Metal Ribbon

The crimped metal ribbon arresdng element, shown in Fignre 5-1, is one of die most widely nsed types, especially for detonadon flame arresters. Crimped metal ribbon arresters are made of alternate layers of diin corm- 

One crimped metal ribbon flame arrester mannfactnrer has a composite element design consisting of mnltiple crimped metal ribbon elements with diverter shields (tnrbnlence-indncing devices) between the elements (Enardo n.d.). This design is based on the patent issned to Ronssakis and Brooker (1995). 

Crimped metal ribbon arresting elements can be made circnlar, rect-angnlar, or sqnare depending on the shape of the pipe or honsing in which they are to be installed. The element is often reinforced by inserting metal rods radially throngh the assembly. 

FIGURE 5-1. Typical crimped metal flame arrester element details. 

Crimped metal ribbon flame arresters are applicable for both deflagrations and detonations. They are especially used for detonations, since the apertures can be made very small, which is necessary to stop a detonation. 

---

It was not nndl the 1950s that detonation flame arresters made of crimped metal ribbon elements were developed and began to be used more freqnendy (Binks 1999). The major impetus for die use of crimped metal ribbon detonation flame arresters in the US was the enactment of clean air legislation (Clean Air Act of 1990) which inadvertently created a safety problem by requiring reductions in volatile organic compound (VOC) emissions. To do this, manifolded vent systems (vapor collection systems) were increasingly installed in many chemical process industry plants which captured VOC vapors and transported them to suitable recovery, recycle, or destruction systems. This emission control requirement has led to the introdnction of ignition risks, for example, from a flare or via spontaneous combustion of an activated carbon adsorber bed. Multiple... 

Eor noncircular apertures, the equivalent hydraulic diameter should be used. Eor crimped metal ribbon elements, the equivalent hydraulic diameter of a right isosceles triangle is 0.83 times the crimp height, and the thickness (width) should be at least 0.5 inches (EISE 1980). 

The HSE Guide (1980) presents two equations for detonation flame speeds, one for crimped metal ribbon arresters, and one for pipes. 

Eor crimped metal ribbon arresters it provides the following equation for the maximum flame speed obtained by Cubbage (1959) for the stoppage of town gas-air mixture detonations by arresters with a crimp height of 0.017 inches ... 

Depending on the design, the pressnre drop throngh a crimped metal ribbon flame arrester may exceed that of a parallel plate type of the same size. If a crimped metal ribbon type arrester is nsed for end-of-line service... 

Protego offers a crimped metal ribbon flame arrester approved in Germany for acetylene service. It is similar in design to their flame arresters for hydrogen service bnt the hydranlic diameter of the flame arrester apertures for qnenching acetylene flames is 0.15 mm rather than 0.20 mm for hydrogen. 

Crimped Metal Ribbon A flame arrester element that is manufactured of alternate layers of thin corrugated metal rihhon and a flat metal rihhon that are wound together on a mandrel to form a cylindrical assembly of many layers to produce a range of different sized triangular cells. The height and width of the triangular cells can he varied to provide the required quenching diameter. 

Static Flame Arrester A flame arrester designed to prevent flame transmission by qnenching gaps (apertnres). These are nsnally dry type flame arresters with elements snch as crimped metal ribbon, parallel plates, wire ganze (mesh), and sintered metal. 

An alternative method of manufacturing is to employ a coil of flat metal ribbon as the element, each turn spaced from the next by small lateral protuberances. The principle of filtration is the same. Porosity of both types are identical and cover a wide range, usually from 100 microns down to 0.5 microns. 

Figure 25 indicates the principle of one of the arrangements used. A metal ribbon 1 is loaded with a weight 2 and suspended from a membrane 3 it is surrounded by the electrolytic solution 4. When alternating current passes through the ribbon,... 

Fig. 25. One of the arrangements used to demonstrate the effect of electric charge on the 7S. 1 is a metal ribbon loaded with weight 2, suspended on membrane 3, and immersed in an electrolyte solution 4. The vibrations are recorded by piezoelectric indicator 5. Simplified from Ref.162 ...

Ferrous ammonium sulphate Q. 73 Ferrous sulphide for H2S generator IV, VIII, X, P. 70 Lead dioxide IV, IX Lead monoxide IV, IX Lead nitrate Q. 47, IX Litmus paper, blue Litmus paper, red Magnesium metal, powder IV Magnesium metal, ribbon II, IV, V, VIII... 

Leaks past barriers or float can be tested for by sprinkling talc on the surface this travels with the film leaking past, and can be seen at once. With metallic ribbons leaks can be stopped by leading the water surface up, by stroking with a thin wire, preferably heated just previously so as to agitate the water surface. Once stopped, leaks rarely recur. 

Electrothermal atomisers come in many shapes and sizes, ranging from tube furnaces to metal ribbons. At present, the most popular form is the graphite tube furnace of which a number of designs are commercially available. The electrothermal devices vary markedly in their atomisation characteristics and a method suitable for one design will not necessarily work on another without some modification. 

---