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Limitorque® Valve Actuators & Gear Operators | Flowserve Valve Automation
Limitorque® Valve Actuators & Gear Operators
Electric, Pneumatic, Multi-Turn & Quarter-Turn
Valve actuation for isolation, modulating, emergency shutdown, waterworks, power, refining, chemical, pipeline and severe-service applications. From MXb and QXb smart electric actuators to L120 and SMB electromechanical workhorses, LPC and LPS pneumatic Scotch-yoke actuators, and Limitorque gear operators for high-torque and high-thrust valve packages.
Limitorque® is Flowserve®'s established valve actuation platform for electric actuators, pneumatic actuators, gear operators, controls and severe-duty valve automation. The range spans intelligent non-intrusive electric actuation, conventional electromechanical multi-turn actuators, compact and heavy-duty pneumatic Scotch-yoke actuators, and manual or motorized worm and bevel gear operators.
For most new electric valve automation projects, the starting point is the MXb for multi-turn service and the QXb for direct quarter-turn service. For proven electromechanical architecture and installed-base replacement, the L120 remains a major platform. For the most demanding severe-duty and nuclear-oriented applications, the SMB remains one of the industry's best-known heavy-duty multi-turn actuator families. Pneumatic quarter-turn service is covered by the compact LPC and heavy-duty LPS Scotch-yoke ranges.
Limitorque gear operators extend those actuator families into much larger torque and thrust duties. WG and HBC worm gear operators adapt multi-turn electric actuators to quarter-turn valves and dampers. V Series and B320 bevel gear operators provide mechanical advantage for multi-turn gate, globe, sluice and slide-gate applications.
If you already know the valve type, required torque or thrust, stem dimensions, power supply, operating time and failure position, call 281.664.8000 or email sales@e4industrial.com and E4 Industrial can review the application and build a selection package for quotation.
Limitorque® is a Flowserve® brand.E4 Industrial sizes, specifies and supplies complete Limitorque actuation packages.
E4 Industrial is an independent supplier. Limitorque® products referenced on this page are sourced through authorized Flowserve® distributors. Specifications shown are summarized from Flowserve product literature for identification and selection purposes.
E4 Industrial supports Limitorque applications with valve torque and thrust review, actuator and gearbox sizing, mounting-interface review, coupling and stem-nut requirements, actuator-speed selection, control and accessory definition, replacement identification, and commissioning support. Contact E4 for current availability, pricing and lead time.
Where To Start In The Limitorque® Product Line
The catalog is broad, but the core application logic is straightforward. Start with valve motion, required output, power source, failure mode and duty.
Smart Electric Actuation
Use MXb when the valve is multi-turn or linear and the application benefits from non-intrusive setup, electronic torque sensing, absolute position feedback, advanced diagnostics and plant-network integration. Use QXb when the valve is inherently quarter-turn and direct mounting is preferred. Both platforms share modern control architecture, high-resolution local indication, Bluetooth capability, built-in diagnostics and multiple network protocol options.
Conventional Electromechanical Actuation
Use L120 where a rugged, conventional multi-turn actuator is preferred or where an existing installed base makes like-for-like serviceability important. Use SMB where extreme mechanical durability, very high output capability, long service life or nuclear/severe-duty pedigree drives the selection.
Pneumatic Quarter-Turn Actuation
Use LPC for compact to medium quarter-turn ball, butterfly and plug valves. Use LPS when torque requirements, valve size, service severity or safety requirements move beyond the compact range. Both are modular Scotch-yoke designs available in spring-return and double-acting configurations.
Gear Operators
Use a WG or HBC worm gear when a multi-turn actuator needs to operate a quarter-turn valve, damper, radial gate or similar device. Use a V Series or B320 bevel gear operator when a gate, globe, sluice or slide gate requires additional mechanical advantage, thrust capacity, manual operation, or a geared interface to an electric actuator.
Limitorque® Product Comparison
A practical selection matrix for the main actuator and gear-operator families covered on this page.
| 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 |
Ratings vary by model, speed, ratio, mounting base, duty, spring configuration, temperature and other options. Final selections must be checked against current factory-certified data.
