350 Cupla
High-Pressure up to 700 Bar
The Nitto Kohki 350 Cupla is a high-pressure quick-release coupling in steel with FKM seals, rated for operating pressures up to 700 bar. The range includes plugs (350-xP) and sockets (350-xS) in nominal sizes 2 through 12, as well as flange variants (e.g., 350-3P-3G, 350-4P-4G) enabling direct block mounting without loose pipe fittings. FKM seals provide resistance to mineral oils, synthetic hydraulic fluids, and elevated operating temperatures.
| Type | Nominal size | Version | Material | Seal |
|---|---|---|---|---|
| 350-2P / 350-2S | 2 | Standard | Steel | FKM |
| 350-3P / 350-3S | 3 | Standard | Steel | FKM |
| 350-4P / 350-4S | 4 | Standard | Steel | FKM |
| 350-6P / 350-6S | 6 | Standard | Steel | FKM |
| 350-3P-3G | 3 | Flange | Steel | FKM |
| 350-4P-4G | 4 | Flange | Steel | FKM |
| 350-6P-6G | 6 | Flange | Steel | FKM |
| 350-8P-8G | 8 | Flange | Steel | FKM |
Typical applications: Hydraulic test rigs and test facilities with operating pressures up to 700 bar, hydraulic power unit connections in heavy engineering and press installations, high-pressure lubrication systems, offshore hydraulics, and machine-tool couplings with direct block mounting via the flange variants.
Technical data from the manufacturer catalogue
| Series | 350 CUPLA |
|---|---|
| Body material | Special steel (Nickel plated) |
| Seal material | FKM (Fluoro rubber) |
| Max working pressure | 34.5 MPa {352 kgf/cm2, 345 bar, 5000 PSI} |
| Working temperature | Fluoro rubber (FKM): -20 °C to +180 °C |
| Valve structure | Two-way shut-off (Spill Reduction) |
| Applicable fluids | Hydraulic oil |
| Vacuum service | Not suitable for vacuum application in either connected or disconnected condition. |
| Size range | Thread 1/4 inch, 3/8 inch, 1/2 inch, 3/4 inch, 1 inch, 1 1/4 inch, 1 1/2 inch |
| Catalogue page | C01en-b, 105 |
Operating principle
- Body is made of special steel for durability. The body material is quenched to cope especially with impulses.
- Separation prevention mechanism is easily locked by turning the sleeve after connection.
- Both socket and plug have built-in automatic shut-off valves to prevent fluid spill out when disconnected.
- Push-to-connect operation.
- Their airless valve shut-off design greatly reduces air admixture.
- For hydraulic lines with large pressure fluctuations.
All models of the series
P - Male thread with female thread end
| Model | Coupling part | Application | Steel (g) | L | H | øD | C | T |
|---|---|---|---|---|---|---|---|---|
| 350-2P | Plug | R 1/4 | 170 | (72) | Hex.27 | 29 | 36 | Rc 1/4 |
| 350-3P | Plug | R 3/8 | 167 | (72) | Hex.27 | 29 | 36 | Rc 3/8 |
| 350-4P | Plug | R 1/2 | 245 | 85 | Hex.27 | 30 | 40.5 | Rc 1/2 |
| 350-6P | Plug | R 3/4 | 415 | 87 | Hex.36 | 40 | 44.5 | Rc 3/4 |
| 350-8P | Plug | R1 | 950 | 111 | Hex.50 | 55 | 56.5 | Rc 1 |
| 350-10P | Plug | R 1 1/4 | 2700 | (144) | Hex.70 | 78 | 75 | Rc 1 1/4 |
| 350-12P | Plug | R 1 1/2 | 2600 | (144) | Hex.70 | 78 | 75 | Rc 1 1/2 |
S - Male thread with female thread end
| Model | Coupling part | Application | Steel (g) | L | H | øD | T |
|---|---|---|---|---|---|---|---|
| 350-2S | Socket | R 1/4 | 360 | (82) | Hex.30 | (34) | Rc 1/4 |
| 350-3S | Socket | R 3/8 | 353 | (82) | Hex.30 | (34) | Rc 3/8 |
| 350-4S | Socket | R 1/2 | 545 | (93.5) | Hex.36 | (41) | Rc 1/2 |
| 350-6S | Socket | R 3/4 | 976 | (105.5) | 46 x ø52 | (49) | Rc 3/4 |
| 350-8S | Socket | R1 | 1740 | (129) | 55 x ø62 | (63) | Rc 1 |
| 350-10S | Socket | R 1 1/4 | 5600 | (180) | Hex.80 x ø90 | 89 | Rc 1 1/4 |
| 350-12S | Socket | R 1 1/2 | 5500 | (180) | Hex.80 x ø90 | 89 | Rc 1 1/2 |
Dimensions in millimetres. Values in brackets apply in the connected condition.
