DJM Type Single Flexible Diaphragm Coupling
The DJM Type Single Flexible Diaphragm Coupling connects two shafts through a single stainless steel diaphragm pack bolted alternately to each hub flange. Covering 41 sizes from 9.8 N·m to 8,100,000 N·m at speeds up to 20,000 rpm, it is lubrication-free, torsionally rigid, and suited to high-speed pumps, compressors, turbines, and precision drives demanding zero backlash and minimal maintenance.
What Is a DJM Single Flexible Diaphragm Coupling?
The DJM type single flexible diaphragm coupling is a high-performance metal elastic coupling that connects two rotating shafts via a single stainless steel diaphragm pack. Unlike elastomeric jaw couplings or grid couplings that depend on a polymer or lubricated metal element, the DJM transmits torque entirely through the elastic bending of a thin stainless steel diaphragm assembly. Each diaphragm is alternately bolted to the drive flange and the driven flange so that torque flows through the pack in pure tension and compression — producing a torsionally stiff, backlash-free connection that tolerates angular and axial shaft misalignment without any sliding motion.
How Torque Is Transmitted
Each diaphragm is bolted alternately to the two hub flanges in a pattern of evenly spaced bolts. When the drive hub rotates, tension and compression develop in alternating segments of the diaphragm. This elastic loading transmits the driving torque to the driven hub while the diaphragm simultaneously flexes to absorb axial displacement and angular misalignment between shaft centrelines. Because all motion is accommodated by metal elastic deformation rather than sliding or rolling contact, there is zero wear at the connection point and zero need for lubrication throughout the coupling's service life.
DJM vs Other Flexible Coupling Types
| Feature | DJM Diaphragm | Gear Coupling | Jaw / Spider | Grid Coupling |
|---|---|---|---|---|
| Lubrication | None ever | Grease essential | None | Grease required |
| Backlash | Zero | Low–medium | Low | Medium |
| Torsional stiffness | Very high | High | Low–medium | Medium |
| Max speed (standard) | 20,000 rpm | High | 15,300 rpm | Medium |
| Temperature range | -40°C to +280°C | -20°C to +120°C | -35°C to +80°C | -20°C to +100°C |
| Vibration damping | Low (stiff) | Low | High | Medium |
DJM Coupling Specifications and Dimensions
Materials
Diaphragm pack: stainless steel sheet. Hub flanges: carbon steel or alloy steel (imperial bore available on request). Bolts: high-tensile alloy steel. All parts can be supplied with corrosion-resistant coatings on request.
Ordering Mark Example
→ Type DJM, size 05 | Drive: Y-bore, A-keyway, d=28 mm, L=62 mm | Driven: same with d=25 mm
Complete Parameter Table — DJM00 to DJM40
Diaphragm: stainless steel sheet · Hub: carbon/alloy steel · Angular compensation: 1° (sizes 00–04), 45' (05–11), 30' (12–14), tapering to 20' for large sizes · Axial compensation: ±0.8 mm (size 00) to ±8.2 mm (size 40)
| Size | Nom. Torque N·m | Max Speed rpm | Bore d mm | D mm | A mm | B mm | L mm | J mm | Axial comp. mm | Angle comp. | Weight kg |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 00 | 9,800 | 20,000 | 3–20 | 57 | 4.9 | 20 | 44.9 | 10 | ±0.8 | 1° | 0.4 |
| 01 | 33,000 | 20,000 | 5–22 | 68 | 6.1 | 26 | 58.1 | 13 | ±0.8 | 1° | 0.6 |
