Boiler Operation; Feedwater Treatment

Front 1

What is a sootblower and why is it important?

Back 1

Sootblowers clear ash from furnace surfaces since the ash forms a coating which insulates, resulting in reduced heating efficiency.

Front 2

2 types of cleaning mediums used in sootblowers and pros and cons of each.

Back 2

Air: Requires compressors to be used.
Steam: In operation whenever the boiler is in operation. Steam must be depressurized to be used by the sootblowers.

*Note: The boiler should be operating above 50% capacity whenever a sootblower is to to be used.

Front 3

Retractable vs Stationary

Back 3

Retractable: 2-types, retractable and long retractable. Used for furnace walls (short) and super heater, economizer, and air heater sections.

Front 4

4 precautions for operation of sootblowers

Back 4

-Sootblower must not impinge directly on tubes or else erosion of pipes occurs

-Boiler must be above 50% output when sootblowers in use, except in air heaters

-Furnace pressure should be below atmospheric to prevent blowback

-If air is used, must be dry, if steam is used, must be dry and or superheated.

Front 5

What is shot cleaning?

Back 5

used in the economizer, air heater, and superheater sections, a shot cleaner uses small iron pellets, usually of 6mm diameter fall from above and ricochet around the tubes, dislodging deposits. The pellets are collected in a hopper at the bottom and the dislodged pieces are recycled for use until they are broken down into fine particles and carried away with the flue gas.

Front 6

Define continuous blowdown

Back 6

Continuous blowdown is an ongoing process that removes dissolved or suspended solids from boiler water.

Front 7

Difference between blowdown and blow-off

Back 7

blowdown usually refers to the removal of dissolved solids and suspended solid from boiler water where as blow-off usually applies to the actual equipment.

Front 8

How does water in a steam boiler get high concentrations of impurities?

Back 8

Dissolved and suspended solids left over from external water treatment or chemicals injected into the boiler from internal water treatment collect in the boiler below the normal operating level.

Front 9

How is the TDS in a boiler regulated using CBD?

Back 9

At the point below the normal operating level of water, a pipe with inlet holes runs inside the steam drum. This pipe is connected to a blow-off tank or pond.

Front 10

Typical flow rate of CBD line in an industrial power boiler that doesn't use demineralized water?

Back 10

1% of total steam output.

Front 11

Effects of insufficient continuous blowdown

Back 11

Foaming and carryover of impurities with the steam. Sludge also builds up within the boiler.

Front 12

Effects of excessive continuous blowdown

Back 12

Though the TDS levels will be low, some boilers operate with water with high TDS water will be wasting valuable treated water.

Front 13

How does a heat recovery system work?

Back 13

the CBD flows to a heat exchanger that takes the water from the CBD and transfers it to the feedwater.

Front 14

Where are the greatest concentrations of dissolved solids in a watertube and firetube boiler located?

Back 14

Watertube: Bottom of the mud drum

Firetube: Bottom of the boiler shell

Front 15

What is the effect of using blow-off valves when a steam generator is operating at very high pressures?

Back 15

With respect to water circulation, opening of blow-off valves interrupts water circulationwater wall tubes and can cause to fail due to overheating.

Front 16

The 3 main components of a boiler's intermittent blowdown system

Back 16

-Blow-off drum/tank/vessel

-Blow-off piping

-Blow-off valves

Front 17

CSA Code B51(paragraph 6.5.1) requires the installation of a 1._________ or other suitable registered device for all boiler operating above 2. _____, if the vessel discharges into a sewer system. The vessel(blow-off tank) is not required if the boiler is low pressure(operating below 103kPa gauge), or if the boiler discharges to a separate pond, such as often occurs in large, remote, thermal stations. The water temperature at the blow-off tank outlet may not exceed 3.___ degrees celsius.

Back 17

1. Blow-off vessel

2. 103 kPa

3. 65 degrees Celsius

Front 18

Why do high pressure steam boilers require the use of a blow-off tank?

Back 18

It is required to use a blow-off tank due to the combination of high temperature, vapour, and pressure when blow-off is used. This could seriously damage sewer piping. The tank is used for the flash vapours and water to cool. A vent is used to collect the steam for low-pressure.

Front 19

Why does blowoff piping need to be properly designed and anchored

Back 19

The piping is subject to short duration flows which lead to rapid changes in temperature when blowdown occurs. Allowance must be made for the piping to expand and contract.

Front 20

Code for boiler blow-off piping and blow-off valves.

Back 20

ASME B31.1

Front 21

How many turns for a slow opening valve to open, and special features of some of them.

Back 21

At least 5 turns, doesn't allow for sediment to collect under the valve seat.

Front 22

If quick and slow opening valves are used, how should they be arranged?

Back 22

Quick nearest the boiler because it is a sealing valve, where as the slow valve is used to control the blow-off.

