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Modular Boilers Controls and Instrumentation
Courtesy of Slant/Fin
NB Members Technical Meeting 2016 1
ASME Section IV and CSD-1
Steam
Module Assembled Modular Boiler
Pressure Gage HG-602; One required Range 1-1/2 to 3-1/2 times
low PRV set pressure
Not required
Pressure Relief Device HG-701; “V” or “HV” Valve (s) Not Required
Water Gage Glass HG-603; one Not Required
Pressure Controls HG-605; CW-620 Operating Control Limit Control
Low-Water Fuel Cutoff HG-606;
CW-610
One One
Heat Generating Apparatus HG-
640; CF-900
ANSI Z21.13, ASME CSD-1, UL Standards ANSI/UL 732, ANSI Z21.10.3/CSA 4.3, &
several UL Standards
Feedwater connection HG-705 Split from manifold Manifold feeds modules
Blowoff valve sized in Table
HG-715;
Minimum of one Not Required
Manifold/ header HG-716 Each module connection, no intervening
valves
Collecting from each module
Combustion Side control Part CF Burner and fuel Train Not applicable
Manual Shut down switch CE-110 Provided on each module Required on Modular boiler
NB Members Technical Meeting 2016 2
NB Members Technical Meeting 2016 3
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ASME Section IV and CSD-1
Hot Water Heating
Module Assembled Modular Boiler
Pressure Relief Device HG-700 “V” or “HV” Valve Not Required
Pressure / Altitude Gage HG-611 Minimum One Required Not Required
Water Gage Glass Not required Not Required
Temperature Controls HG-615;
CW-640
Operating control Limit control)
Thermometer HG-612 One Required One Required
Make up with check valve HG-705 Not Required One on manifold
Low-Water Fuel Cutoff HG-614;
CW-630
Not Required One
Heat Generating Apparatus
HG-640; CF-900
ANSI Z21.13, ASME CSD-1, UL
Standards
ANSI/UL 732, ANSI Z21.10.3/CSA
4.3, & several UL Standards
Drain valve HG-715 One required none
Provision for Thermal Expansion
HG-709
Not Required One for system
Stop valves HG-710 Not Required On headers
Manifold/ header HG-716 No intervening valves On supply / return
Combustion side control Part CF Burner and fuel train Not applicable
Manual Shut down switch CE-110 Provided on each module Required on modular boiler
NB Members Technical Meeting 2016 4
Hot Water Modular Boiler
NB Members Technical Meeting 2016 5
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NB Members Technical Meeting 2016 6
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ASME Section IV and CSD-1 and
NBIC Part 1- 3.7.8, 3.8.1.6
Steam
Module Assembled Modular Boiler
Pressure Gage HG-602; One required Range 1-1/2 to 3-1/2 times
low PRV set pressure
Not required
Pressure Relief Device HG-701; “V” or “HV” Valve (s) Not Required
Water Gage Glass HG-603; one Not Required
Pressure Controls HG-605; CW-620 Operating Control Limit Control
Low-Water Fuel Cutoff HG-606;
CW-610
One One
Heat Generating Apparatus HG-
640; CF-900
ANSI Z21.13, ASME CSD-1, UL Standards ANSI/UL 732, ANSI Z21.10.3/CSA 4.3, &
several UL Standards
Feedwater connection HG-705 Split from manifold Manifold feeds modules
Blowoff valve sized in Table
HG-715;
Minimum of one Not Required
Manifold/ header HG-716 Each module connection, no intervening
valves
Collecting from each module
Combustion Side control Part CF Burner and fuel Train Not applicable
Manual Shut down switch CE-110 Provided on each module Required on Modular boiler
NB Members Technical Meeting 2016 7
ASME Section IV and CSD-1 and NBIC
Part 1- 3.7.8, 3.8.2.5
Hot Water Heating
Module Assembled Modular Boiler
Pressure Relief Device HG-700 “V” or “HV” Valve Not Required
Pressure / Altitude Gage HG-611 Minimum One Required Not Required
Water Gage Glass Not required Not Required
Temperature Controls HG-615;
CW-640
