Sootblower isolation wall box

1. A wall box assembly for a sootblower of the type having a lance tube for cleaning internal surfaces of a combustion device, and wherein a fluid cleaning medium flows through the lance tube during a cleaning cycle and is ejected from the lance tube within the combustion device, the lance tube passing through the wall box assembly and being retractable into and withdrawn from the combustion device, the wall box assembly comprising:

a clamping seal assembly having a plurality of movable seal assemblies, the movable seal assemblies each having a seal element movable in a radial direction relative to the lance tube, the seal elements engageable with the outside surface of the lance tube in a sealing position and withdrawn from sealing contact with the outside surface of the lance tube in a released position, the seal elements movable between the sealing and released positions through the action of an actuator,

wherein the clamping seal assembly includes a housing forming an internal chamber with a cylindrical wall and a circular jaw plate, the jaw plate mounted within the internal chamber with a clearance gap between the jaw plate and the cylindrical wall, the actuator being formed of a plurality of pistons retained by the jaw plate and each piston coupled with one of the seal elements and configured to move the one of the seal elements radially with respect to the jaw plate, and the jaw plate being radially movable within the internal chamber and self-centering around the lance tube.

2. A wall box assembly for a sootblower in accordance with claim 1 wherein the clamping seal assembly restricts leakage of gasses between the interior of the combustion device and the exterior of the combustion device when the clamping seal assembly is in the sealing position.

3. A wall box assembly for a sootblower in accordance with claim 1 wherein the actuator is in the form of a fluid actuated cylinder with a piston coupled with the seal element.

4. A wall box assembly for a sootblower in accordance with claim 3 wherein the clamping seal assembly includes housing and a plurality of the fluid actuated cylinders are mounted to the housing.

5. A wall box assembly for a sootblower in accordance with claim 1 wherein the clamping seal assembly includes a housing having surfaces which restrain the seal elements of a plurality of the seal assemblies to move in a radial direction between the sealing and released positions.

6. A wall box assembly for a sootblower in accordance with claim 1 wherein the actuator is biased by a spring to a cause the seal element to be urged by the spring toward the released position.

7. A wall box assembly for a sootblower in accordance with claim 1 wherein the clamping seal assembly includes at least three of the movable seal assemblies and are oriented such that each of the seal elements are in substantially equal angular arc segments around the outside surface of the lance tube.

8. A wall box assembly for a sootblower in accordance with claim 1 wherein the seal element is retained within a seal shoe which is connected with the actuator.

9. A wall box assembly for a sootblower in accordance with claim 1 wherein the clamping seal assembly having housing and the seal assemblies forming a pair of radial face surfaces and corresponding sealing surfaces of the housing engage with the radial faces.

10. A wall box assembly for a sootblower in accordance with claim 1 wherein the wall box assembly further comprising a secondary seal assembly for sealing with the outside surface of the lance tube.

11. A wall box assembly for a sootblower in accordance with claim 10 wherein the clamping seal assembly and secondary seal assembly are connected together with the lance tube passing through both the seal assemblies with the secondary seal assembly mounted closer to the cleaning port than the clamping seal assembly.

12. A wall box assembly for a sootblower in accordance with claim 1 wherein the seal elements, when in the sealing position, form a generally continuous circumferential seal against the outside of the lance tube.

13. A wall box assembly for a sootblower in accordance with claim 1 wherein the internal chamber is supplied with pressurized fluid and the pistons are exposed to the fluid, such that applying fluid pressure to the internal chamber actuates the seal elements to move to the sealing position, and wherein the jaw plate is self-centered by the fluid pressure within the internal chamber to engage with the lance tube in the sealing piston as the lance tube is positioned in a range of positions relative to the center defined by the annular chamber.

14. A method of sealing a lance tube for cleaning internal surfaces of a combustion device, and wherein a fluid cleaning medium flows through the lance tube during a cleaning cycle and is ejected from the lance tube within the combustion device, the lance tube being retractable into and withdrawn from the combustion device through a cleaning port, the method comprising the steps of:

providing a wall box at the cleaning port having a clamping seal assembly having a plurality of movable seal assemblies, each of the movable seal assemblies having a seal element movable in a radial direction relative to the lance tube through the action of an actuator, the seal element engageable with the outside surface of the lance tube in a sealing position and withdrawable from the outside surface of the lance tube in a released position, the seal element movable between the sealing and retracted positions through the action of the actuator, wherein the plurality of seal assemblies are arranged in a housing with an internal chamber having a cylindrical wall and with a circular jaw plate mounted within the internal chamber with a clearance gap between the jaw plate and the cylindrical wall, each of the plurality of seal assemblies being formed of at least one piston retained by the jaw plate and each piston coupled with one of the seal elements and configured to move the one of the seal elements radially with respect to the jaw plate, and the jaw plate being radially movable within the internal chamber and self-centering around the lance tube,

withdrawing the seal elements from contact with the outside of the lance tube during the cleaning cycle by moving the seal elements to the released position, and

at the conclusion of the cleaning cycle, actuating the actuator for moving the seal elements into the sealing position in contact with the outside surface of the lance tube.

15. A method of sealing a lance tube for cleaning internal surfaces of a combustion device in accordance with claim 14 further comprising providing a secondary seal assembly having at least one plate having an internal bore which closely conforms with the outside surface of the lance tube and positioning the secondary seal assembly such that the lance tube passes through both the clamping seal assembly and the secondary seal assembly and positioning the secondary seal assembly adjacent the cleaning port with the clamping seal assembly further from the cleaning port.

16. A method of sealing a lance tube for cleaning internal surfaces of a combustion device in accordance with claim 15 wherein the secondary seal assembly defines a longitudinal axis for positioning the lance tube and the clamping seal assembly is provided with means for allowing the seal assemblies to seal with the lance tube with the lance tube positioned at a plurality of displaced radial positions.