In the past two decades BWXT has deployed equipment and services for tube sheet and tube support cleaning in more than 70 deployments in 380 Steam Generators.
BWXT currently designs and builds customized lancing systems to meet the needs of nuclear steam genera¬tors worldwide. Our sludge lancing systems have been designed to meet some of the most challenging environments in the industry.
These challenges include:
- Limited access on the outside of the vessel at the handhole location (as little as twenty four inches free space surrounding the handhole)
- Limited number of accessible handholes along the No-Tube-Lane (NTL), out of position handholes relative to the NTL resulting in even smaller design criteria
- Non-concentric handholes on the shell and shroud, narrow NTL, obstructions (such as the blowdown lines and acorn nuts) within the NTL at the handhole elevation
- Tight inter-tube lane widths
- Tenacious deposit accumulations.
In the environment of tri-pitch, closely packed ½ inch tubes, and the presence of up to 30 inch hard sludge piles, BWXT performs the most challenging sludge lancing in the industry. These systems include high pressure (approximately 10,000 psi) inter-lane systems designed for lanes as narrow as 0.142 inches, and lower pressure systems (approximately 3000 psi) designed for typical NTL or annulus lancing.
Our systems have been developed while making safety, foreign material exclusion and quality a priority. Our sludge lancing systems are robust to handle the wide range of sludge deposits that can be found throughout the industry.
The BWXT sludge lancing system consists of:
- The adaptor flanges which ensure the SG machined handhole faces and threads are protected during the sludge lancing equipment setup and operation
- The drive units which are mounted on the external surface of the SG and provide rotation motion to the NTL rail as well as linear indexing motion to the lance
- The NTL rail which is inserted along the NTL pivoting between the handholes providing a delivery system for the lance while resisting the forces exerted by the lance jets (up to 10,000 psi for inter-lane system)
- The Inter-Lance systems are delivered along the NTL rail and extend into the tube bundle through the tube lanes in order to position focused, high pressure waterjets directly on to deposits in the tube bundle.
- Intertube High Pressure Flushing Waterlances are then introduced to remove loose scale from tube surfaces as well as removing newly formed soft sludge from the Hot and Cold legs as well as from the tube bundle shadow regions
- The NTL flushing lance which is inserted in the NTL flushing rail and provides sweeping motion of the flushing jets from the NTL pushing the sludge out inter-tube regions into the annulus
- The Annulus flushing lance which is mounted in the SG at the handhole interface the NTL and periodically provides a flow of water in the annulus pushing the suction foot for removal
- The suction feet which are inserted in the handholes into the annulus and remove the sludge suspension from the SG via diaphragm pumps
- The process system which is housed in the remote trailer to filter and recirculate for the sludge lancing process
- The control system which is housed in the remote trailer allowing the operator to monitor and control both the on vessel tooling and the process system