Limitorque® Smart Electric Actuators
MXb and QXb are the modern non-intrusive smart-electric platforms for multi-turn and quarter-turn valve automation.
Limitorque MXb
Smart Non-Intrusive Multi-Turn Electric Actuator
MXb is Limitorque's smart multi-turn electric platform for direct operation of rotary multi-turn valves and for geared quarter-turn or high-thrust packages. It combines absolute position feedback, electronic torque sensing, non-intrusive local controls, advanced diagnostics, multiple communication options and a double-sealed enclosure.
- 18-bit absolute encoder with more than 10,000 drive-sleeve rotations and no position battery backup requirement
- Electronic torque sensing for valve control, overload protection and torque trending
- High-resolution multilingual LCD with local graphs, logs, torque and condition information
- Bluetooth LE capability for FlowSync configuration and diagnostic access
- IP68 double-sealed enclosure with separate terminal compartment; NEMA 4, 4X and 6 capability
- Network options include Modbus, Profibus DP/PA, TCP/IP, Foundation Fieldbus H1, HART and DeviceNet in the supplied literature
- Can be paired with WG/HBC worm gearing for quarter-turn valves or V/B320-type bevel gearing for high-thrust multi-turn applications
| Models | MXb-05, -10, -20, -40, -85, -140, -150 |
| Rated Torque | Up to 2,307 Nm (1,700 ft-lb), dependent on frame and output speed |
| Thrust | Up to 333 kN (75,000 lb) with listed thrust-base configurations |
| Interfaces | MSS SP-102 / ISO 5210 mounting configurations |
Limitorque QXb
Smart Non-Intrusive Quarter-Turn Electric Actuator
QXb brings the MXb smart-control architecture to direct quarter-turn applications. Its brushless DC motor and solid-state motor controller allow a broad range of customer-supplied electrical power while the absolute encoder, electronic torque sensing and local diagnostics provide precise position control without a separate gearbox on most normal quarter-turn duties.
- Direct actuation of ball, butterfly, plug valves and dampers
- Redundant 12-bit absolute encoder over 360° using contactless Hall-effect technology
- Brushless DC motor for long life, low mechanical/electrical noise and accurate positioning
- Mechanical stop bolts for 90° movement
- Shared MXb electronics, multilingual display, diagnostics, Bluetooth and communication options
- Multiple speed selections; alternate open/close speeds are standard on QXb according to supplied literature
| Models | QXb-1 through QXb-5 |
| Rated Seating Torque | 136 to 2,033 Nm (100 to 1,500 ft-lb) |
| Operating Time | Model-dependent operating times from approximately 5 to 120 seconds in listed configurations |
| Interfaces | MSS SP-101 / ISO 5211 base options |
Limitorque® Electromechanical Multi-Turn Actuators
L120 and SMB are conventional, mechanically rugged electric actuator platforms with enormous installed bases and broad gearbox compatibility.
Limitorque L120
Proven Multi-Turn Electric Valve Actuator
The L120 is a durable electromechanical multi-turn actuator for petrochemical, power-generation, water and wastewater applications. It can direct-mount to multi-turn valves, operate rising-stem valves through bevel or spur gearing, or drive quarter-turn valves and dampers through WG or HBC worm gearboxes.
- Eight principal actuator sizes in the supplied performance tables: L120-10 through L120-2000
- Torque and position protection through geared limit switches and torque switches
- Manual handwheel/declutch with automatic return to motor operation
- Weatherproof, submersible and explosion-proof configurations listed in product literature
- Direct torque-only and thrust-base configurations; MSS mounting standard with ISO options
- Conventional controls through smart/network packages depending configuration
| Direct Torque | 100 to 20,000 ft-lb in the supplied L120 performance table |
| Direct Thrust | 10,000 to 500,000 lb depending model |
| Geared Packages | WG/HBC combinations for quarter-turn; V/SR combinations for rising-stem/high-thrust duties |
| Submersible | NEMA 6 / IP68 configurations listed |
Limitorque SMB
Heavy-Duty Multi-Turn Electric Actuator
SMB is Limitorque's classic heavy-duty multi-turn actuator for applications where mechanical strength, service life and severe-duty capability are more important than compact size. The platform uses rugged cast or ductile-iron housings, double-reduction gearing, torque limiting and geared position limiting, with commercial, explosion-proof and nuclear-oriented configurations.