Front 23

What is the operating sequence of a slow and quick opening valve?

Back 23

Quick open, slow open, slow close, quick close.

Front 24

Preparation for boiler-waterside

Back 24

Adequate amount of treated water must be available to fill the boiler.

Front 25

Preparation for boiler-fireside

Back 25

Start-up fuel must be available and prepared for the boiler.

Front 26

Preparation for feedwater system

Back 26

-Source of water open

-feedwater treatment equipment is functioning

-tanks at proper levels

-Deaerator operational and full

-Feedwater pumps in service

Front 27

Preparation for fuel and draft systems

Back 27

Check all necessary valves are opened.

Oil is at correct temperature.

Start draft fan and check for normal operation.

Front 28

Purpose of refractory dry out and how is it done?

Back 28

Refractory dry out is required to ensure that water doesn't flash into steam when the boiler is started which will damage the refractory. It is done by creating a light fire in the furnace, just enough to speed up evaporation. Before lighting the fire, fill the boiler to normal level, leave a vent open, and maintain water level. Ensure furnace is adequately purged and maintain the fire for several hours to several days depending on amount of refractory.

Front 29

Why is boil-out required?

Back 29

Removes all the grease and debris from contruction.

Front 30

What is boil-out and what chemicals are used?

Back 30

Boil-out is done by heating the water, adding detergent type chemicals and periodically blowing down to dislodge sludge and debris. Alkaline solutions are used such as soda ash, caustic soda, tridosium phosphate, and sodium silicate.

Front 31

3 major areas of attention when starting up a boiler

Back 31

Ignition

Boiler warm-up

Steam header warm-up

Front 32

Sequence of steps for igniting main burner of a boiler

Back 32

-Pre-purge of furnace

-Reproduction of air flow for stable ignition

-Pilot burner ignition

-Main burner ignition

Front 33

Routine for water level

Back 33

gauge glass, water column, and connecting lines blown through daily. Keep gauge glass clean. Make sure water level steady. Control foaming with antifoam chemicals or blowdown.

Front 34

Routine for steam pressure

Back 34

Check boiler steam pressure. Regulate fuel based on boiler load.

Front 35

Routine for burner operation

Back 35

Natural gas = blue flame

Check for dark smoke.

Front 36

Routine for stack temperature

Back 36

Check stack temperature daily as it is an indicator of boiler heat transfer.

Front 37

Routine for heat transfer

Back 37

Use sootblowers to keep heating surfaces clear of ash and soot. Treatment of feedwater to prevent scale buildup.

Front 38

Routine for water treatment

Back 38

Take samples of boiler water, deaerated feedwater and condensate to perform tests. use the results to determine treatment chemicals.blow down boiler.

Front 39

Routine for inspection

Back 39

Check signs of leakage from

-safety valves

-manholes

-handholes

-clean-out plugs

-valves and pipe connections

Front 40

Low water level causes

Back 40

-Faulty feedwater level controller

-Feedwater or condensate pump failure

-interruption of water supply

-leakage from boiler

Front 41

What to do when water level too low

Back 41

-Move calmly and efficiently

-Turn off fuel and air supply, continue to feed water

-When it is hand-touch temperature, inspect for damage

-do not put back into operation until reason for low water is found and corrected

-if damaged, inform boiler inspector.

Front 42

What to do when High Water level

Back 42

-Shut off feed water or condensate pump or drain excess through blowoff valve

ASME Section VII, C2.2425 "...shut off feedwater, fuel, and combustion air in that order."

Front 43

What to do fan failure

Back 43

Fuel supply shut off immediately.

Front 44

Flame failure reason

Back 44

-Insufficient fuel oil supply

-Water in fuel oil

-Excessive air supply

-Insufficient gas pressure

Front 45

What to do in case of flame failure

Back 45

Burner fuel flow stopped immediately.

Front 46

Define furnace explosion

Back 46

Explosion within the furnace itself or gas passes due to ignition of built up fuel.

Front 47

Causes of furnace explosions

Back 47

-Insufficient purge of the furnace before lighting.

-Fuel before pilot flame ignited

-Weak pilot flame

-Failure of the main fuel valve to close when the main burner flame is lost

-Insufficient combustion air leading to incomplete combustion

-Attempting to light burners from hot refractory

Front 48

Define pressure explosions

Back 48

Bursting of boiler shell or water/fire tubes due to too high steam pressure or structural weakering of the metal

Front 49

Reasons for pressure explosions

Back 49

-Corrosion

-overstressing of the material from heat

-Overheating surfaces from low water condition

-Scale and sludge buildup

-Failure of operating controls combined with failed safety valve

Front 50

Requirements of a typical Provincial Boilers Act in the event of boiler explosions

Back 50

person in charge must fully report all particulars of the event. Including location, names of pppl killed/injured and the cause if known.

