Duplex Links

What are duplex links?

Duplex links are connecting and repair links used to join, shorten, or repair duplex roller chain. Duplex chain has two rows of rollers running side by side, giving greater strength and power capacity than single-strand (simplex) chain, while staying more compact than triplex chain. Because roller chain is supplied in lengths and needs to be joined into a continuous loop, connecting links are used to close the chain, while other links are used to adjust the chain length or replace damaged sections.

Duplex links are made to match the pitch, roller size, and width of the duplex chain exactly, so the joined chain runs smoothly over duplex sprockets and carries its full load.

A typical duplex connecting link has:

• Outer plates - the side plates that hold the link together and connect to the inner links of the chain
• Pins - two-strand-width pins that pass through the chain, usually fixed into one outer plate
• Middle plate - a plate between the two strands that supports the pins and keeps the strands aligned
• Removable side plate - the loose plate fitted over the pin ends to close the link
• Fastener - a spring clip, split pins, or rivets that hold the removable plate in place

Duplex links are usually described by:

• Chain size - such as 06B-2, 08B-2, 10B-2, or 12B-2 for British Standard chain, or 40-2, 50-2, or 60-2 for ANSI chain. The 2 shows it is duplex
• Chain standard - British Standard (BS) or American Standard (ANSI)
• Pitch - the distance between the centres of adjacent pins, such as 3/8 inch, 1/2 inch, 5/8 inch, or 3/4 inch
• Link type - often identified by a number, such as Nr. 26 for a connecting link with a spring clip, or Nr. 11 for a cottered connecting link with split pins

For example, a 10B-2 Nr. 26 duplex connecting link joins 5/8 inch pitch British Standard duplex chain and is secured with a spring clip, while a 10B-2 Nr. 11 link joins the same chain and is secured with split pins.

Key features:

• Joins chain into a loop - closes duplex chain around the sprockets
• Matches the chain exactly - made to the same pitch, roller size, and width as the chain
• Quick fitting - spring clip and cottered links can be fitted and removed with simple tools
• Repairs damaged chain - replace worn or broken sections without replacing the whole chain
• Adjusts chain length - cranked links allow an odd number of links where needed
• Strong construction - made to carry the higher loads of duplex drives
• BS and ANSI sizes - to suit both British Standard and American Standard chains

In simple terms, duplex links are the connecting and repair links that join duplex roller chain into a strong, continuous loop.

Why are duplex links essential?

Duplex links are essential because every roller chain drive needs a reliable way to join the chain, and chains often need repairing or adjusting during their working life. Duplex chain is used on drives that carry more power than simplex chain can handle, so a secure, correctly matched connecting link is vital. The wrong link, or one fitted incorrectly, can come apart, damage sprockets, and stop the machine.

Their main benefits are:

• Secure chain joining - closes the chain loop safely and reliably
• Quick installation - chains can be fitted and removed without special equipment
• Easy repairs - damaged links can be replaced quickly, reducing downtime
• Length adjustment - allows chains to be shortened or adjusted to suit the drive
• Full compatibility - matched to the chain for smooth running over sprockets
• Higher load capacity - suited to the greater loads carried by duplex chain
• Cost-effective - repairing chain is often cheaper than replacing it

Duplex links are used across a wide range of industries and applications, including:

• Industrial drives - medium and heavy-duty chain drives on machinery
• Conveyors - conveyor drives and transfer systems
• Agricultural machinery - drives on harvesters, balers, drills, and processing equipment
• Packaging and food machinery - drive systems on production lines
• Mining and quarrying - conveyors, screens, and crushers
• Pumps, mixers, and compressors - chain-driven equipment
• Timber and paper processing - drive systems and conveyors
• Maintenance and repair - replacing and adjusting chain on existing drives

The main types of duplex links

Duplex links are usually grouped by their design and the chain standard they suit.

By link type:

• Connecting links with spring clip - often referred to as Nr. 26 links. The removable side plate is held in place with a spring clip, allowing quick fitting and removal. Widely used on small and medium duplex chains
• Cottered connecting links - often referred to as Nr. 11 links. The removable side plate is held with split pins through the ends of the pins, giving a secure joint that is less likely to come loose, and commonly used on larger chains and heavier drives
• Riveting connecting links - the pins are riveted over after fitting, giving a strong, permanent joint for high speeds and heavy loads
• Cranked links (offset links) - allow a chain to have an odd number of links. Cranked links reduce chain strength, so they should only be used when necessary
• Double cranked links - two-pitch offset links that also allow odd link counts, giving a stronger option than a single cranked link
• Inner links - the roller links between connecting links, used for repairs

By chain standard:

• British Standard (BS) duplex links - suit European-style roller chains, such as 06B-2, 08B-2, 10B-2, 12B-2, and 16B-2
• ANSI duplex links - suit American-style roller chains, such as 35-2, 40-2, 50-2, 60-2, and 80-2

British Standard and ANSI chains of the same pitch are not interchangeable, as their roller diameters, inner widths, and plate dimensions are different.

