Overlooked Gland Seal Can Be Big Trouble
The steam turbine gland steam seal system is designed to keep steam from leaking out of the turbine and to prevent air from leaking into the turbine. A gland seal system can be as simple as a spray chamber, loop seal and a steam ejector or as complex as surface condensers, air blowers or vacuum pumps. Simple or complex, the system requires timely care and maintenance. An improperly balanced gland system can lead to water in the lubricating oil, loss of vacuum or accelerated wear on the packing gland components.
No matter the configuration of your system, there is a delicate balance between the high pressure and low pressure ends of the turbine. The labyrinth-type seal rings in the gland housings are designed for a certain amount of pressure drop which coincides with the designed operating conditions of the unit. If too much vacuum is being drawn across the seal rings premature wear and loss of vacuum will be experienced at the labyrinth seal. If too much pressure is present at the labyrinth seal then steam leakage, corrosion and premature wear will be evident.
We recommend checking the gland system for proper operation during all scheduled inspections. Corrections to the system will usually be performed during a major inspection, when all of the components are accessible. Maintenance items can include partially plugged gland leak off lines, improperly adjusted balance butterfly valves, severe wear of the spray chamber nozzle, worn out vacuum pumps, gland condenser tube leaks, eroded air blower impellers and malfunctioning steam seal regulators.
Neglect of the perceived small things can lead to bigger and more costly problems. All of the auxiliary systems that support the steam turbine are of a critical nature especially when overlooked and not properly maintained.