Flowserve Limitorque MXa Non-Intrusive Multi-Turn Actuator

Limitorque MXa non-intrusive multi-turn electric actuator: what it is

The MXa is the current non-intrusive multi-turn electric actuator from Flowserve Limitorque, built on the proven MX platform. It is a smart actuator: position is measured by a redundant absolute encoder, torque is measured electronically, and the setup and diagnostics are done through a local LCD and magnetic control knobs without opening the covers. Seven Star LLC supplies MXa actuators in Oman and the GCC as an independent supplier in Muscat. The MXa is a family. The frame, voltage, base type, communication card and approvals are chosen for each valve.

The maker lists torque from 20 ft-lb up to 1,700 ft-lb of output torque on the MXa itself, and higher torque is possible when a gearbox is added. It is built for power, oil and gas and water services and is available in weatherproof, explosion-proof and submersible forms.

MXa technical specifications

Certification applies to the specific build and is shown on the nameplate. State the area classification when you ask for a quotation so the correct version is quoted.

How the MXa works

A motor drives a hardened alloy steel worm and bronze worm gear, which is oil-bath lubricated, and the output passes through a removable torque or thrust bushing to the valve stem. In the maker’s MX platform description, the electronics sit in a double-sealed enclosure with a separate terminal chamber, so site wiring does not expose the control boards. Torque is limited electronically with an adjustable setting, and a boost function helps unseating and cold starts, with jammed-valve detection that retries automatically.

The encoder measures position all the time, including during handwheel operation and with the power off, and it stores the end positions in non-volatile memory. A declutch lever and handwheel provide manual operation, and the handwheel does not turn during motor operation. The actuator also keeps a record of diagnostics such as motor, contactor and cycle data and a torque profile of the valve stroke.

MX-series sizes and ratings for the MXa family

The maker’s MX performance sheet lists these frames, with output torque depending on output speed. Check the exact MXa frame and ratings on the quotation or nameplate, since this table is a guide to the size range.

Maximum stem capacity on a type A1 thrust coupling runs from 32 mm on the MX-05 and MX-10 sizes up to 88 mm on the largest frames, so confirm the valve stem diameter and thread early.

MXa linear base and control-valve duty

A linear base converts torque to linear thrust so that the MXa can drive control and choke valves. Two bases are available, LB1 and LB2, and thrust to 25,000 lb (109 kN) is stated. The MXa with LB1 or LB2 has been tested to the Class C modulating requirement of EN 15714. The maker gives the three-phase motor as S2 15 minutes with an option for S2 30 minutes, and maximum modulating capability as S4 50% at 1,800 starts per hour. Above 600 starts per hour, a solid-state starter is recommended. The MX-20 and MX-40 on an LB2 give seating thrust to 24,431 lb (109 kN) in the maker’s selection tables.

Where the MXa fits and related Limitorque actuators

The MXa is the multi-turn partner of the QX quarter-turn smart actuator, with the same type of interface and diagnostics. For simple quarter-turn work see the LQI. The older intrusive SMB covers heavy-duty gate and globe valve duty with higher thrust, while the MXa is the choice where network communication, diagnostics and non-intrusive setup are wanted.

Selection and ordering checklist for the MXa

• Valve type, stem diameter and thread, rising or non-rising stem.
• Seating and running torque and thrust, including unseating peaks.
• Required output speed or stroke time.
• Supply: three-phase voltage and frequency, single phase or DC.
• Base type: torque-only, thrust, linear base; flange MSS or ISO.
• On-off or modulating duty, with starts per hour.
• Network card and I/O needs, and ESD and inhibit functions.
• Area classification and ambient range, including any arctic option.

Installation, commissioning and maintenance of the MXa

Fit the correct base and stem nut to the valve, mount the actuator, and wire through the terminal chamber. Set the open and closed positions, torque limits and control mode from the LCD by answering the setup questions. Check motor rotation and the handwheel before releasing to operations. Maintenance focuses on lubricant condition per the maker’s manual, seals, conduit entries and stored diagnostic logs. A software dashboard for configuration and diagnostics exists; ask us for the reference if you need it.

Typical MXa applications in Oman and the GCC

In Oman the MXa suits pipeline and terminal gate valves, water transmission and desalination valves, steam and cooling-water isolation in power plants, and control or choke valves when fitted with a linear base. The sealed, non-intrusive design is helpful in heat, dust and humid coastal air, and the network options allow integration with plant DCS systems.

Information to send with an RFQ for the MXa

• Valve make, type, size, stem details and mounting flange.
• Torque and thrust demand and the output speed.
• Power supply, control voltage and communication protocol.
• Area classification and ambient temperature.
• Existing actuator nameplate if replacing a unit.
• Quantity and delivery location.

Documents and quotation

The maker’s MXa and QXM linear base brochure is attached on this page for the control-valve configuration. Other literature, such as installation instructions, is available on request.

Send the MXa frame, voltage and options to Seven Star LLC and we will prepare a quotation for Oman and the GCC.