Operating control Limit control)
Thermometer HG-612 One Required One Required
Make up with check valve HG-705 Not Required One on manifold
Low-Water Fuel Cutoff HG-614;
CW-630
Not Required One
Heat Generating Apparatus
HG-640; CF-900
ANSI Z21.13, ASME CSD-1, UL
Standards
ANSI/UL 732, ANSI Z21.10.3/CSA
4.3, & several UL Standards
Drain valve HG-715 One required none
Provision for Thermal Expansion
HG-709
Not Required One for system
Stop valves HG-710 Not Required On headers
Manifold/ header HG-716 No intervening valves On supply / return
Combustion side control Part CF Burner and fuel train Not applicable
Manual Shut down switch CE-110 Provided on each module Required on modular boiler NB Members Technical Meeting 2016 8
Chief’s Technical Meeting Presented by:
Gary Scribner – Manager of Technical Services
October 2016
Gas Train Venting
2 The National Board of Boiler and Pressure Vessel Inspectors
Gas Train Venting
• Vent Valves
• Vent Lines
• Vent Valve Lines
• Bleed Lines
• Double Block and Bleed
• Regulator Vent
3 The National Board of Boiler and Pressure Vessel Inspectors
Gas Train Venting
• State Regulations
• NFPA 54
• NFPA 85
• CSD-1
4 The National Board of Boiler and Pressure Vessel Inspectors
• A vent line is a section of piping or tubing that conveys the
release of gases from fuel train components.
Vent Line
• A vent line is connected to components such as balancing
diaphragm’s that only expel gas when there is component
failure
Vent Line
Regulator Vent
• The opening in the atmospheric side of the regulator
housing permitting the in and out movement of air to
compensate for the movement of the regulator diaphragm
(2012 NFPA 54 3.3.107.3)
7 The National Board of Boiler and Pressure Vessel Inspectors
• Regulator vents are
always connected to
a vent line unless
they have a vent
limiter installed
Vent on Pressure Switch
8 The National Board of Boiler and Pressure Vessel Inspectors
• A vent valve is a normally open, power-closed valve that is
piped between the two safety shutoff valves and vented to
a safe point of discharge (also known as the bleed in a
double block and bleed)
Vent Valve
• A vent valve line is a section of piping that conveys the
release of gas from an automatic or manually operated vent
valve
Vent Valve Line
Bleed Line
• A bleed line is a section of piping or tubing that
conveys the release of gas from a fuel train
component, which periodically releases gas
pressure to the atmosphere in order to operate
properly
11 The National Board of Boiler and Pressure Vessel Inspectors
Relief Line & Feedback Line
• The term relief line is not currently defined in CSD-1.
However, the relief line is the line from the overpressure
protection device in CF-161 and CF-190(d)
• A feedback line is a section of piping or tubing that normally
communicates air pressure from a point of reference to the
air pressure side of a diaphragm of fuel train component,
but could contain gas under abnormal conditions; or a
section of piping or tubing that communicates flue or gas
pressure from one point of reference to another point of
reference.
12 The National Board of Boiler and Pressure Vessel Inspectors
Combustion Chamber and Flue Passages
• A combustion chamber is the portion of the boiler enclosure
into which the fuel is fed, ignited, and burned
• Also referred to as a furnace or firebox
• A flue passage is the cavities (e.g., flue, exhaust, or vent
system) that convey the products of combustion from the
boiler combustion chamber to an approved location
• Also referred to as breeching
13 The National Board of Boiler and Pressure Vessel Inspectors
Safe Point of Discharge
• Question: What is the definition of ‘safe point of discharge’?
