CleaverBrooks CBEX-DE Operation And Maintenance
CBEX-DE
Dryback Elite Boiler
250-800 HP
Operation and Maintenance
750-392
10/2019
!
WARNING
DANGER
DO NOT OPERATE, SERVICE, OR REPAIR THIS EQUIPMENT UNLESS YOU FULLY UNDERSTAND ALL
APPLICABLE SECTIONS OF THIS MANUAL.
DO NOT ALLOW OTHERS TO OPERATE, SERVICE, OR REPAIR THIS EQUIPMENT UNLESS THEY FULLY
UNDERSTAND ALL APPLICABLE SECTIONS OF THIS MANUAL.
FAILURE TO FOLLOW ALL APPLICABLE WARNINGS AND INSTRUCTIONS MAY RESULT IN SEVERE
PERSONAL INJURY OR DEATH.
TO: Owners, Operators and Maintenance Personnel
This operating manual presents information that will help to properly operate and care for the equipment. Study its contents carefully.
The unit will provide good service and continued operation if proper operating and maintenance instructions are followed. No attempt
should be made to operate the unit until the principles of operation and all of the components are thoroughly understood. Failure to
follow all applicable instructions and warnings may result in severe personal injury or death.
It is the responsibility of the owner to ensure all service, repair, and operating personnel have received proper safety training.
Proper operating techniques and maintenance procedures must be followed at all times. Although the components supplied afford a
high degree of protection and safety, due attention is required to the dangers and hazards inherent in handling and firing of fuel.
“Automatic” features, where present, should not be understood as substituting for the normal responsibilities of the attendant. Such
features merely alleviate certain repetitive chores, allowing more time for proper upkeep of the equipment.
This manual is intended for a general scope of application. Because of state, local, or other applicable codes, controls and safety devices may vary considerably from those described herein.
It is recommended that a boiler room log or record be maintained. Recording of daily, weekly, monthly and yearly maintenance activities and recording of any unusual operation will serve as a valuable guide to any necessary investigation.
Most instances of major boiler damage are the result of operation with low water. We cannot emphasize too strongly the need for the
operator to periodically check the low water controls and to follow good maintenance and testing practices. Cross-connecting piping
to low water devices must be internally inspected periodically to guard against stoppages which could obstruct the free flow of water
to the low water devices. Float bowls of these controls, where applicable, must be inspected frequently to check for the presence of
foreign substances that would impede float ball movement.
The waterside condition of the pressure vessel is of extreme importance. Waterside surfaces should be inspected frequently to check
for mud, sludge, scale and corrosion.
It is essential to obtain the services of a qualified water treating company or a water consultant to recommend the proper boiler water
treating practices for your specific application.
The operation of this equipment must comply with all requirements or regulations of the owner’s insurance company and/or other
authority having jurisdiction. In the event of any conflict or inconsistency between such requirements and the warnings or instructions
contained herein, please contact Cleaver-Brooks before proceeding.
CONTENTS
CHAPTER 1 Introduction 1-1
Overview 1-1
Component Locations 1-3
CHAPTER 2 Waterside Care 2-1
Water requirements - steam boilers 2-1
Water requirements - hot water boilers 2-2
Water Treatment 2-4
Cleaning 2-5
Boil-Out of a New Unit 2-6
Washing Out 2-8
Blowdown - Steam Boilers 2-9
Periodic Inspection 2-12
Preparation for Extended Layup 2-13
CHAPTER 3 Preparations for Startup 3-1
Pre-Startup Adjustments 3-1
Burner Operating Controls: General 3-2
Control Checks 3-5
Low Water Cutoff Devices: Steam and Hot Water 3-6
Combustion Air Proving Switch 3-6
Atomizing Air Proving Switch 3-6
Gas Pilot Flame Adjustment 3-7
Gas Pressure and Flow Information 3-8
Adjusting Combustion 3-12
Linkage Settings (optional single-point systems) 3-12
Low Gas Pressure Switch 3-19
High Gas Pressure Switch 3-20
Burner Drawer Adjustment 3-20
Oil Drawer Switch 3-21
CHAPTER 4 Startup and Operation 4-1
Sequence of Operation 4-1
Flame Loss Sequence 4-4
General Preparation for Startup: All Fuels 4-6
Control Settings: Steam and Hot Water 4-7
Gas Pilot 4-7
Atomizing Air 4-7
Firing Preparations for No. 2 Oil (Series 100, 200) 4-9
Firing Preparations for Gas (Series 200, 700) 4-11
Startup, Operating, and Shutdown: All Fuels 4-12
Control Operational Checks 4-14
Troubleshooting 4-15
Emergency Shutdown 4-19
CHAPTER 5 Inspection and Maintenance 5-1
Periodic Inspection 5-2
Fireside Cleaning 5-3
Water Level Controls 5-3
Water Gauge Glass 5-4
Electrical Controls 5-5
Flame Safety Control 5-5
Removing Burner Drawer 5-7
Oil Burner Maintenance 5-7
Gas Burner Maintenance 5-9
Motorized Gas Valve 5-10
Solenoid Valves 5-10
Air Control Damper 5-10
Fan/Motor Cassette Removal 5-11
IFGR Inspection and Adjustment 5-12
Fan/Motor Cassette Replacement 5-13
Safety Valves 5-14
Fuel Oil Metering Valve 5-15
Air Pump and Lubricating System 5-17
Refractory 5-21
Front and Rear Access 5-26
Lubrication 5-28
Combustion Adjustments 5-28
Linkage Systems 5-29
CHAPTER 6 Parts 6-1
Burner Assembly 30 PPM/60 PPM/Uncontrolled Emissions 6-2
Arch Brick and Liner Tile 6-5
Front Head 6-6
Blower Cassette 6-8
Modbus Actuators (parallel positioning) 6-9
Gas Train 6-12
Light Oil Components 6-13
Low Water Cutoff 6-15
Auxiliary Low Water Cutoff 6-16
Pressure Controls, Steam 6-17
Temperature Controls, Hot Water 6-18
Rear Head 6-19
CHAPTER 1 Introduction
1.1 — Overview
The CBEX-DE boiler is a packaged firetube boiler of welded steel construction and consists of a pressure vessel,
burner, burner controls, forced draft fan, air compressor for oil atomization, oil pump, refractory, and boiler trim
supplied according to customer’s request.
