QXG200 Double Guide Roller Overhead Conveyor Chain

Hangzhou Ocean Industry Co., Ltd. is one of the leading manufacturers and suppliers of qxg200 double guide roller overhead conveyor chain in China. Welcome to wholesale bulk durable industrial chains and power transmission parts made in China here from our factory. All customized products are with high quality and competitive price.

 

When mid-span sway starts putting parts in the wrong place at the spray station, the answer is usually not a heavier single-rail chain. It is a second rail. The QXG200 double guide roller chain runs on a twin-I track, carries the load on two flanges instead of one, and is rated to 250 kg per suspension point with a 160 kN breaking force on the heaviest variant.

The three variants share the 200 mm pitch of the single-rail range and the same attachment interface, so a plant can move from single to dual rail without changing the pitch its process was built around. What changes is the track, the wheels and the load the line can carry.

This page sets out where dual rail beats single rail and where it does not, the three variants and their data, the six components each link is built from, how material and surface treatment are chosen for a given duty, how to read the selection guide, what a conversion from single rail involves, and how the order runs from sample to shipment. Design figures are quoted with their conditions attached; where an answer turns on your own line, the page flags it rather than generalising.

The table compares the two track configurations on the numbers a buyer actually sizes a line with. It compares two technical approaches rather than two suppliers, because both configurations are built in the same plant.

Read the load row together with the breaking-force row. Dual rail roughly doubles the load per point, from 120 kg to 250 kg, and raises the breaking force from 95 kN to 160 kN. That is not a marginal gain: it is the difference between a line that needs a second loop or a transfer to carry the same production, and one that does not.

The radius row is the one that surprises people. Dual rail turns tighter, not wider - R500 against R600 on the same pitch - because each rail carries half the load and the wheel geometry is symmetrical. A conversion therefore does not usually force a layout change at the curves, which is often the assumption going in.

The track-cost row is the honest part of the comparison. Dual rail adds roughly 30–40% to the track cost, plus the support steelwork to carry a second rail. The case for it rests on the load row and the stability row, and on what the line loses in unscheduled stops when fixtures move. Where those do not apply, the single-rail chain is the correct purchase.

 

Comparison	QXG200 Single-I	QXG200 Dual-I
Load per Point	Up to 120 kg	Up to 250 kg
Breaking Force	95 kN max	160 kN max
Min. Horizontal Radius	R600	R500
Lateral Stability	Good	Excellent (twin-flange contact)
Track Cost	Lower	+30-40%
Best For	Light-medium load, single loop	Heavy load, long run, high-speed

 

The last row is the summary: single rail for light-to-medium load on a single loop, dual rail for heavy load on a long run at speed. If your duty sits between the two, the selection guide further down the page resolves it.

 

The table carries the reference data for the three variants. The three columns are stages of one design rather than three products: what moves between them is the load class, the wheel and bearing size, the surface treatment and the permitted temperature. Pitch and suspension geometry do not move.

Two rows get confused with each other constantly. Allowable tensile force is the tension the chain may be pulled at in service; breaking tensile force is the point of failure. On this range the second is roughly 1.7 to 1.8 times the first, which means the working margin already sits inside the allowable number. Size the line on that number.

Single lifting weight answers a different question again: how much may hang at one suspension point. It runs 150 kg on DS, 200 kg on DH and 250 kg on DX, and it is normally the row that picks the variant.

Every variant lists suspension spacing as 200+(200×N). Hanger points therefore land on pitch multiples, which means the process pitch your ovens and booths were built around is obtained by picking a value of N - not by moving to another chain. That property is what lets a conversion happen without disturbing the process equipment.

Temperature separates the variants more aggressively than load does: 180 °C on DS, 220 °C on DH, 260 °C on DX. A line with a hot oven section will often need DX on temperature alone, whatever it is carrying. All the figures above were measured at 60% relative humidity and 20 °C, so a plant running outside that band should settle its variant and finish against its own conditions.

