Ch5 A-12

Bottom Blowoff

A procedure that removes sediment and impurities from the bottom of a boiler using blowdown.

Make-up Water (M/U)

Water added to a boiler to replace lost water, typically treated to reduce impurities.

Blowoff Piping System Design

Design considerations for blowoff piping include resistance to temperature fluctuations and compliance with specifications.

ASME B31.1

A standard for the design of piping systems in boiler applications, including specifications for diameter and materials.

Slow-Opening Blowoff Valves

Valves that require multiple turns to open or close, reducing thermal shock and water hammer.

Quick Opening Blowoff Valves

Valves that can rapidly open to allow quick discharge of water but may cause water hammer.

Continuous Blowdown (CBD)

A procedure to regularly remove a small amount of water from the boiler to control dissolved solids concentration.

Total Dissolved Solids (TDS)

The total concentration of dissolved substances in the boiler water which can lead to scaling and foaming.

Safety and Operational Guidelines during Blowoff

Procedures to ensure safe operation including sequential opening/closing of valves and monitoring boiler levels.

Blowoff Vessel

A tank used to cool and depressurize blowoff water before disposal to protect sewer systems from high temperature and pressure.

Hard-Seated Valves

Blowoff valves designed with a durable metal alloy mechanism for resistance to wear and able to manage flow effectively.

Hydraulic Shock (Water Hammer)

A pressure surge resulting from changes in water flow in piping that can damage systems if not properly managed.

Isolation Valve

A valve used to isolate sections of the blowdown system when maintenance is required.

Sulfur Compounds in Boiler Water

Impurities contributing to corrosion and scaling, often managed through blowdown procedures.

Manual vs. Automated CBD Systems

Automated systems adjust continuously based on TDS levels, while manual systems require operator intervention.

Dissolved Solids and Steam Carryover

High TDS can lead to wet steam which deposits impurities on system surfaces, requiring effective management through blowdown.

Sediment Accumulation

The buildup of sludge at the bottom of the boiler that needs to be controlled through bottom blowoff.

Thermal Shock

Sudden temperature changes that can damage piping or valves in a blowoff system.

Maintenance Inspection for Blowoff Systems

Regular inspection to identify corrosion, leaks, and the condition of components like valves and piping.

Chemical Treatment and Blowdown

The use of chemicals in boiler water which can react with impurities, necessitating blowdown for balance.

major outage- Wash & potential sandblasting

furnace water walls brushed, scarped, blasted compressed air, sandblasted to remove slag & dust. lower flue gas temp, improved heat transfer, & steam production>

Short outage - Wash only

Last 36-48 hours. dwn time utilized to do high-pressure wash of tubes.

Zero outage- In service cleaning only

use of heat resistant equipment such as soot blowers, acoustic horns, falling shot.

Ash, Soot, Slag, & dust coat & insulate boiler fireside surfaces. Affects

Lower efficiency due to reduced heat transfer. Reduced steam production, Higher fireside temp, Higher flue gas temp, Increased pressure differential through flue gas passes. Increased fireside corrosion on tubes.

Soot Blower

Steel lances inserted into boiler betwn rows of tubes. These lances blow high-pressure steam or air, blast impurities off heat transfer surfaces

Soot Blower Arrangement

for large-steam generating unit. located both in radiant & convection zones of furnace. must be designed to withstand more heat than installed in convection zone. Blowing increase frquency when diff pressure acros tube decrease or high superheater temp occur

Soot Blowing: Steam, Air, Water

Steam use for larger boiler. prevent erosion from moisture or condensate. advantage for steam

Air use smaller oil or solid fuel-fired boilers. more compact & no moist for fireside corrosion. manually operated.

Water use deposit strongly adhere to heat transfer surfaces. Soot washers in small boilers

Acoustic Cleaning System

knocks off ashes off boiler tubes with acoustic energy. uses air injected into wave generator

Rapping

removes deposits from heating surfaces without steam, air, water. Heating tube causes oscillation shakes off material build up.

Falling Shot

drop small steel ball from upper boiler sections onto deposit in lower sections. Impact of shot remove deposits from tube surfaces

Explosion

removes slag deposits from heat transfer surfaces that cannot be dislodged with conventional cleaning techniques.

Short Retractable Wall Blower

removes waterwall ash deposit. This buildup of ash, referred to as slag, can greatly restrict heat transfer. Lance has jet at its end. Lance rotate 360*

Long Retractable Soot Blowers

remove deposit from convection & radiant heating surfaces, Lances penetrate spaces between major heat absorbing sections. Made of two cylindrical concentric tubes.

Stationary Soot Blowers

Used in lower temp zones(convection zones), such as economizer, generating bank, and air heaters. low temp will not damage. Ash & soot move to specific point in boiler for removal. Lance tube not retractable, free to rotate tho.

Air Heater oot Blowers

series of flat stationary nozzles, blow high-pressure steam down surface. assh blown free, & fall tubes into dust collection. some are carried in flue gas (ash) where they are seprated by using mechanical mean, electrostatic precipitators.

Soot Blower Operation

during soot blowing, boiler operate 50% load to ensure stable combustion. Furnace pressure below atmospheric prevent backflow.

Falling Shot Cleaning

method for removing soot and ash depostis from economizer, tubular air heater, & superheater tubes.

Advantage FSC include

Supply air or steam not required. air required for pneumatic system.

Turbine supply not affected by steam consumption of soot blowers.