An automated triple offset butterfly valve is a quarter-turn isolation valve whose metal seat closes on a conical contact rather than a flat one, supplied with an actuator bolted to an ISO 5211 pad in place of a handwheel. The body is rated to API 609 Category B, so the pressure limit is read from the ASME B16.34 table for the body material at the design temperature instead of from a single cold working pressure figure. The standard range covers NPS 2 to NPS 48 in Class 150, 300 and 600, and because the pad is standardised the same body takes an electric, pneumatic, hydraulic or worm gear operator without a body change.
Product range and configuration
Size: 3"~80"
Rating: 150#~2500#
Body: CS, SS, Alloy, Duplex SS
Seal Mat: METAL,LAMINATED
Connection: Wafer, Lug, Double flange, Butt-Welding
Temp: -196~650℃
Materials
These are the standard combinations for a Class 150 to 600 carbon steel body. Each line is a separate purchasing decision, and the low temperature and sour service columns change two of them: the bolting moves to A320 L7 and the trim to a NACE compliant hardness.
| Part | Standard | Alternative |
|---|---|---|
| Body | A216 WCB | A352 LCB, A217 WC6 / WC9, A351 CF8 / CF8M, A995 4A duplex |
| Disc | A351 CF8M | WCB with hard chrome, A217 WC9, A995 4A duplex |
| Shaft | A564 630 (17-4PH) | A182 F6a, F51 duplex, Nitronic 50 |
| Body seat ring | 13Cr with Stellite 6 overlay | 316 with Stellite 6, Inconel 625 overlay |
| Disc seal ring | Laminated 316 stainless and graphite | Solid Stellite 6, PTFE insert for soft seat |
| Bearing / bushing | 316 stainless with PTFE liner | Bronze, graphite impregnated |
| Packing | Flexible graphite | PTFE, graphite with anti-extrusion rings |
| Gasket | 316 and graphite spiral wound | Graphite sheet |
| External bolting | A193 B7 with A194 2H nuts | A320 L7 for low temperature, A193 B8 for stainless bodies |
| Shaft retention | Blowout-proof, retained from inside the body per API 609 | Anti-static device between shaft, disc and body |
Body Materials and Service Limits
Body material sets the temperature window before the seat does. Carbon steel carries the graphitisation caution above 425 °C, low temperature carbon steel is impact tested at -46 °C, and the austenitic and duplex grades cover the chloride and sour service cases that carbon steel cannot.
| Material | ASTM specification | Service temperature | Typical service |
|---|---|---|---|
| Carbon steel | A216 WCB | -29 °C to 425 °C | Water, steam, oil, gas |
| Low temperature carbon steel | A352 LCB | -46 °C to 343 °C | LPG, ammonia, cold climate |
| 1.25Cr-0.5Mo | A217 WC6 | -29 °C to 593 °C | High temperature steam |
| 2.25Cr-1Mo | A217 WC9 | -29 °C to 593 °C | High temperature steam, hydrogen |
| 304 stainless | A351 CF8 | -196 °C to 538 °C | Low temperature and oxidising media |
| 316 stainless | A351 CF8M | -196 °C to 538 °C | Chloride bearing water, dilute acid, LNG |
| Duplex | A995 Grade 4A (UNS J92205) | -46 °C to 315 °C | Seawater, sour service |
| Nickel alloy | A494 N12MV (nickel-copper) | -29 °C to 425 °C | Hydrofluoric acid, brine |
For LNG at -162 °C the body moves to A351 CF8M or to 9% nickel steel; low temperature carbon steel stops well short of that and belongs to LPG, ammonia and cold climate service. Sour service to NACE MR0175 / ISO 15156 changes the trim hardness and the bolting rather than the body grade, and is quoted as a separate option.
Operation
Lever / Gearbox
Pneumatic Actuator
Electric Actuator
Hydraulic Actuator
Gas – hydraulic Actuator
Electric – hydraulic Actuator
Available automation solution
- Remote Operated Valves (ROV)
- Emergency Shut Down Valves (ESDV)
- Motor Operated Valves (MOV)
- Hydraulically Operated Valves
- Gas Operated Valves
Pressure-Temperature Ratings
A Class 150 carbon steel body holds 19.6 bar at ambient and only 5.5 bar at 425 °C, a drop of 72% across the same valve. Class 600 with an identical body holds 102.1 bar cold and 57.5 bar at 425 °C. The figures below are the allowable working pressure in bar gauge from ASME B16.34 Table 2, Group 1.1, which covers A216 WCB and A105 bodies.
