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TurbineTopic Page

I How It Operates 2

II Where Turbines are Used 2

III Gas Turbine Application Review 2

IV Steam Turbine Application Review 3

Control Valve Sourcebook — Chemical Unit Operations

Turbine

2

TurbineI. How It OperatesA turbine is a complex rotary mechanical device equipped with a series of stationary and rotating blades Mostly, turbines are divided into three stages and an exhaust section Pressure drop of a high pressure gas or vapor occurs through nozzles, diaphragms, or stationary blades This pressure drop creates high velocity gas or vapor that is directed at a row of blades connected to a rotor, converting the energy to mechanical work There are several different types of turbines commonly used in the chemical industry The most common turbines are gas and steam turbines

II. Where Turbines are UsedTypical plants that use turbines include:

� Chemical � Power � Oil and gas

III. Gas Turbine Application Review The gas turbine shown in Figure 1 is made up of several components and systems, including: turbine, compressor, combustor, generator, air supply, fuel skid, and lube oil skid

Air is compressed in the compressor section then fuel (gas or oil) is injected into the combustion section and fired,

expanding the gas at high temperature and high velocity Turbine section converts the thermal energy into shaft energy and two-thirds of the energy is used to drive the compressor. At the final stage exhaust gas can be used to generate steam for power

1. Air Extraction Valve

The air extraction valve is used to release excess air to the atmosphere during startup and shutdown procedures to protect the compressor Typically, there are up to four of these valves

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

� Typical Valve Construction:

— NPS 6 to 30 Fisher® A81, A31A, A41, A11, or 8532 valve

— Materials of construction: dependent on process design, typically WCC

2. Inlet Bleed Heat Valve (IBHV)

The IBHV utilizes compressed air to heat inlet air to prevent icing during cold and humid condition Typically the inlet bleed heat system consists of three valves: IBHV, drain valve, and manual stop valve The drain and manual valves are on-off applications and the IBHV is a throttling application

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

E1173

OIL

GENERATOR

FUEL SUPPLY

WATER

WATER

COMPRESSOR TURBINE

1

3 4

AIR SUPPLY

COMBUSTOR

HEATEXCHANGER

5

2 7

6

Figure 1. Process Diagram of Gas Turbine

Turbine

3

� Typical Valve Construction:

— IBHV: NPS 6x4 to 12 Fisher EW valve with Whisper Trim™ I or equal percentage trim

— Drain valve: NPS 2 Fisher A41 valve — Manual stop valve: Fisher 8560 or A11 valve — Materials of construction: dependent on process design, typically Alloy 6 Whisper Trim I is used for the IBHV, and SST material is used for the drain valve

3. Fuel Gas Control Valve

The purpose of the fuel gas control valve is to simply control the flow of fuel to combustor. It requires a precise, linearly characterized valve with the ability to choke very quickly at a low pressure drop, which results in no change of Cv during a sudden change in pressure drop

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

� Typical Valve Construction:

— NPS 2 to 6 Fisher ED or ES valve with Class IV shutoff — Materials of construction: dependent on process design, typically WCC with a 17-4 cage is used

4. Stop Ratio Valve (SRV)

The purpose of a SRV valve, also known as the pressure ratio valve, is to control and supply fuel gas with a constant upstream pressure based on various turbine loads Failure to maintain a constant pressure can lead to excess noise, exhaust gas temperature variation and excess nitrogen oxide (NOx) pollutant

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

� Typical Valve Construction:

— NPS 3 to 8 Fisher V300, V200, or SS-260 valve with HD metal or TCM metal seal, Fisher ED or ES valve with ENVIRO-SEAL™ packing system to prevent fugitive emission, and Class VI shutoff

— Materials of construction: dependent on process design, chromium carbide coated ball provides better wear resistance

5. Purge Valve

The two main functions of a purge valve is to protect the fuel nozzles and flush the fuel lines with air. It requires a design that allows a small Cv when barely open and develops into a modified equal percentage as the valve opens. Purge valves operate in pairs in a double block-and-bleed arrangement to prevent the hot air from interacting with the natural gas

