Technical Information


Safety valves are used to maintain pressure under a fixed rate and consequently to protect vessels and pressure equipments from uncontrolled overpressures. Direct load which defines discharge pressure is obtained with helicoidal springs. This system gives the advantage to have an high discharge capacity with a reduced pressure gap from the start of the valve opening to its complete closure.

Characteristics

Our safety valves, with regard to type and employed materials can normally work at the following conditions:

  • set-pressure range from 0,4 to 100 bars for homologated valves, from 2 to 400 bars for ordinary valves;
  • working temperature -270°C ÷ +538°C;
  • overpressure <= 10%;
  • blowdown <= 10% ( <= 15% for "R" type).

Our safety valves are marked on their bodies with the following data:

  • UNIVERSAL stamp;
  • Valve type;
  • Serial number;
  • Set pressure;
  • Year of construction;
  • Working temperature;
  • CE stamp;
  • Notified Body identification number;

We produce safety valves with free discharge in the air or with conveyed discharge for dangerous or toxic fluids. In the last case, valves can have different lifting device types for emergency actions or periodic checks.

Construction

We make all safety valve components directly, with the exception of the smallest ones of brass. Therefore, We can assure:

  • high and constant quality;
  • fast deliveries due to an easy work planning;
  • fast production for all types of safety valves and special connections.
  • Our valves are designed and manufactured in accordance with the following standards/normatives:

    • I.S.P.E.S.L. rules, "E" Collection, E1D2 Dossier;
    • PED 2014/68/EU European Directive;
    • ATEX European Directive;
    • EN ISO 4126-1 European Normative

    Construction and employed materials depend on pressure, temperature, corrosivity and on all other characteristics of the fluid in touch. Safety valves, according to the requested characteristics and quality, can be made out of bars, casting or hot moulding.

    All employed materials have their own original test certificates that can be supplied when customers require them. After machining, to increase ageing strength and corrosion proofness, many other treatments can be made on each valve component, i.e. pickling, sandblasting, buffing, galvanizing, nickel plating, chromium-plating, anodizing, etc.

    Examination of valve components:

    Body:

    It is made out with particular attention respecting dimensions and thickness in conformity with the declared rating. We can supply all possible connections respecting the following conditions:

    • compatibility with the declared rating
    • maintenance of internal dimensions
    • maintenance of inlet and outlet diameter of the valves
    • regular and unconditioned working
    • invariability of the discharge coefficient

    In the upper side of valve body (bonnet) there is an hole to discharge the back pressure that develops during valve opening. Conveyed valves, used for dangerous and toxic fluids, have this hole between bonnet and discharge duct in order to avoid any loss of fluid in the air.

    Orifice and Seat:

    Valve seats are flat. With regard to safety valves with metal to metal seats a perfect tightness is assured by a careful machining. As concerns soft seats, We have various gaskets of different materials according to the valve specific use. In order to avoid a gasket overload, safety valves are usually manufactured to let the disc lay on the bottom of the valve seat when there is no fluid pressure. In this way valve gasket maintains good strength and elasticity for a long time and avoids sticking of the disc on the seat.

    Disc:

    The valve disc has been designed to obtain the maximum discharge capacity. The machining tolerances let it work perfectly in all conditions.

    Push-rod and Spindle:

    They are used to maintain a correct spring alignment.

    Adjusting screw:

    It works also as a guide for the valve spindle. After the valve setting, the adjusting screw is locked by a pin or a rivet.

    Locking cap:

    With regard to safety valves with free discharge in the air, the locking cap has been designed to protect all inner components against tamperings that can be done only by heavy actions on the valve structure. The locking cap is also used to limit the disc lift by stopping of the spindle lift.

    Cover for external protection:

    It is made of aluminium and it is used as a further valve protection against atmospheric agents and dust. It is fixed on the valve locking cap with a blind nut that, after having been blocked and crosswise drilled, is used for the passage of the sealing wire.

    Lifting devices:

    There are different types of valve lifting-devices. The first one is made by a ring nut, the second one by a lever and the third one by a pneumatic actuator. When lifting devices are operated, they make stem lift up and spring compress, so that the valve disc runs freely. These devices don't block or get the valve disc out of the seat when the lifting power fails.

    Spring:

    We generally use helicoidal stainless steel springs, according to EN 10270 European Normative. The upper spring seat is located on the lower side of the adjusting screw, whereas the lower seat is on the push-rod of the valve spindle. In this way there are excellent conditions of alignment and axial load during work.