| Temperature (°C) | Class 150 | Class 300 | Class 600 |
|---|---|---|---|
| -29 to 38 | 19.6 | 51.1 | 102.1 |
| 50 | 19.2 | 50.1 | 100.2 |
| 100 | 17.7 | 46.6 | 93.2 |
| 150 | 15.8 | 45.1 | 90.2 |
| 200 | 13.8 | 43.8 | 87.6 |
| 250 | 12.1 | 41.9 | 83.9 |
| 300 | 10.2 | 39.8 | 79.6 |
| 350 | 8.4 | 37.6 | 75.1 |
| 400 | 6.5 | 34.7 | 69.4 |
| 425 | 5.5 | 28.8 | 57.5 |
ASME B16.34 tabulates Group 1.1 carbon steel up to 538 °C, but note (1) to the table warns that the carbide phase may convert to graphite above 425 °C. The ratings stay permissible there, they are simply not recommended for prolonged service. Most specifications therefore move the body to an A217 WC6 or WC9 casting above that point, which brings a different rating table with it. Raising the class does not extend the temperature window: a Class 600 WCB body is still bound by the same note. The class only raises the allowable pressure inside that window.
Face-to-Face Dimensions
Wafer and lugged bodies follow the API 609 short pattern series and are clamped between ASME B16.5 flanges. They run from 43 mm at NPS 2 to 276 mm at NPS 48, which is why a wafer triple offset valve rarely needs a pipe spool modification when it replaces a concentric valve of the same size.
| NPS | DN | Face-to-face (mm) | Face-to-face (in) |
|---|---|---|---|
| 2 | 50 | 43 | 1.69 |
| 2.5 | 65 | 46 | 1.81 |
| 3 | 80 | 46 | 1.81 |
| 4 | 100 | 52 | 2.06 |
| 5 | 125 | 56 | 2.19 |
| 6 | 150 | 56 | 2.19 |
| 8 | 200 | 60 | 2.38 |
| 10 | 250 | 68 | 2.69 |
| 12 | 300 | 78 | 3.06 |
| 14 | 350 | 78 | 3.06 |
| 16 | 400 | 102 | 4.00 |
| 18 | 450 | 114 | 4.50 |
| 20 | 500 | 127 | 5.00 |
| 24 | 600 | 154 | 6.06 |
| 30 | 750 | 165 | 6.50 |
| 36 | 900 | 200 | 7.88 |
| 42 | 1050 | 251 | 9.88 |
| 48 | 1200 | 276 | 10.88 |
Long pattern double flanged bodies follow API 609 Table 3b for the same class, and that table agrees with ASME B16.10 for flanged gate valves. A 12 in Class 150 triple offset valve is 356 mm face to face - identical to the gate valve it replaces. At Class 600 the same size is 838 mm, still level with the gate valve. That interchangeability is the main reason an automated triple offset valve is specified on revamps where the pipe spool cannot be cut.
| NPS | DN | Class 150 | Class 300 | Class 600 |
|---|---|---|---|---|
| 3 | 80 | 203 | 282 | 356 |
| 4 | 100 | 229 | 305 | 432 |
| 6 | 150 | 267 | 403 | 559 |
| 8 | 200 | 292 | 419 | 660 |
| 10 | 250 | 330 | 457 | 787 |
| 12 | 300 | 356 | 502 | 838 |
| 14 | 350 | 381 | 762 | 889 |
| 16 | 400 | 406 | 838 | 991 |
| 18 | 450 | 432 | 914 | 1092 |
| 20 | 500 | 457 | 991 | 1194 |
| 24 | 600 | 508 | 1143 | 1397 |
| 26 | 650 | 559 | 1245 | 1448 |
| 28 | 700 | 610 | 1346 | 1549 |
| 30 | 750 | 610 | 1397 | 1651 |
| 32 | 800 | 660 | 1524 | 1778 |
| 36 | 900 | 711 | 1727 | 2083 |
Table 3b tolerances are ±3.3 mm for NPS 3 to 24 and ±4.0 mm for NPS 26 to 36. NPS 2 and 2.5 are not covered by that table and are built to the manufacturer's standard length, quoted on the drawing.
