The Experimental Pressurized Fluidized Bed Combustion Facility at Grimethorpe, South Yorkshire, UK incorporates an in-bed tube bank. During the operation of the facility between June and September 1982, an unexpectedly high degree of metal wastage occurred from the external surfaces of this tube bank. Measures were taken to reduce the rate of metal wastage and extend the life of the tube bank, which was subsequently replaced in July 1983 after a total operating period of 1222 hours of coal burning. Using small-scale fluidized bed cold models, experimental investigations were carried out to determine measures to reduce the metal wastage. The results indicated that metal wastage would be reduced by the following changes: a reduction in the fluidizing velocity; the attachment of studs or axial fins to the tubes; a reduction in the height of the space between the distributor plate and the bottom of the tube bank; and the elimination, where possible of any large gaps within the tube bank. Such changes have been incorporated into the design of the replacement tube bank. This has now been installed and has experienced significantly less metal wastage. 9 references, 6 tables, 34 figures.