| 02 | 90,000 | 20,000 | 6–32 | 81 | 6.6 | 26 | 58.6 | 16 | ±1.0 | 1° | 1.1 |
| 03 | 173,000 | 18,000 | 8–35 | 93 | 8.4 | 29 | 66.4 | 22 | ±1.2 | 1° | 1.7 |
| 04 | 245,000 | 15,000 | 10–42 | 104 | 11.2 | 34 | 79.2 | 20 | ±1.4 | 1° | 2.5 |
| 05 | 420,000 | 13,000 | 15–50 | 126 | 11.7 | 42 | 95.7 | 25 | ±1.6 | 45' | 4.3 |
| 06 | 772,000 | 12,000 | 20–60 | 143 | 11.7 | 48 | 107.7 | 28 | ±1.8 | 45' | 6.9 |
| 07 | 1,270,000 | 10,000 | 25–75 | 168 | 16.8 | 58 | 132.8 | 23 | ±2.0 | 45' | 11.3 |
| 08 | 2,080,000 | 10,000 | 30–82 | 194 | 17.0 | 64 | 145 | 30 | ±2.2 | 45' | 16.7 |
| 09 | 3,328,000 | 9,000 | 30–95 | 214 | 21.6 | 77 | 175.6 | 22 | ±2.4 | 45' | 22.7 |
| 10 | 4,900,000 | 8,000 | 40–108 | 150 | 23.9 | 89 | 201.9 | 23 | ±2.6 | 45' | 35.4 |
| 11 | 6,368,000 | 8,000 | 52–118 | 276 | 27.2 | 102 | 231.2 | 40 | ±2.8 | 45' | 52.0 |
| 12 | 8,900,000 | 6,300 | 60–110 | 276 | 17.5 | 128 | 273.5 | – | ±1.8 | 45' | 57.2 |
| 13 | 15,280,000 | 5,000 | 60–135 | 308 | 19.0 | 160 | 339 | – | ±2.0 | 30' | 77.3 |
| 14 | 25,410,000 | 4,700 | 60–155 | 350 | 21.5 | 182 | 385.5 | – | ±2.0 | 30' | 123 |
| 15 | 37,130,000 | 4,300 | 60–165 | 375 | 24.0 | 198 | 420 | – | ±2.0 | 30' | 156 |
| 16 | 47,120,000 | 3,900 | 70–180 | 410 | 29.5 | 214 | 457.5 | – | ±2.2 | 30' | 191 |
| 17 | 57,000,000 | 3,500 | 70–190 | 445 | 29.5 | 225 | 479.5 | – | ±2.2 | 30' | 245 |
| 18 | 63,186,000 | 3,500 | 80–205 | 470 | 31.0 | 248 | 527 | – | ±2.4 | 30' | 329 |
| 19 | 82,590,000 | 3,200 | 90–230 | 512 | 32.0 | 278 | 588 | – | ±2.4 | 30' | 394 |
| 20 | 102,100,000 | 2,800 | 90–255 | 556 | 32.5 | 305 | 642.5 | – | ±2.5 | 30' | 530 |
| 21 | 126,070,000 | 2,450 | 100–265 | 588 | 34.0 | 318 | 670 | – | ±2.7 | 30' | 619 |
| 22 | 146,350,000 | 2,150 | 100–275 | 630 | 34.5 | 332 | 698.5 | – | ±2.8 | 30' | 683 |
| 23 | 173,830,000 | 2,000 | 100–290 | 655 | 35.5 | 348 | 731.5 | – | ±3.0 | 30' | 791 |
| 24 | 200,000,000 | 1,400 | 210–305 | 680 | 44 | 350 | 744 | – | ±3.5 | 30' | 980 |
| 25 | 250,000,000 | 1,250 | 225–340 | 745 | 44 | 350 | 744 | – | ±4.0 | 30' | 1100 |
| 26 | 315,000,000 | 1,200 | 250–365 | 785 | 50 | 350 | 750 | – | ±4.2 | 30' | 1300 |
| 27 | 400,000,000 | 1,150 | 270–380 | 830 | 50 | 380 | 810 | – | ±4.5 | 30' | 1500 |
| 28 | 500,000,000 | 1,100 | 290–400 | 875 | 50 | 400 | 850 | – | ±4.8 | 20' | 1700 |
| 29 | 630,000,000 | 1,000 | 320–425 | 935 | 60 | 400 | 860 | – | ±5 | 20' | 2100 |
| 30 | 800,000,000 | 930 | 340–440 | 1030 | 60 | 440 | 940 | – | ±5.2 | 20' | 2600 |
| 31 | 1,000,000,000 | 880 | 380–460 | 1080 | 66 | 460 | 986 | – | ±5.5 | 20' | 2900 |
| 32 | 1,250,000,000 | 820 | 400–500 | 1160 | 70 | 520 | 1110 | – | ±5.8 | 20' | 3500 |
| 33 | 1,600,000,000 | 740 | 420–560 | 1290 | 82 | 570 | 1222 | – | ±6.2 | 20' | 5100 |
| 34 | 2,000,000,000 | 680 | 440–600 | 1410 | 92 | 570 | 1232 | – | ±6.5 | 20' | 5900 |
| 35 | 2,500,000,000 | 620 | 450–650 | 1530 | 105 | 610 | 1325 | – | ±6.8 | 20' | 6800 |
| 36 | 3,020,000,000 | 570 | 500–710 | 1670 | 115 | 730 | 1575 | – | ±7.2 | 20' | 7900 |
| 37 | 4,050,000,000 | 520 | 600–780 | 1830 | 125 | 800 | 1725 | – | ±7.5 | 20' | 10700 |
| 38 | 5,300,000,000 | 480 | 650–860 | 2000 | 130 | 800 | 1730 | – | ±7.8 | 20' | 14000 |
| 39 | 6,600,000,000 | 430 | 700–945 | 2200 | 140 | 960 | 2060 | – | ±8.0 | 20' | 17100 |
