The CLZ Type Gear Coupling is the extended sleeve variant of the CL crowned tooth gear coupling per GB/T5843, covering 16 sizes (CLZ1–CLZ16) from 40 N·m to 40,000 N·m at up to 4750 RPM. Inner hubs are identical and interchangeable with the CL type. Custom sleeve lengths are available, and no shaft modification is required. With Y, J1, and Z bore options, it is the solution for drives where shaft gaps exceed the standard CL sleeve length.
The extended sleeve variant of the CL crowned tooth gear coupling per GB/T5843. When your motor-to-machine shaft gap is too wide for a standard CL, the CLZ bridges it without modifying either shaft. Same inner hubs as CL — only the sleeve is longer.
The CLZ type gear coupling is the extended sleeve variant of the standard CL crowned tooth gear coupling family per GB/T5843. It is selected whenever the gap between a motor shaft end and a driven machine shaft end is larger than the standard CL sleeve can bridge — without requiring any modification to either shaft, any change to the shaft-mounted hubs, or any repositioning of the motor or driven machine.
The CLZ achieves this through a single structural change from the CL: the outer sleeve is manufactured longer. Both inner hubs are dimensionally identical to the CL inner hubs for the same size number — the same external crowned gear teeth, the same bore range, the same keyway specification. Only the outer sleeve length changes. The CLZ therefore delivers the full crowned tooth misalignment tolerance, shock load resistance, and axial displacement capability of the CL, at the same torque rating and bore range, across a wider shaft gap.
RP manufactures CLZ couplings factory-direct with full material traceability and supplies to global maintenance engineers, plant designers, and OEM machine builders.
The CLZ coupling shares the same torque transmission mechanism as the CL: two inner hubs, each with external crowned (barrel-shaped) gear teeth, engaging an outer sleeve with internal straight teeth at each end. The crowned tooth geometry — where each tooth is thickest at its midpoint and tapers toward both ends — produces a self-centring Hertzian contact ellipse near the tooth centre that remains centred regardless of angular or radial misalignment. This eliminates the edge loading that destroys straight-tooth gear couplings under misalignment conditions.
The critical engineering insight of the CLZ is that torque transmission occurs entirely at the two tooth mesh interfaces — one at each end of the outer sleeve. The sleeve itself is a structural tube that carries torque in torsion between the two meshes; its length does not change the torque capacity of either mesh. A longer CLZ sleeve transmits exactly the same rated torque as the shorter CL sleeve of the same size number.
What the longer sleeve does change is the torsional stiffness of the coupling assembly and — at high speeds — the critical rotational speed of the sleeve acting as a rotating beam. For standard CLZ catalogue dimensions and standard operating speeds, neither effect is significant. For non-standard very long sleeves at high operating speeds, our engineering team verifies both torsional compliance and critical speed as part of the order process.
The CLZ accommodates the same three misalignment modes as the CL, through the same mechanisms at each tooth mesh interface.
The shaft gap in a coupled drive is defined as the distance from the end face of one shaft to the end face of the other shaft. For a CL coupling, the sleeve must be long enough to engage both inner hubs simultaneously — if the shaft gap exceeds the CL sleeve's B dimension, the coupling cannot be assembled. The CLZ's extended B1 dimension solves this directly without any other design change.
A motor frame change (for example, from IE2 to IE3 for energy efficiency compliance) may produce a different shaft extension length, changing the effective shaft gap for the same coupling size. A VFD enclosure added between a motor and gearbox may introduce a structural standoff that increases shaft gap. In all these cases, the CLZ provides the solution without requiring shaft machining, shaft extension pieces, or motor repositioning.
| Feature | CLZ (this product) | CL + Shaft Extension | Flexible Disc Spacer | Jaw Coupling (max size) |
|---|---|---|---|---|
| Shaft modification required | None — sleeve only change | Yes — shaft extension machining | None — spacer adapts gap | Limited gap adaptation |
| Shock load tolerance | Excellent — crowned gear mesh | Excellent — CL mesh | Poor — disc pack fatigues | Good (elastomer absorbs) |
| Misalignment tolerance | High — crowned tooth both ends | High — CL mesh both ends | Moderate (disc pack limits) | Moderate (elastomer) |
| Hub interchangeability | Identical to CL hubs — interchangeable | CL hubs plus new shaft | Specific to spacer design | No interchangeability with gear type |
| Maintenance access | Sleeve removal gives shaft-end clearance | Same as CL — requires shaft movement | Spacer drops out for access | Requires full disassembly |
CL and CLZ are variants of the same coupling family. The decision between them is purely a shaft gap question.