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

� Typical Valve Construction:

— Fisher CV500 valve with Class V shutoff — Materials of construction: dependent on process design, typically SST body is recommended, chrome carbide coating on the ball, nitronic 50 shaft (NACE option) or 17-4PH shaft (High H2S concentration could cause corrosion with 17-4PH), Alloy 6 bearing and seal ring

6. 3-Way Temperature Regulator Valve

Purpose of 3-way temperature regulator valve is to maintain the appropriate temperature of the oil lubricant by controlling flow of cooling water to the lube oil heat exchanger Failure of this valve can affect the bearing system reliability

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

� Typical Valve Construction:

— 3-way Fisher YD valve — Materials of construction: dependent on process design, typically WCC

7. Lube Oil Pressure Valve

The lube oil pressure valve is used to maintain the pressure of the lube oil that is pumped to the bearing A lube oil pressure valve regulates the flow based on a control signal coming from a downstream pressure transmitter It provides high lubricant pressure at low turbine speed and low lubricant pressure at high turbine speed

� Typical Process Conditions:

— Pressure, temperature, and flow are dependent on process design

� Typical Valve Construction:

— NPS 3 to 4 Fisher easy-e™ valve, Fisher GX valve — Materials of construction: dependent on process design, typically WCC

IV. Steam Turbine Application Review Steam turbines are utilized in a variety of industries to capture energy associated with the expansion of process generated steam Turbines convert thermal energy from steam and use it to do mechanical work on a rotating shaft Steam turbines are commonly classified by the condition of the exhaust, for example non-condensing or extraction

Non-condensing or backpressure turbines are most widely used for process steam applications The exhaust pressure is controlled by a regulating valve to suit the needs of the process steam pressure As shown in Figure 2, high pressure steam enters the turbine and does the work in front of turbine and exits the turbine at the low pressure side

Turbine

4

Extracting type turbines are also used in process steam applications As shown in Figure 3, high pressure steam enters the extracting type turbine and steam is released from various stages of the turbine Steam from each section is used for industrial process needs or sent to boiler feedwater heaters to improve overall cycle efficiency. In commercial power plants the remainder of steam is directed to the condenser, turning the steam into water that is then recycled

A steam turbine package has several components and systems including: a steam turbine, generator, gland steam seal system, lube oil system, shaft seal oil system, hydraulic system, and a control system The three areas covered in this document are the main steam turbine, the steam seal system, and the lube oil system

Main Steam TurbineAs shown in Figure 4, a main steam turbine consists of several control systems and valve applications The valve applications for the main steam turbine section are numbered from one to five.

1. Main Steam Control Valve

The purpose of main steam control valve is to control the amount of steam from the boiler or heat recovery steam generator (HRSG) to high pressure (HP) turbine These valves are usually part of the turbine casing itself and are designed and manufactured by steam turbine original equipment manufacturer

E1174

POWER

LOW PRESSURESTEAM TOPROCESS

HIGH PRESSURESTEAM

Figure 2. Non-Condensing Turbine

E1175

POWER

STEAM TO CONDENSERLOW PRESSURESTEAM TOPROCESS

HIGH PRESSURESTEAM

Figure 3. Extraction Turbine

E1176

HP

IP

LPLP

5

1

PACKINGGLAND

22

SHAFT

4

CONDENSER

STEAM FROM HRSG

3

5

Figure 4. Process Diagram of Main Steam Turbine

Turbine

5

2. Low Pressure (LP) Induction Admission Steam Valves

The LP induction admission steam valve typically consists of two valves in series One controls the amount of steam entering the LP turbine and the other quickly shuts off steam to the turbine through an on-off application

� Typical Process Conditions:

— Fluid = steam — P1 = 50 to 150 psig (3 45 to 10 34 bar) — T = 500 to 700°F (260 to 371°C) — Q = 0 to 120,000 lb/hr or higher ( 0 to 54 3 ton/hr)

� Typical Valve Construction:

— NPS 16 to 24 Fisher butterfly valve construction — Materials of construction: dependent on process design, typical construction includes WCC or SST

