DE4338226A1 - Flame arrester - Google Patents

Description

The invention relates to flame arrestors according to the preamble of claim 1.

Flame arresters are safety devices in connection with welding, cutting or similar devices are used, which with fuel gases, for. B. acetylene, compressed air or compressed oxygen become.

Flame flashbacks can occur with such devices, where the flame through the feed line (s) to the Control devices and the feed gas containing pressurized gas who strikes back.

To minimize the risk due to flashbacks To keep possible, a flashback arrestor inserted downstream in relation to the feed cylinders, preferably as at the outlet of the control device or in the line downstream with respect to the control device.

A typical flame arrester has two or more machined, assembled metal devices on, in particular a flame arrester in the form a sintered, e.g. B. porous component from corrosion permanent steel, e.g. B. a hollow cylinder or a hollow ticket be, through which the gas to the point of consumption is fed. If a flashback occurs, the Front of the flame stopped on the sintered filter, which is the gases that pass through the filter upstream direction due to back pressure, cools, so the possibility of re-ignition on the stream prevents upward side of the sintered filter becomes.  

A flashback safety device usually also has a spring loaded check valve on the upstream side of the flame arrester. The through the flame flashback protection transfers back pressure a closure of this valve to the gas supply in the event of a Turn off gas reflux. This conclusion is only over walking; once the flame has been secured and the If the back pressure decreases, the check valve opens again automatically under the normal pressure of the upstream takes place gas feed, so that the welding, cutting or the same process for which the gases are used again can be included.

Sometimes a flashback safety device has overpressure valve to relieve excessive back pressure, so under other, sooting of the sintered filter is reduced.

A flame arrester often also has either a pressure sensitive or a heat sensitive Valve on the downstream side of the flame back Impact protection to switch off the gas feed when a sustained flashback occurs or from a other reason the back pressure and / or the temperature on the downstream side of the flame arrester becomes abnormally high. The heat sensitive valve in particular is not meant to be in the case of a normal Setback is actuated by the flame setback is handled reliably, but only if dangerous conditions persist.

For this reason, when using a heat sensitive Valve this valve by melting solvent or glue released frequently and cannot be reset become. It forms a disposable part of the device.

According to the invention is a flame arrester with a flame arrester and an upstream or downstream in with regard to the flame arrester, resettable, Heat sensitive valve device proposed, which  a certain temperature range below the range, in which a flame passes through the flame arrester to switch off the gas supply through the device, is operated, the heat sensitive valve device at least one element made of magnetically sensitive material has, which is arranged in the field of a magnet, and the magnetic material being such that it its magnetic sensitivity loses if it is sufficient is warmed accordingly. Many have this property magnetically sensitive materials.

The heat sensitive valve can reset automatically if the temperature is below this valve a certain value falls, or can be reset by hand after the temperature has dropped.

If the magnetically sensitive valve device a certain temperature value below the value reached at which a flame pass through the flame arrester can, the valve device is preferably out of the field of the magnet that is to be moved against a valve seat and thereby switches off the gas feed through the device, Approved. Such a shift is preferably carried out under the action of a spring; the spring action becomes normal se overcome by the attraction that is on the valve device acts due to the field of the magnet.

In the preferred embodiment, the valve device normally due to the attraction of the magnet withdrawn from the valve seat, but if by heating due to a flashback or a fire Valve device loses its magnetic sensitivity, the spring is actuated so that it the valve device away from the magnet into engagement with the valve seat. The pressure of the gas feed can then be maintained assist in closing the valve. When executing form overcomes the attraction generated by the magnet the spring force when the flame flashback is safe cools and the valve device its magnetic  Regains sensitivity, and pulls the valve device tion from the valve seat, so that an automatic return position of the valve is reached. The pressure of the gas feed solution can then help to keep the valve open becomes.

In another embodiment, the Release gas pressure by hand, which causes the valve in the Connection to an actuator is kept closed. A Reset valve that can be used for this purpose also work as a pressure relief valve for the arrangement and is preferably on the upstream side of the Flame arrester arranged.