- Double-reduction helical and worm gearing with alloy bronze worm gear and heat-treated steel gearing
- "Hammer-blow" feature allows the motor to reach speed before engaging load for high seating/unseating demand
- Automatic torque-limiting protection against valve obstruction
- Insertable stem nut simplifies actuator relocation and service
- SB and SBD spring-compensated versions for high-temperature or high-speed torque-seated service
- Extensive nuclear qualification history and severe-service installed base
| Commercial Range | SMB-000 through SMB-5 / 5T, plus SMB-5XT high-torque configuration |
| Torque | Commercial table through 20,000 ft-lb; SMB-5XT listed to 60,000 ft-lb |
| Thrust | Up to 500,000 lb on listed thrust-capable models |
| Gearbox Use | HBC/WG for quarter-turn; V and other gearheads for multi-turn/high-thrust applications |
Limitorque® Pneumatic Scotch-Yoke Actuators
LPC covers compact quarter-turn pneumatic service. LPS extends the same basic Scotch-yoke philosophy into very large, heavy-duty torque requirements.
Limitorque LPC
Compact Pneumatic Scotch-Yoke Actuator
LPC is a compact, modular Scotch-yoke actuator for small and medium ball, butterfly and plug valves. It is offered in spring-return and double-acting configurations with symmetric or canted yokes to match the valve's torque profile.
- Spring-return single-acting or double-acting execution
- Field conversion between fail-close CW and fail-open CCW configurations
- Symmetric and canted Scotch-yoke options
- Suitable for on/off, modulating, control, ESD and HIPPS-related applications
- Accessory options include switch boxes, positioners, ESD/PST functions, control panels, fire protection and manual overrides
- Standard literature lists SIL 3, ATEX, NEMA 4/4X, IP66/IP67, ISO 5211, NACE MR0175 and other compliance options depending configuration
| Models | LPC-05, -10, -12, -14 |
| Torque | 50 to 5,500 Nm (37 to 4,057 ft-lb) |
| MAWP | 12 barg (174 psig) |
| Temperature | Standard -29°C to 100°C (-20°F to 212°F); special low/high-temperature configurations listed |
Limitorque LPS
Heavy-Duty Pneumatic Scotch-Yoke Actuator
LPS is the heavy-duty pneumatic platform for large quarter-turn valves and safety-related process applications. Its modular fabricated-steel construction supports spring-return and double-acting configurations, symmetric or canted yoke geometry, high torque and broad environmental options.
- Modular CW/CCW, fail-open/fail-close configuration flexibility
- Fabricated carbon-steel center body, pressure module and spring module
- On/off, modulating, control, ESD and HIPPS-related service capability
- Symmetric and canted Scotch-yoke options to match valve torque demand
- Adjustable travel stops ±5°
- Accessory options for position indication, ESD, PST, line-break functionality, manual/hydraulic override, control panels and fire protection
- Supplied literature lists SIL 3, ATEX, IP66/IP67, NEMA 4/4X, ISO 5211, NACE MR0175 and pressure-vessel compliance options depending build
| Models | LPS-15 through LPS-60 |
| Torque | 6,000 to 300,000 Nm (4,425 to 221,268 ft-lb) through LPS-50; LPS-60 consult factory |
| MAWP | 12 barg (174 psig) |
| Temperature | Configurations listed from -60°C (-76°F) to 160°C (320°F) |
Limitorque® Gear Operators
Gear operators are not secondary accessories. They are what allow a correctly selected Limitorque actuator to reach the torque, thrust, speed and valve-interface requirements of much larger valves and gates.
