The safe operation of General Purpose and Special Purpose industrial steam turbines has become a more urgent issue in recent years after multiple worldwide catastrophic accidents have been suffered which have incurred loss of life and major economic impacts. A common conclusion of post-accident investigations has been that the disasters could have been prevented if vital control safety components had properly operated.

For the API-611 General Purpose steam turbines the overwhelming weak link has been the Overspeed Trip Systems. The substandard function of multiple components will eventually result in damage to the turbine blades, the simultaneous failure of both the overspeed and governing systems immediately results in disaster. This package deals with the replacement of the mechanical overspeed trip system with modern high-reliability components engineered for the exact turbine fit.

The LCC Pneumatic Trip Actuation System replaces the turbine shaft fly-bolt, trip hammer, extension linkage, mechanical latch, connecting trip arm, and manual trip lever.

There are three common API-611 steam turbine emergency stop valve configurations:

• 1. Valve Body Side, Rotary Actuation
• 2. Valve Body Top, Rotary Actuation
• 3. Valve Body Top, Linear Actuation

The primary new system active components include:

• The primary new system active components include:
• Digital Electronic Overspeed Monitor (LCC Simplex 470)
• Rotary or Linear Pneumatic Actuator and Mounting Hardware
• Redundant 3-Way Pneumatic Trip Valves
• Local Manual Trip Pull Button
• Air Manifold Cooled Fiberglass Enclosure

Installation

The electronic components are installed in a local cabinet (provided) near each turbine. In harsh environments the electronics cabinet is vortex cooled. In explosive environments the electronics cabinet is purged.

For horizontal rotary stop valve actuation applications the Stop Valve Rotary Actuator is fitted with a welded attachment bracket with a post-fit hydrostatic pressure test is required. The hardware is LCC-supplied, however the welding and hydrostatic pressure testing is to be performed at a customer assigned shop facility.

For vertical stop valve actuation applications a 12-inch length spoolpiece is installed extending between the valve body and the fiberglass enclosure. A weld on flange is LCC-supplied, however the welding and hydrostatic pressure testing is to be performed at a customer assigned shop facility.

Flapper-Disk Trip-Throttle Valve Units

LCC recommends full valve replacement of flapper-disk TTV with a modern valve including pneumatic trip interface options. Contact LCC for details.