FIGURE 1-1. CBEX-DE cutaway view
Like all CBEX boilers, the CBEX-DE features spiral tubes for enhanced heat transfer. Other features include:
• 30 ppm NOx standard
• Hinged or davited insulated rear door with sight port
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CBEX-DE
1-1
Introduction
The CBEX-DE is a 2-pass dry-back design. The flame originates in the furnace. As the combustion gases travel
down the furnace and through the firetubes, heat from the flame and combustion gases is transferred to the
water to generate steam.
For lower emissions the CBEX-DE firetube boiler line is designed to incorporate induced Flue Gas Recirculation
(FGR). FGR may be used when firing either natural gas and/or light oil.
The FGR system mixes a portion of the relatively cool flue gas from the exit of the second-pass tubes with the
incoming combustion air to reduce the furnace flame temperature, thereby reducing NOx emissions. In this
approach, the combustion air fan handles both the combustion air and the recirculated flue gases. Carbon monoxide (CO) emissions also tend to be lower due to increased turbulence caused by the addition of the flue gases
into the combustion air stream.
The low emission design can affect the selection of the combustion air fan, motor, burner, and other components.
Several different system configurations are available, depending on the requirements for NOx emissions and the
fuels used. All systems use similar primary components, but fan and motor sizes as well as the FGR damper may
differ.
Installation should conform to state and local codes. Prior to installation, the proper authorities having jurisdiction are to be consulted, permits obtained, etc.
CBEX-DE boilers offer compliance with multiple insurers’ requirements. Equipment provided may vary depending
on insurance.
Steam boilers are built for a specific design pressure, which is the pressure used in calculating the minimum permissible thickness or physical characteristics of the pressure vessel components. Typically, the safety valves are
set at or below design pressure.
Care taken in placing the pressure vessel into initial service is vital. The waterside of new boilers and new or
remodeled steam or hot water systems may contain oil, grease, or other foreign matter. Waterside care will continue to be important throughout the lifetime of the boiler. A boilout method for new boilers, as well as general
waterside care information, can be found in Chapter 2.
1.1.1 — Construction
Steam boilers designed for 15 psig and hot water boilers designed for 250º F at 125 psi or less are constructed
in accordance with Section IV, Heating Boilers, of ASME Code.
Steam boilers designed for operating pressures exceeding 15 psig are constructed in accordance with Section I,
Power Boilers, of the ASME Code. Hot water boilers designed for operating temperatures above 250º F or 125
psi are likewise built to Section I of the ASME Code.
1-2
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Component Locations
1.2 — Component Locations
1. Blower assembly
2. Feedwater piping
3. Main gas train
4. Burner drawer
5. Oil system
6. Aux low water cutoff
7. Control panel/entrance panel
8. Low water cutoff
9. Pressure controls
1
6
5
4
2
3
FIGURE 1-2. Boiler front view (67” boiler - configurations may vary)
11. Oil supply piping
12. Air compressor
13. Bottom blowdown piping
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CBEX-DE
10. Safety valves
11
FIGURE 1-3. Boiler side view (67” boiler - configurations may vary)
1
10
8
9
7
12
13
1-3
1.2.1 — Blower assembly
The blower assembly, also called the cassette,
comprises the fan and motor and can be removed
as a unit from the front of the boiler without opening the front door. The front davit arm is used to
support the blower cassette during removal.
1.2.2 — Feedwater piping
Introduction
FIGURE 1-4. Fan/motor cassette
Feedwater piping configurations can vary. A typical configuration is shown below, comprising three-valve bypass
piping with strainer and a modulating feedwater valve.
FIGURE 1-5. Feedwater piping
1-4
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Component Locations
1.2.3 — Main gas train
4
2
5
6
1
1
FIGURE 1-6. Main gas train
Depending upon the requirements of the insurance carrier or other governing agencies, the gas train may consist
of some or all of the following items.
1. Shutoff Cocks: For manually opening and closing the main fuel gas supply downstream of the main gas line
pressure regulator. A second shutoff cock, downstream of the main gas valve(s), is installed to provide a
means of shutting off the gas line whenever a test is made for leakage across the main gas valve.
2. Main Gas Valve: Double body safety shutoff valve. Electrically actuated valves open simultaneously to admit
gas to the burner. The downstream valve is equipped with a with a regulating actuator and a proof of closure
switch that is connected to the pre-ignition interlock circuit.
3. Main Gas Vent Valve (if required): A normally open solenoid valve installed between the two main gas valves
to vent gas to the atmosphere, should any be present in the main gas line when the gas valves are deenergized. The vent valve closes when the gas valves are energized.
4. Low Gas Pressure Switch: A pressure-actuated switch; closed whenever main gas line pressure is above a pre-
selected pressure. Should the pressure drop below the setting, the switch contacts open a circuit causing the
main gas valve(s) to close, or prevent the burner from starting. The switch is usually equipped with a device
that must be manually reset after being tripped.
5. High Gas Pressure Switch: A pressure actuated switch; closed whenever main gas line pressure is below a
preselected pressure. Should the pressure rise above the setting, the switch contacts will open a circuit causing the main gas valve(s) to close, or prevent the burner from starting. The switch is usually equipped with a
device that must be manually reset after being tripped.
6. Test Cocks: The body of the gas valve has 1/4-inch NPT fittings for pressure test connection.
7. Butterfly Gas Valve (not shown): The pivoted disc in the valve is directly driven by a servo motor actuator to
regulate the rate of gas flow to the burner. In optional 700-800 HP single point systems, the valve is driven by
the modulating motor through connecting linkage.
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1-5
1.2.4 — Pilot train
Introduction
4
3
1
2
FIGURE 1-7. Pilot train
1. Gas Pilot Valve: A solenoid valve that opens during the ignition period to admit fuel to the pilot. It closes after
main flame is established. The sequence of energizing and de-energizing is controlled by the programming
relay. A second gas pilot valve may be required by insurance regulations.
