Limitorque’s (Flowserve) catalogue is broad, but the selection logic has one line: valve motion, required output, power source, failure mode and duty come first — the model number comes last. The lineup falls into four blocks: smart electric MXb (multi-turn, up to 2,307 Nm) and QXb (direct quarter-turn, 136–2,033 Nm); conventional electromechanical L120 (100–20,000 ft-lb) and heavy-duty SMB (through 20,000 ft-lb, 5XT to 60,000); pneumatic Scotch-yoke LPC (50–5,500 Nm) and LPS (6,000–300,000 Nm); and gearboxes WG/HBC/V/B320 extending the electric families into much larger torque and thrust duties. This guide compiles the full-lineup comparison table, key ratings, sizing checklists and nine FAQs.
| Product | Technology / Motion | Output Range From Supplied Literature | Typical Valve / Device | Best Fit |
|---|---|---|---|---|
| MXb | Smart electric, multi-turn | Up to 2,307 Nm (1,700 ft-lb) rated torque; thrust up to 333 kN (75,000 lb), model/configuration dependent | Gate, globe, sluice, slide gate; quarter-turn through gearbox | New smart-electric multi-turn projects, diagnostics, networked plants |
| QXb | Smart electric, quarter-turn | 136 to 2,033 Nm (100 to 1,500 ft-lb) rated seating torque | Ball, butterfly, plug, damper | Direct quarter-turn smart actuation |
| L120 | Electromechanical electric, multi-turn | 100 to 20,000 ft-lb direct actuator ratings; thrust to 500,000 lb; larger geared package output available | Gate, globe, penstock, sluice gate; quarter-turn through gearbox | Proven conventional architecture, industrial and water infrastructure |
| SMB | Heavy-duty electromechanical electric, multi-turn | Commercial ratings through 20,000 ft-lb; SMB-5XT listed to 60,000 ft-lb; thrust to 500,000 lb | Gate, globe, severe-duty valves; quarter-turn through gearbox | Critical, severe-duty, nuclear and very long-life service |
| LPC | Pneumatic Scotch yoke, quarter-turn | 50 to 5,500 Nm (37 to 4,057 ft-lb) | Ball, butterfly, plug | Compact pneumatic automation, ESD and modulating service |
| LPS | Heavy-duty pneumatic Scotch yoke, quarter-turn | 6,000 to 300,000 Nm (4,425 to 221,268 ft-lb); larger sizes by factory consultation | Large ball, butterfly, plug and control valves | Large-valve ESD, HIPPS, severe service and high torque |
| WG | Worm gearbox, quarter-turn / 360° option | Up to 970,000 Nm (715,435 ft-lb) | Butterfly, ball, plug, dampers; other rotary devices | High-torque quarter-turn packages, waterworks, buried/submersible service |
| HBC | Worm gear operator, manual or motorized | Up to 126,204 Nm (93,000 ft-lb) | Butterfly, plug, ball, damper, radial gate, guillotine damper | Proven installed-base quarter-turn gearing, power and infrastructure |
| V Series | Bevel gearbox, multi-turn | V_H ratings to 104,734 ft-lb torque and 2.585 million lb thrust | Gate, globe, sluice gate, slide gate | High-thrust / high-torque multi-turn gearing |
| B320 | Bevel gear operator, multi-turn | Up to 8,000 ft-lb output torque and 325,000 lb thrust | Gate, globe, sluice / slide gates | Manual or motorized mechanical advantage with broad mounting options |
 MXb smart multi-turn |  QXb smart quarter-turn |  L120 electromechanical multi-turn |  SMB heavy-duty multi-turn |  LPC pneumatic Scotch yoke |
 LPS heavy-duty pneumatic |  WG worm gearbox |  HBC worm gear operator |  V Series bevel gearbox |  B320 bevel gear operator |
The Limitorque product family (image source: E4 Industrial, e4industrial.com)
Electric families:
| Series | Models / range | Output & interface highlights |
|---|---|---|
| MXb (smart multi-turn) | MXb-05, -10, -20, -40, -85, -140, -150 | Rated torque up to 2,307 Nm (1,700 ft-lb) depending on frame and output speed; thrust to 333 kN (75,000 lb) with listed thrust bases; MSS SP-102 / ISO 5210 mounting |