In the event of an automatic reset, the valve Do not open again until the device is sufficient has cooled down so that it can operate safely again can record what normally takes several minutes takes. The valve device therefore preferably has two Valve elements in the form of upstream and downstream arranged valve disks, one behind the other and through a seal are arranged separately, the downstream disc has a peripheral annular Approach that lies directly on the valve seat. The upstream disc is made of magnetic sensitive material, e.g. B. Monel (registered trademark chen) metal, and the downstream disk exists made of brass. A slotted steel ring clip, the diametrical center is aligned with the seal, connects the two valve elements with each other and enables light a limited freedom of movement between them, the is sufficiently large so that the seal in the appropriate case Arranged downstream through a small axial opening open brass disc.

When the valve is closed, a pressure build-up builds up occurred on the valve seat and the valve can not again open, d. H. be reset until this pressure in is substantially relieved. The upstream  Valve disc that is removed from the valve seat however only in the closed position of the valve the pressure difference kept on the area of the small Opening in the downstream disc acts which rests directly on the valve seat, and is thereby in the limited extent by the slotted steel bracket is allowed to be deducted relatively quickly when the device cools, which opens the seal. So then the pressure difference at the valve seat slowly over the small opening in the disc resting on the valve seat released so that a corresponding and previously determinable Time later the full valve device will be able to is to withdraw completely and thereby close the valve to open. A shield of steel or preferably protects more appropriately made of brass, that of the downstream Valve disc is added, the seal against direct Influence of a flashback by the little one axial opening in the downstream valve disc. In addition, a baffle plate in the gas feed channel downstream in relation to the flame arrester act the speed of a flashback reduced before it has reached the kickback protection.

In case of manual reset, the valve device can a single, magnetically sensitive valve element normally from a valve seat to one Permanent magnet is kept deducted and the spring provision is tight to close against the valve seat when the magnetic sensitivity due to intense heating, which occurs in the event of a longer flashback, get lost.

If the valve is closed in the event of a flashback pressure difference builds up on the valve, and the higher pressure on the upstream side must be relieved before the valve is opened again can. It is therefore first necessary to upstream this to relieve downward pressure, e.g. B. by partial or full permanent suppression of the gas feed, or on  other way, and then when the device has cooled sufficiently is the check valve on the upstream side of the Flame arrester to open by hand to the higher Pressure on the upstream side of the valve relieve pressure so that the valve element under the influence of the Magnet can stand out. The gas feed can then again getting produced.

As mentioned earlier, it is known to be a spring loaded Check valve on the downstream side of the Flame arrester must be provided. Expediently in the preferred arrangement according to the invention the back check valve also used for resetting. To this The gas is normally used through the check valve fed that against the closed position by a suitable spring is pressed, the effect of which is normally is overcome by the feed pressure. If an essential Pressure build-up on the downstream side of the valve occurs, this pressure acts on the valve component and closes the valve by supporting the action of the Spring so that the gas feed is switched off. The However, valve can be opened by hand Element that is pressed onto the valve component via the compressed spring acts like this for resetting afterwards required to operate the heat sensitive valve is.

Below are two embodiments of a flame back impact protection according to the invention in connection with the Drawing described. It shows:

Fig. 1 is a flame arrester with a self-resetting conditions in axial section, and

Fig. 2 shows a device with manual reset in axial section.

The flame arrestor device according to Fig. 1 has three devices from machined metal, which are arranged in a housing 10. The housing contains a cylinder 12 made of sintered, corrosion-resistant steel, which is a flame arrester. A one-way valve 14 with an associated return spring 16 is inserted into the housing 10 on the upstream width of the flame flashback safety device 12 . This valve has a conventional structure and is not described in detail. Although the valve is shown in the closed state, it is automatically opened when gases under pressure, e.g. B. oxygen and acetylene, are fed through the end fitting 18 on the upstream side of the device, the feed gases entering the chamber 20 .

These feed gases are then directed radially outwards through the wall of the porous flame arrester 12 into the channel 22 and flow downwards into radial channels 24 which open into the chamber 26 and from there when a heat-sensitive valve according to the invention is opened is, lead in lines or hoses through the downstream end fitting 28 to the user point. In Fig. 1, the heat sensitive valve of the invention on the downstream side of the flame check valve 12 is shown closed or actuated.

A machined body 30 is received in the housing 10 and its downstream end receives the prescribed radial channels 24 which open into the chamber 26 ; chamber 26 is formed between the downstream end of body 30 and end fitting 28 . The heat sensitive valve is in principle taken up in the chamber 26 and prevents the entry of feed gases from the chamber 26 into the end fitting 28 in the closed state.