2. Gas Pilot Shutoff Cock: For manually opening or closing the gas supply to gas pilot valve.
3. Gas Pressure Gauge: Indicates gas pressure to pilot.
4. Gas Pressure Regulator: Reduces incoming gas pressure to suit the pilot.
1.2.5 — Burner drawer
GAS HOUSING
BURNER SUPPORT
BURNER DRAWER
FIGURE 1-8. Burner drawer
The burner is a nozzle-mixing orifice design with interrupted gas pilot. Burners equipped for oil use a low pressure, air-atomized oil system.
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Component Locations
Combination gas/oil burners include equipment for each fuel, with a fuel selector switch mounted in the control
panel. Regardless of which fuel is used, the burner operates with full modulation within its rated operating range.
The burner returns to minimum firing position for ignition.
The flame safeguard includes a flame detector to supervise both oil and gas flames, and to shut the burner down
in the event of loss of flame. The burner sequence provides a pre-purging period, proving of the pilot and main
flame, and a period of continued blower operation after shutoff to postpurge the boiler of all unburned fuel vapor.
Other safety controls shut down the burner under low-water conditions, excess steam pressure, or water temperature.
Safety interlock controls include combustion and atomizing air proving switches and, depending upon the fuel
and insurance carrier requirements, controls that prove the presence of adequate fuel pressure.
The sequence of burner operation from startup through shutdown is governed by the program relay in conjunction with the operating, limit and interlock devices. The devices are wired into the circuitry to provide safe operation and protect against incorrect operating techniques.
All CBEX-DE boilers have the burner assembly integral with the front head. The burner drawer can be removed as
a unit, or the entire head may be swung open for inspection and maintenance.
Combustion air is provided by a centrifugal blower located in the front head.
Filtered primary air for atomizing fuel oil is furnished independently of combustion air by an air compressor. The
burner control circuit operates on 115 volt, single phase 60 Hz (or 50 Hz when equipped) alternating current.
The forced draft fan motor is generally operated on 3-phase service at the available main power supply voltage.
In addition to the standard basic controls supplied, other devices may be required to meet specific requirements
of an insurance carrier or local code.
Refer to the wiring diagram prepared by Cleaver-Brooks for your installation to determine the specific controls in
the burner and limit control circuits.
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1-7
1.2.6 — Oil system
Introduction
2B
2A
1
2D
1
FIGURE 1-9. Front head oil piping
2C
The following items are applicable to all oil fired or gas and oil fired boilers.
1. Oil Shutoff Valve: Opens when energized through contacts in the programmer and allows fuel oil flow from the
oil metering valve to the burner nozzle. A light oil fired burner uses two valves operating simultaneously.
2. Fuel Oil Controller: An assembly combining into a single unit the gauges, regulators and valves required for
regulating the flow of fuel oil. All controllers have the following integral parts.
A - Oil Metering Valve: Valve metering stem moves to increase or decrease the orifice area to regulate the supply of fuel
oil to the burner nozzle in accordance with boiler load variances. Stem movement is controlled by the oil actuator or in
linkage systems by an oil metering cam.
B - Actuator: Positions the oil metering valve stem.
C - Oil Burner Pressure Gauge: Indicates pressure of the fuel oil at the metering valve.
D - Oil Pressure Regulator: For adjustment of the pressure of oil at the metering valve.
3. Oil Relief Valve: Maintains a constant oil supply pressure to the fuel
oil controller by bypassing excess fuel oil.
4. Terminal Block: Provides the connection for fuel oil input and return
to storage tank.
5. Fuel Oil Strainer: Prevents foreign matter from entering the burner
system.
6. Pressure Gauge for oil supply pressure
7. Fuel Oil Pump (not shown): Transfers fuel oil from the storage tank
and delivers it under pressure to the burner system.
1-8
6
5
FIGURE 1-10. Oil terminal block
CBEX -DE
3
4
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Component Locations
1.2.7 — Actuators
Individual actuators for fuel, air, and FGR are part of the
standard parallel positioning combustion control system,
and are positioned via Modbus signal from the Hawk control system.
Actuators are connected in series with the air damper actuator last in the sequence. Actuators may use quick disconnect cables or may be hard wired depending on the
installation.
For actuator setup and configuration information as well as
combustion setup procedures, see the appropriate Hawk
controls manual.
FLUE GAS
RECIRCULATION
COMBUSTION AIR
FUEL 2
(FUEL OIL
CONTROLLER)
A single-point positioning linkage system is available for
700/800 HP boilers.
FUEL 1 (GAS BUTTERFLY VALVE)
FIGURE 1-11. Actuators
1.2.8 — Control Panel
A common enclosure houses both the control panel and the electrical entrance
panel. The upper and lower sections are divided by a partition with a separate
hinged door for each section.
The upper section (low voltage) houses the boiler control system, including the PLC
and associated modules, the flame safeguard, the Hawk HMI touch screen, and the
LevelMaster panel.
External switches and indicator lights can vary according to options selected. A typical configuration will include switches for:
• FSG reset
• ALWCO reset
• Burner switch
• Fuel selector switch
The standard control system is the Cleaver-Brooks Hawk 1000, which includes a
4” touch screen.
The optional Hawk 4000 features a 7” touch screen, with a 10” screen optional.
FIGURE 1-12. Control/
The principal components of the HAWK 1000 are the Programmable Logic Control-
entrance panel
ler (PLC), touch screen Human Machine Interface (HMI), and the Flame Safety
Control. The system also includes 24VDC power supplies and various relays and circuit breakers.
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1-9
Introduction
1. Base Unit
1
1a
686
1b
2
4
3
5
7
1a. L24ER Programmable Logic Controller (PLC)
1b. Embedded I/O
2. SM2 Modbus Communications Module
3. Digital Inputs
4. Digital Outputs
5. Analog Inputs (optional)
6. Burner Control
7. Power supplies
8. Circuit breakers, relays, fuses,
9. ALWCO control
etc.
9
FIGURE 1-13. Hawk 1000 components, typical
The Base Unit consists of the Processor (CPU) which holds the program logic and configuration for the boiler
controller and embedded I/O modules which consist of discrete inputs, discrete outputs, and analog inputs. The
program logic is password-secured at the factory.
The SM2 module handles the Modbus communications between the PLC and other devices.
The Module Power Supply powers the Base Unit and the I/O modules. The remainder of the PLC rack is for the
discrete input and output modules, and for analog input module (optional).
I/O modules are used to send and receive control and communication signals to/from other parts of the system.
