AUMA GSTI Multi-Turn Gearbox for Nuclear Valves (2-16 kNm)

AUMA GSTI multi-turn gearbox for nuclear plant valves

The AUMA GSTI is a multi-turn spur gearbox designed for operating gate valves and globe valves in nuclear power plants, both inside and outside containment. It is used between a multi-turn electric actuator and the valve, or alone with a handwheel for manual operation, and it covers a torque range of 2,000 Nm to 16,000 Nm. Seven Star LLC supplies AUMA products in Oman and the GCC as an independent supplier in Muscat. The GSTI is a specialised nuclear-service gearbox, so this page explains what it is and how the nuclear data should be handled in an enquiry.

GSTI technical data

What the GSTI does

A spur gearbox reduces the speed and multiplies the torque of the input shaft. In the GSTI the reduction is arranged for rising-stem gate and globe valves that need high stem torque or thrust. When an actuator is fitted, the gearbox converts the actuator torque to the higher valve torque. Without an actuator, a handwheel on the input permits manual operation, which is useful for valves that are rarely moved and have to be available for local intervention.

Qualification and accident conditions

For nuclear service the key point is the demonstrated behaviour under design-basis events. The GSTI is described as resistant to earthquake loading and to loss-of-coolant accident (LOCA) and design-basis event (DBE) conditions with a temperature of up to 185 °C for a short time. The listed standards are IEEE 382-1996 and KTA 3504-2006. The qualification status of each delivered unit is documented in its own certificate, which must be requested with the order; this page does not replace those documents.

Combination with nuclear actuators

The GSTI is combined with the AUMA SAI/SARI actuators (inside containment) or SAN/SARN actuators (outside containment). These actuator families are covered by existing pages on this website under the SAI-SARI and SAN-SARN titles. Observe that the gearbox, the actuator and the controls must match in torque, speed and flange; the complete combination is defined in the order data.

GSTI selection checklist

• Valve torque and thrust at opening, closing and seating
• Whether the installation is inside or outside containment
• Required qualification documents and standards
• Actuator to be combined, or handwheel-only operation
• Valve flange per DIN or ISO and stem type
• Ambient temperature and radiation environment
• Duty: S2 – 15 min open-close

Installation and maintenance of the GSTI

Nuclear installation procedures are governed by the plant quality assurance programme. In general, the gearbox is mounted on the valve flange, the stem nut or drive bush is fitted and the actuator or handwheel is attached to the input. Easy maintenance and simple installation are listed advantages. Lubricant type and change interval follow the manufacturer instructions for the unit, and the maintenance record should be kept with the qualification file.

Where the GSTI is used

The GSTI belongs to the nuclear segment of AUMA products. Enquiries in Oman and the GCC for this product are uncommon and usually relate to new-build nuclear programmes in the region or to spare parts and documentation. Because requirements are project-specific, quote preparation requires the full nuclear specification.

Related gearboxes

Operating modes of the GSTI: motor and handwheel

The manufacturer describes the GSTI as suitable for both electrical and manual operation. In motor mode an SAI/SARI or SAN/SARN actuator supplies the input torque and the gearbox multiplies it to the valve level. In manual mode the operator turns a handwheel directly on the gearbox input. This matters for nuclear plants in particular, because valves with an isolating or backup role may only be operated during outages or tests, and a gearbox without a motor is simpler and has fewer components that need qualification and ageing management.

The duty rating is short-time duty S2 – 15 min for open-close service. This means the unit is intended for infrequent strokes of limited length, not for continuous modulating control. If the process requires frequent positioning, an industrial modulating combination with SAR actuators and a standard GST gearbox should be considered instead.

Documentation and ageing management for the GSTI

Nuclear equipment is delivered with a documentation package that supports the plant licensing basis: material and test records, qualification references and installation instructions. Operators also maintain an ageing management programme for lubricants, seals and elastomers, and a gearbox that has been stored for a long time needs the storage conditions and shelf-life documented. When ordering a GSTI, state clearly which documents are required, because the scope can influence delivery planning.

Information to send with an RFQ

• Part number: GSTI with torque range required
• Nuclear quality and documentation requirements
• Containment location
• Valve type, torque and flange
• Actuator combination required
• Quantity and delivery location

Documents and quotation

Send the part number GSTI, the application and the quantity, and Seven Star LLC will confirm which official documents are available for your configuration. Please do not rely on a general description alone: the order data, wiring diagram number and explosion-protection marking of the delivered unit are what count for engineering and commissioning.

Seven Star LLC is an independent supplier in Muscat serving customers across Oman and the GCC. Quotations are prepared against your enquiry data and are confirmed individually.