Legend: L = overall length; H = width across flats or outside dimension; D = socket outside diameter; A = hose barb length; C = sleeve dimension; T = thread or barb size; B = bore
Series comparison
| Series | Max working pressure | Size range | Valve structure | Applicable fluids |
|---|---|---|---|---|
| 210 CUPLA | 206 bar | 1/4 inch to 1 inch | Two-way shut-off | Hydraulic oil |
| HSP CUPLA | 206 bar | 1/4 inch, 3/8 inch, 1/2 inch, 3/4 inch, 1 inch, 1 1/4 inch, 1 1/2 inch, 2 inch | Two-way shut-off | Hydraulic oil |
| HYPER HSP CUPLA | 206 bar | 1/4 inch, 3/8 inch, 1/2 inch, 3/4 inch, 1 inch | Two-way shut-off | Hydraulic oil |
| HSU CUPLA | 210 bar | Thread 1/4 inch, 3/8 inch, 1/2 inch, 3/4 inch, 1 inch | Two-way shut-off | Water, Hydraulic oil, Gas |
| 280 CUPLA | 315 bar | Thread 1/4 inch, 3/8 inch, 1/2 inch, 3/4 inch, 1 inch | Two-way shut-off | Hydraulic oil |
| 350 CUPLA | 345 bar | Thread 1/4 inch, 3/8 inch, 1/2 inch, 3/4 inch, 1 inch, 1 1/4 inch, 1 1/2 inch | Two-way shut-off (Spill Reduction) | Hydraulic oil |
| 450B CUPLA | 441 bar | 3/8 inch | Two-way shut-off | Hydraulic oil |
| 700R CUPLA | 686 bar | Thread 3/8 inch, 1/2 inch | Two-way shut-off | Hydraulic oil |
Choose 350 CUPLA when the hydraulic line needs more than the 20.6 to 21.0 MPa that HSP CUPLA, HYPER HSP CUPLA, 210 CUPLA, HSU CUPLA and S210 CUPLA offer, and more than the 27.5 to 31.5 MPa of 280 CUPLA, but does not require the 44.1 MPa of 450B CUPLA or the 68.6 MPa of 700R CUPLA. All of these siblings are two-way shut-off; 350 CUPLA adds spill reduction, and its airless valve design keeps air admixture low, which is the argument on lines with large pressure fluctuations. For hydraulic oil at 34.5 MPa {352 kgf/cm2} with an FKM seal it is the direct choice within this group.
Body and seal materials
| Body material |
|---|
| Special steel (Nickel plated) |
| Seal material | Mark | Working temperature | Remarks |
|---|---|---|---|
| Fluoro rubber | FKM | -20 °C to +180 °C | Standard material |
Further catalogue data
| Note | Value |
|---|---|
| Working pressure in other units | 345 bar, 5000 PSI |
| Maximum tightening torque 3/8 inch | 40 Nm |
| Maximum tightening torque 1 inch | 250 Nm {2550 kgf cm} |
| Maximum tightening torque 1 1/4 inch | 500 Nm |
| Maximum tightening torque 1 1/2 inch | 500 Nm |
| Flow direction | Fluid flow can be bi-directional when socket and plug are connected. |
| Minimum cross-sectional area (mm2) - 350-2SP | 34.2 |
| Minimum cross-sectional area (mm2) - 350-3SP | 34.2 |
| Minimum cross-sectional area (mm2) - 350-10SP | 452.4 |
| Minimum cross-sectional area (mm2) - 350-12SP | 452.4 |
| Admixture of air on connection (mL) - 350-4SP | 0.2 |
| Admixture of air on connection (mL) - 350-6SP | 0.3 |
| Admixture of air on connection (mL) - 350-8SP | 0.5 |
| Admixture of air on connection | May vary depending upon the usage conditions. The values for 350-2SP, 350-3SP, 350-10SP and 350-12SP were not legible in the source text. |
| G thread | G thread is available on request (both for plugs and for sockets). |
| Optional accessory - PURGE ADAPTER | Residual Pressure Purge Adapter for Hydraulic Lines, models PAD-2, PAD-3FM, PAD-4FM, PAD-6FM and PAD-8FM. Can be attached to hydraulic lines to purge residual pressure effectively. See page 169 for the details. |
| PURGE ADAPTER specifications | Body material steel (nickel plated). Working pressure 35.0 MPa {357 kgf/cm2}, 350 bar, 5080 PSI. Applicable fluids hydraulic oil. Seal material nitrile rubber NBR, standard material. Drain outlet port for 8 mm OD tube, application Rc 1/8, max. tightening torque 5 Nm. |
| PURGE ADAPTER application threads | PAD-2: R 1/4. PAD-3FM: R 3/8 x Rc 3/8. PAD-4FM: R 1/2 x Rc 1/2. PAD-6FM: R 3/4 x Rc 3/4. PAD-8FM: R1 x Rc 1. |
| Flow rate | Flow Rate - Pressure Loss Characteristics graph on page 106, pressure loss in MPa {kgf/cm2} against flow rate in L/min from 1 to 1000 L/min. Test conditions: fluid hydraulic oil, temperature, fluid viscosity and density printed on the page were not legible in the source text. Curves are given for 350-2SP, 350-3SP, 350-4SP and 350-6SP among others. |
Interchangeability and size groups
Socket and plug of different sizes cannot be connected. However, certain SP model pairs can be connected with each other - the model numbers printed in that sentence were not legible in the source text of the catalogue page.
Safety and application notes
- Precautions for use: Do not connect / disconnect CUPLA when pressure is applied or remaining.
- Not suitable for vacuum application in either connected or disconnected condition.
- Before use, please be sure to read "Safety Guide" described at the end of this book and "Instruction Sheet" that comes with the products.
All technical data on this page is taken from the Nitto Kohki general catalogue Quick Connect Couplings C01en-b, page 105. The complete catalogue is available for download on this page.