| 40 | 8,100,000,000 | 400 | 800–1030 | 2400 | 140 | 960 | 2060 | – | ±8.2 | 20' | 21100 |
Note: Torque values in the table above are in N·m (the listed N·m values 9800–8,100,000,000 represent mN·m in the original catalogue notation; nominal torque range is 9.8 N·m to 8,100,000 N·m). Imperial bore and custom shaft lengths available on request.
How to Select a DJM Diaphragm Coupling
Design Torque Formula
K = service factor | P = motor rated power (kW) | N = operating speed (rpm) | Tn = nominal torque of selected size (must satisfy TC ≤ Tn)
| Load Character | K | Typical Applications |
|---|---|---|
| Electric motor, smooth / uniform | 1.25–1.50 | Centrifugal pumps, fans, generators |
| Electric motor, moderate shock | 1.50–2.00 | Compressors, mixers, reciprocating pumps |
| IC engine, 4-cylinder+, moderate shock | 2.00–2.50 | Diesel pump sets, marine auxiliaries |
| Heavy shock / frequent reversal | 2.50–3.00 | Crushers, hoists, rolling mill drives |
Step-by-Step Selection
- Calculate TC: Apply service factor K to the rated motor torque using the formula above.
- Select size: Choose the DJM size whose nominal torque Tn ≥ TC. Check the bore range includes both shaft diameters.
- Verify speed: Confirm operating speed ≤ rated maximum for the selected size.
- Check misalignment: Confirm actual angular and axial offsets are within the compensation limits listed in the table. If radial offset is the dominant alignment challenge, consider the double-diaphragm SJM type.
- Specify bore: Select hole form (Y = standard cylindrical keyway; J1 = short cylindrical; tapered available on request) and bore diameter for each shaft end.
Single vs Double Diaphragm
| Criterion | DJM (Single) | SJM (Double) |
|---|---|---|
| Axial compensation | ±0.8–±8.2 mm | ±1.6–±16.4 mm |
| Angular compensation | Up to 1° | Up to 2° |
| Radial compensation | Via angular flex only | Direct radial: 0.5–3.0 mm |
| Overall length | Shorter | Longer |
| Best for | Well-aligned, space-limited drives | Multi-axis misalignment; long shaft spans |
Metal Diaphragm Coupling Series — Related Types
GBC manufactures the complete diaphragm coupling family. Explore the full range on our coupling catalogue.
Torque: 9.8–8,100,000 N·m · 41 sizes · Single pack · Compact length · Shaft key connection
Torque: 9.8–8,100,000 N·m · 41 sizes · Dual pack · Greater misalignment tolerance · Radial compensation
Torque: 33–1,270 N·m · 7 sizes · Interference-fit locking device · Zero backlash · CNC / servo drives
Taper cone hub connection · For CNC machine tool feed shafts · Best replacement for Z1 locking device
Torque: 33–8,100,000 N·m · Z7B locking disc · Large bore capacity · Single and double diaphragm
Torque: 420–25,410 N·m · Integrated disc brake · D0 315–1,000 mm · For disc brake drive systems
Rod-type · Shaft spans 35–350 mm · Torque 40–180,000 N·m · High misalignment capacity
Rod-type · Dual pack · Maximum compensation · Torque up to 280,000 N·m and beyond
DJM Coupling Industry Applications
Petrochemical centrifugal pumps running at 8,000–20,000 rpm demand a coupling with zero lubrication and high torsional rigidity. The DJM's all-metal construction eliminates the grease contamination risk of gear couplings and the temperature limits of elastomeric types, making it the standard choice for API 610 pump applications.
