LCC
30
11.2 Underwater Pump Operation with Duo-Cone Bearing Seals
The Underwater Cartridge Bearing Assembly (UCBA) uses Duo-Cone seals in the end cover. Sealing is
accomplished with two hardened, precision ground faces running against each other. An elastomer toric applies
pressure to the faces and allows the seal rings to accommodate axial and radial run out. The contact pressure
and shaft speed will generate heat in the seal faces that must be removed by the surrounding water as the pump
is running. Correct installation and adjustment is extremely critical to the proper function and life of these seals.
Due to the angular position of ladder mounted pumps in most dredge operations, the UCBA must be completely
filled with oil to provide lubrication to the rear thrust bearing when the cutter head is lowered. This requires the
use of tank mounted above the deck to detect leaks and accommodate internal pressure changes. A pressurized
recirculating system can be used, but the simplest method is an expansion tank suitable for operation within the
marine environment. This must be designed to prevent dirt, water or other contaminants from entering the oil
system while providing a vent to atmosphere.
This tank keeps a positive pressure on the bearing side of the Duo-Cone seals to counteract the water pressure
as the pump is submerged. The tank should be mounted high enough to maintain a pressure of about 7 psi (0.5
bar) above what is created by the maximum water depth. Note that the specific gravity of oil is only about 85% of
water and must be taken into account when calculating the mounting height of the tank.
The tank should have an oil level indicator to allow the operator to see if the level changes. After the oil
temperature stabilizes, the level should remain constant and any significant change would indicate a leaking seal.
This early warning can prevent oil from leaking into the surrounding water and avoid bearing failure.
Dredge pumps are designed to run with the UCBA and Duo-Cone seals fully submerged. This enables the
surrounding water to dissipate heat generated by the bearings and seal faces. If the pump will be operated above
the water line for extended periods, the bearings can create extra heat in the oil and the seal faces may overheat.
Provisions should be made to provide a supply of cooling water to each Duo-Cone seal and a water spray onto
the UCBA itself. If the pump will run continuously above water, other sealing systems are recommended, or oil
circulating and seal cooling systems will be required.
Care should be taken to operate the pump within the speed limitations specified by GIW on the pump drawing for
the particular seal size installed. If a seal is replaced, it must be installed with the correct gap (specified by GIW
for each seal size) between the seal holders, as this distance provides the correct seal face pressure for proper
operation.
Failure to operate the seals within the above parameters may result in premature seal failure or oil leakage
through the Duo-Cone seals. Any change in the operating conditions should be discussed with your GIW / KSB
representative to establish if the new conditions are suitable for the equipment.
Isopropyl Alcohol
Lube for Seal Faces
Содержание GIW LCC 100-400
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