Limitorque WG Series
High-Torque Worm Gearboxes
WG worm gearboxes are designed for manual or motorized operation and are the primary high-torque gearing platform in the supplied literature. When motorized by MX, L120 or SMB actuators, the WG provides a reliable quarter-turn or multi-turn process-control package while maintaining self-locking mechanical advantage.
- Up to 970,000 Nm (715,435 ft-lb) torque output capability in listed range
- Self-locking gearing and high mechanical advantage
- Lubricated for life
- 90° ±5° adjustable quarter-turn travel; 360° operation available
- Buried-service and IP68 submersible configurations
- Ductile-iron enclosure with bronze or ductile-iron worm gear options
- Meets AWWA C504 manual requirements and AWWA C542 when motorized in the listed configurations
| Primary Use | Quarter-turn torque multiplication and rotary process-control service |
| Motorized By | MX / MXb, L120 or SMB actuator packages |
| Environment | Weatherproof, buried and submersible applications |
Limitorque HBC Series
Proven Worm Gear Operators
HBC is a long-established worm-gear platform for manual or motorized quarter-turn operation. It is widely associated with power-generation, refinery, transmission, damper and water applications and can be paired with SMB, L120 or MX electric actuators.
- Manual operation with optional handwheel or motorized operation with Limitorque electric actuators
- Output torque ratings to 93,000 ft-lb (126,204 Nm) in listed HBC-7M configurations
- Optional spur-gear attachments reduce input torque and can enable smaller electric actuators
- Optional 360° worm gear for guillotine dampers and radial gates
- Cast-iron housing, alloy-steel worm shaft and bronze worm gear
- All HBCs described as built to meet AWWA requirements in the supplied literature
| Models | HBC-0 through HBC-7 / 7M |
| Motorized By | MX, L120 or SMB |
| Motion | Quarter-turn standard applications; 360° option for selected duties |
Limitorque V Series
Multi-Turn Bevel Gearboxes
V Series bevel gearboxes provide mechanical advantage for multi-turn valves and gates. They are available for manual operation or can be motorized with MX, L120 or SMB actuators. The V_H variants extend the platform into very high-thrust and high-torque duties.
- Ductile-iron housing with roller-bearing-supported drive sleeve, bevel pinion and optional spur-gear shafts
- Weatherproof and temporary submersion construction to IP67 in supplied literature
- Maintenance-free design
- MSS SP-102 input flanges; MSS mounting standard with ISO options
- Removable splined bronze-alloy stem nut for thread machining
- Optional spur-gear attachments reduce input torque and handwheel rim pull
- V_H high-capacity versions available for very large thrust and torque requirements
| High-Capacity Rating | V_H listed through 2.585 million lb thrust and 104,734 ft-lb torque |
| Motorized By | MX, L120 or SMB |
| Temperature | -35°C to 90°C continuous listed; options to -50°C |
Limitorque B320 Series
Bevel Gear Operators
B320 bevel gear operators provide mechanical advantage for multi-turn actuation and are designed to be easy to operate manually and easy to convert to motorized service. A broad range of standard sizes, handwheels, chainwheels, spur-gear attachments and operating-wrench options make the platform useful for valve and gate packages that need a simple, rugged gearbox.
- Manual or motorized operation
- High-strength alloy-steel gearing with low-friction bearings
- Permanently lubricated and waterproof construction
- Weatherproof NEMA 4 and temporary-submergence NEMA 6 / IP67/68 configurations listed
- Removable bronze-alloy stem nut for threading or custom bore/key
- Optional spur-gear attachments for lower input torque
- Direct mounting to electric valve actuators for economical motorized packages
| Models | B320-20 through B320-90 |
| Output Torque | Up to 8,000 ft-lb (10,856 Nm) |
| Thrust | Up to 325,000 lb (1,446 kN) |
Common Limitorque® Actuator + Gearbox Configurations
The actuator supplies controlled input torque and speed. The gearbox converts that input into the torque, thrust, stroke and valve interface the application actually requires.
MXb Direct
Gate and globe valves, wedge gates and other multi-turn applications when direct torque/thrust ratings and mounting geometry are adequate.
