Patented Guardian Seals

The ONLY Modified Turbine Labyrinth Seal That Can:

  • Work in any OEM Designed Turbine
  • Work in any Labyrinth Seal Ring Location or Application
  • Work in any Steam Condition
  • Work in any Pressure Condition
  • Prevent Damage to Delicate Teeth in any Rub Condition
  • Extend Seal Efficiency Life
  • Extend Unit Heat Rate Between Outages
  • Improve Unit Reliability
  • Limit Seal Degradation

Typical Efficiency Losses per Stage for a General Electric Style Turbine

Note: The typical efficiency losses per stage for a General Electric turbine are represented by the pie chart. Shaft Packing only accounts for 7% of efficiency loss due to leakage per stage.

Steam Forces Around the Gland Ring at "Start-Up" and under "Normal Operating Conditions"

The steam forces around a Labyrinth Seal during start up are modest and typically will balance out each other. But once the unit is up to operational speed and you begin loading, the forces radially inward on the Seal become much larger then forces pushing radially outward. So if rubs occur during operation from transients only the Guardian Seals are designed to prevent or limit damage to the delicate teeth.

What Occurs During Rubs For OTHER Than Guardian Design Seals?

  • Conventional tooth material mushrooms increasing the discharge area of the seal. This adds to a greater efficiency loss.
  • Scoring of rotor can occur from rubbing at all tooth locations.
  • Rubbing can result in multiple heat zones on the rotor.

For conventional or retractable labyrinth seals what occurs during a rub condition? First all the teeth will typically contact the rotor and the resulting rub condition will increase the radial clearances, most importantly there is a permanent loss of efficiency. The conventional tooth material mushrooms resulting in an increased discharge area. The more the seals mushroom the greater the efficiency loss will be. Rubbing can result in multiple heat-effected zones on the rotor; this is because of the higher coefficient of friction between metals. Rotor Cutting or Scoring can occur as a result of the hard contact between conventional seal teeth and rotor body.

What Occurs During Rubs For Guardian Designed Seals?

  • Some mushrooming does occur at point of contact
  • No scoring of rotor occurs from rubbing
  • No change in hardness at point of contact between the Guardian Seal and rotor

What Occurs during rub conditions for the Guardian Seal? The leaf or arch springs are replaced with coil springs that are only useful during startup. If a rub condition should occur during startup this would allow the ring segment to move more freely with less radial forces on the seal. Guardian Posts are set typically .005" closer to the rotor so that the Guardian posts contact the rotor first and absorb any potential damage as a result of the contact. The teeth will maintain their factory radial clearances during and after the rub condition occurs. The Guardian Posts will experience some mushrooming at point of contact. This is held to minimum because of the non-galling nature of the Proprietary Material. When contact occurs between the rotor and the Guardian Seal several things happen. First the contact is held to only light contact because the Proprietary Material has a very low coefficient of friction. Second the Guardian post transfers a protective layer of the Proprietary Material to the rotor of approximately .001". When the Proprietary Material rubs on Proprietary Material this has an even lower coefficient of friction. The high level of Silicone in the Proprietary Material acts a barrier lubricant. The Proprietary Material is a slow wearing material therefore it will take the abuse of a rubbing condition for a long period of time before any damage could happen to the teeth. Because of the self-lubricating effect and very low coefficients of friction no rotor scoring, no rotor bluing or change of rotor hardness occurs on the rotor body.

Laboratory Hard Rub Test

To prove the statements made previously Turbo Parts performed a rub condition test on the Guardian Seal and a Standard Tooth Seal. The test parameters had the rotor material spinning at 3600 RPM, and the test segment, under a constant spring force, pushing downward against the rotor. The test ran for 40 minutes.

Standard Tooth Seal

Intense heat at the point of contact between the standard teeth and the rotor is apparent by the discoloration at the tooth tips. This type of hard contact also often results in heat-affected zones on the rotor and/or cutting or grooving of the rotor by the teeth.

Guardian Designed Seal

The Guardian Posts protect the rotor and the seal teeth by only allowing light contact. Teeth only contact the rotor after the Guardian Posts have worn by .005", then the contact is light because of the long wearing and low coefficient of friction characteristics of the Proprietary Material.

TEST ROTOR

Showing the Guardian Test

Before Cleaning

  • Guardian transferred a protective layer of Proprietary Material to the rotor.
  • Proprietary Material rubbing on Proprietary Material has an extremely low coefficient of friction.
  • Low coefficient of friction means very little heat generated by contact.

After Partial Cleaning

  • No scoring or Grooving on rotor where the Guardian Seal contacted the rotor.
  • No heat effected zone where the Guardian Seal contacted the rotor.
  • No change in rotor hardness where the Guardian Seal contacted the rotor.

What Causes Rub's ?

  • Misalignment, for all current seal designs on the market today ALIGNMENT IS CRITICAL. If component misalignment exists in your unit you will have seal rubs.
  • Stationary Seals DO NOT CAUSE RUB's.
  • Balancing
  • Thermal Distortion
  • Harmonics
  • Bearing Oil Whip
  • Generator Transients
  • Incorrect Operation of the Boiler, Condenser, Generator, or Extractions
  • Improper Starting and Loading Procedures for the Turbine Generator

Turbo Parts Patented Advantages

  • The Guardian Seal returns the unit to design efficiency and maintains that efficiency until the next outage cycle, extending the efficiency life of the seal.
  • The Guardian Seal improves unit reliability through reduced wear and life extension of the seals.
  • The Guardian Seal CANNOT remain in a Retracted position. Therefore eliminating these potentials for sever efficiency losses due to this condition.
  • If a rub should occur, the Guardian Seals do not grow to the rub or "bow" as conventional materials or Brush seal do. In part due to the extremely low coefficient of friction for the Proprietary Material and its self lubricating properties from the silicone. Combined reduce heat build up from contacting the rotor.
  • Longer unit Operation at Higher Efficiencies
  • Bottom Line the Guardian Seals Make You Money

copyright 2004 Turbo Parts LLC.