Patent Number: 
Section: claims

1. A buckstay system for a wall of a steam generator having a first wall section which meets a second wall section at an angle to form a corner, the system comprising:a plurality of horizontal buckstay assemblies each comprisinga horizontal buckstay extending generally horizontally across each wall section such as to form a connected pair with an adjacent horizontal buckstay at the said corner,an elongate tie bar formation extending across each wall section such as to form a fixedly mounted pair with an adjacent tie bar formation at the said corner, andan anchor assembly associated with each horizontal buckstay and providing engagement means by which each horizontal buckstay engages with a respective tie bar; and the system further comprisinga plurality of vertical buckstays connected to support and space said horizontal buckstay assemblies vertically up the steam generator; whereineach said horizontal buckstay is split to comprise at least two rigid elongate horizontal buckstay elements mounted together to be relatively slidable in a buckstay longitudinal direction;vertical buckstays are provided in the vicinity of some or all of the points where horizontal buckstay elements of a horizontal buckstay are slidingly engaged; andat a sliding engagement point between two horizontal buckstay elements a vertical support is provided having a fixed engagement with one said horizontal buckstay element, and having a sliding engagement with the other said horizontal buckstay element whereby the other said horizontal buckstay element may slide horizontally relative to the vertical support and relative to the one said horizontal buckstay element. 2. A buckstay system in accordance with claim 1 wherein the connected pair of horizontal buckstays is connected at the said corner by a mechanical connection that does not provide for any expansion in a longitudinal direction. 3. A buckstay system in accordance with claim 1 wherein the connected pair of horizontal buckstays is connected at the said corner by fixed mechanical engagement between a bracket portion on an end of a first such buckstay and a receiving portion on an end of a second such buckstay. 4. A buckstay system in accordance with claim 1 wherein each anchor assembly comprises a support formation fixedly engaged with a horizontal buckstay element, and a bearing surface located to bear upon and engage in use with a surface of a tie bar. 5. A buckstay system in accordance with claim 4 wherein the support formation is a support plate. 6. A buckstay system in accordance with claim 5 wherein two rectangular support plates, comprising an upper and a lower support plate, are deployed above and below a horizontal buckstay element. 7. A buckstay system in accordance with claim 6 wherein the support plates comprise additional stiffening plates in a direction parallel to and/or perpendicular to a longitudinal direction of the horizontal buckstay. 8. A buckstay system in accordance with claim 1 wherein each anchor assembly is provided on a horizontal buckstay element no more than 600 mm inboard of a corner formed by its associated wall and the adjacent wall. 9. A buckstay system in accordance with claim 1 wherein the adjacent tie bars are fixedly mounted to each other at the corner by means of an end connection corner angle reinforcement tie welded to the pair of tie bars. 10. A buckstay system in accordance with claim 1 wherein each horizontal buckstay element comprises a rigid elongate structural member having a web shaped surface. 11. A buckstay system in accordance with claim 10 wherein a sliding engagement connection is provided between a pair of horizontal buckstay elements which permits sliding movement in a longitudinal direction of the two horizontal buckstay elements by means of relative sliding of the web surfaces. 12. A buckstay system for a wall of a steam generator having plural wall sections which meet adjacent wall sections at an angle comprising:a plurality of horizontal buckstay assemblies each comprisinga horizontal buckstay extending generally horizontally across each wall section such as to form a connected pair with an adjacent horizontal buckstay at each said corner,an elongate tie bar formation extending across each wall section such as to form a fixedly mounted pair with an adjacent tie bar formation at each said corner, andan anchor assembly associated with each horizontal buckstay and providing engagement means by which each horizontal buckstay engages with a respective tie bar; and the system further comprisinga plurality of vertical buckstays connected to support and space said horizontal buckstay assemblies vertically up the steam generator; whereineach said horizontal buckstay is split to comprise at least two rigid elongate horizontal buckstay elements mounted together to be relatively slidable in a buckstay longitudinal direction;vertical buckstays are provided in the vicinity of some or all of the points where horizontal buckstay elements of a horizontal buckstay are slidingly engaged; andat a sliding engagement point between two horizontal buckstay elements a vertical support is provided having a fixed engagement with one said horizontal buckstay element, and having a sliding engagement with the other said horizontal buckstay element whereby the other said horizontal buckstay element may slide horizontally relative to the vertical support and relative to the one said horizontal buckstay element. 13. A buckstay system in accordance with claim 12 wherein each anchor assembly comprises a support formation fixedly engaged with a horizontal buckstay element, and a bearing surface located to bear upon and engage in use with a surface of a tie bar. 14. A buckstay system in accordance with claim 13 wherein the support formation is a support plate. 15. A buckstay system in accordance with claim 14 wherein two rectangular support plates, comprising an upper and a lower support plate, are deployed above and below a horizontal buckstay element. 16. A buckstay system in accordance with claim 15 wherein the support plates comprise additional stiffening plates in a direction parallel to and/or perpendicular to a longitudinal direction of the horizontal buckstay. 17. A buckstay system in accordance with claim 12 wherein each anchor assembly is provided on a horizontal buckstay element no more than 2 m inboard of a corner formed by its associated wall and the adjacent wall. 18. A buckstay system in accordance with claim 17 wherein each anchor assembly is within 600 mm of such a corner. 19. A buckstay system in accordance with claim 12 wherein the adjacent tie bars are fixedly mounted to each other at the corner by means of an end connection corner angle reinforcement tie welded to the pair of tie bars. 20. A buckstay system in accordance with claim 12 wherein each horizontal buckstay element comprises a rigid elongate structural member having a web shaped surface. 21. A buckstay system in accordance with claim 20 wherein a sliding engagement connection is provided between a pair of horizontal buckstay elements which permits sliding movement in a longitudinal direction of the two horizontal buckstay elements by means of relative sliding of the web surfaces.