Duplex Chains

What is duplex roller chain?

Duplex roller chain is a power transmission chain with two rows of rollers running side by side. It is used to transmit power between sprockets on parallel shafts, and because its load is shared across two strands, it can carry significantly more power than single-strand (simplex) chain of the same pitch. This makes duplex chain a popular choice for industrial drives that need extra strength and power capacity without moving up to a larger chain size.

Roller chain works by meshing with the teeth of sprockets. As the drive sprocket turns, its teeth pull the chain along, and the chain in turn drives the sprocket on the driven shaft. Chain drives are strong, efficient, and give positive drive with no slipping.

Duplex chain is made up of alternating inner and outer links:

• Inner links - made up of inner plates, bushes, and rollers. The rollers turn on the bushes and engage with the sprocket teeth
• Outer links - made up of outer plates and pins. The pins pass through the bushes, allowing the chain to flex as it wraps around the sprockets
• Middle plates - plates between the two strands that join them together and share the load
• Connecting link - a removable link used to join the chain into a continuous loop

Duplex roller chain is usually described by:

• Chain size - such as 06B-2, 08B-2, 10B-2, or 12B-2 for British Standard chain, or 35-2, 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
• Length - often supplied in standard lengths, such as 5 metres or 10 feet, which can be cut to size
• Quality and material - such as standard duty, heavy duty, nickel plated, or stainless steel

For example, 10B-2 BS duplex roller chain has a 5/8 inch pitch and two strands, and is made to British Standard dimensions.

Key features:

• Higher power capacity - two strands share the load for greater strength than simplex chain
• Compact - carries more power without moving to a larger pitch and bigger sprockets
• Positive drive - no slipping, giving accurate and reliable power transmission
• High efficiency - transmits power with very low losses
• Handles shock loads - suitable for demanding industrial drives
• Supplied in lengths - can be cut to the length needed and joined with connecting links
• BS and ANSI sizes - to suit British Standard and American Standard sprockets

In simple terms, duplex roller chain is a strong, two-strand chain that transmits more power than simplex chain while keeping drives compact.

Why is duplex roller chain essential?

Duplex roller chain is essential for drives that need more power than simplex chain can provide, but where space or speed makes a larger pitch chain unsuitable. Larger pitch chains need bigger sprockets and run less smoothly at higher speeds. Duplex chain allows a smaller pitch to carry more power, keeping drives compact, smooth running, and reliable.

Its main benefits are:

• More power in a compact drive - higher capacity than simplex chain of the same pitch
• Smoother running - smaller pitches with two strands can run more smoothly than larger single-strand chains
• Positive drive - no slipping, keeping drives accurate and reliable
• High efficiency - transmits power with very little loss
• Durable - handles heavy loads, shock, and continuous operation
• Flexible layouts - can drive over long and short centre distances
• Easy to install and repair - can be cut to length and joined with connecting links
• Widely available - standard sizes make replacement chain and sprockets easy to source

Duplex roller chain is used across a wide range of industries and applications, including:

• Industrial drives - medium and heavy-duty 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, compressors, and mixers - chain-driven equipment
• Timber, paper, and steel processing - drive systems and conveyors
• Construction and plant machinery - power transmission on heavy equipment

The main types of duplex roller chain

Duplex roller chain is usually grouped by standard, quality, material, and finish.

By chain standard:

• British Standard (BS) duplex chain - made to British and European dimensions, such as 06B-2, 08B-2, 10B-2, 12B-2, and 16B-2. Widely used on European machinery
• ANSI duplex chain - made to American Standard dimensions, such as 35-2, 40-2, 50-2, 60-2, and 80-2. Widely used on American and international machinery

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

By quality:

• Standard duty chain - for general industrial drives
• Heavy duty chain - with thicker plates or stronger components for higher loads and shock
• Premium chain - made to tighter tolerances with improved materials and treatments for longer wear life

By material and finish:

• Plain steel chain - the standard choice for general use, usually supplied pre-lubricated
• Nickel plated chain - offers improved corrosion resistance for damp environments
• Stainless steel chain - resists rust and corrosion, ideal for food, marine, and washdown environments

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

Related products:

• Duplex links - connecting links, cranked links, and repair links for duplex chain
• Duplex sprockets - sprockets with two rows of teeth to suit duplex chain
• Chain tools - chain breakers and pullers for cutting and fitting chain
• Chain lubricants - to reduce wear and extend chain life

How to choose the right duplex roller chain?