 

Project	QXG200-DS (Dual Standard)	QXG200-DH (Dual Heavy)	QXG200-DX (Dual Extra)
Track Configuration	Dual-Rail (Twin-I)	Dual-Rail (Twin-I)	Dual-Rail (Twin-I)
Chain Pitch (mm)	200	200	200
Chain Self-Weight (kg/m)	12.4	13.6	15.2
Allowable Tensile Force (kN)	65	80	95
Breaking Tensile Force (kN)	120	140	160
Single Lifting Weight (kg)	150	200	250
Suspension Spacing (mm)	200+(200*N)	200+(200*N)	200+(200*N)
Horizontal Wheel Diameter (mm)	90	100	110
Vertical Wheel Diameter (mm)	90	100	110
Bearing Type	Sealed Ball 6204	Sealed Ball 6205	Tapered Roller 30206
Min. Horizontal Turning Radius (mm)	R500	R550	R600
Min. Vertical Bending Radius (mm)	R2000	R2400	R2800
Operating Temperature (℃)	≤180	≤220	≤260
Surface Treatment	E-Coating (Black)	E-Coating + Zinc Plate	Hot-Dip Galvanized

Note: the figures above are quoted at 60% relative humidity and 20 °C. Made-to-order variants are quoted on request, and the full technical data sheet is available from the engineering team.

 

 

Five things separate the dual-rail chain from the single-rail chain of the same pitch. Each one can be checked independently against the numbers in the tables above.

Twin-flange load distribution. The suspended weight is carried across two parallel I-beam rails rather than one, which cuts peak stress at each contact point by approximately 45% and is what allows 250 kg per point on the DX variant without increasing pitch or wheel diameter.

Lateral stability. The symmetrical dual-wheel layout removes the pendulum sway of long single-rail runs. On loops beyond about 80 m, lateral drift at mid-span is reduced to less than 5 mm, which is what holds fixture position at spray, inspection and transfer stations.

Higher travel speed. The chain has been run continuously at 18 m/min under a full 200 kg load on the DH variant with no derailment recorded. Single-rail equivalents typically reach about 12 m/min before vibration becomes the limiting factor, and short indexing bursts up to 25 m/min fall inside its rating.

Integrated anti-derailment geometry. Inner and outer horizontal wheels both engage the flange lips, so the chain runs fully trapped. Even during a power loss or an emergency stop it stays in the track, which is the property that matters on a line passing above workstations.

Compatibility with single-rail systems. The pitch, pin diameter and attachment interface are shared with the single-rail range, so a drive, a take-up and most of the accessory list transfer across with bracket adapters.

 

Every QXG200 dual-rail link is assembled from six components, each replaceable on its own. That matters more on a dual-rail line than on a single one, because the track is more expensive and the case for keeping the chain rather than the line is stronger.

 

1. Outer link plate (40Cr). Forged from 40Cr, then quenched and tempered to HRC 38–42. It carries the outer horizontal wheel and forms the main tensile load path, with pin holes machined to a tolerance of ±0.05 mm.

2. Inner link plate (40Cr). The mirror of the outer plate, on the inside of the track. The pair between them forms the pocket that holds the wheels in the rail.

3. Forged pin (20CrMnTi). Case-hardened to HRC 56–60 where it bears, with a lubrication groove down the centre. Retained by a split pin or a self-locking nut.

4. Composite bushing (20Cr, carburized). This is the part designed to wear, so that it is changed before the pin is and the whole link lasts longer. Inner race hardness runs HRC 58–62.

5. Dual horizontal wheel set. Two wheels, each pressed into a forged hub and rated at 125 kg static, running on sealed ball bearings in size 6204 or 6205, or on 30206 tapered rollers.

6. Dual-side vertical guide wheel. Fitted to both plates and setting lateral position against the I-beam web, adjustable independently with a shim stack.

The replacement order is worth noting: bushing first, then pin, then wheel. A maintenance schedule that replaces the whole link when the bushing is worn is paying for the other five components unnecessarily.

 

Grade and surface treatment are chosen from the environment rather than from the load, and the two decisions are separate.

A dry finishing line: primer, base coat, clear coat. E-coating covers it. What the chain meets here is heat and paint mist, with no liquid attack, so DS with E-coat is the usual specification.

A line with rinse zones or an unheated building in a wet climate. E-coating over zinc plating. The zinc is sacrificial: where the coating is damaged, the plating corrodes instead of the steel. This is the DH specification and the one most conversions land on.

A plating shop, an outdoor run, or a line with process mist. Hot-dip galvanizing, with the DX variant. The coating is thicker and metallurgically bonded, so it also survives the mechanical handling that strips thinner finishes.