Actuator Mounting to ISO 5211
The mounting pad is named after its bolt circle in millimetres: F10 is 102 mm, F12 is 125 mm, F16 is 165 mm. ISO 5211 also fixes the thread, the bolt count and the spigot diameter, and it sets a maximum allowable torque for each pad. An F10 pad is limited to 500 N·m and an F12 pad to 1000 N·m, so a valve whose seating torque exceeds 500 N·m cannot be supplied on F10 whatever actuator is offered with it.
| Flange | Bolt circle (mm) | Thread | Spigot Ø (mm) | Bolts | Max torque (N·m) |
|---|---|---|---|---|---|
| F07 | 70 | M8 | 55 | 4 | 250 |
| F10 | 102 | M10 | 70 | 4 | 500 |
| F12 | 125 | M12 | 85 | 4 | 1000 |
| F14 | 140 | M16 | 100 | 4 | 2000 |
| F16 | 165 | M20 | 130 | 4 | 4000 |
| F25 | 254 | M16 | 200 | 8 | 8000 |
| F30 | 298 | M20 | 230 | 8 | 16000 |
Two details decide whether the actuator actually bolts on. The drive form has to match - a male square on the stem against a female square in the actuator, or a double-D, or a keyed bore from F16 upward. The engagement length above the pad face has to match as well; a coupling bored deeper than the stem square bottoms out and holds the actuator base off the pad.
Actuator Sizing and Torque
Triple offset torque does not follow a size-based rule, because the metal seat seals by wedging. Seating torque at the last 5° of travel is normally the governing figure on a large valve, while breakaway torque governs on a small one. Both are quoted at the design differential pressure, not at line pressure.
| Component | When it applies | Sizing treatment |
|---|---|---|
| Breakaway torque | First movement out of the closed position | Measured at maximum differential pressure |
| Seating torque | Final 5° before the closed stop | Often exceeds breakaway above NPS 16 |
| Running torque | During the 90° travel | Used for motor duty, not for seat load |
| Service factor, on-off | Any open-close duty | 1.25 to 1.5 on the governing torque |
| Service factor, modulating | Throttling duty | 1.5 to 2.0 on the governing torque |
| Temperature allowance | Service above 200 °C | Stem and seat friction both rise |
Measured torque for a given size, class and differential is issued on the order datasheet together with the breaking and seating values the actuator is sized against. Those figures depend on the seat design and the trim, so they are not transferable between makers - send the line conditions with the enquiry and the torque curve comes back with the drawing.
Applicable industry
- Petrochemical & refining plants
- Marine, paper mills & minerals processing
- LNG
- Throttling flow
- Water, oil & gas
- Unsuitable for dry powder media
- Cryogenic or high-temperature modified design
Test and inspection
Send the line conditions and the configuration. You get back a general arrangement drawing, the breaking and seating torque for that size and class, a price and a delivery date.
Need the torque curve, a drawing or a price for one size?
FAQ
What pressure class is an automated triple offset butterfly valve rated to?
Class 150, 300 and 600 to ASME B16.34. A Class 150 A216 WCB body is rated 19.6 bar between -29 °C and 38 °C and derates to 5.5 bar at 425 °C; Class 600 with the same body holds 102.1 bar cold and 57.5 bar at 425 °C.
Which leakage rate applies to a metal-seated triple offset butterfly valve?
ISO 5208 Rate D, which allows 0.1 × DN mm³/s of water and 30 × DN mm³/s of gas. A soft-seated variant is specified at Rate A, no visible leakage for the duration of the test.
How is the actuator torque for a triple offset butterfly valve calculated?
Take the higher of breakaway torque and seating torque at the design differential pressure, then apply a service factor: 1.25 to 1.5 for on-off duty and 1.5 to 2.0 for modulating duty. The result must stay under the maximum torque of the ISO 5211 pad fitted to the valve.
What is the difference between API 609 Category A and Category B?
Category A valves are rated by cold working pressure, which is typical of concentric resilient-seated designs. Category B valves are rated by ASME class pressure-temperature tables, which covers double and triple offset designs.
Can a triple offset butterfly valve be used for dead-end service?
Yes, when the body is lugged or double flanged and the downstream flange is bolted. A wafer body has no downstream bolting and is limited to installation between two flanges.
Does a triple offset butterfly valve seal in both directions?
Yes. The conical seat contact is symmetrical about the disc, so the valve is rated for the full differential pressure from either side. Lugged and double flanged bodies can also be tested in both directions without removing the valve from the line.
What documents are supplied with the valve?
An EN 10204 3.1 mill certificate, a general arrangement drawing, an inspection and test plan, a pressure test record and an installation and maintenance manual. Positive material identification, radiographic or dye penetrant reports and a witnessed test to EN 10204 3.2 are added when the order calls for them.