Common pitches:

• 3/8 inch - such as 06B-2 and ANSI 35-2
• 1/2 inch - such as 08B-2 and ANSI 40-2
• 5/8 inch - such as 10B-2 and ANSI 50-2
• 3/4 inch - such as 12B-2 and ANSI 60-2
• 1 inch - such as 16B-2 and ANSI 80-2

How to choose the right duplex links?

Choosing the right duplex link means matching it exactly to the chain. Work through these points in order:

• Chain standard - check whether the chain is British Standard or ANSI. This is often stamped on the chain plates
• Chain size - match the chain size, such as 08B-2 or 40-2
• Number of strands - make sure the link is duplex, to match a two-strand chain
• Pitch - check the pitch by measuring the distance between the centres of adjacent pins
• Link type - choose a connecting link to join the chain, a cranked link if you need an odd number of links, or inner links for repairs
• Fastening method - choose spring clip links for quick fitting on most drives, cottered links for larger chains and heavier drives, or riveting links for high speeds and heavy loads
• Load and speed - for high speeds and heavy loads, consider cottered or riveting links and avoid cranked links where possible
• Material and finish - choose links that match the chain material and finish, such as standard steel, nickel plated, or stainless steel
• Quality and brand - choose links from reputable suppliers that match the chain manufacturer’s quality

How to fit a duplex connecting link

Fitting a connecting link correctly is important for safety and reliability:

• Isolate the drive - switch off and isolate the machine before working on the chain
• Prepare the chain - wrap the chain around the sprockets so the two ends meet, using a chain puller if needed to hold them together
• Insert the link - push the pins of the connecting link through the two end rollers of the chain from the back
• Fit the plate - fit the removable side plate over the pin ends, pressing it fully into place
• Fit the fastener - fit the spring clip, insert and bend the split pins, or rivet the pins, depending on the link type
• Check the spring clip direction - fit the spring clip so its closed end faces the direction of chain travel, reducing the risk of it catching and coming off
• Check the joint - make sure the link moves freely and is fully secured
• Set the tension - adjust the chain tension, then turn the drive by hand to check it runs smoothly

FAQ - All you need to know about duplex links

What is a duplex link?

A duplex link is a connecting or repair link designed for duplex roller chain, which has two rows of rollers side by side.

What does Nr. 26 mean?

Nr. 26 usually refers to a connecting link with a spring clip, used to join roller chain into a loop.

What does Nr. 11 mean?

Nr. 11 usually refers to a cottered connecting link, where the side plate is held in place with split pins instead of a spring clip.

What does the 2 in 08B-2 mean?

The 2 shows the chain is duplex, with two strands. For example, 08B-1 is simplex, 08B-2 is duplex, and 08B-3 is triplex.

What is the difference between BS and ANSI chain links?

BS links suit British Standard roller chain, and ANSI links suit American Standard roller chain. They have different dimensions, even at the same pitch, and are not interchangeable.

How do I know which chain I have?

Check the markings on the chain plates, which often show the size and standard. If there are no markings, measure the pitch, roller diameter, and inner width, and compare them with a chain chart.

What is a cranked link?

A cranked link, also known as an offset link, allows a chain to have an odd number of links. It is weaker than standard links, so it should only be used when an odd number of links is unavoidable.

Which way should the spring clip face?

The closed end of the spring clip should face the direction of chain travel. This helps stop the clip catching on anything and coming off.

When should I use a cottered link instead of a spring clip link?

Cottered links are often used on larger chains, heavier drives, and higher speeds, where a more secure joint is needed and there is a higher risk of a spring clip coming loose.

Can I reuse a connecting link?

It is best to fit a new connecting link. Spring clips and split pins can weaken once removed, and worn links can fail.

Can I join new chain to old chain?

It is not recommended. Old chain will have stretched through wear, and mixing it with new chain can cause poor running, noise, and rapid wear on the sprockets.