A hot section above 220 °C. The DX variant on temperature, with the high-temperature bearing option. The bearing is the part that limits the assembly in a hot zone, not the plate or the pin.

Two things are easy to get wrong here. First, choose for the worst station rather than for the loop as a whole: a line that runs dry for twenty metres and wet for one corrodes at the wet section, and gets replaced for a reason that touches a fraction of its length. Second, plate and pin materials already follow the load class, so going to a heavier finish buys durability rather than strength.

 

The mechanical case for a second rail is about where the load goes when it reaches the track, and it is worth understanding because it explains why the gain is larger than the extra rail alone suggests.

A single-rail chain loads one flange. The flange is a cantilevered edge on the lower face of the I-beam, so the load produces a bending moment in the web and a contact stress in the wheel tread, and both of those concentrate at the point where the wheel touches.

A dual-rail chain divides the same suspended weight between two rails and two sets of wheels. The load each contact carries is halved, which is why peak stress at each contact point comes down by approximately 45% rather than by 50%: the remaining difference is the chain's own weight and the geometry of the moment arm, which do not divide as neatly as the payload does.

The practical consequence is the load rating. Because peak stress at the contact is the limiting quantity, halving it allows a much heavier part to be carried on the same pitch and the same wheel diameter. That is where the 250 kg per point on the DX variant comes from, and it is why a conversion to dual rail does not require the process to be rebuilt around a longer pitch.

One qualification. The 45% figure is a design-analysis result for the standard geometry, not a measurement taken on every line. It describes the change in stress distribution between the two configurations; a plant with an unusual fixture that imposes a torque rather than a vertical load should have the layout reviewed rather than reading the figure as a guarantee.

 

Load capacity is the headline reason to specify dual rail. Stability at speed is the reason many lines end up there anyway, because the two problems arrive together as a loop gets longer.

On a long single-rail run the suspended part behaves as a pendulum. The swing is small at any one station, but a loop of eighty metres gives it time to build, and by mid-span the fixture can be moving when the layout assumed it would be still. That shows up at the spray station as inconsistent coverage, and at a transfer station as a part that arrives slightly off position.

Dual rail removes the pendulum by supporting the assembly at two points instead of one. On loops beyond about 80 m, lateral drift at mid-span is held to less than 5 mm, and fixture position across the whole loop is held within about ±3 mm. On a coating line those two figures are the difference between consistent film thickness and a station that has to be re-run.

Speed follows from stability. The chain has run continuously at 18 m/min under a full 200 kg load on the DH variant without a derailment, where an equivalent single-rail line typically becomes vibration-limited at around 12 m/min. Indexing operations can take short bursts up to 25 m/min, which is what allows a line to move between stations quickly and then dwell.

Anti-derailment is the safety half of the same geometry. Both the inner and outer horizontal wheels engage the flange lips, so the chain is trapped rather than merely seated. During a power loss or an emergency stop, when a single-rail chain can be thrown by the deceleration of the load it is carrying, the dual-rail chain stays in the track. On a line passing above workstations that property is a requirement rather than an advantage.

 

The dual-rail chain was designed to sit inside an existing QXG200 installation rather than beside it, because the alternative - a plant with two incompatible chain ranges - costs more in spares and training than the rail costs to install.

What is shared. Pitch, pin diameter and the attachment interface are common to both ranges. The drive, the take-up and most of the accessory list transfer across with bracket adapters, and the maintenance procedure is unchanged, bushing-first replacement included.

What is not shared. The track. A dual-rail line needs a twin-I configuration and the support steelwork to carry a second rail. The chain itself cannot be run on a single-rail track, and a single-rail chain cannot be run on a twin-I track.

What this means for a conversion. The chain, the drive and the accessories are a chain purchase; the track and its steelwork are a separate scope, and on most conversions the track is the larger item. Work out which of the two is the constraint before ordering: if the existing track is sound and the load is inside its rating, no conversion is needed at all.

What carries over for the operator. A maintenance team already familiar with the single-rail range needs one additional procedure, which is the shim adjustment on the dual-side vertical guide wheel. Everything else is the same part in a different arrangement.

 

Choosing between the three variants is normally decided by one of three rows: load per point, loop length, or temperature. The matrix below resolves the common combinations; where your duty sits between two rows, step up rather than down, because the cost difference between variants is small compared with the cost of a line that has to be upgraded later.

