Vapor generator wall buckstay arrangement

Claim 1

A FLUID HEATING UNIT COMPRISING A PAIR OF SPACED UPRIGHT WALLS DEFINING THEREBETWEEN A HEATING CHAMBER WHEREIN THE FLOW OF HOT COMBUSTION GASES IS CONFINED, A RIGID SUPPORT STRUCTURE EXTENDING ABOVE SAID HEATING CHAMBER, SUPPORT RODS INTERCONNECTING SAID SUPPORT STRUCTURE AND SAID WALLS FOR THE PENDENT SUPPORT THEREOF, A BUCKSTAY SYSTEM DISPOSED OUTSIDE OF SAID HEATING CHAMBER FOR PROVIDING LATERAL SUPPORT AND REINFORCEMENT TO SAID WALLS, SAID WALLS AND SAID BUCKSTAY SYSTEM BEING SUBJECT TO DIFFERENT RATES OF LINEAR THERMAL EXPANSION, SAID BUCKSTAY SYSTEM INCLUDING A GRID ADJACENT EACH OF SAID WALLS, EACH OF SAID GRIDS INCLUDING A HORIZONTAL STRUCTRAL MEMBER AND AT LEAST ONE VERTICAL STRUCTURAL MEMBER ENGAGED WITH SAID HORIZONTAL STRUCTURAL MEMBER AT THE APPROXIMATE MIDPOINT OF THE ADJACENT WALL, MEANS RESTRAINING SAID GRIDS FROM MOVEMENT AWAY FROM SAID WALLS, MEANS RIGIDLY CONNECTING ONE OF SAID GRIDS WITH ITS ADJACENT WALL AT ONE LOCATION, AND MEANS PERMITTING RELATIVE VERTICAL MOVEMENT BETWEEN SAID ONE GRID AND ITS ADJACENT WALL IN OPPOSITE DIRECTIONS ABOVE AND BELOW THE LOCATION OF THE CONNECTION.