Installation Method for Danfoss STC65-DN80-PS25 Refrigerant Globe Valve

Installation

During valve installation, the valve stem must be vertically upward or in a horizontal position (Figure 1). The valve should be opened manually; tools or other devices should not be used (Figure 3). The valve is designed to withstand high internal pressure. Nevertheless, the piping system design must avoid liquid traps to prevent damage from excessive pressure due to thermal expansion. The piping design should include effective protection against instantaneous "liquid hammer" phenomena in the system.

Note!

The STC is a globe valve and must always remain fully closed or fully open. It must not be used in a partially open state.

Recommended Flow Direction

For optimal flow characteristics, the valve should be installed according to the flow direction indicated by the arrow on the valve body (Figure 2). The valve can also accept flow in the opposite direction (Figure 2), but this will slightly reduce the Kv-/Cv value.

Welding

Before welding, the bonnet should be removed (Figure 4) to prevent damage to the O-rings in the stuffing box, between the valve body and bonnet, and the PTFE washer on the valve plug. Welding to the valve body must be done using materials compatible with the valve body material and appropriate welding methods. The interior of the valve should be cleaned to remove welding slag after welding is completed, before reassembling the valve. Clean promptly to avoid the presence of welding slag and foreign matter in the threads of the valve body and bonnet.

The bonnet does not need to be removed under the following conditions: during welding, the temperature in the area between the valve body and bonnet does not exceed +150°C/+302°F.

This temperature depends on the welding process and the cooling of the valve body during welding (e.g., wrapping the valve body with a wet cloth for cooling). Avoid allowing dust, welding debris, or other foreign matter to enter the valve body during welding. Ensure the PTFE valve plug sealing washer remains intact. After installation, the valve body must not be subjected to external pressure (external loads). The outlet end of the globe valve must not be left open and exposed to the air after installation. The outlet side of the valve must always be connected to the system or sealed, for example, with a welded end plate.

Assembly

Before assembly, thoroughly remove welding slag and dust from the pipes and valve body. Before reinstalling the valve plug into the valve body, check and ensure the valve is in the fully open position.

Tightening

Use a torque wrench to connect the bonnet to the valve body according to the torque values specified in the table (Figure 5).

Color and Marking

The STC is coated with a gray water-based primer at the factory. After welding and assembly, the valve must be sprayed with an appropriate protective coating to prevent corrosion on the external surface of the valve body.