• According to the NBIC, a safe point of discharge is a location
that will not cause property damage, equipment damage, or
create a health or safety threat to personnel in the event of
discharge
14 The National Board of Boiler and Pressure Vessel Inspectors
• Vent lines
• Bleed lines
• Gas-pressure relief lines
• Vent valve lines
• Feedback lines for fuel train components
CF-190 Requirements
(a) Vent Lines
(1) Gas-pressure regulators, combination gas controls,
pressure interlock switches, and all other fuel train
components requiring atmospheric air pressure to balance a
diaphragm shall have the atmospheric side of the diaphragm
connected to a vent line that shall be piped by the installer to
the outdoors at a safe point of discharge as determined by the
authority having jurisdiction unless otherwise allowed in CF-
190(c) or CF-190(h).
CF-190 – Vent Lines
9.1.19 (1)- Appliance pressure regulators requiring access to
the atmosphere for successful operation shall be equipped
with vent piping leading outdoors or, if the regulator vent is an
integral part of the appliance, into the combustion chamber
adjacent to a continuous pilot, unless constructed or equipped
with a vent-limiting means to limit the escape of gas from the
vent opening in the event of a diaphragm failure.
NFPA-54 – Vent Lines
CSD-1 CF-190 –(c)
Components With Vent Limiters. A listed and labeled gas-
pressure regulator, combination gas control, pressure
interlock switch, or other fuel train component incorporating a
vent limiter shall be permitted to vent directly into ambient
space.
NFPA 54 9.1.19 (2)
Vent-limiting means shall be employed on listed appliance
pressure regulators only.
Vent Limiters
Purpose- To limit the amount of gas released in the event of
diaphragm failure to 1 cu. Ft. of gas per hour. The reasoning is
that normal ventilation of the space would be able to safely
remove the gas venting through a vent limiter.
Other considerations – multiple vent limiters in one space.
Vent Limiters
(b) Bleed Lines
(1) Gas-pressure regulators, combination gas controls,
pressure interlock switches, or all other fuel train components
that use an atmospheric diaphragm and periodically release
gas into the atmosphere in order to properly operate shall
have the atmospheric side of the diaphragm connected to a
bleed line that shall be piped by the installer to the outdoors
at a safe point of discharge as determined by the authority
having jurisdiction unless otherwise allowed in CF-190(c) or
CF-190(h).
CF-190 – Bleed Lines
9.1.20 (1) – Diaphragm-type valves shall be equipped to
convey bleed gas to the outdoors or into the combustion
chamber adjacent to a continuous pilot.
9.1.20(2) – In the case of bleed lines leading outdoors, means
shall be employed to prevent water from entering this piping
and also to prevent blockage of vents by insects and foreign
matter.
NFPA 54 – Bleed Lines
(d) Gas-Pressure Relief Lines
(1) If an overpressure protection device incorporating a gas-pressure relief valve is installed, the outlet of the gas-pressure relief valve shall be connected to a gas-pressure relief line that shall be piped by the installer to the outdoors at a safe point of discharge as determined by the authority having jurisdiction.
(2) The gas-pressure relief line shall be sized in accordance with the component manufacturer ’s instructions and shall be at least the same size as the outlet connection of the gas-pressure relief valve
(3) Where there is more than one gas-pressure relief valve at a location, each gas-pressure relief valve shall have a separate relief line piped by the installer to the outdoors at a safe point of discharge as determined by the authority having jurisdiction unless otherwise permitted by CF-190(f).
CF-190 – Gas-Pressure Relief Lines
(e) Lines From Vent Valves
(1) A vent valve, if installed, shall be connected to
a vent valve line that shall be piped by the installer to
the outdoors at a safe point of discharge as determined
by the authority having jurisdiction.
(2) The vent valve line shall be at least the same
size as the outlet connection of the vent valve.
(3) Where there is more than one vent valve at a
location, each vent valve shall be piped by the installer
to the outdoors at a safe point of discharge as determined by the authority having jurisdiction unless otherwise permitted by CF-190(f).
CF-190 – Lines from Vent Valves
(f) Manifolding of Lines. If approved by the authority having
jurisdiction, the manifolding of lines of the same type shall be
permitted, and the manifolding of vent lines and bleed lines
shall be permitted. In order to minimize backpressure in the
event of gas being released through the manifolded line, the
manifolded line shall have a cross-sectional area not less than
the area of the largest branch line directly piped to the
manifolded line plus 50% of the additional cross-sectional
areas of the manifolded branch lines.