3. Combined Reheat Intercept Valve

The combined reheat intercept valve is used to control the hot reheat admission steam from a boiler or heat recovery steam generator (HRSG) to the intermediate pressure section of turbine

� Typical Process Conditions:

— Fluid = steam — P1 = 485 to 586 psia (33 44 to 40 40 bar) — T = 950 to 1050°F (510 to 565°C)

� Typical Valve Construction:

— NPS 16 to 20 Fisher Large easy-e valve — Materials of construction: dependent on process design, typical construction C12A and Class V shutoff

4. Packing Blowdown Valve

The packing blowdown valve slows down the turbine or quickly discharges the turbine during a turbine trip During a turbine trip the main steam valve, LP induction admission steam valve, and intercept valve will shut off, trapping high pressure steam in the boiler and HP turbine The high pressure steam will flow from the HP turbine through the packing into the IP turbine causing the turbine to spin to the point of overspeed. In order to avoid this overspeed, flow is diverted with the reverse flow valve.

� Typical Process Conditions:

— Fluid = steam — P1 = 400 to 700 psig (27 57 to 48 26 bar) — T = 650 to 950°F (343 to 510°C)

� Typical Valve Construction:

— NPS 3 to 6 Fisher HPD valve with butt weld end — Materials of construction: dependent on process design, typical material construction includes WC9, linear cage, and Class V shutoff

5. Drain Valves

The purpose of the drain valve is to collect any water from the turbine or steam system Drain valves will be located throughout the system

� Typical Process Conditions:

— Fluid = water/ condensate — P1 = 486 to 5000 psi (33 5 to 345 bar) — P2 = condenser pressure — T = 300 to 1150°F (148 8 to 621°C)

� Typical Valve Construction:

— NPS 1 to 2 metal seated valve — Materials of construction: dependent on process design, typically includes a WCC, WC9, or C12 body, 316 SST/CoCr-A trim

Steam Seal TurbineSteam seal turbine section as shown in Figure 5 consists of the valve applications numbered from six to nine

6. Steam Seal Regulator (SSR) Valve

The purpose of this valve is to adjust the flow of steam into the steam seal system It is mainly used during startup and it is closed during normal operation

� Typical Process Conditions:

— Fluid = steam — P1 = main steam pressure — P2 = 3 to 5 psig (0 207 to 0 344 bar) — T = 650 to 1050°F (343 to 565 5°C) — Q = 0 to 50,000 lb/hr (0 to 22 68 ton/hr)

� Typical Valve Construction:

— NPS 1 to 6 Fisher HP valve that may require a diffuser or Whisper Trim due to the high pressure drop

— Materials of construction: dependent on process design, typically WCC, WC9, C12A, 316SST/CoCr-A trim

7. Auxiliary Steam Seal Feed (ASSF) Valve

The ASSF valve is used to adjust the flow of steam into the steam seal system Supply steam for ASSF is from a secondary source, usually the cold reheat header If available this is used instead of main header steam This valve is only open during startup

� Typical Process Conditions:

— Fluid = steam — P1 = 600 to 700 psig (41 37 to 48 26 bar) — P2 = 3 to 5 psig (0 207 to 0 344 bar) — T = 400 to 700°F (204 to 371°C)

Turbine

6

� Typical Valve Construction:

— NPS 4 to 8 Fisher easy-e valve with Class IV or V shutoff — Materials of construction: dependent on process design, typically WCC, WC9, C12A, 316SST/CoCr-A trim

8 & 9. Steam Seal HP/LP Desuperheater

The purpose of this valve is to reduce and regulate the temperature of steam entering the steam seal system Water from condensate system is typically used

� Typical Spray Water Process Conditions:

— P1 = 150 to 400 psig (10 34 to 27 58 bar) — P2 = 75 psig (5 17 bar) — T = 100°F (37 7°C)

� Typical Valve Construction:

— NPS 1 Fisher easy-e valve with MicroForm trim and Class V shutoff

— Materials of construction: dependent on process design, typically WCC, 17-4SST cage, 416 SST plug

