Reference 8th September 2026

What Are the ISO 5211 Actuator Flange Dimensions?

Q: Can I take the maximum flange torque as the torque the joint will carry?

Only under the conditions it was derived for: bolts in tension only at 290 MPa and a coefficient of friction of 0,2 at the interface. The standard states that variation in those parameters changes the transmittable torque.

Q: Does ISO 5211 say how the pad is attached to the valve body?

No. It specifies flange dimensions, driving component dimensions and reference torques for interfaces and couplings. Whether the pad is machined into the body, cast integrally or carried on a bolted bracket is outside the standard, as is the attachment of an intermediate support to the valve.

Key Takeaway

ISO 5211 fixes the interface between a part-turn actuator and a valve, and the number in a designation such as F05 is the bolt circle diameter in millimetres: F05 is a 50 mm circle, F07 is 70 mm, F10 is 102 mm. The table below is Table 2 of ISO 5211:2017, all sixteen flange types from F03 to F100, with the pilot recess, the bolt thread and the flange heights. Two things people look up separately are also in the standard and are given here: the hole position angle, which is 45 degrees for F03 through F16 and changes above that, and the designation letters, where Y or N says whether there is a spigot and V, W, X, L, D or H says which drive form the coupling takes. The maximum flange torques the standard lists are not a free number either: they assume bolts in tension only at 290 MPa and a friction coefficient of 0,2 at the interface.

Flange dimensions, F03 to F100

Dimensions in millimetres, reproduced from Table 2 of ISO 5211:2017. The letters follow the standard's own key: d1 is the minimum flange diameter, d2 the spigot or recess diameter, d3 the bolt circle, d4 the bolt thread, n the number of screws, studs or bolts, and h1, h2 and h3 the flange heights.

Flange	d1 min	d2	d3 bolt circle	d4 thread	n	h1 max	h2 min	h3 min
F03	46	25	36	M5	3	8	5	4
F04	54	30	42	M5	3	8	5	4
F05	65	35	50	M6	3	9	6	4
F07	90	55	70	M8	3	12	8	4
F10	125	70	102	M10	3	15	10	4
F12	150	85	125	M12	3	18	12	4
F14	175	100	140	M16	4	24	16	4
F16	210	130	165	M20	5	30	20	4
F25	300	200	254	M16	5	24	16	8
F30	350	230	298	M20	5	30	20	8
F35	415	260	356	M30	5	45	30	8
F40	475	300	406	M36	8	54	36	8
F48	560	370	483	M36	8	54	36	12
F60	686	470	603	M36	8	54	36	20
F80	900	670	813	M42	10	63	42	20
F100	1200	870	1042	M42	10	63	42	32

The standard notes that d2 is to be manufactured within diameter tolerance f8, and that holes are to be equi-spaced, positioned off-centre and made to ISO 273 for clearance. Where through bolting is used rather than studs or screws, the clearance holes have to admit a bolt of the size given by d4.

Which letter is measured where. The table above gives d1 as a minimum and h1 as a maximum, so a flange can be larger across than the figure shown and must not be taller. Bolt holes are drawn at four for clarity; the count is the column n in the table.

Where the holes sit

Equi-spaced is only half the information. The standard also fixes the angular position, and it is not the same across the range, which is the detail that catches people transferring a pattern from a small valve to a large one.

Flange type	Half-angle to the first hole
F03 to F16	45°
F25 to F40	22,5°
F48	15°
F60 to F80	9°
F100	5,625°

How a designation is written

A flange size on its own does not describe the interface. The standard gives a designation built from three parts, and the two letters after the flange type carry information a bolt circle cannot.

Position	Letter	What it says
Spigot	Y	With spigot
Spigot	N	Without spigot
Drive	V	Single-key drive
	W	Two-key drive at 90°
	X	Two-key drive at 180°
	L	Parallel square drive
	D	Diagonal square drive
	H	Flat head drive

The distinction between L and D is the one worth reading twice. Both are square drives of the same size. They differ by 45 degrees of orientation relative to the flange, which decides where the valve sits when the actuator reaches its end of travel. An actuator and a valve can share a flange type, a bolt circle and a drive size and still be wrong for each other on this letter alone.

Which interface the standard is describing

ISO 5211 covers four arrangements, and a specification that names the standard without saying which one leaves the most consequential part open.

Direct interface. The part-turn actuator bolts to the valve.
Intermediate support interface. The actuator bolts to a support, and the support carries the valve. The standard covers the actuator to support joint and stops there.
Direct, with a gearbox. A multi-turn actuator and a part-turn gearbox together form the part-turn actuator, and that assembly bolts to the valve. The joint between the multi-turn actuator and the gearbox is ISO 5210, not this standard.
Intermediate support, with a gearbox. The same, through a support.