Turbine-driven compressor and generator trains operate at elevated temperatures where elastomeric elements are unsuitable. The DJM handles continuous service at up to +280°C with no wear element to degrade — critical for plant availability in power generation and LNG terminals.
Reciprocating and centrifugal compressor drives transmit high torque with pulsating loads. The DJM's torsional stiffness prevents resonant amplification that can damage impellers, while its zero-backlash characteristic protects precision balance in multi-stage machines.
Shipboard pump and generator sets require maintenance-free couplings in humid, salt-laden environments. The stainless steel diaphragm pack resists corrosion without coatings, and the absence of grease eliminates the pollution risk associated with gear coupling re-lubrication over water.
High-speed web offset printing demands precise angular transmission with no rotational play. The DJM's zero-backlash, high-stiffness characteristic keeps print registration stable across the full speed range, reducing misprint waste and rework.
Generator couplings in hydroelectric and wind turbines must withstand years of continuous operation with zero maintenance access. The DJM diaphragm pack requires no lubrication and has no wear-limited components under normal service conditions.
Installation and Maintenance
Installation Steps
- Shaft preparation: Clean shaft ends and bores; remove burrs. Verify bore diameters and keyway dimensions against coupling data.
- Hub fitting: Press or heat-fit hubs (induction heater, max 120°C). Torque setscrews to specification. For key connection: check key-to-keyway fit; key should be hand-push fit with no rock.
- Alignment: Align shafts to within the angular and axial compensation limits for the selected size. Laser alignment recommended for sizes 07 and above. Parallel offset should be minimised — the DJM single-pack has limited direct radial compensation.
- Diaphragm assembly: Fit the diaphragm pack between the two hub flanges. Torque all mounting bolts in a cross-pattern in three incremental passes to the specified torque. Use calibrated torque wrench only — over-torquing stresses the diaphragm; under-torquing causes fretting at the bolt holes.
- Verification: Rotate by hand for two full turns. Check axial float is within specification. Listen for any metallic contact indicating incorrect assembly.
Fault Diagnosis
| Symptom | Likely Cause | Action |
|---|---|---|
| Excessive vibration | Shaft misalignment beyond limits; diaphragm fatigue | Re-align shafts; inspect diaphragm pack for cracks |
| Diaphragm cracking | Chronic overload; misalignment exceeding limits; incorrect bolt torque | Replace diaphragm pack; recalculate TC; verify alignment |
| Bolt hole fretting / wear marks | Under-torqued bolts allowing micro-slip | Replace diaphragm; retorque all bolts to spec |
| Hub bore fretting | Inadequate interference fit; loose setscrew | Verify fit tolerance; re-torque setscrews |
Inspection interval: Inspect diaphragm pack visually every 12 months or at each major shutdown. Replacement of the diaphragm pack does not require hub removal — only the pack mounting bolts need to be undone. Check alignment at every diaphragm inspection; thermal growth and foundation settlement can move shafts outside specification over time.
DJM vs Alternative Coupling Solutions
vs Gear Coupling: The DJM eliminates the grease lubrication that gear couplings require every 6–12 months. In food, pharmaceutical, and clean-room environments, grease-free operation is a compliance requirement. At high speed, grease separation in gear couplings creates residue that can cause balance changes and vibration — a problem the DJM avoids entirely by having no lubricated contact.
vs Elastomeric Jaw Coupling: Jaw couplings damp vibration well at the cost of torsional compliance — the polyurethane spider allows some rotational wind-up before torque is fully transmitted. The DJM is torsionally rigid, making it suitable for precision positioning, servo drives, and any application where shaft angle accuracy must be maintained across load changes. The DJM also operates at higher continuous temperatures and speeds than any polyurethane-element coupling.
Single vs Double Diaphragm: The DJM single-pack compensates axial and angular misalignment but has limited direct radial offset capacity. The SJM-diaphragm type provides up to twice the axial compensation and meaningful direct radial offset capacity at the cost of greater overall length. Choose DJM for well-aligned, space-limited installations; choose SJM where multi-directional misalignment or long shaft spans are involved.
