ISO 7241 Series A – Dimensions and requirements of quick-action couplings
In hydraulic fluid power systems, power is transmitted and controlled through a liquid under pressure within an enclosed circuit. Quick-action couplings are used to join or separate fluid conductors quickly and without the use of tools or special devices.
When hydraulic quick-action couplings are used on agricultural machinery, the female coupling half is normally assembled on the tractor and the male coupling half is normally assembled on the tractor attachment.
This International Standard specifies the interface dimensions and basic performance requirements for two series of hydraulic quick-action couplings. Both series are in widespread use and have similar technological advantages. Series A is used predominantly in Europe and is preferred worldwide for agricultural and forestry machinery, and this International Standard also specifies additional requirements for Series A for use in agricultural machinery applications covered in ISO 5675. Series B is used predominantly in North America and in the chemical industry.
ISO 7241 Series A Dimensional requirements
- Dimension D1 is the gauge diameter
- The shape of the valve is optional, and dimension D4 is used unless the valve has a spherical form.
- Dimension L4 is measured to the ball
- Dimension D5 is the diameter of the gauge ball
- The shape of the groove that receives the bearings in the coupled position is left to the manufacturer.
- Maximum valve travel against the stop.
- Minimum length of diameter D8
- Minimum hardness shall be 86HR 15N at the ball contact point, in accordance with ISO 6508-1.
| Body Size(mm) | Body Size (inch) |
D1 | D2 | D3 | D4b min | D5 | L1 | L2c | L3 | L4 | L5 min |
L6 max |
L7 min |
α1 |
| 6,3 | 1/4” | 18.7 | 12.9 13 |
11.73 11.86 |
1.9 | 3.698 | 2.8 | 0.7 1.5 |
5.5 5.7 |
6.6 6.8 |
14.5 | 0.5 | 3.7 | 44˚ 46˚ |
| 10 | 3/8” | 24.1 | 18.3 18.4 |
17.2 17.3 |
3 | 3.698 | 3.8 | 0.7 1.5 | 8.8 9 |
9.8 10 |
18 | 0.5 | 7 | |
| 12,5 | 1/2” | 30.3 | 23.66 23.74 |
20.48 20.56 |
4.5 | 4.762 | 4 | 0.7 1.5 |
9.2 9.4 |
11.6 11.8 |
24 | 0.5 | 8 | |
| 20 | 3/4” | 37.1 | 30.4 30.5 |
29 29.1 |
5.4 | 4.762 | 7.2 | 1 2.5 |
15.9 16.1 |
17.5 17.7 |
27.5 | 0.6 | 13.7 | |
| 25 | 1” | 43.0 | 36.5 36.6 |
34.21 34.34 |
7.8 | 4.762 | 8.5 | 1.5 3 |
19.7 20 |
22.8 23 |
34 | 0.7 | 16.3 | |
| 31,5 | 1-1/4” | 56.0 | 47.7 47.8 |
44.9 45 |
8.9 | 6 | 11 | 2 4.5 |
24.9 25.1 |
28.4 28.6 |
43 | 0.7 | 24 | |
| 40 | 1-1/2” | 68.5 | 57.5 57.6 |
54.9 55 |
9.9 | 8 | 13 | 3 6 |
30.6 30.8 |
33.7 33.9 |
51 | 0.8 | 29.6 | |
| 50 | 2” | 83.7 | 69.9 70 |
65 65.1 |
9.9 | 10 | 16.6 | 3 7 |
35 35.2 |
39.6 39.8 |
61 | 0.8 | 34 |
- Dimensions in millimeters
- The size designation corresponds to the nominal size of the hose recommended for use with the coupling; see ISO 4397
- Use dimension D4 unless the valve has a spherical form; a spherical form is not preferred.
- Radius or chamfer length. Radius with chamfer is optional.
Additional dimensional requirements for Series A couplings used in agricultural applications
additional requirements for Series A for use in agricultural machinery applications covered in ISO 5675
| Body Size (mm) |
Body Size (inch) |
D6 max. |
L8 min. |
L9 min. |
| 12.5 | 1/2” | 31 | 28.5 | 37.2 |
| 20 | 3/4” | 38 | 27.5 | - |
| The size designation corresponds to the nominal size of the hose recommended for use with the coupling; see ISO 4397. |
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Performance Requirements
The performance values specified in this International Standard apply to standard couplings made from carbon steel. The use of any combination of other materials and related performance values shall be agreed upon between the customer and manufacturer.