| QXb (smart quarter-turn) | QXb-1 through QXb-5 | Rated seating torque 136–2,033 Nm (100–1,500 ft-lb); operating times approx. 5–120 s in listed configurations; MSS SP-101 / ISO 5211 bases |
| L120 (electromechanical multi-turn) | Per performance table | Direct torque 100–20,000 ft-lb; direct thrust 10,000–500,000 lb by model; WG/HBC geared quarter-turn and V/SR rising-stem/high-thrust packages; NEMA 6 / IP68 configurations listed |
| SMB (heavy-duty multi-turn) | SMB-000 through SMB-5/5T, plus SMB-5XT | Commercial torque table through 20,000 ft-lb; SMB-5XT listed to 60,000 ft-lb; thrust to 500,000 lb on listed thrust bases; HBC/WG quarter-turn gearing |
Pneumatic Scotch-yoke families:
| Series | Models | Torque | MAWP | Temperature |
|---|---|---|---|---|
| LPC (compact Scotch yoke) | LPC-05, -10, -12, -14 | 50 to 5,500 Nm (37–4,057 ft-lb) | 12 barg (174 psig) | Standard −29 °C to 100 °C; special low/high-temperature configurations listed |
| LPS (heavy-duty Scotch yoke) | LPS-15 through LPS-60 | 6,000 to 300,000 Nm through LPS-50; LPS-60 consult factory | 12 barg (174 psig) | Configurations listed from −60 °C to 160 °C |
Gearbox families:
| Gearbox | Models / rating step | Output capability | Drive & service |
|---|---|---|---|
| WG (worm gearbox) | — | Up to 970,000 Nm (715,435 ft-lb) | Motorized by MX/MXb/L120/SMB; weatherproof, buried and submersible; quarter-turn torque multiplication |
| HBC (worm gear operator) | HBC-0 through HBC-7/7M | Up to 126,204 Nm (93,000 ft-lb) in HBC-7M | Motorized by MX/L120/SMB; quarter-turn standard, 360° option for guillotine dampers and radial gates; cast-iron housing, alloy-steel worm shaft, bronze worm gear; built to AWWA requirements per the literature |
| V Series (bevel gearbox) | V_H high-capacity step | V_H rated to 104,734 ft-lb torque and 2.585 million lb thrust | Motorized by MX/L120/SMB; −35 °C to 90 °C continuous |
| B320 (bevel gear operator) | B320-20 through B320-90 | Output torque to 8,000 ft-lb (10,856 Nm); thrust to 325,000 lb (1,446 kN) | Manual or motorized; broad mounting options |
As the source guide puts it: a correct actuator selection has to do more than exceed a single published torque number — the actual valve load changes over the stroke, and the actuator’s available torque can change with output speed, supply conditions and media temperature.
| # | Information needed for electric actuators |
|---|---|
| 1 | Valve manufacturer, type, size, pressure class and tag number |
| 2 | Required running, seating/unseating torque or thrust; MAST/MAT where applicable |
| 3 | Stem diameter, thread, keyway, square drive or other output interface |
| 4 | Required turns or quarter-turn travel |
| 5 | Required opening and closing time |
| 6 | Available voltage, phase and frequency |
| 7 | On/off, inching or modulating duty and expected starts/hour |
| 8 | Control signal: discrete, 4-20 mA, network protocol, ESD/inhibit requirements |
| 9 | Area classification, enclosure rating, ambient temperature and submergence/buried requirements |
| 10 | Local controls, indication, remote feedback and communications |
| 11 | For pneumatic actuators additionally: BTO/RTO/ETO and BTC/RTC/ETC torque profile; fail-safe direction; minimum/normal/maximum air supply; project safety factor and SIS requirements; accessories (switchbox, solenoid, positioner, PST, ESD, manual override) |
Gearbox sizing matters: for WG, HBC, V and B320 selections, output torque or thrust is only half the calculation — also verify input torque, mechanical advantage, ratio, efficiency, stem capacity, mounting flange and drive sleeve.