Customer Case Studies
Australia — Petrochemical Pump Station
Replaced gear couplings on six high-pressure booster pump sets with DJM-09 units. Grease carryover into the product stream had been causing quality failures at our refinery. Eighteen months on — zero lubrication events, zero coupling-related downtime. The maintenance cost saving alone justified the upgrade within the first year.
Rotating Equipment Engineer, Queensland AU
★★★★★
Germany — Turbine OEM
Standardised on DJM-14 through DJM-18 for our steam turbine auxiliary skid range. Dimensional drawings were accurate to ±0.1 mm on every batch. High-speed balance certification came with each shipment. Our in-house assembly team rates GBC's diaphragm quality on par with European suppliers at a significantly better price point.
Mechanical Design Manager, Bavaria DE
★★★★★
USA — Industrial Compressor Manufacturer
DJM-07 through DJM-12 fitted to a range of single-stage centrifugal compressors for HVAC applications. The zero-backlash characteristic eliminated the torsional noise issue we had with previous jaw couplings on fast start-stop cycles. Bore tolerance was consistent across 200 units — reduced our assembly time considerably.
Product Engineer, Ohio US
★★★★☆
South Korea — Printing Machinery
DJM-04 and DJM-05 on high-speed web offset press impression cylinder drives. The torsional rigidity keeps our print registration within 0.02 mm at 60,000 impressions per hour — we tried three other coupling types before settling on the DJM. No maintenance required in two years of continuous production.
Production Engineering Lead, Gyeonggi KR
★★★★★
Frequently Asked Questions
▶ What is a DJM type diaphragm coupling and how does it work?
The DJM is a single-diaphragm flexible metal coupling. Two steel hubs are bolted alternately to a stainless steel diaphragm pack — one set of bolts to the drive hub, the interleaved set to the driven hub. Torque is transmitted through the elastic tension and compression of the diaphragm segments. The same elastic flexing accommodates axial extension and angular misalignment without any sliding or rolling contact, making the coupling entirely lubrication-free.
▶ Does a DJM coupling require any lubrication or scheduled maintenance?
No. The diaphragm transmits torque and accommodates misalignment purely through elastic metal deformation — there are no sliding or wear surfaces. The only maintenance requirement is a periodic visual inspection of the diaphragm pack for cracks or fretting at bolt holes, typically at 12-month intervals or at each major machine shutdown.
▶ What is the difference between DJM and SJM type couplings?
DJM uses a single diaphragm pack and provides axial and angular compensation with limited direct radial offset capacity. SJM uses two diaphragm packs separated by a spacer, providing approximately double the axial compensation (±1.6–±16.4 mm), greater angular tolerance (up to 2°), and meaningful direct radial offset capacity (up to 3 mm on large sizes). The SJM is longer overall. Choose DJM for space-limited, well-aligned installations; SJM for applications with multi-directional misalignment.
▶ How do I specify the correct bore and keyway when ordering?
Use the ordering mark format: type, size, drive shaft hole form + diameter × length / driven shaft hole form + diameter × length. Example: DJM-05 YA28×62 / YA25×62 — Y-type bore with A-keyway, drive shaft diameter 28 mm bore length 62 mm, driven shaft diameter 25 mm bore length 62 mm. Custom bore forms including taper and imperial bore are available; contact GBC with shaft-end drawings for custom configurations.
▶ At what temperature can a DJM diaphragm coupling operate?
The stainless steel diaphragm pack and steel hub construction allow continuous service from -40°C to approximately +280°C — well above the temperature limit of elastomeric couplings. For applications above 200°C, confirm hub material and surface treatment selection with GBC engineering. The coupling is not affected by oil or steam exposure within these temperature limits.
Source DJM Diaphragm Couplings — Engineering Support Included
GBC supplies all 41 DJM sizes with full dimensional documentation, custom bore configurations, and material certificates. Send us your motor power, speed, shaft diameters, and application details and our engineering team will confirm the correct size and bore mark within 24 hours.
The DJM Type Single Flexible Diaphragm Coupling connects two shafts through a single stainless steel diaphragm pack bolted alternately to each hub flange. Covering 41 sizes from 9.8 N·m to 8,100,000 N·m at speeds up to 20,000 rpm, it is lubrication-free, torsionally rigid, and suited to high-speed pumps, compressors, turbines, and precision drives demanding zero backlash and minimal maintenance.
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