AUMA SAR 25.1 Modulating Multi-Turn Actuator

Overview

AUMA SAR 25.1 is an AUMA NORM multi-turn actuator for modulating duty (class C, ISO 22153) with a tripping-torque window of 1,000 to 2,000 Nm and 4 output speeds from 4 to 11 rpm. SAR 25.1 is the first modulating AUMA actuator of the heavy 25.1 generation, with a 1,000 to 2,000 Nm tripping-torque window, 800 Nm of modulating torque at S4-25 percent, an F25 flange and a 95 mm stem bore. It weighs approximately 150 kg.

The AUMA SAR 25.1 is supplied by Seven Star LLC, a trusted AUMA supplier for Oman and the GCC, with correct documentation and a regional contact for commissioning.

Operating Principle

A slow modulating actuator, the SAR 25.1 receives short pulses from an AM or AC positioner and holds position by self-locking. Duty is S4 – 25 percent, class C, with 800 Nm modulating torque, 300 starts per hour and a 100 ms minimum pulse.

Engineering Design of the AUMA SAR 25.1

The standard enclosure is IP67 with IP68 as an option, and AUMA states that modulating duty is not possible during immersion. The motor connection is made in a separate terminal compartment. Because the SAR 25.1 is only available at slow speeds, response to set-point changes is slower than on smaller modulating sizes.

Key Features

Specifying the AUMA SAR 25.1 comes down to these points:

• Heavy modulating multi-turn actuator, 1,000 to 2,000 Nm.
• Adjustment range: 1,000 to 2,000 Nm per direction, a ratio of 2.0 to 1 between lowest and highest setting.
• Under S4 – 50 percent duty the limit is 1,400 Nm, which is 70 percent of the top tripping value.
• Power density works out at roughly 13.3 Nm of maximum torque per kilogram.
• An illustrative stroke of 55 turns takes about 412 seconds at 8 rpm.
• In torque class it ranks above the SAR 16.2 and below the SAR 30.1.
• Dimension drawings and electrical data are covered by separate AUMA sheets.

Selecting the AUMA SAR 25.1

The AUMA SAR 25.1 differs from the SAR 16.2 in several practical ways. The output speed list is short, 4 to 11 rpm only (and 4 and 5.6 rpm are on request). Starts per hour are limited to 300, the pulse duration is at least 100 ms, and the reversal pulse runs from 275 ms at 4 rpm to 130 ms at 11 rpm. Modulating torque is 800 Nm at S4-25 percent and 700 Nm at S4-50 percent.

Typical partners are large control gate valves, heavy angle and globe control valves, sluice gates used for flow and level regulation and large regulating valves in water transmission systems.

A SAR 25.1 is typically bought for a handful of critical regulating points, and its slow speeds, 4 to 11 rpm, are a feature rather than a limitation. Level and flow control gates should not move abruptly, and the long stroke time suppresses water-hammer. Because only 300 starts per hour are permitted, the controller dead band and the filter time constants should be set so that the actuator moves in a few larger steps, not in constant small corrections. When the plant is commissioned, record the as-found modulating torque at several stroke positions as a baseline for later maintenance. During commissioning, record the as-found position feedback and the torque trace for a full stroke, store them with the plant documents, and repeat the measurement at each shutdown, because slowly rising torque is an early warning of packing or stem problems.

Sizing example for the AUMA SAR 25.1

Consider an illustrative regulating gate that needs 700 Nm running torque and 1,500 Nm at the seat. The running torque is under the 800 Nm modulating limit at S4-25 percent, and the seat torque lies within the 1,000 to 2,000 Nm window of the AUMA SAR 25.1. A 60-turn stroke at 8 rpm takes 450 seconds and at 11 rpm about 327 seconds, so a 1 percent change in position takes 3 to 4.5 seconds, which is long enough that the minimum pulse of 100 ms does not limit resolution. These numbers are an illustrative calculation and not AUMA data.

Installation and Mounting of the AUMA SAR 25.1

At approximately 150 kg the AUMA SAR 25.1 needs crane lifting and a verified mounting structure. The F25 flange takes a stem up to 95 mm, the 400 mm handwheel is used for setting and emergency operation, and the enclosure is IP67 as standard, so specify IP68 where flooding is possible. Remember that modulating duty is not possible while the actuator is submerged.

Industrial Applications

Applications in the Gulf include the regulation of large cooling-water flows, flow-control gates at reservoir outlets and level control at wastewater plants. For Omani utilities, a SAR 25.1 on a reservoir or pumping-station regulating valve provides precise continuous positioning that an open-close SA 25.1 cannot offer.

Projects often pair the SAR 25.1 with the AUMA SAR 14.1 multi-turn actuator, the AUMA MATIC AM/AC integral actuator controls and the AUMA SAREx explosion-proof modulating actuator, all available from Seven Star LLC as trusted AUMA supplier.

Neighbouring sizes and counterparts: AUMA SAR 16.2 modulating actuator, AUMA SAR 30.1 modulating actuator, AUMA SA 25.1 multi-turn actuator and AUMA SAREx 25.1 explosion-proof modulating actuator.

Technical Specifications

Data of the AUMA SAR 25.1 from the AUMA technical data sheet for 3-phase AC motors.

Setpoint guide for the SAR 25.1 (illustrative calculation, not AUMA data)

Stroking time for 55 turns at the SAR 25.1 (illustrative calculation, not AUMA data)

Request a Quote for AUMA SAR 25.1

Planning a project around the AUMA SAR 25.1? Submit an RFQ listing quantities, supply voltage and valve data, and download the AUMA datasheet from this page.