Blades for isolators

#This invention relates to improvements in or relating to blades for isolators, i.e. isolating valves, especially diverter and flap isolators. The invention is particularly concerned with the flap and blade construction (hereinafter referred to as the blade) of large such isolators.

#One of the main problems in the design of isolator blades is to provide a structure that can resist the applied loadings due to gas pressure, weight and seal loading, and will also not distort under start-up/shut down temperature transients as well as steady state elevated temperature operating conditions.

#In the usual construction the blade assembly consists of a blade arm frame with individual blades attached to it, one for flap isolators, two for diverter valves, the attachment being carried out in such a way that differential movements are possible between the blades and blade arm frame.

#FIG. 1 is an exploded isometric view of a known type of blade structure for a divefret isolator;

#FIG. 2a is a perspective illustration of the blade structure of FIG. 1 in its assembled state;

#FIGS. 2b, 2c and 2d are, respectively, fragmentary detail views, in perspective and partly in section or broken away, showing, on an enlarged scale, the portions of the blade structure encompassed by the circled regions A, B and C in FIG. 2a;

#The blade structure of the present invention shown in the drawings comprises a number of plate arms 21, the actual number of arms depending upon the operation conditions and size. At the shaft end these are suitably stiffened to increase the section modulus as required. Between each two adjacent arm 21 two thin plates 22, separated by a gas space 23, are welded to the arms 21. Depending on the size these skin or blade plates are provided with convolutions 24 to give stiffness in the direction parallel to the isolator shaft and to limit the size of each flat plate area to a roughly square aspect ratio, as shown. The blade plates 22 are provided with additional support by means of short tubes 25 protruding through each plate and welded to the plates on the outside. In the same way insulation cladding pins 26 are taken right through each plate and thus provide additional support. The thin plates 22 are each provided on the outside surface thereof with insulation 27 retained by cladding 28.

#The edges of the blade are provided with a special edge section 29 to form the seal mountings. The shape of this edge section is so arranged to allow the greatest possible contact to the gas. At the edges perpendicular to the shaft the seal edge section is welded to the outside of the outer arms. Between each two arms, on each side of the blade there are provided trays to allow the convenient fitting of the thermal insulation 27, retained by the cladding panels 28. This performs the function not only of reducing the heat transfer across the blade when in the terminal position(s), but also serves to maintain the structural skin at the gas temperature to miniraise distortion.

#The arms 21 are provided with extensions 30 which function as blade s tops.