During the initial operation stage of the turbine, the front and rear shafts of the turbine were faced with sealing problem. The water invasion into bearing housing, shaft high vibration, and burned-out of the sliding bearings occurred frequently, which have seriously affected the long-term safe production of the chemical plant. The regular labyrinth seal structure is the most widely used sealing solution on the turbine. The sealing mechanism of labyrinth seal is to reduce the leakage of gas through multi-stage throttling and expansion to produce damping, but because of the labyrinth structure does not have floating properties, the  teeth will contact the shaft during operation, resulting in seal failure.

The following problems are existing: 1) the sealing performance is poor,  water can ingress in easily, which damages the quality of the lubrication; 2) the energy loss is too large, and the efficiency of turbine is lowered; 3) the teeth of the labyrinth seal are easy to be worn out, and the vibration of the shaft is large, which affects the service life and safety of the turbine; within the low-pressure section, the seal is not tight, causing air leakage, making the condenser vacuum reducing. A large amount of high-temperature leaking gas enters into the bearing box through the oil block, which makes the turbine oil heated and emulsified, and the oil film lubrication is destroyed, and aggravates the vibration of the shaft. And it leads to quickly bearing failure, resulting in a vicious cycle of vapor seal leakage and exacerbation.

 The custom designed bearing isolator for steam turbine can be applied to most of the industrial driving steam turbines. The rotor ring is made of stainless steel with high-temperature graphite packing ring, and the stator ring has interference fit with the bore and reserving for shaft thermal expansion clearance. For some cases the split design is available to facilitate installation. Many turbines produced by international brand manufacturers have adopted a composite structure of labyrinth seal to replace the original labyrinth oil retainer.