AT Control Valve
The AT series from Carraro is an even modulating temperature regulator, which utilizes steam pressure as the activating force. The reason for the rapid reaction is due to bellows seal, calibrated spring and the low thermal inertia.
This series gives you:
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The AT series of self-modulating temperature regulators operate using vapor tension as the driving force.
Their quick response is achieved through the elimination of gland packing, which is substituted by a bellows, coupled with precise spring selection and minimal thermal inertia.
These features enable the regulator to be highly sensitive and react swiftly to even minor temperature fluctuations.
The AT series offers a reliable and cost-effective solution for a wide range of temperature control applications, removing the need for external electrical or pneumatic power sources.
The valves from the AT series has several benefits. See some of them listed below:
The AT temperature regulators are widely utilized across various process industries due to their efficiency in controlling temperature. These regulators offer opportunities for reducing operating costs in several key applications, including:
In addition to these applications, three-way valves are commonly employed in fluid heating systems. They are primarily used in:
You can read more and see examples of the applications of the AT series in the brochure here.
Fig. 1 illustrates the temperature regulation system for a tank where steam heats the water via a coil.
Initially, the water in the tank is at ambient temperature, and the saturated steam pressure in the sensing system is low. The spring (1) keeps the valve plug open, allowing steam to flow into the coil and raise the water temperature. As the water temperature increases, so does the temperature and pressure of the saturated steam in the bellows (2). Once the pressure surpasses the force of the spring (1), the bellows (2) moves downward, initiating the closing movement of the plug (3).
When the target temperature is achieved, the plug settles in a partially closed position to regulate the steam flow and maintain the desired temperature. Any fluctuation in this thermal equilibrium affects the saturated vapor pressure in the bulb liquid, prompting the regulator to adjust accordingly to stabilize the temperature. The filling fluids in the bulb are specially designed to ensure the regulator maintains a temperature accuracy within ±5% of the set point.
The AT valves series has several parts, we have listed them for the AT/S2 double seated control valve below (and see the drawing):
1 - Valve body cover
* 2 - Gasket
3 - Valve body
4 - Seat
* 5 - Plug
* 6 - Plug guide
7 - Sleeve
8 - Frame
* 9 - Stem with bellows
10 - Spring adjusting ring
*11 - Sensitive element assembly
12 - Washer
13 - "Seeger” ring
14 - Load limiting device assembly
15 - Set spring
16 - Screw
17 - Stem guide bushing
18 - Spring adjusting pointer
19 - Frame nut
20 - Washer
21 - Adjusting pin
* Is the recommended spare parts.
The AT temperature regulators come in single, double-seated, two-way, and three-way designs. They feature flanged body connections compliant with UNI-DIN-BS-AFNOR norms NP 16 to 40 and face-to-face dimensions according to EN 558-1 (DIN 3356). The design incorporates a bellows to eliminate leakage and internal moving parts. A load-limiting spring allows the sensing bellows to extend beyond the valve stem's stroke, providing safety in case of excessive temperature rise. The AT series regulators are versatile, suitable for both heating (direct action) and cooling (inverse action) processes.
Standard Construction:
Special Construction:
| Technical Specifications | |||||||||||||||||||
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| Function | Temperature control |
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| Design | 2 or 3 way |
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| Size | From 1/2 "to 2" |
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| Connection | Flanges (ANSI and PN) |
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| Seat | Single or double |
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| Pressue step | Max ANSI 300, PN 16-40 |
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| Pressure | 17.5 bar(g) |
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| CV | From 0.84 to 38 |
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| Valve housing | Steel or stainless steel |
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| Trim | Stainless steel and other "exotic" materials |
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| Temperature control range | From -25 ° C to 225 ° C |
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| Temperature |
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