AUMA GST 25.1 Spur Gearbox (2,000 Nm)

Overview

AUMA GST 25.1 is the first double-stage size of the GST spur gearbox family. Where the bevel gearboxes of the GK range turn the drive through 90 degrees, a spur gearbox such as the AUMA GST 25.1 keeps the input shaft parallel to the output and offsets it sideways, which is exactly what is needed when an actuator has to be placed beside a rising stem rather than above it. It carries 2,000 Nm of nominal valve torque with 800 Nm for modulating duty, offers four ratios from 3:1 to 8:1 and weighs 82 kg.

In Oman and the GCC, Seven Star LLC supplies the AUMA GST 25.1 to water, power and process projects in the Sultanate of Oman and the GCC. We select the ratio against the valve torque and the actuator frame, and we issue AUMA’s documentation with every unit so that your commissioning team has the exact data for the combination.

Spur Gear Principle of the AUMA GST 25.1

Inside the AUMA GST 25.1 two stages of spur gears transmit rotation from the input shaft to the output drive sleeve, and the parallel axes allow the gearbox to be mounted in any position. Clockwise rotation at the input produces clockwise rotation at the output by default, and a GW 14.1 reversing gearbox can change the direction of rotation for manual and motor operation up to the GST 30.1 size. As a multi-turn gearbox the AUMA GST 25.1 can withstand axial thrust, so it can carry a stem nut to act as a screw jack on rising-stem valves.

The four ratios give clearly differentiated input requirements. The 3:1 ratio has a conversion factor of 2.7 and needs 740 Nm at the input shaft with 296 Nm for modulating duty, the 4:1 ratio has a factor of 3.6 and needs 556 Nm (222 Nm modulating), the 5.6:1 ratio has a factor of 5.0 and needs 397 Nm (160 Nm modulating) and the 8:1 ratio has a factor of 7.2 and needs 278 Nm (111 Nm modulating). Each ratio has a 30 mm standard input shaft with a 40 mm option, and the average output torque for ATEX open-close duty is 1,000 Nm.

Engineering Design of the AUMA GST 25.1

Valve attachment is F25 according to EN ISO 5210 (G4 according to DIN 3210), and output drive types A, B1, B2, B3 and B4 as well as special attachments AF, AK, AG, IB1, IB3 and IB4 are available. The 3:1 and 4:1 ratios accept an SA 14.6 (F14, up to 80 kg) or an SA 16.2 (F16, up to 160 kg), the 5.6:1 ratio accepts an SA 14.6, and the 8:1 ratio accepts an SA 14.2, SAR 14.2 or SA 14.6, so the actuator frame can be sized to the ratio instead of the valve.

Maximum permissible input speed for motor operation is 240 rpm, and the gearbox is protected to IP68 with KS corrosion protection and a double-layer powder coating in AUMA silver-grey. The ambient range is -40 to +80 degrees Celsius with -60 to +60 and 0 to +120 degree options, and a 500 mm handwheel is the standard size for manual duty on this size, with a lockable version and a WSH limit switching device as options. In explosive atmospheres the standard marking is II 2G c IIC T4 and II 2D c T130 degrees Celsius.

Ratio and Input Torque Data of the AUMA GST 25.1

The four ratios of the AUMA GST 25.1 are listed in AUMA’s data sheet with the following values.

All four ratios deliver the same 2,000 Nm of nominal valve torque and 800 Nm of modulating torque.

Key Features

The AUMA GST 25.1 is an offset-axis alternative to a bevel gearbox for large multi-turn valves:

• Spur gearing keeps input and output axes parallel but offset, which suits layouts where a bevel gearbox would collide with piping or structure.
• The four ratios 3:1, 4:1, 5.6:1 and 8:1, with factors of 2.7 to 7.2, need 740 Nm down to 278 Nm at the input.
• Nominal torque is 2,000 Nm, with modulating duty permitted up to 800 Nm.
• An F25 flange (G4 to DIN 3210) offers output drive types A and B1 to B4 under EN ISO 5210.
• SA 14.2, SA 14.6 and SA 16.2 actuators, with their SAR versions, fit the input flange.
• The 82 kg gearbox weight includes the output drive sleeve and grease filling.
• Input speeds of up to 240 rpm are permitted for motor operation.
• Standard ATEX marking is II 2G c IIC T4, alongside IP68 and KS protection.

Industrial Applications

Large gate valves in water transmission, globe valves in steam and condensate systems and big isolation valves on pump discharge headers use gearboxes in the 2,000 Nm class of the AUMA GST 25.1. The offset geometry is helpful in valve pits and pipe galleries around Muscat and Sohar where the actuator has to sit beside the stem and the available height is limited, and the 3:1 ratio gives a quick stroke when closing time is critical.

In Oman and the GCC, Seven Star LLC supplies the GST 25.1 with matching SA and SAR actuators to EPC contractors, utilities and plant operators across Oman and the GCC, including projects in the Sohar and Salalah economic zones. See also the AUMA GST spur gearbox family, the AUMA SA 10.2 multi-turn actuator and the AUMA SAR 14.1 modulating actuator.

Related pages on our site: AUMA GST 40.1, AUMA GK 25.2 and AUMA GK bevel gearbox family.

Technical Specifications

Values for the AUMA GST 25.1 come from the GST 10.1 to GST 40.1 sheet and apply to the standard spur design.

With four ratios for one valve torque, the actuator decides: 3:1 needs 740 Nm at the input, while 8:1 needs only 278 Nm and suits an SA 14.2 or SAR 14.2.

Request a Quote for AUMA GST 25.1

Send Seven Star LLC an RFQ for the AUMA GST 25.1 stating the valve torque, the stem interface and the actuator, and we will confirm the ratio and quote regional delivery. The AUMA technical data sheet can be downloaded from this page, and our instrumentation team in Muscat can advise on handwheels, reversing gearboxes and stem protection. In Oman and the GCC, we supply every gearbox on request with local support.