CF-190 – Manifolding of Lines
(f) Manifolding of lines of the following types shall be
permitted:
• 1. Manifolding of vent lines with vent lines on the same
boiler
• 2. Manifolding of bleed lines with bleed lines on the same
boiler
• 3. Manifolding of vent lines and bleed lines shall be on the
same boiler
CF-190 – Manifolding of Lines
Manifolding of lines of the following types shall not be
permitted:
(1) the manifolding of gas-pressure relief lines with vent lines,
bleed lines, or vent valve lines.
(2) the manifolding of vent valve lines with vent lines or bleed
lines
(3) the manifolding of vent lines, bleed lines, gas pressure
relief lines, and vent valve lines of one boiler unit to any lines
of another boiler unit.
CF-190 – Manifolding of Lines
CF-190 (g) No vent line, bleed line, gas-pressure relief line, or vent valve line shall connect to a boiler’s flue passages.
NFPA 54, 9.1.19 (4)
Under no circumstances shall a regulator be vented to the appliance flue or exhaust system.
NFPA 54, 9.1.20.(3)
Bleed lines shall not terminate in the appliance flue or exhaust system
CF-190 and NFPA 54 – Connecting Lines to
Flue Passages
(h) Points of Discharge: Outdoor Requirements, Special
Exceptions, and Prohibited Practices
(1) Unless otherwise terminated as permitted by CF-190(h)(2)
or CF-190(h)(4), vent lines, bleed lines, gas-pressure relief
lines, or vent valve lines shall have provisions to be piped by
the installer to the outdoors at a safe point of discharge as
determined by the authority having jurisdiction. A means shall
be provided at the point of discharge to prevent stoppage of
the lines by foreign material, moisture, or insects.
CF-190 – Points of Discharge
CF-190 Points of Discharge
29 The National Board of Boiler and Pressure Vessel Inspectors
(2) A combination gas control integrating an internal (within
the valve) gas bleed line shall be permitted to discharge its
bleed line back into the valve body, provided that the
construction of the combination gas control is such that when
it is in the closed position, a damaged diaphragm will not allow
gas to flow through the bleed line to the main burner.
(3) At locations where a point of discharge may be submerged
during floods, a special antiflood-type breather vent fitting
shall also be installed at the point of discharge, or the line
shall be extended above the height of the expected flood
waters.
CF-190 – Points of Discharge
9.1.19 (3)
In the case of vent lines leading outdoors, means shall be
employed to prevent water from entering this piping and also
to prevent blockage of vents by insects or foreign matter.
9.1.20 (2)
In the case of bleed lines leading outdoors, means shall be
employed to prevent water from entering this piping and also
to prevent blockage of vents by insects or foreign matter.
NFPA 54 – Points of Discharge
Anti-flooding device
An anti- flooding device protects gas train components from damage from water
and debris that may cause corrosion of internal parts, operational failure, gas
leakage, or elevated outlet pressure. These devices are a normally open assembly.
When submerged an internal float will rise with the water and seal the vent line
closed. The process reverses as water recedes allowing the float to drop and re-
opening the valve.
32 The National Board of Boiler and Pressure Vessel Inspectors
(i) The point of discharge from a vent line, bleed line, gas-
pressure relief line, or vent valve line that is piped by the
installer to the outdoors shall have clearances as determined
by the authority having jurisdiction, and the point of discharge
shall extend above the boiler and adjacent structures to
prevent gaseous discharge from being drawn into combustion
air intakes, ventilating systems, mechanical air intakes, or
windows of the boiler room or of an adjacent building.
CF-190 – Clearances for Points of Discharge
(4) A bleed line or a vent line shall be permitted to discharge
into a continuous pilot, provided that the line is not
manifolded and the point of discharge uses a burner tip.
(5) A bleed line or a vent line shall not discharge
into a positive-pressure-type combustion chamber.
