Recemat International
In long uninterrupted lengths of pipe, flames can easily attain very high velocities e.g. typically 2000 m/s, for town gas-air mixture. Shorter lengths produce flames of correspondingly lower velocity - type of gas also has an effect. The lower hydrocarbons methane, butane etc., have a lower velocity than hydrogen or acetylene. RECEMAT metal foam type RCM-NC 2733.13 has been shown to be capable of arresting flames in pipes containing ethylene-air mixtures, having velocities up to 550 m/s. Work carried out by the Electrical Research Association has proved RCM-NC-4753 grade RECEMAT metal foam capable of arresting hydrogen-oxygen flames where the initial gas pressure was 2.75 bar-g.
In practice, long runs of pipe containing pre-mixed gas are protected near to possible sources of ignition, fan outlets, pumps, valves etc, so that if ignition does occur, the flame does not have enough length of pipe to accelerate to high velocities. In these cases, the task of the arrester is very much easier and RECEMAT metal foam type RCM-NC 2733 is being considered as the 'standard' arrester material for gases other than hydrogen or acetylene. For low order hydrocarbons, metal foam type RCM-NC-1116.20 could be considered adequate.
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Figure 1
shows the dependence of flame velocity arrested on thickness of RECEMAT metal foam types RCM-NC-1116 and RCM-NC 2733 for ethylene-air mixtures. Similar relationships can be predicted for other grades and an estimated curve, based on a few tests is shown for metal foam RCM-NC-4753 grade. |
RECEMAT metal foam as a pipeline arrester has the approval of the Fire Research Station, UK, who have conducted extensive investigations into the behaviour of metal foam,
Areas where RECEMAT metal foam is and could be used:
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| Example of RECEMAT inline flame arresters, to be mounted between two standard flanges | |
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Mounting of Flange Only Sandwich type
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In-line type
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Switch gear enclosures and boxes containing electrical or electronic control mechanisms are often required to operate in hazardous areas. In these circumstances, the construction of the enclosure has to conform to very strict and rigid design criteria. Flange gaps have to be of a certain size and the housting needs to be massive to contain any explosion which might occur inside.
Investigations carried out by both the Electrical Research Association and Fire Research Station have proved RECEMAT metal foam to be an excellent vent and flame arrester for these applications.
If switch gear is enclosed in a box with large vents covered by RECEMAT metal foam type RCM-NC-2733.l3 explosions can occur within the box with no transmission of flame to the external atmosphere. Furthermore, the internal pressure can be kept as low as 0.07-0.14 bar-g, thus obviating the need for heavy, cumbersome box construction.
All groups of gas have been covered, including hydrogen and acetylene.
Should an enclosure need to be sealed, pressure build up on ignition could rupture the walls of the box, By packing the free volume with RECEMAT metal foam grade RCM-NC-4753, the pressure can be absorbed within the pores of the metal foam; flames are also quenched
Pressure reduction of 6.2 bar, has been produced by filling 50% of the volume with RECEMAT metal foam grade RCM-NC-4753.
Areas where RECEMAT metal foam is being or could be used:
Because of the tortuous nature of the air passages in RECEMAT metal foam, solid particles or sparks ejected during an explosion have difficulty in penetrating a sheet of RECEMAT metal foam. This gives metal foam an added advantage over competitive material.
GENERAL INFORMATION
In order to make full use of the typical characteristics of RECEMAT metal foam forming and machining the material requiers special care. Recemat International has developed the necessary expertise and is happy to supply not only parts but even so complete equipment manufactured to customerspecification. Over and above this Recemat International itself developes products on the basis of RECEMAT metal foam.
RECEMAT metal foam is an extremely strong light weight material having a density typically in the range of only 0,6 - 0,65 g/cm3.
RECEMAT metal foam is over 90% void, in all grades. Or in other words less than 10% of the volume taken is material.
We are designing and producing Flame arrestors, Spark arrestors and the like customized to you specification. In order to make that possible, we would like to know details about the application and other parameters.
You can use our Checklist page or Inquiry Form page as an aid for the specification in your inquiry.