What is the difference between SA121, SA122, SA128, and SA1219?

The main differences are valve size compatibility and set point adjustment location. SA121 covers 2-port valves up to DN80 and 3-port valves up to DN50 with adjustment at the sensor. SA122 is for smaller valves (up to DN25) with adjustment at the valve body. SA128 is similar to SA122 but with sensor-side adjustment. SA1219 is specifically for larger 3-port valves (DN80–DN100).

Do these controllers require electrical power or instrument air?

No. These are fully self-acting systems powered by the thermal expansion of the liquid fill. They require no external power source, making them suitable for hazardous areas and locations without utilities.

Can the sensor be installed directly in the process medium?

Yes, using the union kit for direct immersion. Alternatively, a stainless steel pocket can be used for indirect immersion, which allows sensor replacement without draining the system.

What is the maximum capillary tube length available?

Standard lengths are 2 m, 4 m, and 8 m. Special orders can extend up to 16 m for installations where the sensor must be located far from the valve.

How do I select the correct temperature range?

Choose a range where your normal operating temperature falls in the middle third of the span. This ensures optimal control accuracy and sufficient over-temperature protection margin.

SPIRAX SARCO · CONTROL VALVES

Spirax Sarco SA121, SA122, SA128, SA1219 Self-Acting Temperature Control Systems

Name: Spirax Sarco SA121, SA122, SA128, SA1219 Self-Acting Temperature Control Systems
Brand: Spirax Sarco

Spirax Sarco SA121/SA122/SA128/SA1219 self-acting temperature controllers for 2-port & 3-port valves. No external power needed.

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Overview

The Spirax Sarco SA121, SA122, SA128, and SA1219 are self-powered temperature control systems designed for automatic process temperature regulation without requiring external power or compressed air. These systems integrate the sensor, actuator, and set point adjustment into a single unit, providing reliable and autonomous temperature control for industrial heating and cooling applications.

The operating principle is based on a liquid-filled thermal system. As the process temperature changes, the kerosene fill expands or contracts, actuating the valve to maintain the desired set point. This makes the system ideal for applications where electrical instrumentation is impractical or where fail-safe, self-contained control is preferred.

These controllers are compatible with Spirax Sarco 2-port valves (KA, KB, KC, KX, KY, SB, SBRA, BX, BXRA, BM, BMRA, BMF, BMFRA, NS, NSRA) and 3-port mixing/diverting valves (TW series), covering a wide range of process requirements in steam, hot water, and HVAC systems.

Key Features

Fully self-acting operation — no external power or air supply required
Integrated sensor, actuator, and set point adjuster in one unit
Available with set point adjustment at sensor (SA121, SA128, SA1219) or at valve (SA122)
Multiple temperature ranges from -20°C to 170°C
Over-temperature protection up to 190°C maximum
Capillary tube lengths available: 2 m, 4 m, 8 m, and up to 16 m (special order)
Compatible with both direct immersion (union kit) and indirect immersion (stainless steel pocket)
Optional accessories: wall bracket, duct adaptor, dial-type set point adjuster, nickel plating

Specifications

Parameter	SA121	SA122	SA128	SA1219
Valve Compatibility (2-port)	DN15–DN80	DN15–DN25	DN15–DN25	—
Valve Compatibility (3-port)	DN20–DN50	DN20–DN25	DN20–DN25	DN80–DN100
Set Point Adjustment Location	At sensor	At valve	At sensor	At sensor
Temperature Range 1	-15°C to 50°C	-20°C to 120°C	-20°C to 110°C	-15°C to 50°C
Temperature Range 2	40°C to 105°C	40°C to 170°C	40°C to 170°C	40°C to 105°C
Temperature Range 3	95°C to 160°C	—	—	95°C to 160°C
Over-Temperature Protection	55°C over set value (max 190°C)	55°C over set value	55°C over set value (max 190°C)	55°C over set value (max 190°C)
Ambient Temperature Range	-35°C to +50°C	-35°C to +50°C	-35°C to +50°C	-35°C to +50°C
Capillary Tube Length	2 m, 4 m, 8 m (max 16 m)	2 m, 4 m, 8 m (max 16 m)	2 m, 4 m, 8 m (max 16 m)	2 m, 4 m, 8 m (max 16 m)
Weight (excl. pocket)	2.0 kg	1.8 kg	1.8 kg	2.3 kg
Component	Material
Sensor	Brass
Actuator	Brass
Capillary Tube	Copper with PVC-coated armoured covering
Adjustment Head	Polypropylene
Union Kit	Brass
Mounting Bracket	Steel
Pocket	Stainless Steel (BS 3605 CFS 316S 18)
Liquid Fill	Kerosene

Applications

Spirax Sarco SA121/SA122/SA128/SA1219 self-acting temperature controllers are widely used across industries requiring precise, autonomous temperature regulation:

- Steam and hot water systems — heating coils, calorifiers, heat exchangers - HVAC applications — air handling units, duct heating/cooling control - Process heating — tank heating, jacketed vessels, process water temperature control - Food & beverage — pasteurisation, cooking, cleaning-in-place (CIP) systems - Pharmaceutical manufacturing — temperature-controlled batch processes - Textile and paper industries — drying and finishing processes

Frequently Asked Questions

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