Moneypoint Gains 8 MW with Upgrades Based on Recent DRAG® Technology

The Irish Electric Supply Board’s Moneypoint Generating Station is made up of three identical coal-fired, 305 MW units commissioned in the ’85–’97 time frame. Main steam and emergency heater-drain valve trim and associated piping systems had long suffered from the high velocity erosive effects of magnetite/iron oxide exfoliation.

In early 2000, CCI was asked to conduct a system study to address this chronic problem. It was determined that the basis of the problem lay in the fact that control valve capacities far exceeded system line capacity. As a result, head loss was actually the flow-control mechanism. It was recommended that control valves, which were also very noisy, be replaced (retrofit was not an option) with multi-stage pressure-reducing valves to accommodate a reduced flow rate which would reduce line velocity and system and trim erosion while still having the capability of passing the exfoliation particles.

Recent studies on the effects of these valve replacements in Unit 1 improved the heat rate in excess of 8 MW.

As a direct result of this demonstrated success in the operating characteristics of Unit 1, ESB is now replacing the main and emergency heater-drain steam valves in Moneypoint’s Units 2 and 3.

As was the case in Unit 1, the up-to-200- × 150-millimeter (8 × 6-inch) emergency heater-drain valves are rated for a steam flow of up to 56 kilograms/second (440,000 pounds/hour) at an inlet pressure of 46 barA (670 psia) and a DP of 43 bar (625 psi) at 500 F (260 C).

Duplicating the replacements in Unit 1 last year, the new main steam and emergency heater-drain valves are fitted with disk-stack trim incorporating pressure equalizing rings (PERs) to prevent unbalanced radial-force plug loading and balanced plugs for reduced actuator loading. Operationally, these valve replacements, now in all the duplicate Moneypoint generating units, will increase plant generating capacity by over 20 MW.

Published in SOLUTIONS Spring 2001