How to Write a Copper-Nickel RFQ That Gets You the Right Fittings, Flanges and Certificates — First Time

Introduction

If you've ever received a shipment of "Cu-Ni 90/10" flanges only to discover they were actually closer to 80/20 in composition, or waited three extra weeks because the mill test certificate format didn't match your project specification, you already know: the RFQ is where most copper-nickel procurement problems begin.

Copper-nickel fittings, flanges, and the certificates that accompany them sit at the intersection of material science, international standards, and project compliance. A vague RFQ invites a vague quotation. And on a seawater project, vague is expensive.

This guide walks through exactly what to put in your copper-nickel RFQ so that the first quotation you receive is the one you can actually place a purchase order against.

Step 1: Lock the Engineering Inputs Before You Write a Single Line

A useful RFQ starts with engineering work that is already finished, not engineering work the supplier is expected to do. Before you open your email client, you should be able to write down the following on one page:

• Service fluid: Seawater cooling, ballast, firefighting, brine, or chemical service

• Design temperature and minimum operating temperature

• Design pressure and any surge or hammer transients

• Maximum sustained flow velocity (m/s) at the fitting location

• External environment: Immersed, splash zone, buried, indoor, or fire-rated zone

These five items determine whether you are buying 90/10, 70/30, or a higher-nickel alloy for the application. If you can't answer them, stop and get the answers before you issue the RFQ. The supplier cannot do this engineering for you — and if they try, you're both guessing.

Step 2: Specify the Alloy by UNS Number, Not by Nickname

"Cu-Ni 90/10" is not a specification. It is a nickname.

Your RFQ must call out the exact UNS designation:

• C70600 for 90/10 copper-nickel (Werkstoff 2.0872)

• C70620 for the welded version with controlled carbon content

• C71500 for 70/30 copper-nickel (Werkstoff 2.0882)

• C71520 for the welded version of 70/30

This matters because the chemical composition ranges — particularly the iron and manganese content — directly drive corrosion performance in seawater. Iron content in Cu-Ni alloys must be maintained within the specified range (typically 1.0–1.8% for 90/10) for the protective surface film to form properly. A fitting that meets the general "90/10" description but has iron content below the minimum will corrode at an accelerated rate under flowing seawater.

Your RFQ should include:

For butt weld fittings, the relevant standard is ASTM B466/B466M for seamless copper-nickel pipe fittings, while ASTM B467 covers welded fittings. MSS SP-129-2021 establishes requirements for copper-nickel fittings from NPS 1/4 through NPS 12 for use with pipe manufactured to MIL-T-16420K, ASTM B466/B466M, and ASTM B467. If your project spec calls for MSS SP-129, include that in the RFQ — it signals to the mill that you understand the difference between product standards and dimensional standards.

Step 3: Specify the Certificate Type — and Understand What You're Asking For

This is where most buyers lose time and money. "Mill test certificate" means different things to different people, and the difference between EN 10204 3.1 and 3.2 is not a technicality — it's a cost and schedule driver.

EN 10204 3.1 is the standard inspection certificate. It contains specific test results from the actual production batch, validated by the manufacturer's authorized inspection representative who is independent of the manufacturing department. The manufacturer issues it. This is what most copper-nickel fitting and flange suppliers provide as standard.

EN 10204 3.2 is the same document, but validated by an independent third-party inspector — typically a classification society or an independent inspection body such as SGS, TUV, or BV. This is required for many marine and offshore projects where the end user (shipowner, class society, or EPC contractor) demands third-party witness of the testing.

What your RFQ should say:

• "EN 10204 3.1 Mill Test Certificate required for each heat number."

• If 3.2 is required: "EN 10204 3.2 Inspection Certificate required, witnessed by [ABS / DNV / CCS / LR / BV / RINA]. Third-party inspection costs to be included in quotation."

• "MTC to include chemical composition (including Fe and Mn ranges), mechanical properties (tensile, yield, elongation), and heat treatment condition."

Third-party inspection adds typically 2–4 weeks to the delivery schedule because the TPI must be scheduled and the testing witnessed. Include this in your RFQ from the start; retrofitting a TPI requirement after the order is placed is where schedules fall apart.

Step 4: Be Specific About Flange Details

If your RFQ includes flanges, you need more than just "Cu-Ni flange, Class 150." The flange is both a connection and a corrosion boundary — it's where the alloy ends and the bolting, gasket, and mating equipment begin.