Choosing the right duplex chain means matching it to the sprockets, the power, and the conditions of the drive. Work through these points in order:

• Chain standard - check whether the drive uses British Standard or ANSI chain and sprockets
• Pitch - match the chain pitch to the sprockets
• Number of strands - make sure the sprockets are duplex, with two rows of teeth
• Power and speed - check the chain can transmit the power at the drive speed, using the manufacturer’s power rating tables
• Shock loads - consider heavy duty or premium chain for drives with shock loads, frequent starts, or reversing
• Length - work out the number of links needed for the sprocket sizes and centre distance, ideally using an even number of links
• Environment - choose nickel plated or stainless steel chain for wet, food, or corrosive environments
• Lubrication - plan how the chain will be lubricated, as this has a major effect on wear life
• Quality and brand - choose chain from reputable manufacturers for accurate dimensions, strength, and long wear life

How to fit duplex roller chain

Fitting duplex chain correctly helps it run smoothly and last longer:

• Isolate the drive - switch off and isolate the machine before starting work
• Check the sprockets - make sure the sprockets are in good condition, aligned, and securely fixed. Replace worn sprockets when fitting new chain
• Cut the chain to length - use a chain breaker to remove pins and shorten the chain to the required number of links
• Join the chain - wrap the chain around the sprockets and join the ends with a duplex connecting link, fitting the spring clip with its closed end facing the direction of travel
• Set the tension - adjust the chain so it has a small amount of slack on the slack side, as recommended by the chain manufacturer
• Check alignment - make sure the sprockets are in line and the shafts are parallel, so the chain runs straight
• Lubricate - apply suitable chain lubricant before running
• Check after running - recheck tension after a short running-in period, as new chains can settle

FAQ - All you need to know about duplex roller chain

What is duplex roller chain?

Duplex roller chain is a power transmission chain with two rows of rollers side by side, giving greater strength and power capacity than simplex chain of the same pitch.

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?

BS chain is made to British and European dimensions, and ANSI chain is made to American dimensions. Even at the same pitch, they have different roller diameters and widths, so they are not interchangeable and need matching sprockets.

How do I measure chain pitch?

Measure the distance between the centres of two adjacent pins. For example, 08B-2 and ANSI 40-2 chains both have a 1/2 inch pitch.

Can I cut duplex chain to length?

Yes. Duplex chain is supplied in standard lengths and can be shortened using a chain breaker to remove pins. Join the ends with a matching duplex connecting link.

Why should a chain have an even number of links?

An even number of links allows the chain to be joined with a standard connecting link. An odd number needs a cranked link, which reduces chain strength.

How tight should duplex chain be?

The chain should have a small amount of slack on the slack side, as recommended by the manufacturer. A chain that is too tight increases wear on the chain, sprockets, and bearings, while a chain that is too loose can whip and jump teeth.

How often should duplex chain be lubricated?

It depends on the speed, load, and environment. Chains in continuous or heavy-duty use need regular lubrication, and some drives use automatic lubrication systems. Follow the chain manufacturer’s guidance.

When should duplex chain be replaced?

Replace the chain when it has stretched beyond the manufacturer’s wear limit, commonly around 2% to 3% elongation, or if links are stiff, cracked, or damaged.

Should I replace the sprockets with the chain?

It is good practice to check the sprockets whenever the chain is replaced. Worn sprockets with hooked or pointed teeth will wear new chain quickly and should be replaced at the same time.

Can I use duplex chain on simplex sprockets?

No. Duplex chain needs duplex sprockets with two rows of teeth. Always match the chain and sprockets for the correct number of strands.