Part-turn and multi-turn are defined by thrust as well as travel

The standard's definitions separate the two on more than the number of revolutions, and the second half is the part that decides what the interface has to carry.

Term	Travel	Axial thrust
Part-turn actuator	One revolution or less	Does not have to withstand it
Multi-turn actuator	At least one revolution	May be capable of withstanding it

A part-turn interface is a torque joint. It is not designed to take axial load, which is why a rising-stem arrangement or anything that pushes on the drive belongs on the multi-turn side of the family rather than here.

What the flange torque figures assume

The standard tabulates a maximum flange torque against each flange type, and those numbers are conditional in a way the table itself does not show. They are derived on the basis of bolts in tension only, at a stress of 290 MPa, with a coefficient of friction of 0,2 at the mounting interface.

The standard states plainly that any variation in those parameters changes the transmittable torque. It also notes that flange selection should account for additional torque generated by inertia or other factors, which is the case that catches a fast-acting actuator on a large valve.

In other words the flange torque is a property of the joint, not of the valve. Two valves with identical F10 pads, bolted with different fasteners to different friction conditions, do not transmit the same torque.

What ISO 5211 does not cover

The scope is narrower than the way the number gets used in specifications, and three exclusions matter.

The attachment of an intermediate support to the valve is out of scope. The standard covers actuator to valve, and actuator to intermediate support. How that support is fixed to the valve is not its business.
Control valves are by agreement. Attaching a part-turn actuator to a control valve in accordance with the standard is subject to agreement between supplier and purchaser rather than being covered outright.
Multi-turn attachment belongs to ISO 5210. Where a multi-turn actuator drives a part-turn gearbox, the interface between those two is the other standard.

Nothing in the standard speaks to torque required by the valve, to endurance, or to whether the pad is cast into the body or bolted on as a bracket. Those are decided elsewhere and are covered in the article on actuated valves in liquid cooling linked below.

Reading a pad on a drawing

Four figures settle whether a given actuator will fit a given valve, and only one of them is the flange number.

Flange type. Match d3, the bolt circle, first. The number is the bolt circle in millimetres for most of the range, which makes it quick to sanity check.
Spigot. Y or N. A valve machined with a recess and an actuator without a spigot will bolt together and locate on the bolts alone.
Drive form. V, W, X, L, D or H, and for a square drive the across-flats dimension. L against D is a 45 degree difference that a bolt circle will not reveal.
Height. h1, h2 and h3 have to clear whatever the valve carries between the body and the pad.

Frequently Asked Questions

Does the number in F05 mean anything?

It is the bolt circle diameter in millimetres. F05 is a 50 mm bolt circle, F07 is 70 mm, F12 is 125 mm, F60 is 603 mm. The relationship is close enough through the range to use as a check, and the exact figure is d3 in the table above rather than the designation itself.

What is the difference between an L drive and a D drive?

Both are square drives. L is a parallel square, D is a diagonal square, and the two are rotated 45 degrees from one another relative to the flange. Since the drive orientation sets where the valve sits at each end of the actuator's travel, an otherwise matching pair with the wrong letter puts the ball or disc at 45 degrees to where it should be.

Can I take the maximum flange torque as the torque the joint will carry?

Only under the conditions the figure was derived for: bolts in tension only at 290 MPa and a friction coefficient of 0,2 at the interface. The standard says that variation in those parameters changes the transmittable torque, so a different fastener grade, a different clamp load or a different surface condition gives a different answer.

Does ISO 5211 say how the pad is attached to the valve body?

No. It specifies the flange dimensions, the driving component dimensions and reference torques for interfaces and couplings. Whether the pad is machined into the body, cast integrally with it or carried on a bolted bracket is outside the standard, and so is the attachment of an intermediate support to the valve.

Which edition is current?

The figures here are from ISO 5211:2017, the second edition. Later editions exist in the ISO catalogue, so a drawing that cites the standard without an edition should be checked against the edition the parties intended.

Published by LINS Valve Industrial Co., Ltd., Taichung, Taiwan. Last Updated: 2026-09-08

Referenced standards: ISO 5211:2017, Industrial valves, part-turn actuator attachments. Table 2 for flange dimensions, Table 3 for hole positions, Clause 4 for maximum flange torques and Clause 6 for the designation. ISO 273 (clearance holes for bolts and screws) and ISO 5210 (multi-turn actuator attachments) are referenced by it.

Dimensions are quoted from the published standard and are given here for reference. They do not replace the actuator or valve drawing for a specific product, and the number of fasteners, the clamp load and the interface condition all sit outside the dimensional table while deciding what the joint actually transmits.