Spirax Sarco SA121 Self-Acting Temperature Control System

The Spirax Sarco SA121 is a self-acting temperature control system that maintains a set temperature automatically, with no electrical or pneumatic power required. Using a liquid-filled capillary tube and brass sensor, the system detects changes in process temperature and modulates a connected control valve accordingly. A kerosene-filled sensing element drives the actuator directly, making the system entirely self-contained. The blue polypropylene adjustment knob allows for straightforward setpoint changes across a temperature range of -15°C to +50°C. The 4 m copper capillary, clad in PVC-armoured covering, gives enough reach to position the sensor accurately within the process fluid while keeping the actuator close to the valve. Compatible with Spirax Sarco 2-port and 3-port temperature control valves, the SA121 suits both heating and cooling duties. It complies with the EU Pressure Equipment Directive and UK Pressure Equipment (Safety) Regulations, and is rated for Group 2 fluids including steam, water, and compressed air. Weight is approximately 2.0 kg.

Applications:

• HVAC and building services heating systems
• Heat exchangers
• Hot water generation systems
• Steam-heated process equipment
• Food and beverage processing
• Pharmaceutical and industrial process plants
• Heating and cooling control applications

Summary:

• Self-acting operation — no electricity or pneumatic supply needed
• Temperature range: -15°C to +50°C
• 4 m copper capillary with PVC-armoured covering
• Knob-adjustable setpoint
• Brass sensor and actuator; polypropylene adjustment head; steel mounting bracket
• Kerosene-filled sensing element
• Compatible with Spirax Sarco 2-port and 3-port temperature control valves
• Compliant with EU PED and UK Pressure Equipment (Safety) Regulations
• Rated for Group 2 fluids: steam, water, compressed air, and other non-hazardous fluids
• Manufactured under ISO 9001 quality management systems
• Weight: approximately 2.0 kg