Description
GY8/GYS8/GYH8 Flanged Coupling – 56–80mm Bore Rigid Flange Coupling to GB/T 5843-2003
The GY8/GYS8/GYH8 type flanged coupling is the most widely used rigid coupling for cylindrical shaft connections in industrial machinery — conforming to Chinese national standard GB/T 5843-2003. Three structural subtypes are available within each model number: GY type, which uses a hinge bolt hole system allowing assembly and disassembly without moving the coupling along the axial direction; GYS type, which adds a precision alignment boss (凸楔) at the flange mating face to ensure accurate shaft concentricity on reassembly without realignment measurement; and GYH type, which uses a ring (sleeve) design that assembles and disassembles by axial movement. All three subtypes share the same outer diameter (200 mm), bore range (56–80 mm), nominal torque (3150 N·m), and maximum speed (4800 rpm). At 3,150 N·m and 56–80 mm bore, GY8/GYS8/GYH8 serves the largest directly coupled industrial drives in the 90–250 kW motor class. The coupling group at 4800 rpm covers all direct motor connection configurations. GYS8 with alignment boss is standard for API process pump applications at this bore and torque level.
The coupling transmits torque through a bolted flange joint — each hub mounts on one shaft via keyway and key, and the two hub flanges are bolted together with reamed-hole precision bolts. This provides a rigid, zero-backlash connection with no flexible elements. The GY-type hinge bolt design allows the coupling to be disconnected by removing the flange bolts without requiring either shaft to move axially — a significant maintenance advantage over sleeve couplings. The GYS-type alignment boss further improves maintenance efficiency by ensuring the two hub halves re-centre precisely on reconnection, eliminating the need for dial indicator verification after each coupling reconnection in planned maintenance schedules.
Shaft hole dimensions and keyway forms comply with GB3852-1997. Both Y-type and J-type bores are available; tapered bores are also available. The complete GY/GYS/GYH coupling series is listed on our product catalog page.
Technical Specifications
| Parameter | Value |
|---|---|
| Model Numbers | GY8, GYS8, GYH8 |
| Standard | GB/T 5843-2003 |
| Bore Range (d1, d2) | 56–80 mm |
| Outer Diameter (D) | 200 mm |
| Flange Boss Width (b) | 50 mm |
| Ring Width (b1, GYH) | 68 mm |
| Face Gap (S) | 10 mm |
| Nominal Torque (Tn) | 3150 N·m |
| Maximum Speed [n] | 4800 rpm |
| Rotational Inertia | 0.103 kg·m² |
| Mass (approx.) | 27.5 kg |
| Material | Cast Iron (HT200) standard; cast steel available |
| Bore Type | Y-type, J-type, or tapered bore |
GY, GYS and GYH Subtype Dimension Reference
Three Subtype Comparison
GY Type – Hinge Bolt
The standard GY type uses a hinge bolt hole system. Assembly and disassembly are performed by removing the flange bolts — no axial shaft movement required. This is the simplest GY subtype and is specified when maintenance reconnection frequency is low or when realignment is acceptable.
GYS Type – Alignment Boss
GYS type adds a precision alignment boss (凸楔) at the flange mating face. When reassembled after maintenance, the boss centres the two hub halves concentrically, eliminating realignment measurement. Specified where frequent planned maintenance disconnection is required and realignment time must be minimised.
GYH Type – Ring Design
GYH type uses a ring (sleeve) structural element and assembles by axial movement along the shaft. This method suits installations where the coupling geometry requires axial assembly access. Processing convenience is noted as a feature; disassembly also moves along the axial direction.
Zero Backlash – All Subtypes
All three GY subtypes transmit torque through rigid bolted flange joints and key-keyway shaft connections — providing absolute zero backlash. The rated 3150 N·m and 4800 rpm apply equally to GY, GYS, and GYH configurations.
Manufacturing Quality
Typical Applications
- Large industrial drive motor connections — primary conveyor, mill, and agitator rigid flanged coupling
- Power station auxiliary drive connections — boiler feed pump and forced draft fan motor shaft coupling
- Large API process pump motor connections — GYS type for planned maintenance efficiency
- Heavy industrial equipment drive shaft connections — highest-torque rigid flanged coupling in the GY series
For volume supply and custom bore configurations, visit our contact page.
Customer Reviews and Case Studies
★★★★★
United Kingdom — Large Industrial Pump OEM
GY8, GYS8, and GYH8 type flanged couplings are standard on our large API centrifugal pump range. At 3,150 N·m, the coupling covers our 100–500 kW pump class and GYS8 is specified for API pump applications requiring seal access.
— Chief Engineer, Birmingham
★★★★★
United States — Chemical Plant Operations
GY8 and GYS8 type couplings are installed on our large centrifugal pump drives. The GYS8 alignment boss has eliminated our post-maintenance shaft alignment step — reducing our planned maintenance time on each pump by approximately 4 hours.
— Process Engineer, Baton Rouge
★★★★☆
Chile — Copper Mining Processing
GY8 type couplings are used on large concentrate pump drive connections. The coupling handles the sustained torque of our slurry pump drives reliably through continuous mining production.
— Maintenance Superintendent, Antofagasta
Frequently Asked Questions
Can GY/GYS/GYH couplings connect shafts of different diameters?
Yes. The two hub halves can be bored to different diameters within the model’s bore range. Specify both d1 (active side bore) and d2 (driven side bore) independently when placing your order. Each hub is machined separately, allowing any combination of bore sizes within the model range.
What is the rotational inertia of GY/GYS/GYH couplings?
Rotational inertia values are listed in the specification table for each model, ranging from 0.0008 kg·m² for GY1 to 5.923 kg·m² for GY12. These are calculated values for the Y/J bore type at minimum shaft bore. The actual inertia will be slightly lower at larger bore diameters (more material removed). Include coupling inertia in motor sizing and drive system dynamics calculations.
Is a coupling guard required for GY/GYS/GYH flanged couplings?
Yes. A close-fitting coupling guard is required for all rotating coupling installations for personnel safety. The guard should contain any components in the event of coupling failure and allow ventilation airflow to prevent heat buildup at higher operating speeds. The guard should not contact the rotating coupling under normal operating conditions.
What documentation can be provided with GY/GYS/GYH couplings for procurement compliance?
Material certificates, dimensional inspection reports, and test certificates are available on request. For regulated industries (petrochemical, pharmaceutical, food), specify documentation requirements when placing your enquiry. Drawings in PDF and DXF format are available for all GY model sizes and bore combinations.
What is the marking standard for GY/GYS/GYH coupling identification?
Standard marking follows the GB/T 5843-2003 convention. Example: GYS6 45×84 GB/T5843-2003 indicates GYS type (with alignment boss), size 6, drive side bore 45 mm, outer diameter 84 mm, conforming to GB/T 5843-2003. Both active (master) and slave side bores and hub types are specified separately in the full marking.
Source GY8/GYS8/GYH8 Flanged Couplings
Ever Power manufactures GY, GYS, and GYH type flanged couplings from GY1 to GY12 per GB/T 5843-2003, direct from our factory. Specify subtype (GY/GYS/GYH), bore sizes, bore type (Y/J/tapered), and material for a prompt technical and commercial response.