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RELIEF VALVES
Technical Specifications
Connection: threaded UNI EN 10226-1
Maximum inlet pressure: 2 bar
Ambient temperature: -10÷60°C
Response pressure: red spring 30÷130 mbar
blue spring 80÷600 mbar
Fuel: all three families of gas (city gas, methane, LPG);
non-aggressive gases.
Material: aluminium valve's body and cover; stainless
steel springs; steel control piston; NBR rubber gasket and
O-ring; other parts made of brass, aluminium and gal-
vanised steel.
General information
The relief valves in the MS Series are normally closed.
The valves open solely is the inlet pressure is greater than
the calibration value. The valves close automatically when
the pressure returns to below the calibration value.
Installation
The relief valves in the MS Series conform to Directive
2014/34/EU (ATEX) in group II category 2G and in group
II category 2D; as such they are suitable for installation in
zones 1 and 21 and, even more so, in zones 2 and 22 as
classified in enclosure I of Directive 99/92/EC.
The relief valves described here are not suitable for use in
zones 0 and 20 as defined in Directive 99/92/EC.
To determine the qualification and extension of the hazard-
ous zones, see standard EN 60079-10.
If installed and maintained as per the conditions and
instructions given in the enclosed technical manual, the
relief valve is not a source of specific danger.
In particular, under normal operating conditions, the device
only rarely emits inflammable substances such as to gener-
ate an explosive atmosphere.
The relief valve has a work membrane and a safety mem-
brane; if the work membrane breaks, the safety membrane
guarantees gas emission with flow rate no higher than 30
dm
/h. A continuous explosive atmosphere able to gener-
3
ate a hazardous zone 0 is emitted solely in the event both
membranes break simultaneously.
In the event the valve is installed in an unmanned or poorly
aired location, all the necessary precautions should be
taken to prevent the valve from being the cause of a zone 0.
For example, the breather may be routed outside via a
copper pipe connected to the threaded hole G1/8" by
removing the dustproof brass cap.
The descriptions and photographs contained in this product specification sheet are supplied by way of information only and are not binding. Watts Industries reserves the right to
carry out any technical and design improvements to its products without prior notice. Warranty: All sales and contracts for sale are expressly conditioned on the buyer's assent
to Watts terms and conditions found on its website at www.wattswater.eu. Watts hereby objects to any term, different from or additional to Watts terms, contained in any buyer
communication in any form, unless agreed to in a writing signed by an officer of Watts.
MB-MOI-IT-W-ML-10-20-Rev1
4
The valve may be assembled in a variety of positions; on
horizontal piping it is advisable to keep the valve sleeve fac-
ing upwards.
The following guidelines should be followed:
• do not lever on the sleeve when assembling the valve;
• ensure that the piping is well aligned and that there are no
obstructions or dirt inside;
• observe the flow direction as shown by the arrow printed
on the valve body;
• check that all pressure, temperature etc. parameters are
complied with;
• do not install the valve in contact with plastered walls.
The relief valve should be installed upstream of the pres-
sure regulator.
Calibration
1. Check that all the utilities are off.
2. Screw down the relief valve adjusting screw completely.
3. Slowly open the on/off valve upstream of the system.
4. Increase the pressure downstream of the regulator by
turning the adjusting screw until the required pressure for
the breather is reached.
5. Slowly unscrew the relief valve adjusting screw until gas
begins to escape.
6. Restore the initial regulator outlet pressure.
7. Screw on the plastic safety caps on the screws that
adjust the regulator and the relief valve.
Maintenance
The relief valves do not require any special maintenance.
In the event of a fault, run a general overhaul and relative
test on site.
Periodically check the working efficiency of the entire safety
system by increasing the regulator pressure until the device
is triggered.
If the valve must be disassembled for any reason, make
sure there is no pressure in the circuit.
ALL
INSTALLATION,
REARMING,
MAINTENANCE OPERATIONS MUST BE CARRIED OUT SOLELY
BY QUALIFIED PERSONNEL.
UK
CALIBRATION
AND
K0108S – Rev. B 10/2020
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