Tube support grid

Supporting grid for tubes in a casing for use in a steam generator heat exchanger and other similar apparatus, comprising:

• a central reticular structure for supporting tubes comprised of a first material and being formed of a plurality of lower (1) and upper (2) equally spaced main intersecting strips being provided with inter-engaging main milled slots at the intersecting zones and with equally spaced secondary milled slots therebetween, said structure also comprising a plurality of lower (3) and upper (4) secondary strips which are housed in said secondary slots, said main lower (1) and upper (2) strips terminating with opposed L-shaped ends (1c,1r,2c,2v);
• a peripheral structure connectable to the casing comprised of two parts:
• an inner annular frame (5,6,7;
• 45) capable of receiving the strip ends of an outer annular frame consisting of two opposed L-shaped rings (8,9) capable of receiving said inner frame and blocking, at room temperature, said reticular structure by means of annular dogs (8a,9a) which are provided in the inner zone of said outer annular frame, said dogs extending axially and being directed towards the inside of the structure;
• said inner annular frame (5,6,7;
• 45) being formed of the same first material as said strips and being capable of receiving the ends of said strips (1,2,3,4);
• said inner annular frame being higher than the central reticular structure, thus forming, at both ends, projecting portions (6-t, 45-t, 7-t, 45-t'), together with cleaning ducts therebetween (6e, 45e;
• 7e, 45-e');
• said outer annular frame being formed of a second material and having an outer lower box-ring (8) and an outer upper cap-ring (9), said rings being capable of receiving and containing said projecting portions (6-t, 45-t, 7-t, 45-t') of said inner annular frame (5,6,7;
• 45), thus blocking, at room temperature, said reticular structure through said projecting portions;
• and
• said outer rings (8,9) being assembled to said inner annular frame (5,6,7;
• 45) so that, at room temperature, said annular dogs (8a,9a) of said outer rings (8,9) are assembled to the inner cylindrical surfaces of said projecting portions (6-t, 45-t, 7-t, 45-t') of said inner annular frame, while there is a play (17) between the outer cylindrical surface (6-s, 5-s, 7-s;
• 45-s) of said inner annular frame and the inner cylindrical surface (8-s) of the outer annular frame in order to allow the free thermic expansion of the two materials.