Enshi Tangkou — 4 × 11 MW modernisation

1 The plant

Enshi Tangkou is an 11 MW × 4 unit plant in Enshi, Hubei, operated by a state power group. The units’ original control systems had aged past the point of economic repair: parts availability, control behaviour and maintenance burden all pointed to a modernisation programme rather than another repair cycle.

2 Scope of the retrofit

• Oil-free blade pitch control systems on all four units. The double-regulated units’ runner blades were re-equipped with oil-free pitch control, removing the oil-filled runner hub entirely.
• Governor and control modernisation across the four units. New governor hardware and control logic in place of the obsolete systems, integrated with the plant’s existing electrical infrastructure.

3 Why oil-free pitch control

Conventionally, adjustable-blade (Kaplan-type) runners keep an oil-filled hub: the oil transmits pressure to the blade mechanism. That oil is also a permanent liability — hub seals weep, and any leakage ends up in the river. An oil-free hub removes the oil from the equation altogether: no leak risk to the watercourse, and one less fluid system to monitor and maintain.

For plant owners, the practical consequences are environmental compliance and a maintenance schedule with an entire subsystem deleted from it. This is the same oil-free pitch technology we now supply as a product line (OFBP) and apply in retrofit programmes such as this one.

4 How the work was executed

Control retrofits live or die on outage planning. Factory acceptance testing was completed before shipment, so that site time was spent installing and commissioning proven equipment rather than debugging it. Work was organised around the plant’s outage windows, unit by unit, so that the remaining units kept serving the grid while each unit was converted.