Flange RFQ essentials:

A common mistake is specifying the flange class without specifying the facing. Class 150 RF and Class 150 RTJ are not interchangeable, and the gasket and bolting requirements differ completely. If the mating equipment has an RTJ face and your flange arrives with an RF face, you have a rework order, not a fitting.

Step 5: Don't Forget the Bolting and Gaskets

This is where copper-nickel procurement most often goes sideways. The bolts and gaskets are not copper-nickel — and they shouldn't be. But they must be specified to match the flange class, the operating temperature, and the seawater environment.

Bolting: For Cu-Ni flanges in seawater service, the most common bolting materials are:

• B7 (alloy steel, A193 B7) with 2H nuts — acceptable for Class 150/300 in moderate temperatures

• B8 (304 stainless) or B8M (316 stainless) — better corrosion resistance, suitable for most seawater bolted joints

• B16 (chrome-moly steel) — for high-temperature service

• Monel K-500 — for the most demanding seawater applications where galvanic compatibility with Cu-Ni is critical

Gaskets: The gasket material must be compatible with both the flange facing and the seawater chemistry. For Class 150 RF service, compressed non-asbestos sheet is common. For higher temperatures or more aggressive service, spiral-wound gaskets with a PTFE or graphite filler are used.

Your RFQ should state:

• "Bolting material: [B7/2H, B8/8M, Monel K-500, or specified grade]. Include bolting in quotation."

• "Gasket material: [compressed non-asbestos, spiral-wound with PTFE filler, or specified]. Include gaskets in quotation."

• "Galvanic isolation requirements: [insulating gaskets/sleeves required / not required]."

If the bolting and gaskets are not in the RFQ, they will not be in the quotation — and you will be sourcing them separately, from a different supplier, with a different lead time. Treat the bolted joint as one package, not three line items.

Step 6: State the Inspection and Documentation Requirements Explicitly

A copper-nickel RFQ that doesn't specify inspection requirements invites a supplier to provide the minimum. The following should be stated as deliverables, not assumed:

• Mill Test Certificate (EN 10204 3.1 or 3.2, as specified in Step 3)

• PMI (Positive Material Identification) report — verifies the alloy composition on the actual parts, not just the heat certificate

• Dimensional inspection report — confirms critical dimensions (wall thickness, bore, flange face dimensions)

• Third-party inspection certificate (if required) — from the named class society or inspection body

• Heat treatment records — particularly for welded fittings and stress-relieved components

• Packing list with heat number traceability — links each physical piece to the certificate

The difference between a certificate that says "C70600" and a certificate that shows the actual Fe content at 1.45% and Mn at 0.62% is the difference between a fitting that will last 20 years and one that will pit in three. Specify what you need on the certificate.

Step 7: Include the Commercial and Logistics Terms

Technical specification without commercial terms is an incomplete RFQ. Include:

• Quantity breakdown by size, type, and class — drawn directly from the piping isometric or bill of materials

• Required delivery date and delivery location

• Incoterms (FOB, CIF, EXW, etc.)

• Marking requirements — heat number, size, standard, and alloy must be marked on each piece

• Packaging requirements — end caps, wooden cases, moisture barrier for seawater transport

• Partial shipment allowed — yes or no

A quantity breakdown by size, class, and facing drawn from the isometric saves at least two weeks on a typical order because the supplier can batch-forge by size rather than setting up single-piece runs.

A Practical RFQ Template

Here is a condensed RFQ structure you can adapt:

Subject: RFQ — Copper-Nickel Fittings and Flanges for [Project Name]

1. Scope: Butt weld fittings, forged fittings, and flanges in Cu-Ni 90/10 (UNS C70600) for seawater cooling system.

2. Technical Requirements:

• Alloy: UNS C70600, chemical composition per ASTM B466/B467/B151

• Fittings: ASTM B466 (seamless), ASME B16.9 dimensions

• Forged fittings: ASTM B151, ASME B16.11 dimensions, 3000 lb

• Flanges: ASTM B151/B122, ASME B16.5, Class 150 RF

• Bolting: A193 B8M / A194 8M, included

• Gaskets: Compressed non-asbestos, Class 150 RF, included

3. Certification:

• EN 10204 3.1 MTC per heat number

• PMI report on 100% of flanges

• Dimensional inspection report

4. Third-Party Inspection: [Required / Not required]. If required: [ABS / DNV / CCS].

5. Quantity: [Attached line list by size, type, and class]

6. Delivery: [Date] to [Location], [Incoterms]

7. Marking: Heat number, size, standard, and alloy on each piece.