VALVES AND SOOT BLOWERSS.RAJEEV KUMAR B.E ( EEE )

INTRODUCTIONValves are mechanical devices that are used to isolate, regulate or release the process fluid flowing through pipelines.

Proper working of valves ensure better availability of unit, safety of the plant, equipment, processes and men.

FUNCTIONS OF VALVESTo stop or allow the flow - globe valve, gate valve

To act as safety device a) safety valves to release excess pressureb) non-return valves to prevent back flow

To Regulate quantity/pressure - attemperater spray, PRV

TYPES OF VALVESIsolating valve Regulating valve Non-return valveSafety valveControl valve

ISOLATING VALVES:

It is normally fully open or fully closed.

It must stop flow of fluid completely when required.

Example: gate valve

REGULATING VALVES:

A regulating valve controls the rate of flow of fluid, according to requirements.

It may be operated in any position from fully open to fully closed .

Examples : globe valves ,angle valves etc.,

NON-RETURN VALVES:

Permits flow of fluid in one direction only & shuts off if a reversal of fluid flow occurs

Direction of flow of fluid through the valve is indicated by an arrow on the valve body

Examples: Swing check non-return valve, Lift check non-return valve

SAFETY VALVES:

This valve is designed to open when a predetermined and set pressure has been reached in the system .

This type of valve is used for safety of the equipment.

Examples: spring loaded safety valve , Torsion bar type safety valve etc

CONTROL VALVES:

The control valve is a fine control element which is used in control system .

It is operated by the signal given by the control circuit.

Examples: Flow control valve, Trip valve etc

COMPONENTS OF VALVES

BodyYoke, bonnet and coverDisc/wedgesSeatStem Gland

INLETOUTLET

GLOBE VALVE INLETOUTLET

GATE VALVEINLETOUTLET

COMPARISION

Globe valve Gate valveStem lift for full open D>DLapping & maintenanceEasy to approach from 3rd flangeBoth side wedge tapered seat not approachableSize< 200mm, more force required to close>200mm,Less force required to closeTurbulence/pr. drop> Turbulence & pr. Drop< turbulence & pr. drop

LIFT CHECK NON-RETURN VALVEINLETOUTLET

SWING CHECK NON- RETURN VALVESHINGE PINFLAPINLETOUTLET

SAFTEY VALVEINLETOUTLET

BLOW DOWN % OF SAFETY VALVE% Blow down =Set pressure Reseat pressure Set pressure 100 = 3 to 5%

Set pressure Opening/Popping Pressure

Reseat Pressure Closing pressure

VALVE OPERATION:MANUAL

ELECTRICAL

PNEUMATIC

HYDRAULIC

VALVE MAINTENANCE:GENERAL Joints & flange maintenance Gland packing maintenance Valve seats & disc maintenance SAFETY VALVES opening pressure setting Closing pressure setting Opening Pr. & blow down setting by ring adjustment

SOOT BLOWERS

TYPES OF SOOT DEPOSITS:

Fused slag depositHigh temperature bonded depositLow temperature fly ash deposit

SOOT BLOWERSoot blower is a device used for ON LOAD CLEANING of heat transfer surfaces when boiler is in operating conditionTYPES OF SOOT BLOWERS:WALL BLOWERSLONG RETRACTABLE SOOT BLOWERSROTARY BLOWERS

WALL BLOWER

LONG RETRACTABLE SOOT BLOWER

ROTARY BLOWER

FURNACE TEMPERATURE PROBE

TROUBLE SHOOTINGRETRACTABLE SOOT BLOWER: 1. overheating of lance tube 2. leakage of steam through glands 3. chain breakage 4. motor failure 5. limit switch failure

WALL DESLAGER:

1. Electrical operation not possible 2. Difficult in manual operation 3. swivel tube will require replacement 4.Cutting/polishing/frequent fouling of water wall tubes

FURNACE TEMPERATURE PROBE: 1.Temperature indication not available 2.position indicator not readings

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