QXb Direct
Ball, butterfly, plug valves and dampers within the direct quarter-turn torque and base limits of the QXb frame.
MXb + WG / HBC
Large quarter-turn ball, butterfly, plug valves and dampers that exceed direct QXb torque or need a particular operating time.
L120 + WG / HBC
Conventional electromechanical motorization of quarter-turn valves and dampers where an L120 architecture is preferred.
SMB + WG / HBC
Heavy-duty and severe-service quarter-turn packages requiring the mechanical robustness of an SMB with worm-gear torque multiplication.
MXb / L120 / SMB + V
Multi-turn gate, globe, sluice and slide-gate applications requiring additional torque, thrust, ratio or manual mechanical advantage.
How We Size A Limitorque® Valve Actuation Package
The actuator model number comes last. The valve load, duty, power, environment, speed and failure philosophy come first.
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, electrical supply, pneumatic pressure, gear ratio, temperature and operating mode. For pneumatic Scotch-yoke actuators, the output curve is intentionally non-linear and must be checked against the valve demand at multiple points through the stroke. For motorized gear operators, gearbox input torque, output torque, ratio, mechanical efficiency and operating time all have to agree with the selected actuator.
Information Needed For Electric Actuators
- Valve manufacturer, type, size, pressure class and tag number
- Required running, seating/unseating torque or thrust; MAST/MAT where applicable
- Stem diameter, thread, keyway, square drive or other output interface
- Required turns or quarter-turn travel
- Required opening and closing time
- Available voltage, phase and frequency
- On/off, inching or modulating duty and expected starts/hour
- Control signal: discrete, 4-20 mA, network protocol, ESD/inhibit requirements
- Area classification, enclosure rating, ambient temperature and submergence/buried requirements
- Local controls, indication, remote feedback and communications
Information Needed For Pneumatic Actuators
- Break-to-open (BTO), running-to-open (RTO), end-to-open (ETO)
- Break-to-close (BTC), running-to-close (RTC), end-to-close (ETC)
- Valve maximum allowable stem torque (MAST)
- Fail-safe direction: fail close, fail open or fail last/as-is
- Minimum, normal and maximum pneumatic supply pressure
- Project safety factor and any safety-instrumented requirements
- Ambient/operating temperature range
- Required opening and closing times
- Switch box, solenoid, positioner, PST, ESD, manual override or control-panel requirements
- Corrosion category, offshore/sour-gas or special material requirements
MXb & QXb Smart Control, Diagnostics & Communications
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
- Direct-wired open / stop / close control alternatives
- Digital, analog and network control modes
- Emergency shutdown inputs, configurable user inputs and inhibit signals
- Status contacts and monitor relay
- Autophase protection/correction on applicable three-phase configurations
- Jammed-valve, instantaneous-reversal and motor-thermal protection
- LimiGard circuit monitoring with built-in self-test functions
Diagnostics & Connectivity
- Time-stamped event and alarm logging
- Torque, travel, cycle-count, temperature and vibration diagnostics
- Local high-resolution display with real-time and historical graphs
- Bluetooth LE for FlowSync monitoring and configuration
- Network options listed for Modbus, Profibus DP/PA, TCP/IP, Foundation Fieldbus H1, HART and DeviceNet
- IoT / RedRaven compatibility described in the Series B literature
Mounting Standards, Enclosures & Certifications
Limitorque® products span many industries and certification regimes. The exact approval set is product- and configuration-specific.
Valve interfaces: MXb literature references ISO 5210 and MSS SP-102 for multi-turn interfaces; QXb references ISO 5211 and MSS SP-101 for quarter-turn bases. LPC and LPS literature references ISO 5211 valve interfaces. Gearbox literature includes MSS and ISO mounting options depending product and size.
Enclosures: MXb/QXb Series B literature describes IP68 double-sealed enclosures and NEMA 4, 4X and 6 capability. L120 literature includes weatherproof, submersible and explosion-proof configurations. WG literature includes buried-service and IP68 submersibility. HBC includes buried and submersible service designs. V Series literature lists IP67 temporary submersion service. B320 literature lists NEMA 4 and NEMA 6 / IP67/68 configurations.
