A custom packing set supplied by Garlock Sealing Technologies has helped a customer eliminate a recurring maintenance problem in their combustion turbines. Garlock’s solution has also enabled significant savings in maintenance costs for the company.
A critical component in combustion turbines used by utilities to generate electricity is the crossfire tube, which feeds natural gas to the turbine. This tube contains a packing set which, should it fail, will result in a significant gas leak, requiring shutdown of the unit and repacking the crossfire tube.
Repacking is a difficult process since it involves accessing the crossfire tube, which is encapsulated by a cooling system. In the interest of efficiency, plant maintenance personnel would schedule repacking to coincide with other repairs to the turbine.
One utility was experiencing such failures at approximately four-week intervals, necessitating frequent maintenance. The failures were caused by the configuration of the packing set, which included a 7/16” laminated graphite ring and a 3/8” graphite square-braid ring, both of which were split.
When the laminated graphite ring was expanded to encircle the tube, it tended to come apart. In addition the 3/16” compression lip of the follower severely limited adjustment of the packing set.
Garlock Sealing Technologies worked closely with plant personnel to develop a custom-engineered solution.
Garlock recommended replacing the existing packing set with a three-ring packing set, comprising of two 3/8” rings of Style 1303-FEP compression packing and a third 3/8” ring cut in half to make a 3/16” x 3/8” ring.
Key advantages of the fire-safe packing sets:
- Compliance with stringent VOC and VHAP emissions standards
- Dimensionally stable
- Impervious to gases and fluids
- Resistance to heat, pressure and chemicals
- Retains integrity when cut and formed
The custom packing sets provide more than twice the longevity of the sets they replaced, enabling the customer to realise significant ongoing maintenance savings.