Use the matrix as a starting point rather than a substitute for the layout. It uses the figures in the specification table and the conditions each variant is rated for, but it cannot see your fixture, your speed profile or your building steelwork. Send us the loop drawing and the load and we will confirm the variant against them.

 

Your Condition	Variant	Why
Load per point up to 120 kg, loop under 40 m, dry finishing	Single-rail QXG200	Inside the single-rail rating; dual rail adds track cost for no gain
Load per point 120–150 kg, or loop over 80 m at moderate speed	QXG200-DS	250 kg class track; mid-span drift held below 5 mm
Load per point 150–200 kg, top speed around 18 m/min, or a rinse zone	QXG200-DH	200 kg class with E-coat over zinc for humid stations
Load per point 200–250 kg, or an oven section above 220 °C	QXG200-DX	250 kg class, 260 °C rating, hot-dip galvanized
Indexing line needing bursts above 18 m/min	QXG200-DH or DX	Rated for intermittent bursts up to 25 m/min
Curve radius tighter than R600 on a 200 mm pitch	Any dual variant	Dual rail turns R500–R600, tighter than single rail at the same pitch

 

 

Converting a line from single rail to dual rail is a track project with a chain purchase attached, not the other way round, and planning it in that order is what keeps the conversion inside a shutdown.

Confirm the case first. Measure the load per point and compare it against the single-rail rating. If the existing chain is within rating and the problem is stability rather than capacity, the answer may be a change of speed or of fixture rather than of track.

Survey the steelwork. A twin-I track needs support points that can carry a second rail and hold the two rails parallel within tolerance. On an existing line this is usually the longest lead item, so it is the first thing to price.

Set the rails in relation to each other. The two rails must be parallel and level relative to one another, not merely each level on its own. A pair that is individually true but twisted relative to each other will wear the inner and outer wheels unevenly from the first week.

Reuse what can be reused. Drive units, take-up assemblies and most accessories carry over with bracket adapters, and the pitch does not change, so the ovens, booths and process equipment stay where they are. That is the part of the conversion that keeps the project small.

Expect the curves to be easier, not harder. Dual rail turns tighter than single rail at the same pitch, so a conversion rarely forces a layout change at the bends. The place to check is where vertical bends meet horizontal curves, because that is where the two rails interact most.

 

Automotive body-in-white lines. Doors, hoods and side panels move through pre-treatment and electrophoretic coating on this chain. The 200–250 kg per-point capacity matches typical BIW fixture weights, and the lateral stability is what stops a door panel swinging into the adjacent station during the dip-and-rotate sequence.

Heavy appliance production. Cabinet lines, tub painting and oven assembly conveyors are the DH application, chosen for the 200 kg rating. A pre-heat zone at 220 °C sits inside that rating, with the high-temperature bearing specified for that section.

Long-run powder coating. Past roughly 80 m a single-rail line starts to sway at mid-span. Twin-flange support keeps the fixture within about ±3 mm anywhere on the loop, which is the mechanical half of an even film.

Warehouse and logistics. Storage-and-retrieval loops overhead, garment conveyors in distribution centres, parcel handling. Here it is the ambient range rather than the weight that decides: one specification covers a cold store near −10 °C and a loading dock at 35 °C.

One comment on the list. The first three applications are where the dual-rail case is strongest, because each combines a heavy or large part with a long line and a process that cares about position. The fourth is where a single-rail chain is often the better purchase, and it is worth saying so rather than quoting dual rail by default.

 

These are the numbers worth putting side by side when quotations are compared. They come from the original specification, with the conditions attached wherever the source states them.

Load. Up to 250 kg per suspension point on the DX variant, with a 160 kN breaking force.

Vibration. Dual-rail geometry is quoted as cutting mid-span vertical oscillation by 60% against an equivalent single-rail installation.

Maintenance interval. Quoted as 18–24 months under standard conditions, with sealed bearings removing routine greasing. Treat the interval as the outside figure on a line running abrasive dust or a wet process.

Service life. Quoted at 10 to 15 years for a typical automotive paint shop. The qualifier matters: that is a clean, temperature-controlled finishing line on three shifts, which is the friendliest environment this chain sees.

