What is a bare shaft ball valve?
A bare shaft ball valve is a ball valve supplied without a mounted actuator or handle. The ball switches 90° between open and closed: in the open position the bore aligns with the pipeline for minimal pressure drop; in the closed position the bore is perpendicular to the pipeline for leak-tight shut-off within the specified leakage class. The defining feature is the preparation on top of the stem: an ISO 5211 mounting pad with the correct square or keyed shaft profile. This allows a handle, gearbox or actuator to be fitted at any time and without replacing the valve. Connection dimensions in the pipeline — threaded, weld or flange — remain unchanged.
ISO 5211 – the foundation for future automation
ISO 5211 is the international standard for the interface between quarter-turn valves and actuators. The standard defines the mounting flange size (F03, F05, F07, F10 and above), the bolt hole pattern and position, and the shaft profile (square or keyed). By selecting the correct ISO 5211 flange size and shaft connection at the time of purchase, any future actuator or gearbox can be fitted without modification or custom parts. Always verify at the specification stage that the selected ISO 5211 size can also handle the expected maximum torque of the future actuator.
Determining torque before installation
Torque is the critical design parameter for a bare shaft application. Three values are relevant: break torque to open the valve from standstill, run torque during the stroke and seat torque for leak-tight shut-off. All three are influenced by medium, pressure, temperature and seat material. Always calculate with sufficient margin — changing process conditions, medium contamination or temperature peaks can increase the required torque. Select the ISO 5211 flange size and shaft profile such that a heavier actuator can also be fitted retrospectively without replacing the valve.
Actuation options on the same valve
One of the key advantages of the bare shaft design is that different actuation methods can be used on the same ISO 5211 interface.
| Actuation |
When to use |
Characteristics |
| Lever handle |
Manual operation now, simple on/off |
Compact, low cost, direct position indication |
| Gearbox |
High torque, large diameters, confined space |
Reduced hand torque, optional locking |
| Pneumatic actuator |
Fast switching, fail-safe required, compressed air available |
Single or double-acting, fast cycles |
| Electric actuator |
Modulating, bus integration, no compressed air available |
Remote positioning, position feedback |
Want to start with manual operation and automate later? Fit a lever handle or gearbox to the ISO 5211 pad first. When automation is required, remove the handle and mount the actuator on the same interface — without removing the valve from the pipeline.
Own range: ball valve with handle and ISO 5211 mounting pad
Ebora also supplies an own range of ball valves that are standard-equipped with both a lever handle and an ISO 5211 top flange. These valves function directly as a manual ball valve while being prepared for future automation at the same time. For retrofit, only the handle is removed and the actuator is mounted on the existing ISO 5211 pad — without replacing the valve or modifying the pipework. This is the most cost-effective choice when manual operation is required now but automation is expected at a later project stage.
Materials, seats and connections
Bodies are available in brass (water, compressed air, neutral media), carbon steel (general industry, higher pressure) and stainless steel 316 (corrosive or hygienic applications). Seats are selected based on chemical compatibility, temperature and wear resistance; PTFE is the most widely used option, with filled grades (glass fibre, graphite or carbon) applied under higher mechanical load or with abrasive media. For dry or abrasive media, additional torque margin is calculated and wear-resistant seats are selected to maintain the leakage class over the service life. Connections are available as threaded (BSP or NPT), butt-weld or flange to DIN/EN or ANSI.
Valve Automation Centre
Ebora handles the complete preparation and assembly in the Valve Automation Centre. We select adapters and brackets, mount the actuator on the bare shaft valve and validate the complete assembly. Test reports and full documentation are available on request. The set is delivered fully assembled and tested, ready for installation. This applies to both new projects and retrofit on existing valves with the correct ISO 5211 preparation. If you require a fully automated assembly straight away, see also the electric ball valves or the pneumatic ball valves.
Request advice or a quotation
Provide the following data with your enquiry: medium, pressure, temperature, required connection (BSP/NPT, weld or flange), diameter, ISO 5211 flange size and the intended or expected actuator. Also state whether you require manual operation now with preparation for future automation, or a complete assembly immediately. We will size the bare shaft ball valve, calculate the torque and prepare the valve for your current or future automation.
Provide your process data and request a quotation via the contact page, or contact our technical team for selection advice.
Frequently asked questions about bare shaft ball valves
What is the difference between a bare shaft ball valve and a manual ball valve?
A manual ball valve is supplied with a fitted lever handle or gearbox and is ready for immediate operation. A bare shaft ball valve is supplied without actuation but prepared with an ISO 5211 mounting pad so that a handle, gearbox or actuator can be fitted by the user. The bare shaft version is not an actuation method in itself — it is a preparation strategy for flexible or phased installations.
Which ISO 5211 flange size do I need?
The ISO 5211 flange size is determined by the required torque of your application. Common sizes are F03, F05, F07 and F10; larger sizes are available for bigger diameters or higher pressures. Always select a size that can also accommodate the expected future actuator, including a torque margin for changing process conditions. We calculate the correct size based on your process data.
Can I automate an existing bare shaft ball valve without modifying the pipework?
In most cases yes, provided the valve has the correct ISO 5211 mounting pad and shaft profile and sufficient space is available for an adapter or bracket. Connection dimensions in the pipeline remain unchanged because the valve stays in line. Our Valve Automation Centre handles adapter selection, assembly and testing of the complete set.
What if the required torque turns out to be higher than expected later?
If process conditions change — higher pressure, a different medium or temperature peaks — the required torque may increase. For this reason, select an ISO 5211 flange size and shaft profile with sufficient margin for a heavier actuator at the specification stage. If needed, we can supply an adapter or switch to a gearbox as an intermediate step. The Valve Automation Centre can carry out the upgrade quickly and in a controlled manner.