A Right End Cap Terminator is required to complete the modular communication bus. It attaches to the right side
of the last module in the rack.
An optional analog input module can be added to the PLC to provide additional functionality.
The HMI displays numerous boiler parameters at a glance and provides easy menu navigation for configuring
system parameters, setting of combustion, monitoring the boiler processes, and managing and annunciating system alarms.
The HMI communicates with the PLC via Ethernet and is
powered
by a 24
VDC
din-rail mounted power
supply.
NOTE: For complete information on the boiler control system consult the Hawk manual, provided separately.
1-10
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CBEX -DE
Component Locations
1.2.9 — Pressure Controls
1.Pressure Gauge: Indicates boiler internal pressure.
1
2.Operating Limit Pressure Control: Breaks a circuit to stop burner operation on a rise of
boiler pressure at a selected setting. It is adjusted to stop or start the burner at a preselected pressure setting.
3.High Limit Pressure Control: Breaks a circuit to stop burner operation on a rise of pres-
sure above a selected setting. It is adjusted to stop the burner at a preselected pressure
4
above the operating limit control setting. The high limit pressure control is normally
equipped with a manual reset.
2
4.Pressure Transmitter: Senses changing boiler pressure and transmits a signal to the
boiler control system.
FIGURE 1-14. Boiler Overview screen, Hawk 1000
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CBEX-DE
3
FIGURE 1-15. Steam Controls
1-11
Introduction
1.2.10 — Temperature Controls (hot water boilers)
High Limit Temperature Control: Breaks a circuit to stop burner operation on a rise of temperature at a selected
setting. It is adjusted to stop the burner at a preselected temperature above the operating control setting. The
high limit temperature control normally is equipped with a manual reset.
Operating Limit Temperature Control: Breaks a circuit to stop burner operation on a rise of boiler temperature at
a selected setting. It is adjusted to stop or start the burner at a preselected operating temperature.
1.2.11 — Water Level Controls
The Low Water Cutoff (LWCO) shuts down the burner if water level goes
3
below the safe operating point. The LWCO is also responsible for starting
and stopping the feedwater pump to maintain the proper boiler water
level. The Cleaver-Brooks Level Master is the standard LWCO on CBEXDE boilers.
1
1.Low Water Cutoff and Pump Control: Float-operated control responds to the water
level in the boiler. It performs two distinct functions:
•Stops firing of the burner if water level lowers below the safe operating point. Energizes
the low-water light in the control panel; also causes low-water alarm bell (optional
equipment) to ring. Code requirements of some models require a manual reset type of
ALWCO
low water cutoff.
•Starts and stops the feedwater pump (if used) to maintain water at the proper operat-
ing level.
LWCO
5
2
4
2.Water Gauge Glass Drain Valve: Provided to flush the gauge glass.
3.Vent Valve: Allows the boiler to be vented during filling and facilitates routine boiler
inspection as required by ASME Code.
4.Water Column Drain Valve: Provided so that the LWCO and its piping can be flushed
regularly to assist in maintaining cross-connecting piping and in keeping the float bowl
clean and free of sediment. A similar drain valve is furnished with the auxiliary low water
cutoff.
5.The Auxiliary Low Water Cutoff (ALWCO) stops burner operation in the event boiler
water drops below the primary low water cutoff point. May require manual reset in order
to restart the boiler after a low water condition.
FIGURE 1-16. Low Water Cutoff, Aux. Low Water Cutoff
Level Master safety features include float detection, routines for water column
blowdown and ALWCO testing, and an independent watchdog system for
shutdown in the event of microprocessor failure. An internal clock provides
time-stamped event logging for all blowdown cycles and alarm occurrences.
The Level Master keypad/display unit is mounted in the control panel next to
the Hawk HMI. A bar graph provides a continuous reading of water level,
while a two row backlit LCD display shows controller messages. The sensor
component is mounted in the water column and can be easily removed for
inspection or cleaning.
Expanded programming features can be accessed via RS-232 computer connection.
For further information see the Level Master manual provided separately.
1-12
FIGURE 1-17. Level Master
display
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Component Locations
1.2.12 — Bottom blowdown piping
Quick and slow opening valves are provided as standard for bottom blowdown. See Chapter 2 for procedure.
1.2.13 — Air Compressor
A side mounted air compressor provides atomizing air when burning #2 oil. It is started automatically by the
combustion control system. It includes the following components:
1
2
5
7
3
6
8
4
FIGURE 1-18. Air compressor
1. Air Pump Motor: Drives the air pump and an air cooling fan. The motor is started and stopped simultaneously
with the forced draft fan motor.
2. Air Pump: Provides air for atomization of the fuel oil.
3. Air Filter: The filter cleans the air supply prior to entering air pump.
4. Check Valve: Prevents lubricating oil and compressed air from surging back through the pump and air filter
when the pump stops.
5. Air-Oil Receiver Tank: Holds a supply of oil for lubricating the air pump. The receiver tank also separates lube
oil from the atomizing air before delivery to nozzle.
6. Lube Oil Level Sight Glass: Indicates the level of lubricating oil in the air-oil receiver tank.
7. Lube Oil Cooling Coil: Cools the lubricating oil before it enters the air pump. A fan driven by the air pump
motor circulates cooling air over the coil.
8. Lube Oil Fill Pipe and Strainer: Used when adding oil to the air-oil receiver tank.
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1.2.14 — Safety Valve(s)
Safety valves prevent pressure in excess of the
design pressure of the vessel. The size, rating,
and number of valves on a boiler is determined
by the ASME Boiler Code. The safety valves
and the discharge piping are to be installed to
conform to the ASME Code requirements. The
installation of a valve is of primary importance
to its service life. A valve must be mounted in a
vertical position so that discharge piping and
code-required drains can be properly piped to
prevent buildup of back pressure and accumulation of foreign material around the valve seat.
Apply only a moderate amount of pipe compound to male threads and avoid over-tightening, which can distort the seats. Use only flatjawed wrenches on the flats provided. When
installing a flange connected valve, use a new
gasket and draw the mounting bolts down
evenly. Do not install or remove side outlet
valves by using a pipe or wrench in the outlet.
Introduction
FIGURE 1-19. Safety Valve Piping
The vent pipe should be supported so as to
ensure no pressure is exerted on the safety valve discharge piping.
