AUMA SAR 07.6 Modulating Multi-Turn Actuator

Overview

AUMA SAR 07.6 is an AUMA NORM multi-turn actuator for modulating duty (class C, ISO 22153) with a tripping-torque window of 30 to 60 Nm and 10 output speeds from 4 to 90 rpm. SAR 07.6 gives AUMA’s compact modulating actuator frame 30 to 60 Nm of tripping torque and 30 Nm of modulating torque at S4-25 percent, twice that of the SAR 07.2 while keeping the same F07 and F10 flange and 160 mm handwheel.

Seven Star LLC supplies AUMA products across Oman and the GCC, and supplies the SAR 07.6 with local technical support from Muscat.

Operating Principle

On the SAR 07.6, the positioner sends short pulses and the actuator holds each position by self-locking. S4 – 25 percent duty, class C, allows 30 Nm modulating torque at 4 to 45 rpm, easing to 20 Nm at 63 to 90 rpm, with a 50 ms minimum pulse.

Engineering Design of the AUMA SAR 07.6

AUMA lists up to 1,500 starts per hour, a minimum pulse of 50 ms and a reversal pulse of 60 to 260 ms depending on speed. The optional S5-25 percent duty requires insulation class H. Always pair the actuator with AUMA MATIC AM or AUMATIC AC controls, since the AUMA NORM version requires external electric controls.

Key Features

Points to weigh when specifying the AUMA SAR 07.6:

• Modulating multi-turn actuator, doubled torque in the compact housing.
• Choose any trip value between 30 and 60 Nm; the span from smallest to largest setting is 2.0 to 1.
• Switching to S4 – 50 percent duty reduces the ceiling to 40 Nm (67 percent of the maximum).
• Each kilogram of actuator mass corresponds to about 2.9 to 3.0 Nm of maximum torque.
• An illustrative stroke of 18 turns takes about 49.1 seconds at 22 rpm.
• Torque class: between the SAR 07.2 (below) and the SAR 10.2 (above).
• For dimensions and wiring data, refer to AUMA’s dedicated sheets for this size.

Selecting the AUMA SAR 07.6

The AUMA SAR 07.6 is distinguished from the SAR 07.2 by torque only: the weight is quoted at 20 to 21 kg instead of 19 to 20 kg and the interfaces are identical. Its modulating torque steps down from 30 Nm to 20 Nm at 63 and 90 rpm in S4-25 percent duty, and from 20 Nm to 15 Nm in S4-50 percent duty, so fast positioning on a stiff valve reduces the torque available. For most control valves a medium speed of 8 to 22 rpm is the best compromise between response time and torque margin.

Typical partners are small and medium globe control valves, modulating gate valves, rising-stem control valves for steam conditioning and attemperation, and flow-control valves in chemical dosing and mixing lines.

On a small control valve the friction of the packing is a large part of the total running torque. When a PTFE chevron packing is replaced with graphite on a steam valve, the running torque can rise and so can the stick-slip effect that causes a modulating actuator to overshoot. The AUMA SAR 07.6 has 30 Nm of modulating torque at S4-25 percent, so there is room to accept a stiffer packing than the 15 Nm of the SAR 07.2 would allow. Compare the running torque of the valve at 25 percent, 50 percent and 75 percent of stroke, because modulating duty is determined by the worst of these points.

Sizing example for the AUMA SAR 07.6

Take an illustrative control valve that needs 25 Nm running torque and 48 Nm at the seat. The running torque is within the 30 Nm modulating limit for S4-25 percent up to 45 rpm, and the seat torque falls inside the 30 to 60 Nm window. At 63 or 90 rpm the modulating limit falls to 20 Nm (S4-25 percent), so the valve would be outside the permitted range, which makes 22 rpm a better selection. A 15-turn stroke at 22 rpm takes about 41 seconds. These numbers are an illustrative calculation and not AUMA data.

Installation and Mounting of the AUMA SAR 07.6

The 20 to 21 kg AUMA SAR 07.6 fits the same F07 and F10 valve interfaces as the SAR 07.2, so existing yokes and adapters can be reused. Mount it so that cable glands point down, protect the 160 mm handwheel from being used as a step, and make sure the position transmitter, potentiometer or 0/4 – 20 mA, is specified with the order since it cannot easily be added when the controls are fitted later.

Industrial Applications

Typical Omani applications are condensate and feed-water control on package boilers, cooling-water temperature control valves for compressors and gas turbines, and mixing valves in district-cooling energy centres. Plant engineers in the Sohar and Salalah industrial zones also use the AUMA SAR 07.6 as a replacement for ageing modulating actuators when the valve flange is F07 or F10.

Projects often pair the SAR 07.6 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 07.2 modulating actuator and AUMA SA 07.6 multi-turn actuator.

Technical Specifications

Data of the AUMA SAR 07.6 from the AUMA technical data sheet for 3-phase AC motors.

Setpoint guide for the SAR 07.6 (illustrative calculation, not AUMA data)

Stroking time for 18 turns at the SAR 07.6 (illustrative calculation, not AUMA data)

Request a Quote for AUMA SAR 07.6

Contact Seven Star LLC to buy the AUMA SAR 07.6 in the 30 to 60 Nm class. Share valve and positioner data, and download the AUMA datasheet from this page.