Series A hydraulic quick-action couplings shall meet or exceed the maximum working pressure and minimum burst pressure ratings given in the Table below. additional requirements for Series A quick-action couplings for use in agricultural machinery applications.
| Characteristic | 6.3(1/4″) | 10(3/8″) | 12.5(1/2″) | 20(3/4″) | 25(1″) | 31.5(1-1/4″) | 40(1-1/2") | 50(2") |
| Maximum Rated Pressure in Accordance with ISO 2944 | 31.5 Mpa (315 bar) |
31.5 Mpa (315 bar) |
25 Mpa (250 bar) |
25 Mpa (250 bar) |
20 Mpa (200 bar) |
20 Mpa (200 bar) |
16Mpa (160 bar) |
10 Mpa (100 bar) |
| Minimum burst pressure | 126 Mpa (1260 bar) |
126 Mpa (1260 bar) |
100 Mpa (1000 bar) |
100 Mpa (1000 bar) |
80Mpa (800 bar) |
80Mpa (800 bar) |
64Mpa (640 bar) |
40Mpa (400 bar) |
| Rated flow | 3 L/min | 23 L/min | 45 L/min | 106 L/min | 189 L/min | 288 L/min | 379 L/min | 757 L/min |
| Maximum pressure drop at rated flow | 130 kPa (1,3 bar) |
180 kPa (1,8 bar) |
200 kPa (2 bar) |
200 kPa (2 bar) |
250 kPa (2,5 bar) |
200 kPa (2 bar) |
200 kPa (2 bar) |
200 kPa (2 bar) |
| Rated surge flow | 9 L/min | 69 L/min | 135 L/min | 300 L/min | 567 L/min | 864 L/min | 1137 L/min | 2271 L/min |
| Maximum fluid loss per disconnect | 1 ml | 2 ml | 2.5 ml | 9 ml | 25 ml | 60 ml | 90 ml | 150 ml |
a The size designation corresponds to the nominal size of the hose recommended for use with the coupling; see ISO 4397.
b 1 bar= 10s Pa= 0,1 MPa = 100 kPa; 1 Pa= 1 N/m 2 .
- The maximum rated pressure shall be verified by cyclic endurance (impulse) testing in the coupled and uncoupled conditions conducted in accordance with ISO 18869 for 100 000 cycles.
- The minimum burst pressure shall be verified by burst pressure testing conducted in accordance with ISO 18869 in the coupled and uncoupled conditions.
- The maximum pressure drop at rated flow shall be verified by pressure drop testing conducted in accordance with ISO 18869.
- The rated surge flow rate shall be verified by either long-duration surge flow testing or short-duration surge flow testing conducted in accordance with ISO 18869.
- The maximum fluid loss per disconnect shall be verified by testing conducted in accordance with ISO 18869.
Additional requirements for Series A quick-action couplings for use in agricultural machinery applications
- Size 12,5 and 20 Series A quick-action couplings designated for use on agricultural machinery shall fulfill the additional requirements specified in this clause unless otherwise agreed between the customer and manufacturer. Any other performance requirements shall be in accordance with ISO 5675
- Connecting and disconnecting
Female and male coupling halves shall fulfill the following requirements.
The connecting force measured in accordance with ISO 18869 shall not exceed 200 N with the male coupling half pressurized to 16 MPa (160 bar) and the female coupling half pressurized to 0,25 MPa (2,5 bar) for sizes 12,5 and 0,10 MPa (1,0 bar) for size 20.
The disconnecting force shall not exceed 1,7 kN for sizes 12,5 and 2,5 kN for size 20 when subjected to an internal pressure of 17,5 MPa (175 bar). The disconnecting force shall be measured in accordance with ISO 18869.
A special female coupling capable of connecting and disconnecting under pressure is required to meet these requirements. - Fluid loss
Fluid loss on disconnecting the coupling under pressure shall not exceed the values given in Table 7 when determined in accordance with ISO 18869.
| Size 12,5 | Size 20 | |
| Discomnecting at 0,1 MPa (1 bar) | 2,5 ml | 4,0ml |
| Disconnecting at 17,5 MPa (175 bar) | 9,0ml | 12,5 ml |
Valve performance
The force required to fully open the valve in the male part of the coupling when there is no internal pressure in the male part shall not exceed 45 N for sizes 12,5 and 70 N for sizes 20.
The coupling shall not check off (i.e. the valve shall not close) when hydraulic fluid with a viscosity of ISO VG 32, in accordance with ISO 3448, flows from the male part to the female part at a flow rate of 190 L/min for size 12,5 and 250 L/min for size 20.
