last order, or to the same supplier after a design revision nobody attached. The third is the accessory afterthought: the pipe line specified in full, the coupling and pup joint lines left as loose references to it. The fourth is the silent substitution request — quote J55, or equivalent — which invites the desk to choose your grade for you and documents nothing. The habit this guide recommends is the full written line, every time, for every product family in the order — the mistakes above are the ones it is meant to catch before the order is placed.

A related habit is worth building into every purchase: the restatement check. When the quotation returns, compare its restated specification against your RFQ line by line before comparing prices across suppliers. Quotations for different specifications cannot be ranked by price at all — a cheaper quote for N80-1 against your N80Q requirement is not a saving, and a quote that quietly changed a thread form has changed the product. The restatement is worth reading as a sample of the desk's care: the closer it matches your RFQ, line by line, the safer the comparison that follows. State in the enquiry the documents your receiving check will need; what arrives can then be checked against the specification you actually accepted.

None of this requires special software or a procurement department. It requires a template — the eight fields as a standing form — and the discipline to refuse to send an enquiry with blanks. Build the template once, from this guide or from the form on this site.

Can I send a well schematic or completion diagram instead?

Send it with the RFQ, not instead of it. Diagrams explain intent beautifully, but the quotation is built from written specification lines. The strongest enquiries carry both.

What if I do not know the PSL or variant my design needs?

Say so in the enquiry and attach the design basis. Name the field as open on the enquiry line, and ask for the assumption behind the quotation to be stated for that line, so the basis of the line is confirmed rather than left unstated.