CF-190 – Points of Discharge
9.1.19 (5) In the case of vents entering the combustion chamber,
the vent shall be located so the escaping gas will re readily ignited
by the pilot and the heat liberated thereby will not adversely affect
the normal operation of the safety shutoff system. The terminus of
the vent shall be securely held in a fixed position relative to the
pilot. For manufactured gas, the need for a flame arrester in the
vent piping shall be determined.
9.1.20 (4) In the case of bleed lines entering the combustion
chamber, the bleed line shall be located so the bleed gas will be
readily ignited by the pilot and the heat liberated thereby will not
adversely affect the normal operation of the safety shutoff system.
The terminus of the bleed line shall be securely held in a fixed
position relative to the pilot. For manufactured gas, the need for a
flame arrester in the bleed line piping shall be determined.
NFPA 54 – Points of Discharge
9.1.19 (6) A vent line(s) from an appliance gas pressure
regulator and a bleed line(s) from a diaphragm-type valve
shall not be connected to a common manifold terminating in a
combustion chamber. Vent lines shall not terminate in
positive-pressure type combustion chambers.
9.1.20 (5) A bleed line(s) from a diaphragm-type valve and a
vent line(s) from an appliance pressure regulator shall not be
connected to a common manifold terminating in a combustion
chamber. Bleed lines shall not terminate in positive-pressure
type combustion chambers.
NFPA 54 – Points of Discharge
(1) Burner tips, when required by CF-190(h)(4), shall be made
of metal having a melting point greater than 1,450°F
(788°C), and its length shall extend from the location as
defined in CF-190(j)(3) to the outer wall of the combustion
chamber.
(2) The installer shall demonstrate compliance to CF-190(j)(1)
with the documentation accompanying the boiler.
(3) Burner tips shall be located so that the escaping gas will
be readily ignited by the pilot flame, and the burner tips shall
be securely held so that the ports are in a fixed position in
relation to the pilot flame.
CF-190 – Burner Tips
(k) Feedback Lines for Fuel Train Components. Feedback lines
shall be piped according to the manufacturer’s instructions.
CF-190 – Feedback Lines
(l) All materials used for bleed lines, vent lines, vent valve
lines, feedback lines, and gas-pressure relief lines shall
possess suitable strength and durability for the environmental
stresses to which the material will be exposed during normal
operation. The materials shall be listed for the intended
purpose in accordance with a nationally recognized standard
acceptable to the authority having jurisdiction. In the absence
of such a standard, NFPA 54, National Fuel Gas Code, shall be
used.
CF-190 – Bleed, Vent, and Relief Lines
4.9.1 The discharge from atmospheric vents shall be located
away from any occupied areas, sources of ignition, combustion
air intakes, building ventilation systems, or the windows of the
boiler or HRSG room or adjacent buildings and shall be extended
above the boiler or HRSG and adjacent structure so that gaseous
discharge does not present a hazard.
4.9.2 Vent line sizes and vent valve port diameters shall not be
less than the values shown in Table 4.9.2
4.9.3.1 Vents of systems operating at different pressure levels
shall not be manifolded.
4.9.3.2 Vents from systems served from different pressure
reducing stations shall not be manifolded.
NFPA 85 – Bleed, Vent, and Relief Lines
4.9.3.3 Vent Systems of different boilers or HRSG’s shall not be
manifolded.
4.9.3.4 Vents of systems using different fuel sources shall not be
manifolded.
4.9.3.5 Headers vents shall be permitted to be manifolded with
other header vents only where they are operated and tripped in
parallel.
4.9.3.6 Burner vents shall be permitted to be manifolded together
only with other burner vents.
4.9.3.7 Igniter vents shall be permitted to be manifolded together
only with other igniter vents.
4.9.3.8 Lance vents shall be permitted to be manifolded together
only with other lance vents.
NFPA 85 – Bleed, Vent, and Relief Lines
Questions
42 The National Board of Boiler and Pressure Vessel Inspectors