Limitorque QXM Limited Multi-Turn Smart Electric Actuator

Overview

The Limitorque QXM is the limited multi-turn member of the QX family. It is aimed at valves that need only a few turns of the drive shaft, typically rising-stem choke valves and control valves with a short stroke and a modest torque demand. Instead of a pneumatic diaphragm or piston actuator with its air supply, positioner and tubing, the Limitorque QXM delivers positioning, diagnostics and fault protection from a single electric unit that keeps the smart features of the QX quarter-turn actuator and the MX multi-turn actuator.

For plants in Oman and the wider GCC, that matters in remote wellheads, metering skids and utility blocks where reliable instrument air is not always available. Seven Star LLC supplies the Limitorque QXM from Muscat with engineering support, and can help you check stroke, thrust and speed against the manufacturer table before you order. Typical enquiries come from oil and gas operators, power producers and water utilities replacing ageing pneumatic control-valve actuators.

Operating Principle of the Limitorque QXM

The Limitorque QXM turns a compact brushless DC motor through a gear train into a limited number of output turns, up to 20 turns according to the manufacturer flyer, at speeds of 6 to 24 rpm. Combined with those faster speeds, the torque range is matched to limited linear travel, so the drive can be fitted to a thrust base that converts rotation into stem movement. An A1 base can be attached for travel of up to 70 mm, and the flyer lists an MX-10 thrust base with 40 mm stem capacity and a 15,000 lb (66.7 kN) thrust rating.

Position is tracked by an absolute encoder built on system-on-chip technology, with a contactless magnet and Hall effect devices giving redundant 12-bit resolution over either 6.5 or 20 turns depending on the version. The encoder works without a battery, and the built-in self-test uses its redundancy to keep operating until faults accumulate. LimiGard fault protection is standard, so the actuator reacts predictably if a control element fails during modulating duty.

Engineering Design

Two motor versions give the Limitorque QXM a wide torque and speed envelope: an H version for higher torque and an L version for lower torque. The manufacturer flyer states a range from 18 ft-lb (24 Nm) to 250 ft-lb (337 Nm), with H-class insulation as standard and motor ratings to IEC 34 S2 15 minutes at 40 percent. Two frame sizes, QXM-1 and QXM-2, are listed, and the table in the flyer gives closing times for both 6.5 and 20 turns at each speed.

Because the motor is brushless, there are no brushes to wear and no sparks inside the housing, and the same unit accepts single-phase, three-phase and DC supplies. The design is non-intrusive, with the electronics sealed away from the gearing and the user interface operated through magnetically coupled knobs and a graphical display, so covers do not have to be opened to commission the unit. The display supports multiple languages and can be rotated 180 degrees, and optional Bluetooth connectivity lets technicians use Limitorque Dashboard software for diagnostics from a laptop or mobile device.

Key Features

Engineers selecting the Limitorque QXM for short-stroke electric actuation should note the following characteristics:

• A limited multi-turn output of up to 20 turns suits rising-stem choke and control valves with short travel.
• Output torque spans 18 to 250 ft-lb (24 to 337 Nm) through two motor versions and frame sizes QXM-1 and QXM-2.
• A battery-free absolute encoder with redundant 12-bit resolution holds position through power loss and manual operation.
• Modulating configurations are available to 1,800 starts per hour, with accuracy meeting EN 15714 Class D and IEC 60034 expectations for modulating service.
• Electromagnetic noise protection of the analogue process signals and an electronic torque switch increase reliability in busy electrical rooms.
• Weatherproof, explosion-proof and submersible applications are covered through the family certifications, which include FM, FM Canada, ATEX and IECEx marking per the flyer.
• Network options include Modbus, Foundation Fieldbus, Profibus DP or PA, DeviceNet, EtherNet/IP, PROFINET and HART.
• Lower operating cost than pneumatic actuation is claimed by the manufacturer, with the added advantages of electrical operation and no air consumption.

Industrial Applications

The typical home for the Limitorque QXM is the control valve or choke valve that was originally specified with a pneumatic actuator. In upstream oil and gas that includes wellhead chokes and test-separator control valves, while in power plants it includes feedwater, desuperheater and bypass control. Where compressed air is unreliable or expensive to run to a remote skid, an electric actuator removes the air line, the filter-regulator and the positioner from the maintenance list, and a replacement can be compared against the existing Masoneilan ACT-D/7 pneumatic spring-diaphragm actuator on cost of ownership.

Water and wastewater users in Muscat, Salalah and Sohar can use the Limitorque QXM on chemical dosing valves and flow-control valves where precise positioning is needed, and the linear-base option suits control valves that require exacting position. When an electrical-only solution is preferred for new projects, engineers can also review the AUMA SVC and SVCR globe valve actuator alongside it, and larger multi-turn duty can be handled by the Limitorque MX multi-turn actuator in the same family.

Technical Specifications

Data below is taken from the manufacturer QXM flyer; confirm the model code and options before ordering.

Request a Quote for Limitorque QXM

To obtain a quotation for the Limitorque QXM, send Seven Star LLC the valve stem travel, required thrust or torque, closing time and supply voltage. We will return a selection, share the official flyer on request and confirm availability from our Muscat base for Oman and GCC projects. Ask our instrumentation team about linear bases, spares and commissioning support so your Limitorque QXM actuators are ready on the day the control valve is.