AUMA SAR 07.2 Modulating Multi-Turn Actuator

Overview

AUMA SAR 07.2 is an AUMA NORM multi-turn actuator for modulating duty (class C, ISO 22153) with a tripping-torque window of 15 to 30 Nm and 10 output speeds from 4 to 90 rpm. SAR 07.2 is the smallest modulating AUMA SAR actuator. It combines a 15 to 30 Nm tripping-torque window with intermittent S4-25 percent duty, class C according to ISO 22153, for valves that must be positioned continuously rather than just opened and closed.

Seven Star LLC, a trusted supplier of AUMA products for Oman and the GCC, supplies the SAR 07.2 as genuine factory product and supports control-loop commissioning from its Muscat office.

Operating Principle

Short motor pulses from an AM or AC positioner move the SAR 07.2, which holds position by self-locking. Duty is S4 – 25 percent, class C, with a modulating torque of 15 Nm and up to 1,500 starts per hour at 4 to 45 rpm. The minimum pulse is 50 ms.

Engineering Design of the AUMA SAR 07.2

Starts per hour are limited to 1,500 up to 45 rpm and 1,200 at 63 and 90 rpm, with a minimum pulse duration of 50 ms. For reversal of rotation direction the motor must be powered for 260 ms at 4 rpm, shortening to 60 ms at 90 rpm, which should be considered in the positioner dead-band.

Key Features

Specifying the SAR 07.2 comes down to these points:

• Compact modulating multi-turn actuator for small control valves.
• Torque switches can be set from 15 up to 30 Nm, giving a 2.0:1 adjustment span.
• At 20 Nm the S4 – 50 percent figure sits at 67 percent of the highest tripping torque.
• Dividing the top torque by the quoted weight gives 1.5 to 1.6 Nm/kg.
• An illustrative stroke of 12 turns takes about 32.7 seconds at 22 rpm.
• It is the smallest torque class in this series and is followed by the SAR 07.6.
• Separate AUMA documents list the dimensions and the electrical data.

Selecting the AUMA SAR 07.2

A modulating actuator is specified differently from an open-close unit. For the AUMA SAR 07.2, the permissible torque during continuous positioning is only 15 Nm at S4-25 percent and 10 Nm at S4-50 percent, which is lower than the 30 Nm maximum tripping torque. The tripping torque protects the valve in the end positions; the modulating torque is what the valve must need while it is being throttled. Always compare the valve’s running torque, not its seating torque, with the modulating column.

Typical partners are small globe control valves, needle and stop valves used for flow regulation, small modulating gate valves and dosing valves where a rising-stem control element needs a 4 to 20 mA position set-point.

The first question on a modulating actuator is whether the valve really needs it. A small control valve that is moved only a few times per shift can run on a SA 07.2 with a simple open-close control, while the AUMA SAR 07.2 pays off when the loop acts every few seconds. In that case the position transmitter, the dead band of the positioner and the minimum pulse of 50 ms decide the accuracy. Setting the dead band too tight makes the actuator hunt and wastes motor life, so start with a dead band of about 0.5 to 1 percent of stroke and tighten only if the process requires it.

Sizing example for the AUMA SAR 07.2

Consider an illustrative small control valve that needs 12 Nm continuous running torque at the plug and 24 Nm at the seat. The running torque is below the 15 Nm modulating limit at S4-25 percent, and the seat torque is below the 30 Nm tripping limit, so the AUMA SAR 07.2 is suitable. Because the S4-50 percent limit is only 10 Nm, this valve cannot be run at the higher duty ratio. A 15-turn stroke at 11 rpm takes about 82 seconds, so 1 percent of stroke is moved in less than a second. These numbers are an illustrative calculation and not AUMA data.

Installation and Mounting of the AUMA SAR 07.2

At 19 to 20 kg the AUMA SAR 07.2 can be lifted by one technician. The F07 or F10 flange and the 26 or 34 mm stem bore suit small control valves, and the 160 mm handwheel is used for setting and emergency operation only. Always mount the actuator with the plug/socket connector pointing down or sideways, and combine it with AUMA MATIC AM or AUMATIC AC controls, because the AUMA NORM version needs external controls.

Industrial Applications

In Oman the AUMA SAR 07.2 suits desalination dosing skids, boiler blow-down and feed-water trim valves, district-cooling bypass valves in Muscat buildings and small flow-control valves at gas and utility stations in industrial estates. Its F07 and F10 interface and IP68 enclosure allow installation on compact skids without a protective cabinet.

Alongside the SAR 07.2, our genuine AUMA range includes the AUMA SAR 14.1 multi-turn actuator, the AUMA MATIC AM/AC integral actuator controls and the AUMA SAREx explosion-proof modulating actuator.

Neighbouring sizes and counterparts: AUMA SAR 07.6 modulating actuator and AUMA SA 07.2 multi-turn actuator.

Technical Specifications

Data of the AUMA SAR 07.2 from the AUMA technical data sheet for 3-phase AC motors.

Setpoint guide for the SAR 07.2 (illustrative calculation, not AUMA data)

Stroking time for 12 turns at the SAR 07.2 (illustrative calculation, not AUMA data)

Request a Quote for AUMA SAR 07.2

Send Seven Star LLC your valve data and loop requirements to receive a quotation for the AUMA SAR 07.2. The AUMA datasheet can be downloaded from this page.