14/11/2021
Resizing of Pressure Control Valve (PCV), Change-Out of 30” Desuperheaters with reduced liner and New Spray nozzles
Sizing and selection of pressure reducing valve and desuperheater are of paramount importance in Combined Cycle Power Plant (CCPP), Combined Heat and Power (CHP) and Cogeneration plants. Proper design, sizing, selection and installation of associated piping and controls save plant owners from unplanned shutdown, maintenance cost and confidence of downstream customers/users.
Issues and solutions at customer site
(1) Guarantee flow rate and temperature requirement – based on installed process data and actual conditions, the Pressure Control Valve (PCV) is being resize with improved Cv with maximum opening up to 95%. Improved rangeability of PCV for normal control up to 80% at the guaranteed outlet flow.
(2) New spray nozzle – with higher cracking pressure improve the “primary atomization” and makes the droplet sizes smaller, which in turn improves “secondary atomization” and the increased relative velocity between steam and water prevents the water carry away.
(3) Poor mixing due to low steam velocity – 30” Desuperheater with oversized internal liner have to be cut-out and replaced with small liner design to achieve proper mixing. The reduced liner improved the “secondary atomization” enabling the steam to have enough kinetic energy and prevent water fallout during the entire range of steam flow operation.
(4) Upstream length before desuperheater – additional 1m of steam pipe after Pressure Control Valve (PCV) and Desuperheater to provide laminar steam flow at inlet of desuperheater.
(5) Distant of temperature sensor downstream of desuperheater – temperature sensor is moved further downstream of the desuperheater and installed with thermal protective pocket. The increased distance between point of spray and temperature sensor improve the “tertiary atomization” process completing the steam conditioning process satisfactorily and completely.
Onsite Turnkey Retrofitting, Change-out, Installation and Commissioning of PCV, Desuperheater and Temperature Sensor. Detail planning, documentations, safety procedures, equipment, staging, pipe cutting, welding, x-ray testing and inspection during planned outage.
