Spirelf

An alternative physical method for fouling control uses inserts within the tubes of a shell and tube exchanger. An example is the Spirelf system that consists of a spiral flexible metal device that is inserted and fixed into the tubes.The action of the device is to vibrate in response to the flow of fluid through the tube in which it is situated, thereby keeping the tube surface clean. The vibration is controlled to avoid erosion of the tube surface. It is claimed that the payback time is low of the order of months. 

Bandelet, C.A. The Spirelf system fouling mitigation in refinery units. Second International Conference on Petroleum Phase Behaviour and Fouling, Copenhagen, Denmark, Aug 27-31, 2000 AIChE, Royal Danish Academy of Sciences and Letters, University of Denmark. 

The Spirelf tube insert is a metallic coil stretched over the length of the tube and held in place at each end by straight wires. In operation, when fluid flows through the tube, the Spirelf coil vibrates axially and radially. 

The main applications for Spirelf so far have been oil refinery preheat trains for CDU, VDU, FCC, water treatment feed exchanger HDS units, and also high-tube velocity applications as foimd in reboilers. 

Figure 27.2 Tube inserts Spirelf, Turbotal, and Fixotal.

The concept is that the tube-side fouling rate will be reduced by continuous scrubbing of the tube wall and also have a favorable impact on heat transfer. The associated increase in tube-side pressure drop with this device is about 1.5 psi per pass at 3 ft/s tube-side velocity, about half that of Spirelf or Fixotal. 

General Comments on Spirelf,Turbotal, and Fixotal Tube Inserts... 

Naturally these tube inserts may be attractive as retrofit items, with potential savings in energy costs and reduction of downtime for exchanger cleaning, but it is important to be careful when selecting these, as with any piece of equipment, to be sure that the tube inserts are appropriate for the service for which you intend to use them. Note that both Spirelf and Fixotal can withstand back flushing for cleaning but Turbotal can not. 

Figure 23.2 Tube inserts Turbotal, Spirelf, and Rxotal.

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