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Safety requirements for application of modern gas technology

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Dipl.-Ing. (FH) Harald Petermann Manager Productmanagement Karl Dungs GmbH & Co. Urbach - Germany


Safety requirements for application of modern gas technology

Safety requirements for application of modern gas technology


Safety requirements for application of modern gas technology

Introduction Armatures which are necessary for the operation of gas appliances may be divided into two groups depending on their function: The first group represents closing valves, that means devices which open or close the gas flow and which are manually operated or by means of auxiliary energy. This group also represents gas control valves and multifunctional gas control valves.

The regulating functions are mainly covered from the second group, the gas pressure regulators. Apart from these functional features, armatures may as well be classified as per mode and size of their connection to other armatures, the max. operating pressure and the rated pressure.

Common connections are threaded pipes as per ISO 7-1 or ISO 228 for threaded tubes and fittings up to DN 50 and an operating pressure of 4 bar. Flanges with connection sizes as per ISO 7005, for example welded flanges as per DIN 2633 represent the other group of common connections.


Safety requirements for application of modern gas technology

Introduction The max. operating pressure is the max. pressure the armature may be operated at and has to be indicated by the manufacturer. As far as gas pressure regulators are concerned, the upper limit of the gas supply pressure as well as the minimum gas supply pressure have to be indicated. This results in a pressure range, which is called gas supply pressure range.

Armatures with an operating pressure lower than 1 bar may carry the pressure stage PN 1. Equipment for gas appliances and gas burners are generally designed for operating pressures below 1,0 bar, as the normally required gas pressure for the combustion is only a few millibar above the atmospheric pressure.


Safety requirements for application of modern gas technology

Equipment of gas appliances and gas burners with safety- and regulating devices Depending on their utilisation, gas appliances and gas burners may be designed very differently. General and safety requirements for gas appliances are described in EN standards. Devices which have to guarantee a safe operation of the gas appliances and gas burners have to fulfil a minimum standard which is settled in the appropriate appliance standards, for example EN 676. Should fuel gases be used for example to fire a steam boiler – whether on sea or land – the technical guidelines for steam boilers have to be observed. These standards, which are especially harmonized with the needs of the gas consuming facility are basically valid in conjunction with the appropriate operating papers of the national authorities. Superior regulations, guidelines and decrees of the legislators have to be considered as well, for an example the Gas Appliance Directive and Pressure Equipment Directive.


Safety requirements for application of modern gas technology

Gas safety- and regulating controls, gas trains, ignition devices, flame- and fan monitoring The necessary armatures for the operation of a gas consuming facility are fitted to a gas train. At the approval of a gas burner, these gas trains are a part of the unit. A gas train for gas burners - with or without fan - has measuring- and test points after the manual shut-off valve (to be installed at site) for pressure measuring and pressure indication of the gas supply pressure. The first armature in the gas flow direction is the gas filter as per DIN 3386, followed by the gas pressure regulator, which generally corresponds to EN 88 or – for higher requirements corresponds to EN 334. Gas pressure governors as per EN 88 are classified as class A, class B or class C , according to the appropriate inlet pressure and flow rate limits. The pressure regulated by these armatures is monitored through a pressure switch. Pressure switches are described in EN 1854 : Pressure sensing devices for gas burners and gas burning devices. Shut-off and release of the gas flow are effected through safety shut-off devices. These gas control valves – operated with auxiliary energy – have to comply with EN 161. Usually a pre-adjustment device is already combined with one of the safety shut-off valves. Based on the EU - Gas Appliance Directive two safety shut-off valves have to be installed. Right before the gas nozzles of the burner a pressure test point or a gas pressure gauge is fitted. Test points and gas pressure gauges in the gas train of a gas burner must be self-closing or manually operated.


Safety requirements for application of modern gas technology

Gas safety- and regulating controls, gas trains, ignition devices, flame- and fan monitoring The combustion of fuel gases starts by means of an ignition device in form of ignition burners or electrical sparks. Flame monitoring is to be carried out via suitable devices. Automatic control for gas burners and gas appliances with or without fan, as specified in EN 298 have to be used. Concerning gas burners with fan the following items must be fitted: - protection device for moving parts - micro-switches for the monitoring of the air flap at low and high air volume - function control device for the fan. Pressure switches as per EN 1854 are used for the function control of the fan. Instead of using an air pressure switch, another control device with signal output, as a flow switch may be used for the function check of the fan.


Safety requirements for application of modern gas technology

Armatures of the gas train, standards Manually operated shut-off devices DIN 3537, part 1 “gas armatures” respectively the sketch of DIN 3537, part 1 “shut-off devices for gas installations” describes the requirements and the acceptance test of non underground-laying, metal and manually operated shut-off devices for a max. operating pressure of 4 bar and a max. connection size of DN 150. EN 331 limits the application of brass containing ball valves to 1 bar. Dirt traps and gas filters DIN 3386 “filters in internal gas pipes” is valid for requirements and testing of gas filters for gases for a max. operating pressure of 4 bar. Gas pressure regulators and gas pressure governors for gas consuming facilities EN 88 describes gas pressure governors for gas consuming facilities for gases for a max. gas supply pressure of 200 mbar. Devices for higher gas supply pressures up to 100 bar are described in EN 334. Due to this large gas supply pressure range, the requirements of EN 334 are obviously higher. EN 88 “pressure regulators for gas appliances for a max. gas supply pressure up to 200 mbar” has replaced DIN 3392 .


