CNC380 Series Pressure Vacuum Relief Valve
Opti-flow 380 Series — weight-loaded tank breather valves
Select optionsAbout the 380 Series
Direct-acting pressure, vacuum and combined pressure/vacuum relief valves for bulk storage tanks, including floating-roof tanks. They prevent excessive pressure or vacuum that could unbalance the system or damage the storage vessel.
Applications include chemical tanks, low-pressure gas pipelines, digesters and gas holders. Flanged outlets and atmosphere-venting configurations are available.
- High gas flow in a compact valve size.
- Sizes from 2 inch (50 mm) to 12 inch (300 mm).
- A choice of materials and pressure/vacuum settings for tank protection with minimum gas loss.
- European ATEX compliance where applicable.
Manufactured in the UK by Motherwell Tank Protection.
Available configurations
↑ Pressure outflow↓ Vacuum inflow
Principle of operation
The cast body is flanged to the storage tank. A weatherhood protects the pressure exhaust port, while a mesh screen prevents foreign matter entering atmosphere-vented valves. Piped-away versions are also available.
Both pressure and vacuum sides use a pallet and diaphragm assembly resting on an O-ring seal to prevent leakage. Leak tested to API 2521. The O-ring can be removed and the seat machined optically flat for metal-to-metal seating when required.
Pallet weight holds the diaphragm against the seat. As pressure or vacuum increases, the pallet and diaphragm lift to allow air or gas to flow.
Construction and specifications
- Valve size
- 2 inch (50 mm); 3 inch (80 mm); 4 inch (100 mm); 6 inch (150 mm); 8 inch (200 mm); 10 inch (250 mm); 12 inch (300 mm)
- Process connection
- ANSI 150# (Standard); PN16; Special — flange drilling as required
- Body material
- Aluminium; Cast iron; Carbon steel; Stainless steel; Special — on request
- Pallet / trim
- Stainless steel; Aluminium; Special — on request
- O-ring seals
- PTFE; Nitrile rubber; Viton; Special — on request
- Dead-weight valve settings
- Low flow from 0.865 inch wg (2.15 mbar); high flow to 30 inch wg (75 mbar).
- Diaphragm
- PTFE; other requirements can be specified in your enquiry.
Valve sizing and support
Free computerised valve sizing to API 2000 is available to help select valve performance and cost.
Configure your CNC380 Series valve
Select the valve arrangement and construction, then enter the required settings. Fields marked * are required.