Breather Valves

Pressure-Vacuum Relief Valves (also known as breather valves) are designed according ISO 28300 and API 2000 for installation on low pressure storage tanks to ensure safe filling and emptying operations, and to compensate for any expansion or contraction of vapors above the liquid level due to changes in ambient temperatures.

Our technical department is available to carry out valve sizing according to international standards like "API 2000" and "ISO 28300". 

Our valves are designed even according to following European Standards that are related to "Atex" Directive

  • EN1127-1: Explosive atmospheres - Explosion prevention and methodology 
  • ISO 80079-36 and 80079-37: Non-electrical equipment for explosive atmospheres 

In order to make easy control and maintenance activities, all our Pressure-Vacuum Relief Valves are designed with pressure side and vacuum side well distinct one from the other. 

All valves are submitted to rigorous seal and set pressure, furthermore we would like to remark the fact that all flow capacity features are real in fact our in-house air capacity testing plant enables valves from size 2" to 12" to be capacity tested in the range between +/- 22 and +/- 700 mmWG. 

All valves are equipped with teflon FEP + PTFE diaphragms, other materials are also available on request. 

All valves may be required with proximity sensors to be connected to control room in order to detect valve opening. 

Five ranges are available. 

  • Aluminium Casted execution “SWV”: available in the sizes from 2” up to 12” is bound for plants where are not present high corrosive process fluid. In this execution body and covers are in casted aluminium while seats and trim are in stainless steel in order to avoid that oxide on the seat surface may compromise valve tightness. This execution is coated by epoxy paint. 
  •  Steel casted available in two executions:

EWW with casted carbon steel A216WCB body. This execution is coated by polyurethane paint for carbon steel parts.

WWW with CF8M (AISI316) body. Sandblasting SA 2 ½ is the finish foreseen for this execution. 

Both executions have seats and trim in stainless steel AISI316. This kind of valve is available in sizes 2”, 3” and 4” and are usually delivered in short time.

  • 400 Series: fabricated stainless steel 316L bodies and available under request in a wide range of exotic alloys (Nickel alloys etc.). Available in the sizes from 2” up to 12” is bound for petrochemical and chemical plants and where corrosive process fluids are present. Thanks to modular way they are designed, it is possible fitting them with a steam jacket. Sandblasting SA 2 ½ is the finish foreseen for this execution. 
  • 700 Series: fabricated stainless steel 316L bodies available in sizes 2”, 3”, 4”, has a modular design as each side is interconnected by tri-clamp connections. They are supplied with electro-polishing bright finish. Its design cares of self-draining feature to satisfy chemical and pharmaceutical industries. 
  • Spring Loaded Valves

All kind of valves mentioned above are weight loaded, however in order to increase the setting range from 100 to 490 mbarg we propose for valves series 400 and 754 a peculiar spring loading system, named by us “bow springs”, that offers an almost linear ratio load-deformation quite similar to weight loaded system. In this way “bow springs” loaded valves work with a consistent lift of the disc (pallet) that allows to get high flow capacities. Flow capacities diagrams for “Bow Spring loaded valves” are obtained from tests carried out by “Politecnico University of Milan”.

  • Polypropylene Series: fabricated polypropylene bodies, recall series 400 design, available in sizes 2”, 3”, 4” are bound for chemical industry where are handled corrosive process fluid like Hydrochloric acids etc.. This execution is supplied with natural finish. 


Aluminium casted

54 WWF Scontornata ridim2

Steel casted

493 454 492 454 asp. conv.3

Stainless Steel 400 Series

1 ridim

Stainless steel 754 Series

valv 4 scont ridim

Polypropylene Series