The upstream end face of the end fitting 28 is grooved to receive an O-ring seal 32 which forms a valve seat. A displaceable valve device, which consists of a downstream valve disk 34 made of brass, a seal 36 and an upstream valve disk 38 made of Monel (registered trademark) metal, is pressed by a spring 40 into a closed position against the valve seat 32 . The Ventilvor direction also has a slotted steel bracket 41 which surrounds the seal 36 and which allows a limited relative axial movement between the valve disks 34 and 38 . A two-part magnet 44 is inserted into the body 30 .

Monel metal is an example of a magnetically sensitive material that verifies its magnetic sensitivity if it is heated to a certain temperature. In practice, this temperature can be roughly selected by choosing one suitable, magnetically sensitive material from many possible materials can be determined.

During normal operation, the magnetic attraction of the disc 38 on the magnet 44 overcomes the force of the spring 40 to withdraw the discs from the valve seat 32 , thereby opening the valve for the passage of feed gases. If the disc 38 is heated to a predetermined temperature at which the magnetic sensitivity is lost due to a sustained flashback or possibly a fire in the area, the magnet 44 is no longer effective and the spring 40 presses the discs against the valve seat 32 , to close the valve and stop the gas supply.

When the disks 34 , 38 have regained their magnetic sensitivity after the device has cooled, the valve is automatically opened again, ie reset. In practice, however, the valve does not need to be reset for a few minutes while the device cools down to a temperature at which restarting the operation of the welding device is suitable. This is possible, in part, by building a pressure differential between the upstream and downstream sides of valve seat 32 when the device is heated intensely due to a sustained kickback or the like that caused the valve to close, and in part by use the composite valve device, which is formed by the valve disks 34 , 38 and the spacer 36 arranged therebetween.

The downstream valve disc 34 has a small central opening 46 , which is shielded by a steel plate 48 , so that the pressure difference at the valve seat 32 of the upstream valve disc 38 (via the seal 36 ) is only given over the small cross-sectional area of the opening. When the device cools, the valve disc 38 is pulled off rather quickly against the magnet and takes the seal 36 with it, as far as this is permitted by the slotted steel clip 41 . This movement is sufficient for the pressure differential at valve seat 32 to be slowly relieved via port 46 on downstream valve disc 34 until a suitable and (due to the dimensions of the port) selectable later point in time the complete valve assembly is withdrawn against the magnet, thereby the valve is fully opened. If the heat sensitive valve is reset in this way, it is ensured that the use of the device can be taken up again.

The steel shield 48 , which is received by the downstream brass valve disk 34 in a recess formed by a peripheral annular projection of the valve disk which is in engagement with the valve seat 32 , protects the seal 36 against a direct influence by a flashback. In addition, a baffle plate 50 acts in the downstream end fitting 28 in such a way that the speed of a flashback is reduced before it reaches the flashback safety device. Finally, the mold 52 in the chamber 26 is essential for utilizing the pressure of the normal gas feed during the operation of the flame check valve device.

The preferred device according to FIG. 2, which has a manual instead of an automatic reset, is designed differently. A normal gas flow from a feed source, which can be switched off at 53 , takes place via a combined, spring-biased check and reset valve 54 in a retaining ring 56 which has grooves which are in contact with spaces outside of the flat areas 58 (see FIGS. 2a and 2b). of an externally square machined body 60 . A normal gas flow thus takes place downstream in the body 60 into the space 62 radially outwards through the flame flashback device 64 and in the radial direction backwards through channels in the component 66 into the free space 68 and from there into the outlet 70 of the cap 72 . The heat sensitive valve provided within the machined body 60 is located upstream of the flame arrester rather than downstream as shown in FIG. 1. This reduces soot in the heat sensitive valve.

The heat-sensitive valve has a permanent magnet 76 , which holds two disk magnets 78 , 80 and a valve disk 62 made of magnetically sensitive material (e.g. Monel metal), on which a spring 84 acts, in position. Although two disc magnets 78 , 80 are shown, a one piece magnet can also be used. The action of the spring 84 is normally overcome by the attraction of the magnets 78 , 80 so that the valve disc 82 is normally pulled against the magnets 78 , 80 , whereby the heat sensitive valve is normally open.