The modern Limitorque value proposition is not only torque — it is visibility into valve position, actuator health and the conditions that lead to failure:
| Control & protection | Diagnostics & connectivity |
|---|---|
| Direct-wired open / stop / close control alternatives | Time-stamped event and alarm logging |
| Digital, analog and network control modes | Torque, travel, cycle-count, temperature and vibration diagnostics |
| Emergency shutdown inputs, configurable user inputs and inhibit signals | Local high-resolution display with real-time and historical graphs |
| Status contacts and monitor relay | Bluetooth LE for FlowSync monitoring and configuration |
| Autophase protection/correction on applicable three-phase configurations | Network options: Modbus, Profibus DP/PA, TCP/IP, Foundation Fieldbus H1, HART, DeviceNet |
| Jammed-valve, instantaneous-reversal and motor-thermal protection; LimiGard circuit monitoring with built-in self-test |
MXb is a smart multi-turn electric actuator. It is used directly on multi-turn valves such as gate and globe valves and can be combined with a gearbox for quarter-turn or high-thrust applications. QXb is a smart direct quarter-turn actuator for ball, butterfly, plug valves and dampers. Both share modern non-intrusive controls, diagnostics and communication capabilities.
Choose L120 when the project prefers a conventional electromechanical architecture, when an installed base or maintenance standard favors L120, or when a like-for-like replacement is important. Choose MXb when advanced diagnostics, non-intrusive setup, electronic torque sensing, modern communications and smart-actuator lifecycle data are priorities.
Both are electromechanical multi-turn actuator families. SMB is the heavier severe-duty platform with a deep nuclear and critical-service history, larger frame options and extremely rugged cast/ductile-iron construction. L120 is a broad industrial multi-turn platform used extensively in petrochemical, power and water applications and is generally the more straightforward conventional choice for many non-nuclear duties.
Yes. A multi-turn actuator such as MXb, L120 or SMB can be coupled to a quarter-turn worm gearbox such as WG or HBC. The gearbox converts the multi-turn actuator output into the required quarter-turn motion while multiplying torque and setting the desired operating time.
Both are worm-gear operator families. WG covers a much higher torque range in the supplied literature and includes modern AWWA, buried and IP68 submersible configurations. HBC is a proven long-installed platform with strong power-generation, damper and process-industry history. For new very-high-torque packages, WG is usually the natural starting point; for existing HBC installations or application-specific compatibility, HBC remains important.
Both are bevel gear operators for multi-turn applications. B320 is a rugged manual-or-motorized bevel gear operator with ratings to 8,000 ft-lb and 325,000 lb thrust in the supplied brochure. V Series covers a broader high-capacity range, and V_H versions extend into extremely high thrust and torque. The correct choice depends on required output, stem capacity, ratio, mounting and manual-operating requirements.
LPC is the compact Scotch-yoke platform, covering torque to 5,500 Nm in the supplied brochure. LPS is the heavy-duty platform, covering torque through 300,000 Nm before factory-consult sizes. Both can be spring return or double acting and can be configured for on/off, modulating, ESD and safety-related service depending on project requirements.
At minimum: valve type and size, required torque or thrust, stem/drive dimensions, operating turns or travel, required stroke time, power supply or pneumatic pressure, failure position, duty cycle, control signal, area classification, ambient temperature and any required accessories or communication protocol. For pneumatic valves, provide the full valve torque profile and MAST when available.
The supplied MX/QX Series B literature includes MXFS and QXFS electrically operated mechanical fail-safe configurations that add independent spring-stored energy to the smart electric platform. Pneumatic LPC/LPS spring-return actuators are also conventional fail-safe solutions where instrument air is available.
Source & disclaimer: compiled/adapted from E4 Industrial’s “Limitorque Valve Automation” guide (e4industrial.com); output ranges and ratings as summarized there from Flowserve product literature (MX/QX Series B, L120, SMB, LPC, LPS, WG, HBC, V Series, B320). Limitorque and Flowserve are registered trademarks of Flowserve Corporation, used here for product identification only. Ratings and certifications are configuration-dependent and may change — final sizing per the Flowserve documentation shipped with the unit.
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