Warning
!
Only properly certified personnel should adjust or repair the boiler safety valves. Failure to follow these instructions
could result in serious injury or death.
1-14
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CHAPTER 2 Waterside Care
The operator should be familiar with this chapter before attempting to place the unit into operation.
Although it is of prime importance, the subject of water supply and treatment cannot thoroughly be covered
within the scope of this manual. For additional assistance with your water treatment needs, contact your CleaverBrooks service and parts representative. Ultimately a water treatment expert should be consulted to obtain the
best treatment plan for your location.
Feedwater equipment should be ready for use upon installation of the boiler. Be sure that all valves, piping, boiler
feed pumps, and receivers are installed in accordance with prevailing codes and practices.
Strict attention to waterside care is essential during initial commissioning and throughout the lifetime of the
boiler. When placing the pressure vessel into initial service, keep in mind that the waterside of new boilers and
new or remodeled steam systems may contain oil, grease or other foreign matter. A method of boiling out the vessel to remove the accumulations is described later in this chapter.
2.1 — Water requirements - steam boilers
Feed Pump Operation
Before turning on the pump motor be certain that all valves in the water feed line are open to prevent possible
damage to the feed pump mechanism. After opening the valves, momentarily energize the feed pump motor to
establish correct pump rotation. With the correct rotation established, close the boiler feed pump entrance
switch. The pump should shut down when the water level reaches the proper level.
Feedwater pumps must have adequate capacity to maintain required water level under all operating conditions.
Check the feedwater pumps periodically and maintain as necessary to prevent unexpected breakdowns.
NOTE: Prior to operating the pump, carefully check the alignment of the flexible coupling, if one is used. A properly
aligned coupling will last a long time and provide trouble-free mechanical operation.
NOTE: For new installations a startup strainer is recommended. Contact the pump manufacturer for details.
NOTE: In the event that water column isolation valves are provided, it must be established that the valves are open
and seated or locked in the open position. It is illegal to operate the boiler with closed or unseated open valves.
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2-1
Waterside Care
Warning
!
The isolation valves and the water column piping must be locked open during operation. Failure to do so may result
in a low water condition. Failure to follow these instructions could result in serious injury or death.
2.2 — Water requirements - hot water boilers
Air Removal - The hot water outlet includes a dip tube which extends 2 to 3 inches into the boiler. The dip tube
reduces the possibility of air, which may be trapped at the top of the shell, from entering the system. Oxygen or
air released in the boiler will collect or be trapped at the top of the boiler shell.
The air vent tapping on the top center line of the boiler should be piped into the expansion or compression tank.
Air trapped at the top of the boiler will find its way out of the boiler through the tapping.
Minimum Water Temperature - The minimum recommended boiler water temperature is 170 deg F. When water
temperatures lower than 170 deg F are used, the combustion gases are reduced in temperature to a point where
water vapor condenses, causing corrosion in the boiler and possible breeching. Condensation is more severe on a
unit that operates intermittently and which is greatly oversized for the actual load. Condensation can be minimized by maintaining boiler water temperatures above 170 deg F.
Notice
References to hot water boilers in this manual apply only to boilers using 100% water. Glycol solutions have
different operating requirements, circulation rates and temperatures, etc.
Rapid Replacement of Boiler Water - The system layout and controls should be arranged to prevent the possibil-
ity of pumping large quantities of cold water into a hot boiler, which will cause thermal stresses. Water temperature in a boiler of 200 deg F or 240 deg F cannot be completely replaced with 80 deg F water in a few minutes
time without causing thermal stress. The same fact applies to periods of normal operation, as well as during initial start-up.
The circulating pumps should be interlocked with the burner so that the burner cannot operate unless the circulating pump is running in order to avoid damage to the equipment.
When individual zone circulating pumps are used, it is recommended that they be kept running-even though the
heat users do not require hot water. The relief device or by-pass valve will thus allow continuous circulation
through the boiler and can help prevent rapid replacement of boiler water with cold zone water.
Continuous Flow Through the Boiler - The system should be piped and the controls arranged to allow water circulation through the boiler under all operating conditions. The operation of three-way valves and system controls
should be checked to be sure that the boiler will not be by-passed. Constant circulation through the boiler
eliminates the possibility of stratification within the unit and results in more even water temperatures to the system. A rule of thumb of 3/4 to 1 gpm per boiler horsepower can be used to determine the minimum continuous
flow rate through the boiler under all operating conditions. The operator should determine that a flow of water
exists through the boiler before initial firing or refiring after boiler has been drained.
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Water requirements - hot water boilers
Water Circulation - The chart in Table 2-1 shows the maximum gpm circulation rate of boiler water in relation to
full boiler output and system temperature drop.
It is advisable to have a thermometer installed in the return line to indicate return water temperature. Knowing
the supply water temperature, the boiler system differential can be established. With knowledge of the pumping
rate, the operator can easily detect any excessive load condition and take appropriate corrective action.
Multiple Boiler Installations - When multiple boilers are used, care must be taken to ensure adequate or proportional flow through the boilers. Proportional flow can best be accomplished by use of balancing valves and
gauges in the supply line from each boiler. If balancing valves or orifice plates are used, a significant pressure
drop (e.g., 3-5 psi) must be taken across the balancing device to accomplish the purpose. If care is not taken to
ensure adequate or proportional flow through the boilers, wide variations in firing rates between the boilers can
result. In extreme cases, one boiler may be in the high-fire position while the other boiler or boilers may be at low
fire. The net result would be that the common header water temperature to the system would not be up to the
desired point.
Note: If the operating water temperature going to the system must be lower than 170 deg F, mixing valves
should be used to avoid damage to the equipment. Operating boiler water temperature should be a minimum
of 170 deg F (200 deg F if used to preheat No. 6 oil).
