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Excess flow valve for gas systems

DVGW

Excess flow valve for gas systems

DVGW
FULL RANGE
Threaded version from DN 15 to DN 50 (VGAS= 1,6 ÷ 16 m3/h)
gst - TECO
Documentation
CERTIFICATIONS AND TECHNICAL SPECIFICATIONS
DVGW
GST®
Standard and certificationDIN 30652-1
DVGW TRGI 2008
DVGW TRF 2012
Pressure15-100 mbar
Temperature-20 °C +60 °C
ApplicationFor all types of gas as specified in EN 437 and DVGW G260/1 (Methane, Butane, Propane)
Pressure drop≤ 0.5 mbar (50 Pa)
Overflow value VL37.5 l/h at 100 mbar (gas)
Fs min1.30
Fs max1.45
External heat resistance650 °C for 30’
Internal heat resistancetrip at 120 °C / 200 °C for 10’

EXCESS FLOW VALVE

GST® instantly blocks gas flow in the pipeline whenever the closure flow rate (Vs) is accidentally exceeded.

GS

GST® is TECO's commercial name for the excess flow safety device, specified as GS in the German standard (Gasströmungswächter).

SINCE 2002
TECO developed and manufactures GST since 2002, when the German technical standards for design and installation of gas systems (TRGI) covered excess flow devices.

OPERATION GST®

OPERATION

OPERATION GST Teco When inserted in the system, the GST® remains inactive (FIG.1) until the closure flow rate is reached (Vs).

As soon as the flow rate reaches the closure valve (Vs) for any accidental reason, the GST® closes instantly (FIG.2).

It is reset automatically by the bypass orifice on the cut-off, and the overflow VL that this creates balances the pressure upstream and downstream from the device when the conditions that caused the GST® to close have been removed (FIG.3)
OPERATION GST Teco
sicurezza

SAFETY

GST® devices are installed to protect the system and guarantee a higher safety level in the following cases:

  • against tampering, both criminal and not, performed by unauthorised personnel;
  • in systems that use non-metal pipes, in order to make them safe against the risk of explosion due to fire (DVGW VP632);
  • breakage/disconnection of hoses for gas appliances;
  • breakage of pipes due to natural disasters.

Installing the GST in a gas system raises the safety level because it intervenes even when the cause is not related to the system itself (passive safety).
Moreover:

  • it is maintenance free;
  • it does not require the periodic checks needed to ensure correct operation of components with active activation;
  • it cannot be disabled by an external action.

It remains functional even while the GST® is undergoing maintenance.

Over 2.5 million installed GST devices manufactured by TECO are a guarantee of the effectiveness and quality of the product. That is why for over than 15 years the German technical regulations on gas installation (TRGI-TRF) prescribe the use of GST® in accordance with VP 305-1.

GST Teco

RELIABILITY

GST® safety devices must guarantee reliable closure only within the tight parameters defined by the DVGW VP305-1 German product standard.
Failure to operate or unwanted closure could potentially create very hazardous situations; for this reason, despite its simple construction, the GST® undergoes strict checks during the manufacturing process. Its reliability is defined by the quality of the components and continual improvement of the manufacturing processes through numerous tests on each lot.

All internal parts of the GST® are built to ensure long-term operation.
The spring in the GST® is fully protected from the flow of gas (patented) so that it does not come into contact with impurities that could alter its proper operation over time. For the same reason, the overflow orifice is also protected when the cut-off is open.
Moreover, the GST® can dampen any flow peaks when attaching a gas appliance, which could cause the device to close.
GST Teco

ALL GST® DEVICES ARE 100% TESTED AND THE TEST PARAMETERS ARE TRACEABLE WITH A UNIQUE IDENTIFICATION CODE FOR EACH DEVICE.

Datasheet GST®

POSITION COMPACT

Right from the development stage, Teco designed the GST® to be installed horizontally or vertically upwards, with a closure factor "fs min. = 1.30 and fs max. = 1.45", giving a closure flow rate 30 – 40% higher than the nominal flow rate.
This performance means that a single device can be used in systems with either metal (M) or plastic (K) pipes.

POSITION COMPACT GST Teco
COMPACT INSTALLATION

COMPACT INSTALLATION

Because of its very small size, the GST® device is built into the gas meter valves.
In addition to the technical benefits, this gives an economic saving without any additional cost to the installer.

COMPACT INSTALLATION GST Teco

CHOOSING THE GST®

The GST must be chosen according to the following parameters:

  • According to the working pressure:
    Pe 15-100 mbar
  • According to the application:
    Natural Gas
    LPG
  • According to the installed power given by the sum of the individual downstream appliances:
    Σ kW
  • According to the type of installation:
    Main pipeline
    Ofttake pipeline
  • According to the type of system piping:
    Metal (M)
    Plastic (K)
PRESSURE DROP GST Teco

GST IDENTIFICATION MARKING

In accordance with the standards, the GST® is supplied with a label that describes its technical specifications (DVGW VP 305-1).

  • Device nominal flow rate (coloured identification)
  • Pressure range "15 mbar - 100 mbar"
  • Gas flow direction (arrow)
  • Nominal diameter
  • Type of GST® (M/K)
  • “DVGW” marking
  • Installation position

The colour of the label identifies the device flow rate

INSTALLATION GST®

INSTALLATION EXAMPLES

UPSTREAM FROM THE METER
INSTALLATION GST Teco

* Where possible, the GST® is usually installed upstream from the gas meter.

DOWNSTREAM FROM THE METER
INSTALLATION GST Teco

* If the supply line is managed by the gas distribution company, the GST® can be installed downstream from the gas meter.

 
* The choice of GST® is the same regardless of whether it is upstream or downstream from the gas meter.
DOWNSTREAM FROM A SYSTEM WITH PLASTIC PIPES
INSTALLATION GST Teco

In installations with plastic pipes, in addition to using the FIREBAG®, it is mandatory to install a GST® on each offtake (according to the TRGI standard).

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