English
20 Explanations of Professional Terms for Industrial Steam Turbine (III)
Created on 11.06
A practical guide to cooling systems, steam integration and performance evaluation
Selecting an industrial steam turbine requires an understanding of how it interacts with the surrounding plant. Cooling conditions, water recovery, process steam demand and performance verification all influence the success of a project.
The third article in the YTS terminology series explains 20 additional terms that help plant owners, engineers and procurement teams evaluate complete steam turbine installations.
1. Steam Surface Condenser
A steam surface condenser converts turbine exhaust steam into liquid water by transferring heat through tube walls to cooling water.
The steam and cooling water remain separate during normal operation. This arrangement allows condensate to be recovered while providing the low-pressure heat sink required by a condensing turbine. Tube cleanliness, cooling water conditions and air removal affect its performance.
2. Air-Cooled Condenser — ACC
An air-cooled condenser condenses turbine exhaust steam inside finned tubes, using ambient air to carry away heat.
A direct dry ACC avoids the evaporative water demand associated with a wet cooling tower. Its performance depends on ambient air temperature, airflow and installation conditions. Hot weather and unfavourable air recirculation can increase condensing pressure.
3. Cooling Tower
A cooling tower rejects heat from circulating water to the atmosphere, primarily through evaporation in a wet tower.
For a water-cooled turbine installation, it cools the water returning from the condenser. Its specification should identify water flow, heat duty, entering air wet-bulb temperature and required cold-water temperature. These conditions establish a meaningful basis for equipment selection.
4. Circulating Water System
The circulating water system transports cooling water between the condenser and the plant’s heat-rejection equipment or water source.
It includes relevant pumps, piping, valves and associated equipment. Its flow capacity and hydraulic resistance influence condenser operation and pumping power. Cooling water should be distinguished from condensate, which belongs to the steam–water circuit.
5. Condenser Air Removal System
An air removal system extracts air and other non-condensable gases from the condenser.
Gas accumulation can impair heat transfer and raise operating pressure. Steam jet ejectors and liquid ring vacuum pumps are common solutions. Selection must distinguish the initial evacuation duty from the continuous gas-removal duty during normal operation.
6. Hotwell
The hotwell is the collection space or vessel that receives condensate from the condenser.
It provides a controlled liquid inventory for the downstream condensate system. Its level must suit both condenser operation and pump requirements. Hotwell capacity, level instrumentation and makeup connections form part of the condenser package specification.
7. Condensate Extraction Pump — CEP
A condensate extraction pump transfers water from the condenser hotwell to the downstream condensate or feedwater system.
Because it draws water from a low-pressure environment, suction conditions require particular attention. The pump arrangement must provide adequate suction head and suitable operating margins to limit cavitation and maintain dependable condensate transfer.
8. Deaerator
A deaerator removes dissolved gases, particularly oxygen, from boiler feedwater.
In a thermal deaerator, heating and steam–water contact release gases, which leave through a controlled vent. Deaeration helps reduce corrosion in the water and steam circuit. It works alongside the plant’s water treatment programme rather than replacing all chemical conditioning.
9. Boiler Feedwater Pump — BFP
A boiler feedwater pump raises treated water to the pressure needed for delivery into the boiler.
Its discharge pressure must overcome boiler pressure and losses through the feedwater circuit. Required flow, water temperature, suction conditions and operating range influence selection. The feedwater pump serves a different pressure duty from the condensate extraction pump.
10. Pressure-Reducing and Desuperheating Station — PRDS
A PRDS adjusts steam pressure and temperature to meet downstream requirements.
Pressure reduction takes place through a regulating valve. Desuperheating commonly uses controlled water injection, with the injected water evaporating into the steam. Successful operation depends on adequate mixing, evaporation distance, water quality and the required operating range.
11. Turbine Bypass System
A turbine bypass provides an alternative steam route around the turbine.
Depending on the plant arrangement, it can supply a process steam header or discharge to a suitably designed condenser system. It may support start-up, shutdown or continuity of process steam supply. Required capacity and pressure–temperature conditioning must match the intended bypass duty.
12. Steam Accumulator
A steam accumulator stores thermal energy to help balance short-term differences between steam supply and demand.
A common design stores pressurised hot water. When pressure falls during discharge, some of the water flashes into steam. This can help serve intermittent loads, such as batch processing, but storage capacity and allowable pressure variation determine the support available.
13. Heat Recovery Steam Generator — HRSG
An HRSG produces steam by recovering heat from a hot gas stream, commonly gas turbine exhaust.
The recovered steam can supply a steam turbine, an industrial process or both. Available exhaust heat and required steam conditions determine the design duty. Some installations also use supplementary firing where the system is designed for it.
14. Heat Balance Diagram — HBD
A heat balance diagram shows the principal energy and mass flows through a steam turbine installation.
It typically identifies steam and water flow rates, pressures, temperatures and enthalpies at important locations. It connects turbine operation with process steam delivery, condensate recovery and heat rejection. Each diagram represents a stated operating case, so one diagram cannot describe every possible load condition.
15. Heat Rate
Heat rate expresses the thermal energy input required to produce a unit of electrical energy, commonly in kJ/kWh.
A lower value indicates less heat input per unit of electricity when the calculation boundaries are equivalent. The specification must identify whether it describes the turbine cycle or the complete plant. For cogeneration, the treatment of useful process heat must also be agreed.
16. Part-Load Performance
Part-load performance describes equipment behaviour below its rated output.
It can include changes in energy consumption, valve losses, extraction capability, cooling demand and auxiliary consumption. A machine selected only for its rated point may not provide the best annual result. Performance should therefore be evaluated at the loads the plant expects to use most often.
17. Load Ramp Rate
Load ramp rate describes how quickly turbine output changes, commonly expressed in MW/min or as a percentage of rated output per minute.
The permissible rate depends on the machine's thermal condition, mechanical limits, steam supply and operating mode. A capability quoted for a fully warmed unit should not automatically be applied during a cold start.
18. Minimum Continuous Load
Minimum continuous load is the lowest output permitted for sustained operation under specified conditions.
Its limits may reflect steam flow requirements, exhaust temperature, blade behaviour, process integration or other design considerations. It should be defined for the actual operating configuration. The ability to pass briefly through a low-load condition does not establish suitability for continuous operation there.
19. Performance Correction Curves
Performance correction curves account for the effect of operating conditions that differ from agreed reference conditions.
For example, changes in inlet conditions or condenser pressure can alter measured output. Appropriate corrections allow results to be compared on a consistent basis. Curves must apply to the specific equipment and test method; they do not improve the machine’s actual measured operation.
20. Performance Acceptance Test
A performance acceptance test determines whether equipment meets agreed contractual performance requirements.
It requires a defined equipment boundary, suitable instruments, controlled test conditions and an agreed calculation procedure. Measurement uncertainty and permitted corrections must be addressed. The contract should identify the applicable test procedure, guaranteed quantities and acceptance criteria before testing takes place.
Discuss Your Steam Turbine Project with YTS
YTS provides industrial steam turbine solutions for power generation and combined heat and power applications. Share your steam availability, process requirements, cooling conditions and expected operating profile with our team to discuss a suitable configuration and project supply scope.
Contact
Leave your information and we will contact you.