| Factor | CLZ — Extended Sleeve | CL — Standard Compact |
|---|---|---|
| Outer Sleeve Length | B1 — extended; wider shaft gap | B — standard; close-coupled drives |
| Typical Shaft Gap Covered | Larger gap — see B1 in spec table | Standard gap — see B in spec table |
| Torque Rating | Same as CL (same size number) | Same as CLZ (same size number) |
| Speed Rating | Same as CL for standard B1 length | Same as CLZ |
| Bore Range | Same as CL | Same as CLZ |
| Inner Hub | Identical to CL — fully interchangeable | Identical to CLZ — fully interchangeable |
| Weight | Slightly heavier — longer sleeve | Lighter — shorter sleeve |
| Price | Slightly higher — more sleeve material | Lower — less sleeve material |
| Shaft-End Access on Sleeve Removal | Better — longer sleeve removal clears more shaft-end space | Standard access after sleeve removal |
| Choose When... | Shaft gap exceeds CL B dimension; structural clearance zone required; upgrading from wider-gap coupling | Standard close-coupled drive; minimum weight; most economical option |
All CLZ specifications per GB/T5843. B1 is the extended sleeve overall length. Bore, torque, and speed ratings are identical to the corresponding CL size. For shaft gap determination, measure the distance between the two shaft end faces — this dimension must be less than B1 minus the sum of the two hub engagement lengths at the specified bores.
| Size | Nominal Torque Tn (N·m) |
Max Speed (rpm) |
Bore Range d (mm) |
Y bore length L range (mm) |
Outer Dia D (mm) |
CL Length B (mm) |
CLZ Length B1 (mm) |
Angular Tolerance |
CLZ Weight (kg approx) |
|---|---|---|---|---|---|---|---|---|---|
| CLZ1 | 40 | 4750 | 10–16 | 25–32 | 80 | 60 | 90 | 1.5 deg | ~1.5 |
| CLZ2 | 63 | 4750 | 10–22 | 25–52 | 100 | 72 | 110 | 1.5 deg | ~2.3 |
| CLZ3 | 100 | 4000 | 12–28 | 25–60 | 120 | 84 | 125 | 1.5 deg | ~4.2 |
| CLZ4 | 160 | 3150 | 16–35 | 32–82 | 145 | 100 | 148 | 1.5 deg | ~6.5 |
| CLZ5 | 250 | 2800 | 20–45 | 42–112 | 175 | 120 | 175 | 1.5 deg | ~10.5 |
| CLZ6 | 400 | 2500 | 25–55 | 52–142 | 210 | 140 | 205 | 1.5 deg | ~19 |
| CLZ7 | 630 | 2240 | 32–65 | 60–172 | 250 | 165 | 240 | 1.5 deg | ~30 |
| CLZ8 | 1000 | 2000 | 40–80 | 84–212 | 295 | 190 | 280 | 1.5 deg | ~48 |
| CLZ9 | 1600 | 1800 | 50–95 | 107–252 | 350 | 225 | 330 | 1.5 deg | ~74 |
| CLZ10 | 2500 | 1600 | 60–110 | 107–302 | 415 | 265 | 390 | 1.5 deg | ~118 |
| CLZ11 | 4000 | 1400 | 75–130 | 132–352 | 485 | 310 | 455 | 1.5 deg | ~185 |
| CLZ12 | 6300 | 1250 | 90–160 | 172–410 | 570 | 365 | 535 | 1.5 deg | ~290 |
| CLZ13 | 10000 | 1120 | 110–200 | 212–470 | 670 | 430 | 630 | 1.5 deg | ~460 |
| CLZ14 | 16000 | 1000 | 130–240 | 252–550 | 790 | 500 | 735 | 1.5 deg | ~720 |
| CLZ15 | 25000 | 900 | 160–280 | 302–650 | 930 | 585 | 860 | 1.5 deg | ~1140 |
| CLZ16 | 40000 | 800 | 190–320 | 352–750 | 1090 | 680 | 1000 | 1.5 deg | ~1760 |
Note: B1 is the CLZ extended sleeve total assembly length. B is the equivalent CL assembly length shown for direct comparison. Weight values are approximate at maximum Y type bore. Torque and speed ratings are identical to the corresponding CL size number.
Custom Sleeve Length, Non-Standard Bore, and Shaft Gap Verification Available
Need a non-standard CLZ sleeve length for a specific shaft gap that the catalogue B1 doesn't match? RP can manufacture CLZ sleeves to any length above the minimum engagement requirement, with critical speed verification for the specified length and operating speed. Send us your measured shaft gap, motor shaft diameter, and driven machine shaft diameter for a same-day CLZ specification.