TABLE 2-1. Maximum Circulating Rate
BOILER SIZE
(BHP)
250 8,370 1,675 838 558 419 335 280 240 210 186 167
300 10,045 2,010 1,005 670 503 402 335 287 251 223 201
350 11,720 2,350 1,175 784 587 470 392 336 294 261 235
400 13,400 2,680 1,340 895 670 535 447 383 335 298 268
500 16,740 3,350 1,675 1,120 838 670 558 479 419 372 335
600 20,080 4,020 2,010 1,340 1,005 805 670 575 502 448 402
700 23,430 4,690 2,345 1,565 1,175 940 785 670 585 520 470
800 26,780 5,360 2,680 1,785 1,340 1,075 895 765 670 595 535
BOILER
OUTPUT
BTU/HR
(1000)
SYSTEM TEMPERATURE DROP - DEGREES °F
10 20 30 40 50 60 70 80 90 100
MAXIMUM CIRCULATING RATE - GPM
Pump Location - It is recommended that the system circulating pumps take suction from the outlet connection
on the boiler, and that they discharge to the system load. In order to put the boiler and the expansion tank on the
suction side of the pump. The suction side is preferred because it decreases air entry into the system and does
not impose the system head on the boiler. It is common practice to install a standby system circulating pump.
The main circulating pumps are usually located adjacent to the boilers in the boiler room.
Pump Operation - Pumps are normally started and stopped by manual switches. It is also desirable to interlock
the pump with the burner so that the burner cannot operate unless the circulating pump is running.
Pressure - The design of the system and usage requirements often dictate the pressure exerted upon the boiler.
Some systems are pressurized with air, or with an inert gas such as nitrogen. Caution must be exercised to
ensure that the proper relationship of pressure to temperature exists within the boiler so that all of the boiler’s
internal surfaces are fully wetted at all times.
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Waterside Care
When initially firing a newly installed boiler, or when cutting an existing boiler into an operating system, the
boiler or boilers to be cut into operation MUST be pressurized equal to the system and/or other boilers prior to
opening the header valves.
Special caution must be taken to guard against any condition, or combination of conditions, that might lead to
the transfer of cold water to a hot boiler or hot water to a cold boiler. It cannot be overemphasized that rapid
changes in temperature within the boiler can cause damage.
FIGURE 2-1. Internal Boiler Pressure
2.3 — Water Treatment
Properly treated boiler feed water, combined with good engineering and operating practices, leads to maximum
effectiveness and long life of pressure vessels. Contact your local Cleaver-Brooks authorized representative for
information on how to prevent the presence of unwanted solids and corrosive gases.
Objectives of water treatment are:
1. Prevent hard scale deposits or soft sludge deposits, which reduce heat transfer and can lead to overheated
metal and costly downtime and repairs.
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Cleaning
2. Eliminate corrosive gases in the supply or boiler water.
3. Prevent inter-crystalline cracking or caustic embrittlement of boiler metal.
4. Prevent carryover and foaming.
Accomplishment of the above objectives generally requires proper feedwater treatment before and after introduction of the water into the boiler. The selection of pre-treatment processes depends upon the water source, its
chemical characteristics, amount of makeup water needed, plant operating practices, etc. Treating methods
include filtering, softening, de-mineralizing, deaerating, and preheating. After-treatment involves chemical treatment of the boiler water. A water treatment expert should be consulted to determine an appropriate treatment
program.
Because of the variables involved, no single boiler compound can be considered a “cure-all” nor is it advisable to
experiment with homemade treating methods. Sound recommendations and their employment should be augmented by a periodic analysis of the feedwater, boiler water, and condensate.
The internal or waterside surfaces of the pressure vessel should be inspected with enough frequency to determine
the presence of any contamination, accumulations of foreign matter, or corrosion, and/or pitting. If any of the conditions are detected, contact your local Cleaver-Brooks authorized representative for advice on corrective action.
A properly sized water meter should be installed in the raw water make-up line in order to accurately determine
the amount of raw water admitted to the boiler (steam or hot water) and to aid in maintaining proper waterside
conditions.
2.4 — Cleaning
2.4.1 — Steam/Hot Water Piping
Steam piping systems connected to the boiler may contain oil, grease, or foreign matter. The impurities must be
removed in order to prevent damage to pressure vessel heating surfaces. On a steam system, the condensate
should be wasted until tests show the elimination of undesirable impurities. During the period that condensate is
wasted, attention must be given to the treatment of the raw water used as make-up so that an accumulation of
unwanted materials or corrosion does not occur. For more information, contact your local Cleaver- Brooks authorized representative.
On a hot water system, chemical cleaning is generally necessary and the entire system should be drained after
treatment. A chemical treatment expert should be consulted regarding the best product for your application.
2.4.2 — Pressure Vessel
The waterside of the pressure vessel must be kept clean from grease, sludge, and foreign material. Such deposits, if present, will shorten the life of the pressure vessel, will interfere with efficient operation and functioning of
control and safety devices, and quite possibly cause unnecessary and expensive rework, repairs, and downtime.
The installation and operating conditions that the boiler will be subjected to should be considered and cleaning of
the waterside of the pressure vessel should be provided during the course of initial start-up.
The pressure vessel and the steam and return lines or hot water piping represent, in effect, a closed system.
Although the steam and return (condensate) lines or the hot water piping system may have been previously
cleaned, it is possible that:
1. Cleaning has been inadequate.
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Waterside Care
2. Partial or total old system is involved.
3. Conditions may prevent adequate cleaning of piping.
The pressure vessel waterside should be inspected on a periodic basis. An inspection will reveal true internal
conditions and serve as a check against conditions indicated by chemical analysis of the boiler water. Inspection
should be made three months after initial starting and at regular 6-, 9-, or 12-month intervals thereafter. The frequency of further periodic inspections will depend upon the internal conditions found.
If any unwanted conditions are observed, contact your local Cleaver-Brooks authorized representative for recommendations.
Any sludge, mud, or sediment found will need to be flushed out. If excessive mud or sludge is noticed during
blowdown, the scheduling or frequency of blowdown may need to be revised. The need for periodic draining or
washout will also be indicated.
Any oil or grease present on the heating surfaces should be removed promptly by a boil-out using an alkaline
detergent solution.
2.5 — Boil-Out of a New Unit
The internal surfaces of a newly installed boiler may have oil, grease or other protective coatings used in manufacturing. Such coatings must be removed because they lower the heat transfer rate and could cause overheating
of a tube. Before boiling out procedures may begin, the burner should be ready for firing. The operator must be
familiar with the procedure outlined under burner operation.
NOTE: Temperature of initial fill of water for hydrostatic tests, boil-out, or for normal operation should be as stated in
the ASME Boiler Code.
Warning
!