Noise. Below 60 dB(A) at 12 m/min with the precision-ground wheel treads.

Energy. An 8–12% reduction in drive motor power against a single-rail system carrying the same payload, from lower rolling resistance. The comparison baseline is the manufacturer's own single-rail range rather than an arbitrary third-party chain.

Two of these are design or test figures rather than field averages: the 60% oscillation reduction and the 8–12% energy figure. Both describe the difference between the two track configurations on comparable duty, which is the useful form of the comparison; neither should be read as a guaranteed saving on a specific line.

 

A dual-rail line is less forgiving of alignment than a single-rail one, because there are now two running surfaces that have to agree with each other. The commissioning checks below are the ones that catch a misalignment while it is still cheap to correct.

Set the rails as a pair. Check parallelism and relative level, not just the level of each rail. A pair that is individually true but twisted relative to each other will load the inner and outer wheels unequally from the first day.

Check wheel engagement at every curve. Walk a loaded carriage round each horizontal curve by hand and confirm that both inner and outer wheels keep contact with the flange lips. A gap at one wheel anywhere on the curve means the rails are not parallel at that point.

Confirm the trapped running condition. With the chain threaded, verify that the wheels cannot be lifted clear of the flange by hand at the tightest curve. This is the anti-derailment property, and it is a physical check rather than a measurement.

Adjust the vertical guide wheels. The shim stacks on the dual-side guide wheels set lateral position. Set them with the chain tensioned, and record the shim count at each station so a later adjustment is made against a known starting point.

Set the take-up and run in. Tension to the middle of the available stroke, run the loop empty for several passes, then loaded. Re-check the tension after the first thermal cycle and again after the first month, because a new chain settles and the loop length changes with temperature.

Handover record. Record the drive current under normal load, the tension position and the shim counts. These three figures are what let a later change be told apart from a fault.

 

The order path is short, and the part of it worth planning is the trial rather than the paperwork. A dual-rail line is an expensive thing to get wrong, and a sample length on the actual track is the cheapest way to avoid it.

1. Assessment. Send the loop drawing, the load per suspension point, the maximum temperature and a photograph of the existing track if there is one. Engineering will confirm whether dual rail is warranted at all, and if the duty is inside the single-rail rating we will say so.

2. Sample. A trial length or a set of links is produced for evaluation on your line. This is the step that confirms the wheel engagement, the guide-wheel shim setting and the take-up behaviour under your own conditions rather than on a test rig.

3. Production. Once the sample is approved, the full quantity is manufactured and the chain is built into the lengths the installation sequence calls for, labelled by position in the loop.

4. Delivery and support. Chain, drive and accessories ship together, with inspection documentation and the finished-goods photographs sent before the balance falls due.

Lead time: 30 working days for a trial length or set of links, 60 for a full production order, both from the deposit. The figure we quote is the one the shop can hold; where stock exists we will say so rather than promising a date that slips.

 

A dual-rail chain is a dense, high-value load, and how it is packed decides both what arrives undamaged and how much of it fits in a container.

Chain. Cut to the lengths the installation sequence needs, then coiled or run straight according to length and tied so it cannot move or rub against itself on the way. Every bundle carries its position in the loop as well as the order number, which lets the installation be staged without unpacking the whole consignment.

Wheels, pins and bushings. Boxed apart from the chain, so the chain's weight cannot mark a running surface and so a single item can go straight to where it is needed. Bushings wear first and are the parts most often wanted on their own later, so they travel as labelled sets.

Surface protection. Galvanized items take transit damage most easily, so they are bundled apart from the rest with protected edges. If a coating does get marked, it is marked where someone will see it on arrival rather than half a loop away.

Loading. On a conversion the track outweighs the chain, so the container is planned around the track sections and the chain fills what is left. When both travel together, the loading plan comes from us rather than from the forwarder.

Documentation. A packing list goes out with photographs of the goods as packed, before dispatch, so anything missing is found while the container is still open.

 

A dual-rail line is normally the bottleneck of the plant it runs in, so the service question is not whether spares exist but how quickly a stopped line is running again.

Spares held. Complete spares are maintained for all three variants: link plates, forged pins, composite bushings, wheel sets and vertical guide wheels. Because the bushing is the designed wear item, a bushing change restores a link without replacing the other five components, which is what keeps the spares cost per year low.

