Safety valve S301

Description of operation

The S301 safety valve is designed as a direct-action normal safety valve which is loaded by a spring assembly (disc springs).

The safety valve meets the requirements of European Parliament Directive 2014/68/EC (pressure vessels). The safety valve is used for pressure safeguarding hydraulic systems (e.g. pressure vessels). The valve is made of stainless steel and thus resistant to corrosion and suitable for use with the specifi ed media. The valve data is included in the chapter „Range of application“.

The required valve function „to trigger reliably and within the set tolerances in case of overpressure“ requires a precise and linear valve seat surface. I.e. as soon as the valve has responded due to over-pressure, the valve seat may be damaged and can thus a leakfree seal can no longer be guaranteed.

Leaking or damaged safety valves must be replacedas a complete unit.
Repairs must only be made by the manufacturer or by the manufacturer‘s certifi ed subsidiaries.


Range of application

The specified range of application can be found on the valve label and in the table 1 below.

Typ = valve model
Ser.-Nr. = serial number / year of manufacture
d0 = diameter of valve seat [mm]
Medium = pressure medium
G = flow rate [l/min]
p = set pressure [Bar]
T = fluid temperature 0 – 50 °C

A safety valve must be engineered and installed in line with the existing directives and the manufacturer‘s specifications. To prevent unintentional opening of the safety valve, allow for system pressure peaks (pulsation) when selecting the set pressure. The safety valve S301 reacts to intermittent pressure peaks that are too short in duration to even register on a pressure gauge.


Technical data

measured with HFA medium 97/3%, at 20°C


Additional information

Installation / Mounting

The safety valve must only be installed by authorised and qualified specialist staff.

The S301 safety valve must only be installed on the P-port with the corresponding hollow bolt (1).

Connecting thread: G 1“ – DIN2999-1
Tightening torque: 300 Nm

No other fastening facility is provided for the safety valve. The supply line (P-port) must have a minimum inner diameter of Di >= 13mm. Expelled medium must be able to flow freely into the open air at connection „T“.

If a return line is installed at the outlet (T) of the safety valve for system reasons, the following rules must be observed.

  • A safety valve with a threaded connection must be used (see table 1).
  • The return line must have a minimum inner diameter of Di >= 17 mm.
  • The return line must be no longer than a maximum of 1.5 m and have a bend of 90°.
  • The return line must be installed with an inclination so that it runs to empty automatically.
  • The return line must be fastened properly so that the reaction forces do not cause a hazard when the safety valve discharges.

Before installation the sealing plug has to be removed from port „T“ and the valve has to be checked for damage. The valve has to be installed so that personnel are not put at risk from discharging pressure medium. The discharged pressure medium must not be directed at sensitive, unprotected plant parts.

Put up a clearly visible information sign: „Caution: Safety valve – Beware of pressure medium discharged suddenly into the open air!“

Function testing

The functional checks to be performed on the valve are set out by the user or in accordance with the regulations for plant inspection. To perform a functional check on the S301 safety valve, the venting nut (3) is unfastened and turned anti-clockwise by hand until there is a noticeable resistance. Then turn the venting nut (3) half a turn further. The valve cone (2) is raised from the valve seat (1) and the pressure medium is expelled from the outlet (T).

After the functional check the venting nut has to be re-fastened properly.


The safety valve can be stored up to fi ve years. After this time the valve must be checked by the manu-facturer. Before the safety valve is taken into operation for the fi rst time, its correct function must be tested.

During storage all ports (P and T) must be sealed and the safety valve must be protected against dirt, mois-ture, frost and corrosion.


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