Use of a suitable face mask, goggles, rubber gloves, and protective garments is strongly recommended when handling or mixing caustic chemicals. Do not permit the dry material or the concentrated solution to come in contact
with skin or clothing. Failure to follow these instructions could result in serious injury or death.
A general procedure for cleaning a boiler is:
1. Refer to the table below to determine water capacity. Have sufficient cleaning material on hand to complete
the job.
TABLE 2-2. Water Capacity and Weights
Boiler HP
250 300 350 400 500 600 700 800
Water Volume - Operating, Gal. 1126 1190 1199 2032 1725 1968 1767 1837
Water Volume - Flooded, Gal. 1589 1680 1718 2618 2515 2869 2630 2733
Water Weight - Operating, lbs. 9378 9915 9991 16926 14366 16393 14723 15300
Water Weight - Flooded, lbs. 13240 13996 14315 21805 20952 23899 21909 22765
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Boil-Out of a New Unit
2. All valves in the piping leading to or from the system must be closed to prevent the cleaning solution from get-
ting into the system.
3. When dissolving chemicals:
A. Put warm water into a suitable container.
B. Slowly introduce the treatment chemical into the water.
C. Add the chemical slowly and in small amounts to prevent excessive heat and turbulence.
4. Water relief valves and steam safety valves must be removed before adding the boilout solution so that neither
the boilout solution nor the grease the solution may carry will contaminate the valves. Use care in removing
and reinstalling the valves.
5. An overflow pipe should be attached to one of the top boiler openings and routed to a safe point of discharge.
The safety valve tapping is usually used.
6. Fill the pressure vessel with clean water at ambient temperature until the top of the tubes are covered. Add
the cleaning solution, slowly and in small amounts, and then fill to the top with water.
7. The boiler should then be fired intermittently at a low rate sufficient to hold solution just at the boiling point.
Boil the water for at least five hours. Do not produce steam pressure.
8. Allow a small amount of fresh water to enter the boiler to create a slight overflow that will carry off surface
impurities.
9. Continue the boil and overflow process until the water clears. Shut the burner down.
10. Let the boiler cool to 120º F or less.
11. Remove handhole plates and wash the waterside surfaces thoroughly using a high pressure water stream.
12. Inspect the surfaces. If they are not clean, repeat the boilout.
13. After closing the handholes and reinstalling the safety or relief valves, fill the boiler and fire it until the water is
heated to at least 180º F to drive off any dissolved gases, which might otherwise corrode the metal.
14. Local authorities and chemical supplier should be consulted as to boil out chemical disposal.
Warning
!
Be sure to drain the hot water to a safe point of discharge to avoid scalding. Failure to follow these instructions could
result in serious injury or death.
The above procedure may be omitted in the case of a unit previously used or known to be internally clean. However, consideration must be given to the possibility of contaminating materials entering the boiler from the system.
NOTE: For new installations, refractory heat-curing can be accomplished at the same time as the boil out. Total firing
time (firing intermittently at a low rate) should be 6-8 hours. The heat curing procedure is essential to prevent damage and cracking in the boiler refractory.
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Waterside Care
Caution
!
AIR-DRYING ALONE WILL NOT SUFFICIENTLY ENSURE AGAINST REFRACTORY DAMAGE. HEAT-CURING
MUST BE PERFORMED AT INITIAL START-UP. RUN THE BURNER AT LOW FIRE FOR A PERIOD OF 6 TO 8
HOURS. AFTER THIS TIME THE FIRING RATE MAY BE GRADUALLY INCREASED. FAILURE TO FOLLOW THIS
PROCEDURE MAY RESULT IN DAMAGE AND CRACKS IN THE REFRACTORY.
Important
!
There are three approximately 1/4 inch holes provided along the bottom of the rear head to remove
water from the refractory curing process. These holes should be sealed shut with a high temperature
caulk upon completion of the refractory cure procedure.
2.6 — Washing Out
2.6.1 — Steam Boiler
No later than three months after initially placing the boiler into operation, and thereafter as conditions warrant,
the pressure vessel should be drained after being properly cooled to near ambient temperature. Handhole covers
should be removed and waterside surfaces should be inspected for corrosion, pitting, or formation of deposits.
Upon completion of the inspection, the pressure vessel interior should be flushed out, as required, with a high
pressure hose. If deposits are not fully removed by flushing, a consultation may be required with your local
Cleaver-Brooks authorized representative. In extreme cases, it may be necessary to resort to acid cleaning. Professional advice is recommended if acid cleaning is required.
The inspections will indicate the effectiveness of the feedwater treatment. The effectiveness of treatment, the
water conditions, and the amount of fresh water make-up required are all factors to be considered in establishing
frequency of future pressure vessel washouts. Contact your local Cleaver-Brooks authorized representative for
more information.
2.6.2 — Hot Water Boiler
In theory, a hot water system and boiler that has been initially cleaned, filled with raw water (and water treated),
and with no make-up water added, will require no further cleaning or treatment. However, since the system (new
or old) can allow entrance of air and unnoticed or undetected leakage of water, introductions of raw water makeup or air may lead to pitting, corrosion and formation of sludge, sediment, scale, etc., on the pressure vessel
waterside. If the operator is absolutely certain that the system is tight, then an annual waterside inspection may
be sufficient. However, if there is any doubt, the pressure vessel waterside should be inspected no later than
three months after initially placing the boiler into operation, and periodically thereafter as indicated by conditions
observed during inspections.
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Blowdown - Steam Boilers
! Warning
Be sure to drain the hot water to a safe point of discharge to avoid scalding. Failure to follow these
instructions could result in serious personal injury or death
2.7 — Blowdown - Steam Boilers
Boiler water blowdown is the removal of some of the concentrated water from the pressure vessel and its replacement with feedwater so that the lowering of concentration of dissolved solids in the boiler water occurs.
Dissolved solids are brought in by the feedwater even though the water may be treated prior to use through external processes that are designed to remove unwanted substances which contribute to scale and deposit formations. However, none of the processes can remove all substances. Regardless of their efficiency, some dissolved
solids will be present in the boiler feedwater.
Dissolved solids become less soluble in the high temperature of the boiler water and tend to accumulate on heating surfaces. Therefore blowdown and internal chemical treatment are required to prevent the solids from forming harmful scale and sludge.