What to hold on site. For a line running three shifts, one or two complete link assemblies plus a set of bushings and a spare wheel set cover the failures that stop a line. Everything beyond that is a planned replacement rather than an emergency.

Technical support. Remote diagnosis is available for alignment, tracking and wear questions, and on-site commissioning support can be arranged for a conversion or a first installation. Where a line has a problem after a conversion, the handover record from commissioning is the useful starting point: drive current, tension position and shim counts tell you what has changed.

Repeat orders. The specification for your chain stays on file, so a repeat order does not start from scratch. That matters most on a mixed fleet, where two QXG200 lines of different variants can otherwise end up with parts ordered against the wrong one.

Response to a stoppage. Send the measured pitch, the variant and a photograph of the failed item. For a standard variant the answer is usually a stock item; for a custom attachment it is a manufacturing date, and we will give the real one rather than the optimistic one.

 

Q1: Is the chain made in your own plant?

A: Chain manufacture is on our own site, and the group's chain plant dates from 2003. Questions about a specific line go to the engineers who build the product rather than to a separate office.

Q2: What is the difference between DS, DH and DX?

A: Load class, wheel and bearing size, permitted temperature and surface treatment. Load per point is 150, 200 and 250 kg; temperature ratings are 180, 220 and 260 °C. Pitch and suspension geometry are the same on all three.

Q3: When should I choose dual rail instead of single rail?

A: When the load per point exceeds the single-rail rating, when the loop is long enough for mid-span sway to matter, or when speed is limited by vibration. If none of those apply, single rail is the cheaper and correct purchase.

Q4: Can a dual-rail chain be fitted to an existing single-rail line?

A: The chain, drive and accessories carry over with bracket adapters, but the track must be reconfigured to twin-I and the support steelwork must carry a second rail. The track is normally the larger part of the conversion.

Q5: Why does dual rail turn tighter than single rail?

A: R500 to R600 against R600 on the same 200 mm pitch. Each rail carries half the load and the wheel geometry is symmetrical, so the chain does not need the extra radius the single-rail version does.

Q6: How tight can the curves be?

A: R500 horizontal and R2000 vertical on DS, R550 and R2400 on DH, R600 and R2800 on DX. Where a curve and a vertical bend fall on the same point, send the layout: the two together are tighter than either radius suggests on its own.

Q7: Is lubrication required in service?

A: The wheel bearings are sealed when the wheels are built, so standard conditions call for no routine greasing. The items on the inspection schedule are the bushings and pins, and the bushing is engineered to be changed first.

Q8: What is the anti-derailment arrangement?

A: Both the inner and outer horizontal wheels engage the I-beam flange lips, so the chain runs trapped rather than seated. That is what keeps it in the track during a power loss or an emergency stop.

Q9: What lead time should I plan for?

A: 30 working days for a trial length, 60 for a full production order, both running from the deposit.

Q10: How often should the chain be inspected?

A: The maintenance interval is quoted at 18 to 24 months under standard conditions. On a line with abrasive dust or a wet process, treat that as the outside figure and inspect earlier, checking bushings first and then pins.

Q11: How much of the chain can be made to order?

A: Made-to-order work covers pitch, attachment and hanger interfaces, bearing type, 304 or 316 stainless construction, and finishes outside the three standard grades. A drawing or a sample link is enough for the drawing office to reply within about two working days.

Q12: What temperature can the chain run at?

A: Up to 180 °C on DS, 220 °C on DH and 260 °C on DX, with a high-temperature bearing option for the hot section. A plant with an oven above 220 °C will normally need DX on temperature alone.

Q13: What should I send with an enquiry?

A: Send the loop drawing, the weight carried at a single suspension point, the highest temperature on the line, the running speed, and a photograph of the track if one already exists. Those five answers settle the variant and whether a conversion is worth doing.

Q14: Do you supply the track and support steelwork?

A: Track sections, curves, vertical bends and hanger clamps are supplied with the chain. Support steelwork is normally site-specific, but we will review your steelwork drawing against the twin-rail loading.

Send us the loop drawing, the load and the track you have.
The loop length, the weight hanging at one suspension point, the highest temperature and the running speed are enough for our engineers to say whether dual rail is warranted, and if it is, which of the three variants the line needs.

 

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