Interpump ZG044 Flexible Coupling 24-28 mm – Pump to Motor Shaft Coupler
The Interpump ZG044 flexible coupling is a shaft coupling used to join a high pressure pump to its drive motor while absorbing vibration and small alignment errors between the two shafts. It carries a 24 mm male pump shaft connection and a 28 mm male motor shaft connection in one coupling body of 102 mm total length and 76 mm diameter.
GIUNTI ELASTICI is the Italian term for elastic or flexible couplings. In a pressure washer or plunger pump set, the coupling sits between the motor shaft and the pump shaft: the elastic element transmits torque, damps torsional shock from the plungers and tolerates limited parallel, angular and axial misalignment. This page explains what the 24-28 mm designation means on the ZG044, how to select the correct insert and bore, and what to check before ordering a replacement.
Technical Specifications
| Parameter | Value | Note |
|---|---|---|
| Model | ZG044 flexible drive coupling | For Interpump plunger pump sets |
| Pump shaft connection | 24 mm male | Fits the pump drive shaft |
| Motor shaft connection | 28 mm male | Fits IEC 100-112 motor shafts |
| Total length | 102 mm | Overall coupling length |
| Diameter | 76 mm | Outside diameter of the coupling body |
| Construction | Cast aluminium | Two hub halves with elastic inserts |
| Pump compatibility | Interpump IP 44-53-58-60-63 series | Check shaft and keyway on the actual pump |
| Motor compatibility | IEC 100-112 motors | 110-112 frame per the published listing |
| Bore tolerance, keyway, insert material | Not published | Confirm with the factory drawing before ordering |
The published data defines the two shaft connections, the overall length, the diameter and the cast aluminium construction. Rated torque, maximum speed, bore tolerance, keyway dimensions and the elastic insert material are not stated, so none are invented. Measure the motor shaft, pump shaft, keyway and hub spacing before ordering a replacement.
Where a Flexible Coupling Is Used
Pump and Motor Sets
A factory-assembled electric pump motor unit depends on a coupling that can transmit the motor torque while protecting both bearings. Plunger pumps produce a pulsating load, and the elastic insert is what keeps that pulsation from being transmitted straight into the motor.
OEM Assembly and Machine Retrofits
When an Interpump IP 44, 53, 58, 60 or 63 series pump is fitted to an IEC 100-112 motor, a CNC conversion or a custom cleaning skid, the ZG044 matches the 24 mm pump shaft to the 28 mm motor shaft. Verify the keyway standard and the required alignment on the actual machine; a coupling that fits the hub but not the shaft will slip or damage the keyway.
Service and Replacement
A worn, cracked or glazed elastic insert is a common cause of noise, vibration and premature seal failure in a washer. Inspect the insert during pump service and replace the elastic element as soon as fretting or hardening appears, before the metal hubs start to contact each other.
Selecting the Correct Coupling
Start with measurements, not with the product name. Record both shaft diameters with a calliper, note the keyway width and depth, measure the distance between shaft ends and read the motor nameplate for power and speed. The ZG044 covers a 24 mm pump shaft and a 28 mm motor shaft in 102 mm of overall length; confirm those values against the machine before ordering.
Next, confirm the elastic insert. Hardness determines how much misalignment and shock the coupling absorbs: a softer insert protects bearings but deflects more, while a harder insert transmits torque more rigidly. Temperature, oil exposure and ozone ageing also affect insert life, so the material should be confirmed with the factory for the site conditions.
Finally, align the shafts with a straightedge or dial indicator before tightening the mounting feet. A flexible coupling is not a substitute for alignment; it compensates only small residual errors. Equipment using 500 bar wire braided hose assemblies and ultra-high-pressure 1500 bar water blasting systems is especially sensitive to vibration because fittings and seals are already working near their limits.
| Duty | Selection point | Equipment |
|---|---|---|
| Joining a pump to an electric motor | Torque, speed, both shaft bores | electric pump motor unit |
| Replacing a worn elastic insert | Insert hardness, hub spacing | This coupling |
| High pressure fluid connection | Pressure rating, bore, end fittings | 500 bar wire braided hose |
| Complete machine integration | Motor power, pressure, flow | AR high pressure washer |
Operating and Maintenance Notes
- Isolate and lock out the motor before removing any coupling guard or inspecting the insert.
- Check the 24 mm pump shaft and 28 mm motor shaft diameters, keyways and shaft-end spacing before ordering.
- Align motor and pump shafts within the coupling manufacturer tolerance; a flexible insert does not correct large misalignment.
- Check insert condition, hub bolts and keyways at every pump service; replace cracked or glazed inserts immediately.
- Keep the coupling guarded during operation and protect the elastic element from oil, solvent and direct heat.
Frequently Asked Questions
What does 24-28 mm refer to?
On this coupling, 24 mm is the male connection for the pump shaft and 28 mm is the male connection for the motor shaft. The coupling therefore joins an Interpump IP series pump directly to an IEC 100-112 motor without additional bushings.
Can one coupling fit two different shaft diameters?
Yes. The ZG044 uses two hub halves with different connections, 24 mm on the pump side and 28 mm on the motor side, joined by one elastic insert. Confirm both keyways against the dimensional drawing before fitting.
How often should the elastic insert be replaced?
Inspect it at every pump service. Replace it when cracked, hardened, glazed or loose. Running with metal-to-metal contact damages bearings and seals.
Does this coupling suit an ultra-high-pressure pump?
Suitability depends on torque and speed, not on the system pressure alone. Use the motor nameplate and pump data sheet to check the coupling rating before fitting it to a 1000 bar or 1500 bar pump set.
Related Cleaning Equipment
the electric pump motor unit with matched motor and plunger pump and 500 bar wire braided high pressure hose and KQ-388A Annovi Reverberi high pressure washer and 1500 bar ultra-high-pressure water blaster and 1000 bar marine water blaster.