Pneumatic safety and hazardous-area compliance: LPC and LPS literature includes SIL 3 certification to IEC 61508, ATEX certification, NEMA 4/4X, IP66/IP67 configurations, ISO 5211, corrosion-protection standards and NACE MR0175 availability, along with pressure-vessel compliance options depending configuration.
Waterworks: WG literature states compliance with AWWA C504 for manual operation and AWWA C542 when motorized with listed Limitorque actuators. HBC literature states the series is built to meet AWWA requirements. L120 literature describes AWWA suitability for water and wastewater applications.
Nuclear / severe duty: SMB has extensive nuclear-qualified configurations and historical use in reactor-containment and naval applications. HBC literature also describes tested SMB/HBC combinations for nuclear environmental and seismic service.
Where Limitorque® Is Commonly Applied
The product family is broad because the valve duties are broad. Limitorque literature specifically emphasizes energy, power, water and process-industry applications.
Oil & Gas / Midstream
Pipeline isolation, tank farms, terminals, wellheads, large ball valves, ESD valves and severe remote service.
Refining & Petrochemical
Process isolation, cokers, critical MOVs, dampers, ESD/HIPPS-related applications and hazardous-area valve automation.
Power Generation
Nuclear and fossil service, high-pressure steam, dampers, FGD systems, safety-related valve applications and cooling-water systems.
Water & Wastewater
Large butterfly valves, gates, penstocks, buried/submersible operators, treatment plants, dams and distribution infrastructure.
Chemical & General Industry
Automated isolation, modulating valves, packaged equipment, process skids, utilities and hazardous-area service.
Infrastructure & Heavy Industry
Dams, flood gates, mining, metals, pulp and paper, steam systems, large sluice/slide gates and mechanical devices requiring controlled rotary or linear motion.
What E4 Industrial Can Do On A Limitorque® Project
We treat the actuator, gearbox, valve interface and control requirement as one mechanical package rather than four separate purchase orders.
Application Engineering
- Valve torque and thrust review
- Actuator-frame and output-speed selection
- Pneumatic spring-return / double-acting sizing
- Gearbox ratio, input-torque and output-torque review
- MAST / maximum stem load verification
- Duty-cycle, starts/hour and operating-time review
- Environmental, enclosure and hazardous-area configuration review
Package Integration & Support
- Valve-to-actuator mounting interface review
- Stem nut, coupling, keyway and drive-sleeve definition
- Accessory and control-package specification
- Replacement and retrofit identification for existing Limitorque units
- Submittal-package and project documentation support
- Commissioning and field troubleshooting support
- Commercial sourcing, pricing and lead-time coordination
Limitorque® Valve Actuation FAQ
The questions that usually decide the product family before detailed sizing begins.
What is the difference between Limitorque MXb and QXb?
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.
When would I choose L120 instead of MXb?
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.
What is the difference between SMB and L120?
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.
Can an MXb or L120 operate a butterfly or ball valve?
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.
When should I use WG instead of HBC?
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.
What is the difference between V Series and B320?
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.
What is the difference between LPC and LPS pneumatic actuators?
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 project requirements.
What information does E4 need to size a Limitorque actuator?
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.
Does Limitorque offer fail-safe electric actuation?
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.
Need A Limitorque® Actuator Sized?
Send us the valve datasheet, torque/thrust requirement, stem details, power or air supply, failure position and required operating time. E4 Industrial will review the application, identify the actuator and gearbox configuration, and return the information needed for a commercial quote.
Technical NoteLimitorque is a registered trademark of Flowserve Corporation. Flowserve is a registered trademark of Flowserve Corporation. Marks are used here for product identification only.
Product descriptions and performance values on this page are summarized from Flowserve® Limitorque® product literature supplied for MX/QX Series B, L120, SMB, LPC, LPS, WG, HBC, V Series and B320. Specifications, certifications, options and product availability are configuration-dependent and may change. Final sizing and selection should be confirmed against current manufacturer data and the specific valve application before purchase.
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