The CLZ has two independent crowned tooth meshes — one at each end of the extended sleeve. Each mesh independently accommodates up to 1.5 degrees of angular misalignment. This is particularly important on the longer drives that need CLZ — longer shaft spans are more susceptible to differential foundation settling between the two shaft ends.
The CLZ's crowned tooth mesh geometry is identical to the CL — the longer sleeve does not affect the shock load performance of either mesh interface. Every torque peak from conveyor belt starts, compressor starts, or extruder material impacts is distributed as a Hertzian contact ellipse at the tooth centre, eliminating the edge stress concentration that fatigues straight-tooth couplings under the same shock events.
Like the CL, the CLZ has no elastomers to degrade, no disc packs to fatigue, and no wear consumables other than the tooth mesh lubricant. Re-lubrication through the fill port every 6–12 months is the only routine maintenance requirement. The CLZ sleeve can also be replaced from outside without hub removal in most installations, reducing the scope of any replacement maintenance event.
CLZ1 through CLZ3 are rated to 4750 and 4000 RPM respectively — compatible with standard 2-pole IEC motors. For custom non-standard sleeve lengths above catalogue B1, our team performs critical speed verification before confirming the specification.
CLZ inner hubs are manufactured from the same forged steel blanks as CL hubs — 45# carbon steel for CLZ1–CLZ8 and 42CrMo4 alloy steel for CLZ9–CLZ16. The outer sleeves are machined from seamless alloy steel tube, with the extended B1 length requiring larger tube diameter material. The internal gear teeth at each end of the CLZ sleeve are hobbed to GB/T10095 Class 8 accuracy on CNC hobbing centres.
The increased sleeve length of the CLZ requires closer attention to sleeve straightness and concentricity than the shorter CL sleeve. RP's CLZ sleeves are checked for straightness (maximum bow 0.05 mm per 100 mm of sleeve length) and bore concentricity at both tooth mesh zones before dispatch.
ISO 9001:2015 quality management certification covers the full CLZ manufacturing and inspection process. CE marking applies to relevant export sizes. Products manufactured per GB/T5843. Every CLZ shipment includes material mill certificates, heat treatment records, hardness test certificates for tooth flanks, bore tolerance inspection records, and sleeve straightness measurement records.
Tell us your measured shaft gap, the bore diameters on each side, and the approximate torque requirement. Our engineering team calculates the required CLZ size and confirms whether the standard B1 sleeve length accommodates your gap, or whether a custom sleeve length is needed. This service is included with every CLZ inquiry.
Our engineers discuss CLZ applications in clear technical English — confirmed bore specifications for your motor and gearbox shaft diameters, sleeve length verification against your measured shaft gap, and GB/T5843 standard interpretation for GB-specified machine documentation. Response within one business day for standard specifications; same-day for urgent maintenance replacement enquiries.
If your CLZ inner hubs are still serviceable but the outer sleeve is worn or your shaft gap has changed, RP supplies CLZ sleeves as standalone components. Order the CLZ sleeve alone — same size number, standard or custom B1 length — without replacing the shaft-mounted hubs. Request sleeve-only pricing here.
For shaft gaps outside the catalogue B1 range, RP manufactures CLZ sleeves to custom lengths with critical speed verification included. Minimum order is one sleeve. Custom sleeve lead time adds 5–10 working days to standard sleeve production. All custom sleeves are individually inspected and include a measurement record with the dispatch documentation.
RP manufactures and supplies both CL and CLZ from the same production facility, allowing projects requiring a mix of CL and CLZ on different drives to be served by one engineering team, one order, and one shipment.
Challenge: During motor specification for 68 drives, the plant's electrical engineer identified that 22 drives required a different motor frame size in IE3 compared to the original IE2 specification — the IE3 motors had longer shaft extensions, increasing shaft gap by 15–35 mm per drive. The original CL couplings on these 22 drives could not accommodate the increased shaft gap.
Solution: We supplied 22 CLZ sleeves across sizes CLZ4 to CLZ8 to replace the existing CL sleeves on the affected drives. All 22 CLZ sleeves matched the catalogue B1 length for the increased shaft gap — no custom lengths required. Inner hubs were reused from the existing CL assemblies.
Result: All 22 drives were converted from CL to CLZ configuration using only sleeve replacement — no shaft modification, no mounting plate rework, and no realignment required. Average conversion time per drive was 35 minutes including grease fill and torque check. Total cost of CLZ sleeve conversions was approximately 8% of the estimated cost of the mounting plate modification alternative.