In the event of significant and / or persistent overheating of the device, the entire device containing the heat sensitive valve is heated and the valve disc 82 loses its magnetic sensitivity so that the action of the spring 84 is effectively to close the valve. and the normal gas supply is switched off, since gas can no longer flow into the space 62 from outside the outside square body 30 . Substantial gas pressure also builds up inside the heat-sensitive valve when gas is present all around the valve disk 82 and behind the valve disk, which does not form a seal seat inside the machined body 30 . This high internal gas pressure helps to keep the heat sensitive valve closed, and resetting at the end of the flashback is only possible by relieving the high internal pressure. For this purpose, the check valve 54 is provided with a reset option. In FIG. 2, the valve disc is shown in the closed position 82nd

During normal operation, this valve 54 acts in a conventional manner in the event of a high back pressure to prevent back flow of gases. The valve opens automatically when the back pressure drops. The valve also acts as a reset valve following the closing or actuation of the heat sensitive valve. The operator must first relieve the upstream pressure, possibly by partially or fully releasing connector 53 (after the gas flow has been shut off at an upstream location). In any case, these processes are desirable if the flashback continues. The valve 54 then closes as a result of the back pressure that overcomes the action of the main spring 86 . When the reset button 90 is manually depressed and held down, the valve 54 is opened through a stack of O-rings 88 to allow a backflow of gases from inside the heat sensitive valve via the outside of the processed body 30 in a reverse path to the normal gas flow to enable when the feed takes place.

Pressure relief within the heat sensitive valve will then operate that valve to reopen, provided that valve disc 82 has cooled sufficiently to restore magnetic sensitivity. If this is not the case, the heat-sensitive valve opens again when it has cooled sufficiently. A renewed connection of the feed source then shows that normal operation can be carried out again.

A number of modifications are possible within the scope of the present invention. For example, a reset valve can be provided separately from the upstream check valve on the downstream side of the heat-sensitive valve, in particular to replace the automatic reset option in the exemplary embodiment according to FIG. 1.

Claims (8)

1. Flame flashback device with a flame arrester ( 12 ; 64 ) and a resettable heat-sensitive valve device ( 32 , 34 , 36 , 38 ; 82 ) arranged downstream or upstream with respect to the flame arrester, which at a certain temperature range is below the range at which a flame can pass through the flame arrester in order to switch off the gas feed through the device, characterized in that the heat-sensitive valve device ( 32 ,...) has at least one element made of magnetically sensitive material, which in the field of a magnet ( 40 ; 78 , 80 ), and that the magnetic material is such that it loses its magnetic sensitivity if it is heated sufficiently. 2. Flame flashback device according to claim 1, characterized in that the heat-responsive Ventilvor direction ( 32 , 34 , 36 , 38 ) is automatically reset when the temperature in the region of this valve falls below a certain value. 3. Flame flashback device according to claim 1, characterized in that the heat-responsive valve ( 82 ) can be reset by hand ( 90 ). 4. Flame flashback device according to claim 1, 2 or 3, characterized in that when the magnetically sensitive valve device has reached a certain temperature value below the temperature value at which a flame can get through the flame arrester ( 12 ; 64 ), the valve device the field of the magnet to be displaced ( 40 ; 78 , 80 ) is released by a spring ( 16 ) against a valve seat ( 32 ) and thereby the gas feed through the device is switched off, and the spring action is normally overcome by the attractive force acting on it the Ventilvor direction acts due to the magnetic field. 5. flame arrester according to claim 4, characterized characterized in that in the closed state of the Heat responsive valve the pressure of the gas feed closing the valve on the valve device supported. 6. flame arrester according to claim 2, characterized in that the valve device ( 32 , 34 , 36 , 38 ) has two valve elements in the form of upstream and downstream valve disks ( 38 , 34 ), and that the two valve disks via a split ring bracket ( 41 ) are connected to one another, which gives a limited range of movement between the valve disks, which is sufficient to release the internal pressure via a small axial opening ( 46 ) in the downstream disk ( 34 ). 7. flame arrester according to claim 3, characterized by a spring-loaded check valve ( 54 ) on the upstream side of the flame arrester ( 64 ), which is a manual reset for the heat-responsive valve ( 76 , 78 , 80 , 82 , 84 ) . 8. flame arrester according to any one of claims 1-7, characterized by a baffle plate ( 50 ) in the gas supply channel ( 22 ) downstream with respect to the flame protection ( 12 ; 64 ), which acts so that it reduces the speed of the flashback, before it has reached the flame arrester ( 12 ; 64 ).