SPRING OPERATED SAFETY VALVES
Spring operated safety valves are used in almost all industries and are characterized by the fact that they open abruptly (i.e. “pop-open”). This means they let out the entire overpressure at once and often more. They open up approx. 5 % before they reach the set pressure and they close approx. 5 % after reaching the set pressure.
The most basic rule of thumb is that this design is not used when the operating pressure is closer to the set pressure than 5 % – then the valve will open and close uselessly. This is also known as chattering.
Spring-operated safety valves are available in various designs and models, designed for a wide range of applications. They are available as full nozzle and semi nozzle. By aggressive media, you usually tempt to use a full nozzle – since in this design it is only nozzle and disc that are exposed to the medium – you can choose to make these two parts in a high-alloy and media-resistant material, and the rest of the valve in a lower alloy and cheaper material – in a semi nozzle valve, several parts of the valve and valve body will be exposed to the medium, which is why this design is often used in less aggressive media.
ProMetal’s valves are provided in several different standards:
- PED 97/23/EC – Pressure Equipment Directive – Classifies pressure equipment into four categories (I, II, III, IV)
- EN4126 – Safety devices for protection against excessive pressure
International (American) standards:
- ASME I – Direct fired pressure vessels
- ASME III – Nuclear power plants
- ASME IV – Heating boilers
- ASME VIII – Unfired pressure vessels
- ANSI/ASME PTC 25.3 – Performance test codes
ProMetal A/S is an agent for Weir / Sarasin / RSBD – they are among the only manufacturers in the world with designs and deliverances with reference to ASME I and ASME III.
The most commonly used standard for safety valves is ASME VIII.
Read about our pilot operated safety valves here.