MIL-C-22521C Open Link Coast Guard Buoy Mooring Chain | 13–48 mm Studless Welded

Product Specification

MIL-C-22521C Open Link Coast Guard Buoy Mooring Chain | 13–48 mm Studless Welded Chain

Product Overview

The MIL-C-22521C open link Coast Guard-type buoy chain is a welded, studless chain used in buoy mooring assemblies for aids to navigation. It connects the buoy or bridle arrangement to the mooring sinker or anchor while allowing the submerged chain to form a compliant catenary under tide, current, wind, and wave movement. This product is a buoy mooring chain, not a ship anchor chain and not a lifting chain.

The supplied range covers 1/2 to 1-7/8 in. common-link bar diameter (approximately 13 to 48 mm), with common links, optional enlarged end links, proof-load values, breaking-load values, and approximate shot weights defined by size. MIL-C-22521C is a legacy procurement reference; the purchase order should identify whether compliance is required to the legacy specification, a current U.S. Coast Guard specification, a customer drawing, or an approved equivalent.

Quick Specifications

• Product type: Open link, studless welded buoy mooring chain → intended for aids-to-navigation buoy moorings rather than vessel windlass service.
• Legacy reference: MIL-C-22521C → specification status and required revision should be confirmed in the purchase order.
• Common-link diameter: 1/2 to 1-7/8 in. / approximately 13 to 48 mm → the primary size for matching the buoy mooring design and existing chain.
• Standard shot reference: 15 fathoms / 90 ft / approximately 27.4 m → cut lengths and half-shots can be quoted when defined by the project.
• Construction: Resistance or flash-butt welded open links → weld fusion, bar-end alignment, link geometry, and surface condition are key inspection points.
• Load data: Proof load and breaking load are stated separately → neither value should be presented as SWL or working load.
• End-link arrangement: Enlarged end links can be supplied where required → end connection dimensions must match shackles, bridles, sinkers, or existing components.
• Inspection scope: Material traceability, dimensional checks, proof testing, breaking-load sampling, and surface inspection → final scope follows the contract or approved inspection plan.

Main Technical Parameters

Selection & Inquiry Guide

Step 1: Confirm the governing requirement: MIL-C-22521C legacy reference, current U.S. Coast Guard specification, customer drawing, or another approved buoy-chain standard.

Step 2: Provide common-link diameter, required shot or cut length, quantity, and whether enlarged end links are required at one end, both ends, or not required.

Step 3: Confirm the buoy system interface: buoy or bridle connection, shackle or joining hardware, sinker or anchor connection, and existing replacement-chain dimensions when applicable.

Step 4: Confirm material and finish. Carbon steel is the normal specification basis; stainless steel, CM490, 20Mn2, hot-dip galvanizing, or painted finishes must be treated as project-specific alternatives and reviewed for compliance.

Step 5: Define the inspection and documentation scope: mill certificate, heat traceability, dimensional report, proof-load record, breaking-load test, crack inspection, third-party witness, and certificate wording.

Step 6: Provide application location, water environment, delivery destination, required delivery time, packing method, and the project drawing or existing-chain photo if available.

Structure

Open studless common links | Resistance / flash-butt welded joints | Enlarged end links when specified | Heat / batch traceability | Permanent end marking when required | Natural, galvanized, or painted finish according to approved order scope

Manufacturing, Testing & Traceability Advantages

• Open studless geometry provides a simple chain form for buoy mooring systems and avoids the stud arrangement used in ship anchor chain.
• Controlled bar forming and link calibration help maintain link length, width, six-link pitch, and connection compatibility across each production batch.
• Weld quality control should cover fusion condition, weld diameter, bar-end alignment, visual indications, and crack-sensitive areas at the weld and inner radius.
• Heat-number and batch traceability allow material certificates, production records, test samples, and completed shots to be linked to the same steel source.
• Proof testing verifies every contracted shot when required by the governing specification; breaking-load tests are destructive sample tests and should be defined separately in the inspection plan.
• Smooth, burr-free link surfaces reduce snagging, localized handling hazards, and chain kinking during deployment and service.
• Replacement supply can be checked against existing chain dimensions and end-connection geometry rather than relying on nominal diameter alone.

Custom Attributes

• Standard Reference: MIL-C-22521C → legacy Coast Guard-type open link buoy-chain reference; revision and compliance basis to be confirmed.
• Product Category: Buoy mooring chain → for aids-to-navigation buoy systems, not for ship windlass calibration and not for lifting.
• Common-Link Diameter: 1/2 to 1-7/8 in. / approximately 13 to 48 mm → select by approved buoy mooring design and replacement dimensions.
• Shot Length: 15 fathoms / 90 ft / approximately 27.4 m as the standard reference → half-shots or cut lengths can be quoted when specified.
• Material: Carbon steel bar stock as the normal legacy basis → exact grade, chemistry, and tensile requirement must follow the purchase specification.
• Finish: To be confirmed → natural / black finish, hot-dip galvanized, or painted supply must be stated in the order and checked against the governing specification.
• End Links: With or without enlarged end links → connection arrangement and end-link dimensions must be confirmed before production.
• Certificate Scope: Available according to project requirement → maker documents, mill certificate, third-party inspection, and class involvement are not assumed unless ordered.

How It Works

Buoy or bridle connection → Open link chain descends through the water column → Chain weight and catenary accommodate environmental movement → Lower end connects to the specified sinker or anchor system → Periodic inspection checks wear, corrosion, deformation, weld condition, and connection security

Applications

Aids-to-navigation buoys | Coastal and inland waterway buoy moorings | Harbor and channel marking buoys | Buoy bridles | Replacement buoy-chain shots | Mooring sinker connections | Government and commercial navigation-aid maintenance

Certifications & Advantages

Certificates and inspection witnessing can be arranged according to the governing specification, project requirement, approved inspection plan, and third-party acceptance procedure.

Certification: CCS, NK, BV, ABS, DNV, LR, KR, IRS, RS, RINA, CRS, Makers Test Certificate.

Drawing & Photos

FAQ

Q1: Is the proof load the chain SWL?

A1: No. Proof load is a specified test load, while breaking load is a destructive strength requirement. Neither value should be used directly as SWL or working load. The allowable operating load must be defined by the buoy mooring design authority using the applicable safety factors, corrosion allowance, wear condition, and system dynamics.

Q2: Is MIL-C-22521C buoy chain the same as ship anchor chain?

A2: No. This product is an open link, studless chain for buoy mooring systems. Ship anchor chain is normally a calibrated stud-link chain designed to work with a windlass or wildcat and follows different dimensional and certification requirements.

Q3: What information is required for a reliable quotation?

A3: Confirm the governing specification, common-link diameter, shot or cut length, quantity, end-link arrangement, material, finish, proof and breaking-load requirements, certificate and witness scope, connection drawings, delivery destination, and required delivery time.