Front 51

3 common reasons for boiler accidents

Back 51

-Inexperienced or untrained personnel

-Improper maintenance of boiler and its controls

-Misconception that automatic boilers do not require supervision

-Overheating due to failure of low water condition from failure of operating/protective controls.

Front 52

Purpose of boiler operating log

Back 52

Provides a continuous record of boiler operation, testing, and maintenance.

Front 53

Reasons for water conditioning

Back 53

-Prevent sludge deposits

-Prevent scale forming

-Prevent impurities from carrying over

-Prevent corrosion

Front 54

3 main groups of water impurities

Back 54

-Suspended matter

-Dissolved solids

-Dissolved gases

-ph values

Front 55

what causes temporary and permanent hardness?

Back 55

Temporary: Calcium Bicarbonate, Magnesium Bicarbonate

Permanent: Calcium Sulphate, Magnesium Sulphate

Front 56

What causes pitting, and how to remove/prevent?

Back 56

CO2 and O2 also usually causes blisters of iron oxide, corroding and creating grooves in metal; also attacks pipe threading.

Removal with chemicals that can absorb O2 and CO2, also prevented with deaerators.

Front 57

Negative effects of incorrect pH values

Back 57

Acidic -> Corrosion

Alkaline-> Foaming and embrittlement of boiler metal.

Front 58

Proper pH value for moderate pressure boiler

Back 58

8.5 at least, 10.5 sufficient.

Front 59

Types of filters for water treatment

Back 59

-Pressure

-Filer-aid tubular

-Cartridge

Front 60

How does a pressure filter work?

Back 60

Water flows downward through a bed of sand, anthracite, or calcite that filters out dissolved matter.

Front 61

What is hard water and why is it softened?

Back 61

Hard water contains calcium and magnesium salts that do not dissolve well in hot water, causing scale to form on heating surfaces. To prevent this, the calcium and magnesium is replaced with sodium through the use of water softeners since sodium salts are soluble in hot water.

Front 62

What is Lime-soda softener and how is it used?

Back 62

Used to remove scale-forming dissolved solids such as magnesium and calcium compounds. It is added to feedwater. There are hot and cold process varieties of this treatment. The hot process lime-sode treatment is more efficient since large amounts can be treated.

Front 63

What is sodium zeolite softening

Back 63

Cation exchange. Zeolite is loaded with sodium cations that replace the magnesium and calcium within their compounds. Must be refreshed with sodium cations.

Front 64

4 steps of sodium zeolite softening

Back 64

-Service

-Backwash

-Regeneration

-Rinsing

Front 65

What does a demineralizer do?

Back 65

Similar process to sodium zeolite softening, however hydrogen is used to replace the calcium and magnesium in the compunds. Cation exchanger replaces the cations for hydrogen, making acids, CO2, and water. Then in the anion exchanger, anions of the acids are changed for hydroxide ions, turning the acid to water.

Front 66

6 problems for operation of water softener

Back 66

1. Change in water quality

2. Improper flow rates

3. Improper brine injection

4. Fouled exchange material

5. Mechanical defects

6. Loss of exchange material by attrition

Front 67

What is used to maintain water alkalinity?

Back 67

Sodium Hydroxide

Front 68

What is added for scale prevention?

Back 68

Sodium hydroxide

sodium carbonate

sodium phosphate

sodium aluminate

Front 69

What is used in chemical deaeration?

Back 69

Sodium sulphite and hydrazine

Front 70

What is used to prevent caustic embrittlement?

Back 70

Sodium nitrate, lignins, and tannins

Front 71

Prevention of return line corrosion

Back 71

Amines

Front 72

2 types of chemical feeders

Back 72

Bypass Feeder- slipstream of water carries briquettes.

Gravity drip feeder- Uses powdered or liquid chemical that drips into the pipeline

Front 73

Purpose of Pheonlphthalein Alkalinity test

Back 73

Used to test for carbonate and hydroxide alkalinity. Sulphuric acid titrated in to test for it. Appears pink.

Front 74

purpose of total alkalinity test (methyl orange test)

Back 74

Tests for dissolved solid which lead to alkalinity. Appears yellow to alkaline water.

Front 75

Dissolved solids test

Back 75

After phenolphthalein test, if positive, sulphuric acid is added to neutralize the hydroxide since its very conductive. Then, a conductivity test is done on the water to determine the TDS.

Front 76

pH testing

Back 76

Done with a pH meter that supplies a voltage to

Front 77

purpose of sodium sulphite test

Back 77

Used to make sure that enough sodium sulphite is added to ensure that there is no pitting due to oxygen.

Front 78

Phosphate test

Back 78

Ensure that there is a sufficient amount of excess phosphate in the water that indicates the proper precipitation of scale forming materials.