Safety requirements for application of modern gas technology

Safety shut-off devices EN 161 specifies the safety, construction and performance requirements for automatic shut-off valves for gas burners and gas appliances. EN 161 is a partial replacement for DIN 3394, part 1. The pressure range above pressure stage PN 4 is not covered by this standard. EN 161 specifies 6 classes of valves : Class A, B and C valves where the sealing force is not decreased by the gas inlet pressure, Class D valves which are not subject to any sealing force requirement. Class E valves where the sealing force is decreased by the gas inlet pressure and Class J valves with reduced requirements to the sealing force. Gas- and air pressure switches The usual pressure switches for monitoring of the pressures of the necessary partial volumes for the combustion are described in EN 1854. It describes pressure sensing devices for gas burners and gas appliances, specific requirements are given for type S approvals. EN 1854 replaced DIN 3398 in its parts. Valve proving systems Valve proving systems for automatic shut-off valves for gas burners and gas appliances are described in EN 1643. VPS is required, based on EN 676 , for main burners with pre-purge above 1200 kW or at main burners without pre-purge in all sizes above 70 kW. Below 70 kW two Class B valve with VPS are an alternative to two Class A valve.


Safety requirements for application of modern gas technology

Multifunctional controls and combination of devices In the past years, we see a significant concentration of above armatures towards compact devices. The manufacturers intend to offer - safe - maintenance-free - service- and operational friendly - compact - good value devices. Consequently a whole range of gas devices were designed which may cover all functions of a gas- safety and regulating line. An example for such a designed gas devices is the GasMultiBloc of DUNGS. This compact armature incorporates in its standard version a gas filter, a gas pressure switch as per EN 1854, a gas pressure regulator as per EN 88 and two automatic shut-off valves as per EN 161, class A. The second control device may be fitted alternatively with a hydraulic brake for slow opening, a main volume restrictor and a two stage operated actuator with low fire and high fire adjustment. The integrated gas valves may be energized together or separately. If energized separately, it offers the possibility to take off an ignition gas volume in front of the second gas control valve. A special version with a third gas control valve as integrated bypass valve meets the requirements of “British Standards�.


Safety requirements for application of modern gas technology

A modular designed accessories system allows individual and customized solutions. The closing of the compact armature and its shut-off valves may be checked at closed position by a valve proving system which is tuned with the compact armature. The integration of the pressure governor in the first valve and the use of double-seat valves allow high gas volumes and low pressure drops at a very compact construction. The ongoing development of these armatures and the introduction of new pressure regulating devices allow a modulating operation of the gas consuming facility. Gas-/air ratio controls with compensation of the combustion chamber pressure are achieved by means of servo pressure governors. The pressure of the combustion air serves as reference input, the combustion chamber pressure compensates. The ratio of gas- and combustion air pressure may be set within a defined range. The system of pneumatic gas / air ratio control can be used for gas burners with fan. A trend of compact gas armatures is seen up to a nominal diameter of DN 125. Furthermore double solenoid valves with a modular accessory system covering all function- and safety relevant functions changed the image of the “traditional gas train� as it has been changed by the GasMultiBloc before.


Safety requirements for application of modern gas technology

The DUNGS Modular Gas Safety System -DLE -D

The Double Solenoid Valve DMV is the main component of the DUNGS Modular Gas Safety System comprised of:

2

2

1 DMV combines two Safety Shut-Off Solenoid Valves in one housing 1

2

2 GAO Gas Pressure Switch 3 Flanges 1/2" to 2" NPT threaded 4 FRI Pressure Regulator with built in 50 micron Filter 5 GML manual reset Low Gas pressure Switch

3

4

6 5

9

6 GMH manual reset High Gas Pressure Switch 7 Visual Indicator

7

8 CPI 400 Closed Position Indicator Switch 9 Pilot Line Connector 10 VPS 504 Valve Proving System 8

10


Safety requirements for application of modern gas technology

Double solenoid valve

Pressure gauge

Pilot-/Startgas valve Valve proving system

Pressure regulator Filter Ball valve

Pressure switch


Safety requirements for application of modern gas technology

Safety blow-off valve

Double solenoid valve Pilot-/Startgas valve

Pressure gauge

Valve proving system Pressure switch Pressure gauge

Filter Ball valve

Pressure regulator with built-in safety shut-off valve

Test burner


Safety requirements for application of modern gas technology

MultiBloc 1-stage operation


Safety requirements for application of modern gas technology

MultiBloc 2-stage operation


Safety requirements for application of modern gas technology

MultiBloc Gas/Air ratio control


Safety requirements for application of modern gas technology

Valve proving systems


Safety requirements for application of modern gas technology

Solenoid valves 1-stage operation


Safety requirements for application of modern gas technology

Solenoid valves 2-stage operation


Safety requirements for application of modern gas technology

Manual shut-off valve


Safety requirements for application of modern gas technology

Gas Pressure Switches


Safety requirements for application of modern gas technology

Air Pressure Switches Centrifugal Switch

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