ARI Armaturen STEVI 426 EN - Manual (Page 3)

Rev. 0040314001 0410 Page 3
Operating and installation instructions
Straight through control valves - STEVI
®
425 / 426
4.0 Description
4.1 Scope of applications
Valves are used for „controlling the flow of liquids, gases and vapours in chemical and other
processing plants and for plant engineering“.
The information complies to the Pressure Equipment Directive 97/23/EC.
It is the responsibility of the machine planner to ensure compliance.
The special markings on the valve must be taken into account.
Refer to the catalogue sheet to see which materials are used in standard versions.
Please contact the supplier or the manufacturer if you have any questions.
4.2 Operating principles
ARI control valves are especially suitable for actuation by pneumatic or electrical actuators.
Three plug types are available to suit the various applications:
V-port plug (standard pattern)
perforated plug
pressure balanced plug
The flow through control valves is always against the closing direction.
In the case of control valves with perforated plugs, gases and vapours flow against the
closing directions, but liquids flow through in the closing direction. If a pneumatic actuator is
to be used on a straight-way valve with a perforated plug with the fluid moving in the closing
direction, a higher closing force will be needed. This is to prevent vibration as the plug
approaches the closed position.
If the forces generated by the actuators are too low, arrangements should be made to
relieve the pressure as far as this is compatible with service conditions.
ATTENTION !
- Refer to the data sheet for applications, limits on use and possibilities.
- Certain media require or preclude the use of special materials.
- The valves are designed for standard operating conditions. If conditions exceed
these requirements, e.g. aggressive or abrasive media, the operator should
state the higher requirements when ordering.
- Valves made from grey cast iron are not authorised for use in systems subject
to TRD 110.