SteamJet as the Preferred Turbine Bypass Solution

Around the world, companies are recognizing CCI’s SteamJet Turbine Bypass System as the superior solution. Florida Power & Light recently awarded a multi-million dollar contract to CCI for SteamJet™ turbine bypass control valves and related CCI products, which are to be used in their Ft. Myers, Florida re-powering project.

The goal in developing the SteamJet system was to combine CCI’s exclusive DRAG valve multi-stage pressure reduction technology with trans-sonic, steam-assisted desuperheating into one light-weight, efficient package. The package is roughly the same size as conventional steam conditioning valves.

CCI achieved this ambitious goal by employing several technological advancements, including thermally compensated trim, which is designed to allow different parts to grow at their respective thermal expansion rates without binding into each other. By rendering the valve impervious to binding and cracking problems associated with thermal shock, CCI solved a challenge for combined cycle and cogeneration power stations, which cycle frequently.

The SteamJet nozzle is another advancement that has put CCI ahead of its competitors in steam-assisted design. With the SteamJet, a small amount of steam is extracted (without external piping) and accelerated to supersonic velocity by means of a convergent/divergent nozzle.

Full thermal compensation design - Impervious to thermal shock for high cycle duty.

1. Pressurized seat plug - Low actuator loads and outstanding shut-off per MSS-SP-61 Isolation valve specification.

2. Easy to service seat - No welding or grinding

3. Multi-stage DRAG® control element - Low noise and low vibration

4. SteamJet Desuperheating Nozzle - Supersonic atomizing steam and "compound swirl" plume shaping

At the divergent portion of the nozzle, water is injected into the flow stream. The high velocity of the atomizing steam and the recovery waves send a great deal of energy into the water as the fluid decelerates, atomizing the water into an extremely fine mist.

SteamJet plume density provides superior atomization

CCI discovered that a swirl or spin could be induced in the mist by extracting an even smaller amount of steam, and introducing it through small holes drilled at a compound angle at the very exit of the divergent portion of the nozzle. The effect of this is to shape the mist into a plume, which does not impinge directly on the pipe, but disperses it in a very even fashion. Laboratory tests demonstrated the significance of this small design feature. Based on testing of the SteamJet nozzle vs. other steam-assisted designs on the market, CCI believes its water atomization and mixing capability is unmatched in the industry.

The first SteamJet units were built as engineered specials (H.P., I.P., and L.P.), and installed throughout Asia , the U.K. , and continental Europe , with additional engineered special designs scheduled to be in service in Australia in the near future. Noise, pressure, and temperature control measurements have produced outstanding results.

Recently, CCI implemented an extensive value-engineering program on the SteamJet, focusing on the H.P. turbine bypass for combined cycle and cogeneration power plants. There are two basic product configurations: one for H.P. bypass to cold reheat, and the other for H.P. bypass to condenser applications. A simplified design reduced weight and the parts count, making the product easier to maintain, and more competitive.

High-performance SteamJet internal parts are easy to maintain, efficient and durable

The SteamJet design, with pilot-operated trim, is to be used with high-speed, high-accuracy pneumatic actuators. Both the unit and the actuator achieve outstanding shut-off per MSS-SP61 (block valve specification) as standard.

As with all DRAG® valves, the disk stack, or cage, is custom-designed for the number of stages required and the characteristic desired. The units will achieve up to a 50–1 rangeability, and the SteamJet nozzles are selected per application. A variety of inlet and outlet connections are available.

Anchored with DRAG® technology, the SteamJet is the finest velocity control valve trim in the world, capable of eliminating excessive noise and vibration. It is one of the reasons why Black & Veatch, FP&L’s Engineer Constructor, recommended CCI’s SteamJet and other advanced DRAG® technology products for severe service valves and related state-of-the-art equipment. The valves will help the re-powered Ft. Myers plant adjust electric generation more effectively to meet changing load demands.

Published in SOLUTIONS Winter 1999