Scale has a low heat transfer value and acts as an insulation barrier. Scale retards heat transfer, which not only
results in lower operating efficiency, and consequently higher fuel consumption, but equally important, can cause
overheating of boiler metal. Overheating of boiler metal can result in tube failures or other pressure vessel metal
damage and lead to boiler downtime and costly repairs.
Scale is caused primarily by calcium and magnesium salts, silica and oil. Any calcium and magnesium salts in
the boiler water are generally precipitated by the use of sodium phosphate, along with organic materials, to
maintain the precipitates or “sludge” in a fluid form. The solids such as sodium salts and suspended dirt do not
readily form scale. But as the boiler water boils off as relatively pure steam, the remaining water is thickened
with the solids. If the concentration is permitted to accumulate, the sludge will build possibly causing overheating of the metal.
Therefore, it is necessary to control the amounts of totally dissolved solids (TDS) and sludge in the following
ways.
2.7.1 — Types of Blowdown
The two principal types of blowdown are intermittent manual blowdown and continuous blowdown.
Intermittent Manual Bottom Blowdown
Manual or sludge blowdown is necessary for the operation of the boiler whether or not continuous blowdown is
employed.
The blowdown tappings are located at the bottom or lowest part of the boiler in order to rid the sludge in the
lower part of the vessel.
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Waterside Care
FIGURE 2-2. Bottom blowdown piping
Equipment generally consists of two quick opening valves and one slow opening valve. The valves and necessary
piping are not normally furnished with the boiler. but supplied by others. All piping must be routed to a safe point
of discharge. Piping must be properly supported and free to expand.
Continuous Blowdown
Continuous blowdown is used in conjunction with a surface blowoff tapping (furnished on units 60” in diameter
and larger) on the top center line of the pressure vessel. It is provided with an internal collecting pipe terminating
slightly below the working water level for the purpose of skimming dissolved solids, oil, or other impurities from
the surface of the pressure vessel water.
A controlled orifice valve or an auto-sensing/metering valve is used to allow a continual, yet controlled flow of
concentrated water to drain or a place of recovery.
The flow control valve and piping are generally provided by others. All piping must be routed to a safe point of
discharge.
2.7.2 — Frequency of Manual Blowdown
When continuous blowdown is utilized, manual blowdown is primarily used to remove suspended solids or
sludge. The continuous blowdown removes sediment and oil from the surface of the water along with a prescribed amount of dissolved solids.
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Blowdown - Steam Boilers
When surface or continuous blowdown is not utilized manual blowdown is used to control the dissolved or suspended solids in addition to the sludge. This will involve chemical treatment to sequester the TDS.
In practice, the valve(s) of the bottom blowdown are opened periodically in accordance with an operating schedule and/or chemical control test. From the standpoint of control, economy and results, frequent short blows are
preferred to infrequent lengthy blows. The length and frequency of the blowdown is particularly important when
the suspended solids content of the water is high. With the use of frequent short blows a more uniform concentration of the pressure vessel water is maintained.
In cases where the feedwater is exceptionally pure, or where there is a high percentage of return condensate,
Blowdown may be employed less frequently since less sludge accumulates in the pressure vessel. When dissolved and/or suspended solids approach or exceed predetermined limits, manual blowdown to lower the concentrations is required.
It is generally recommended that a steam boiler be blown down at least once in every eight-hour period, but frequency may vary depending upon water and operating conditions. The blowdown amounts and schedule should
be recommended by your local Cleaver-Brooks authorized representative.
A hot water boiler does not normally include openings for surface and bottom blowdown since blowdowns are
not practiced. The need remains to be alert to system water losses and corresponding amount of raw water
make-up. A water meter is recommended for water make-up lines.
2.7.3 — Manual Blowdown Procedure
Blowdown is most effective at a point when the generation of steam is at the lowest rate and feedwater input is
also low.
Be sure the blowoff piping and separator tank are in proper operating condition. Discharge vents should be clear
of obstruction, and the waste should be piped to a point of safe discharge.
If a quick opening valve and globe type of slow opening valve are in combination, the former is normally opened
first and closed last with blow down accomplished with the globe or slow opening valve.
When opening the second slow opening valve, crack it slightly to allow the lines to warm, then continue opening
slowly.
The length of each blow should be determined by actual water analysis. Lowering the water in the gauge glass
approximately 1/2” is often acceptable as a guide to adequate blow. However, lowering the water 1/2” should not
be interpreted as a rule since water analysis procedures should prevail. If the glass cannot be viewed by the party
operating the valve, another operator should watch the glass and direct the valve operator.
Close the downstream (slow opening) valve first and as fast as possible. Then close the valve next to the boiler.
Slightly crack the downstream valve and then close it tightly.
Caution
!
Do not pump the lever action valve open and closed, as water hammer is apt to break the valve bodies or pipe fittings. Failure to follow these instructions could cause damage to the equipment.
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Waterside Care
Under no circumstances should a blowdown valve be left open. The operator should never leave until the blowdown operation is completed and the valves are closed.
Quick opening valve
Slow opening valve
Quick opening valve
FIGURE 2-3. Blowdown valves
2.8 — Periodic Inspection
Insurance regulations or local laws will require a periodic inspection of the pressure vessel by an authorized
inspector. Sufficient notice is generally given to permit removal of the boiler from service and preparation for
inspection.
When shutting down the boiler, the load should be reduced gradually and the pressure vessel cooled at a rate
that avoids damaging temperature differential that can cause harmful stresses. Vessels should not normally be
drained until all pressure is relieved, to prevent uneven contraction and temperature differentials that can cause
expanded tubes to leak. Draining the unit too quickly may cause the baking of deposits that may be present on
the heating surfaces. Some heat, however, may be desirable to dry out the interior of the boiler.
Warning
!
To avoid the hazard of electrical shock, we recommend the use of a low voltage flashlight during an internal inspection. Preferably, inspectors should work in pairs. Failure to follow these instructions could result in serious injury or
death.
If the internal inspection is being made at the request of an authorized inspector, it is advisable to ask the inspector to observe the conditions prior to cleaning or flushing of waterside surfaces.
Be certain that a supply of manhole and handhole gaskets is available, along with any other gaskets or items
needed to place the unit back into operation after inspection.
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