Customer Profile: A mineral processing plant retrofitting variable frequency drives to 12 process pump drives rated 22–90 kW, with VFD control panels mounted adjacent to each motor requiring conduit runs through the coupling zone.
Challenge: The VFD installation required a 120 mm conduit run between the VFD panel and the motor terminal box on each drive, passing through the coupling zone and increasing the effective motor-to-pump shaft gap by 110–130 mm on each of the 12 drives. The existing CL couplings could not bridge the new shaft gap.
Solution: We supplied 12× CLZ couplings in sizes CLZ7 to CLZ9 (630–1600 N·m) with custom sleeve lengths of 280–350 mm to match each drive's specific shaft gap. Critical speed was verified for each custom sleeve length at the VFD operating speed range of 0–1800 RPM. Each CLZ assembly used the existing CL inner hubs, replacing only the outer sleeve.
Result: All 12 VFD retrofits were completed without conduit rerouting or motor repositioning. CLZ sleeve replacement took 45 minutes per drive including hub condition check and grease fill. In 20 months since installation, no coupling issues have been reported across the 12 drives.
Customer Profile: A food packaging operation with 6 flow-wrap packaging machines from a Chinese OEM, each with 2 CLZ7 couplings per machine (per GB/T5843, bore 50 mm and 55 mm) requiring replacement after 5 years of continuous operation in a wash-down environment.
Challenge: The maintenance engineer had the original machine documentation showing "CLZ7, bore 50/55, per GB/T5843" but three local coupling suppliers had quoted CL7 instead of CLZ7, which would not fit due to the machine's 165 mm shaft gap requiring the CLZ7's extended B1 sleeve.
Solution: We supplied 12× CLZ7 assemblies (6 machines × 2 couplings) with bore 50 mm Y type on one hub and 55 mm Y type on the other hub per machine, matching the original machine shaft specifications exactly. The CLZ7 B1 sleeve length of 240 mm accommodated the machine's 165 mm shaft gap with correct engagement at both bore ends.
Result: All 12 CLZ7 assemblies installed on first attempt — confirmed fit on all 6 machines without any rework. This was the fourth time RP had supplied CLZ replacement couplings for this facility's Chinese-sourced machines, with our ability to interpret GB/T5843 directly saving the facility from three previous coupling specification errors.
CLZ has an extended outer sleeve (length B1) that bridges a wider shaft gap than the standard CL sleeve (length B) for the same size number. Both CLZ and CL use identical inner hubs, have the same torque rating, bore range, speed rating, and misalignment tolerance. The only structural difference is the outer sleeve length. Hub interchangeability means you can switch between CL and CLZ sleeves on the same installed inner hubs.
The shaft gap is the distance between the end face of the motor shaft and the end face of the driven machine shaft when both shafts are at their nominal operating positions. For the CLZ to fit: the shaft gap must be less than B1 minus (motor hub engagement length L1 at your bore) minus (machine hub engagement length L2 at your bore). Provide your measured shaft gap and bore diameters and we will verify the correct CLZ size and whether the standard B1 length fits, or whether a custom sleeve is needed.
Yes. CLZ sleeves are available as standalone components. If your existing CLZ or CL inner hubs are still serviceable, only the sleeve needs replacement. When ordering a sleeve only, specify the CLZ size number, the required B1 sleeve length (catalogue or custom), and whether both inner mesh zones should use the same tooth specification.
No. The torque rating of the CLZ is set by the inner hub tooth geometry. The sleeve length does not affect any of these parameters. A CLZ7 (630 N·m rated) carries the same rated torque whether its sleeve is the standard B1 = 240 mm or a custom extended length. What the sleeve length does affect at very long values is the critical rotational speed of the sleeve.
Re-lubricate through the fill port at mid-span of the CLZ outer sleeve at 6–12 month intervals using NLGI Grade 2 lithium complex grease. Inject grease at one end of the sleeve fill system until grease emerges from the vent port or purge hole at the opposite end, confirming both tooth mesh zones have been lubricated.
CLZ per GB/T5843 and GICLZ per JB/T8854 are both extended sleeve crowned tooth gear couplings, but with different dimensional geometry — they are not directly interchangeable without a dimensional compatibility check. If you are replacing a GICLZ or WGT with a CLZ, provide both coupling's size number and bore data to our team for a dimensional compatibility assessment before ordering.
Send us your measured shaft gap distance, motor shaft bore, driven machine shaft bore, and approximate drive torque or motor power and speed. Our engineering team confirms the CLZ size and sleeve length — standard or custom — and provides a factory-direct quotation within 24 hours including a shaft gap verification calculation.
RP
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