Purpose
The POV pilot operated safety valve is used in conjunction with the BSV back pressure independent safety valve. It is specifically designed for protecting compressors against excessive pressure (as illustrated in Figure 5, showing the POV valve integrated with a BSV valve).
Specifications
Refrigerants
Applicable to HCFC, HFC, R717 (Ammonia), and R744 (CO2). Flammable hydrocarbons are not recommended. The valve is recommended for use only in closed circuits. For further information, please contact Danfoss.
Temperature Range
POV: -50/+150°C (-58/+302°F)
Pressure Range
The valves are designed for a maximum working pressure of 40 bar g (580 psi g).
Installation
Mounting Orientation
The valve should be installed with the spring housing upwards (as depicted in Figure 1, illustrating the correct mounting orientation with the spring housing upwards). It is important to avoid the influence of thermal and dynamic stress (vibrations) during mounting.
Piping System Design
The valve is designed to withstand high internal pressure. However, the piping system should be designed to avoid liquid traps and reduce the risk of hydraulic pressure caused by thermal expansion. Ensure the valve is protected from pressure transients such as "liquid hammer" in the system.
Recommended Flow Direction
The valve must be installed with the flow towards the valve cone, as indicated by the arrow in Figure 2. Flow in the opposite direction is not acceptable.
Welding
Preparation
The top should be removed before welding (as shown in Figure 3, depicting the valve with its top removed) to prevent damage to the O-rings between the valve body and top, and to the teflon gasket in the valve seat. Do not use high-speed tools for dismantling and reassembling. Ensure that grease on bolts remains intact before reassembling.
Materials and Methods
Only materials and welding methods compatible with the valve housing material should be used for welding to the valve housing.
Cleaning
The valve should be cleaned internally after welding to remove any welding debris before it is reassembled. Avoid welding debris and dirt in the threads of the housing and the top.
Alternative Procedure (Top Omission)
Removing the top can be omitted provided that the temperature in the area between the valve body and top, and between the seat and the teflon cone, does not exceed +150°C/+302°F during welding. This temperature limit depends on the welding method and any cooling applied to the valve body during welding (e.g., by wrapping a wet cloth around the valve body). Ensure no dirt or welding debris enters the valve during the welding procedure.
Precautions
Be careful not to damage the teflon cone ring. The valve housing must be free from stresses (external loads) after installation.
Assembly and Tightening
Assembly Preparation
Remove welding debris and any dirt from pipes and the valve body before assembly.
Tightening
Tighten the top using a torque wrench to the values indicated in the table (Figure 4, presenting a table of torque values). Do not use high-speed tools for dismantling and reassembling. Ensure that grease on bolts is intact before reassembling.
Torque Table (Figure 4)
| Model | Nm | LB-feet |
|---|---|---|
| POV 600 | 44 | 32 |
| POV 1050 | 75 | 53 |
| POV 2150 | 44 | 32 |
Colours and Identification
Precise identification of the valve is made via the ID label on the top and by the stamping on the valve body. The external surface of the valve housing must be protected against corrosion with a suitable protective coating after installation and assembly. Protection of the ID label when painting the valve is recommended.
Important Notes
In cases of doubt, please contact Danfoss. Danfoss accepts no responsibility for errors and omissions. Danfoss Industrial Refrigeration reserves the right to make changes to products and specifications without prior notice.
Danfoss can accept no responsibility for possible errors in catalogues, brochures, and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products already on order provided that such alterations can be made without subsequent changes being necessary in specifications already agreed.
All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.