� Typical Desuperheater Selection:

— Fisher DVI/DMA desuperheater, WCC construction

10. Steam Seal Regulator Dump Valve or Steam Seal Diverter Valve

In this application either a steam seal regulator dump valve or steam seal diverter valve is used. The benefit of using the steam seal diverter valve is to maintain efficiency by recapturing heat

Steam Seal Regulator Dump Valve

The steam seal regulator dump valve is used to maintain the pressure of the steam steal system by regulating the flow of excess steam that is discharged to the condenser This valve is typically closed throughout startup As turbine load increases

and steam leakage from the HP packing increases, this valve is opened to allow excess seal steam to exit to the condenser

� Typical Process Conditions:

— Fluid = steam — P1= 3 to 5 psig (0 207 to 0 344 bar) — P2 = condenser pressure — T = 500 to 600°F (260 to 315 5°C) — Q = 0 to 50,000 lb/hr (0 to 22 68 ton/hr)

� Typical Valve Construction:

— Fisher Vee-Ball™ valve, Class II shutoff — Materials of construction: dependent on process design, typically WCC or SST

Steam Seal Diverter Valve

Steam Seal Diverter Valve is used to maintain the pressure of the steam steal system by diverting the flow of excess steam to the condenser or feedwater heater. Diverting the flow to feedwater heater helps to recapture the heat and hence increase efficiency of the turbine.

� Typical Process Conditions:

— Fluid = steam — P1 = 3 to 5 psig (0 207 to 0 344 bar) — P2 = condenser pressure — T = 500 to 600°F (260 to 315 5°C) — Q = 0 to 50,000 lb/hr (0 to 22 68 ton/hr)

� Typical Valve Construction:

— 3-way valve — Materials of Construction: dependent on process design, typically WCC

E1177 HP IP LPLP

10

6

87

SPRAY WATER FROMCONDENSATE SYSTEM

STEAM TO CONDENSEROR FEEDWATER HEATER

AUXILIARY STEAM

MAIN STEAM

9

DS

DS

Figure 5. Process Diagram of Steam Seal Turbine

Turbine

7

Lube Oil SystemLube oil system valve application as shown in Figure 6 is numbered from eleven to thirteen

11. Back Pressure Valve

The back pressure valve is used to control amount of lube oil that is being sent to oil reservoir

� Typical Process Conditions:

— Fluid = oil — P1 = 100 to 400 psig (6 89 to 27 58 bar) — P2 = 25 to 30 psig (1 72 to 2 07 bar) — T = 70 to 160°F (21 to 71°C) — Q = 60 to 700 lb/hr (0 027 to 0 317ton/hr)

� Typical Valve Construction:

— NPS 3 Fisher easy-e valve or Fisher GX valve — Materials of construction: dependent on process design, typically WCC

12. Lube Oil Pressure Valve

The lube oil pressure control valve is self-operating and regulates the flow of lube oil based on a control signal coming from a downstream pressure transmitter

� Typical Process Conditions:

— Fluid = oil — P1 = 100 to 400 psig (6 89 to 27 58 bar) — P2 = 25 to 30 psig (1 72 to 2 07 bar) — T = 50 to 160 °F (10 to 71°C) — Q = 60 to 700 lb/hr (0 027 to 0 317 ton/hr)

� Typical Valve Construction:

— NPS 2 to 4 Fisher easy-e valve or Fisher GX valve — Materials of construction: dependent on process design, typically WCC

13. Temperature Control Valve

The purpose of this valve is to control the temperature of the lubricant as it can affect bearing system reliability

� Typical Process Conditions:

— Fluid = cooling water — P1 = 150 psig (10 34 bar) — P2 = 135 psig (9 31 bar) — T = 70 to 150°F (21 to 65 5°C)

� Typical Valve Construction:

— Fisher GX 3-way valve or Fisher YD valve — Materials of construction: dependent on process design, typically WCC

E1178 HP IP LPLP

11

12

13

RESERVOIR

Figure 6. Process Diagram of Lube Oil System

D352317X012 / MBB55 / Jul15

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