Forney UV-4 User manual

UV-4 Flame Detector
372000-28 Rev J

UV-4 Flame Detector
372000-28 Rev J
i
INTRODUCTION
This manual contains information for the UV-4 Flame Detector from Forney Corporation, 16479 Dallas
Parkway, Suite 600, Addison, Texas. www.forneycorp.com
All personnel should become thoroughly familiar with the contents of this manual before attempting to
use the UV-4 Flame Detector. Because it is virtually impossible to cover every situation that might occur
during operation and maintenance of the equipment described in this publication, personnel are expected
to use good engineering judgment when confronted with situations that are not specifically mentioned
herein.
PROPRIETARY NOTICE
The contents of this publication are proprietary data of Forney Corporation. Forney reserves all
proprietary rights to this document, including all design, manufacturing, reproduction, use, and sales
rights thereto, except to the extent said rights are expressly granted to others.
SAFETY ICON DEFINITIONS
DANGER
Indicates a hazardous situation which, if not avoided, will result in
death or serious injury.
WARNING Indicates a hazardous situation which, if not avoided, could result
in death or serious injury.
CAUTION Indicates a hazardous situation which, if not avoided, could result
in minor or moderate injury.
NOTICE
Indicates unsafe practices that can result in property damage only.
Revisions
Revision
Date
Comments
A
Initial Release
B
C
D
10/2003
E
11/2003
F
12/2006
G
11/2009
H
6/2011
J
5/2019
Update Safety Icons, Logos and addresses

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TABLE OF CONTENTS
Section 1 General Description ..................................................................................... 1
Figure 1 UV-4 Head Configuration................................................................................................... 1
Figure 2 Base Assembly with Bulkhead Connector......................................................................... 2
Figure 3 Base Assemblies with Pigtail Wiring.................................................................................. 2
Figure 4 Base Assemblies with Fiber-Optics Light Guide................................................................ 3
1.1 Mechanical Specifications................................................................................................................ 4
1.2 Electrical Specifications ................................................................................................................... 4
Section 2 Safety ............................................................................................................ 5
Figure 5 Cable Connections to Detector Head ................................................................................ 5
Section 3 Commissioning ............................................................................................ 6
Section 4 Removal / Installation................................................................................... 6
Section 5 Operation ...................................................................................................... 7
5.1 Normal Operation............................................................................................................................. 7
5.2 Self-Test Operation .......................................................................................................................... 7
Section 6 Maintenance.................................................................................................. 7
Section 7 Troubleshooting ........................................................................................... 8
Table 1 UV-4 Flame Detector Troubleshooting .............................................................................. 8
Section 8 Storage .......................................................................................................... 8
Section 9 Return or Repair Service ............................................................................. 9

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Section 1 General Description
The Forney UV-4 flame detector contains an ultraviolet (UV) sensor tube and signal-processing electronics
inside a protective case. These components receive operating power and control inputs from an external
amplifier assembly. During normal operation, light passes through a sight tube or a fiber-optic light guide
and strikes the UV sensor tube. The signal-processing electronics inside the head convert pulses form the
tube into a digital output signal whose frequency is directly proportional to the intensity of UV light striking
the sensor tube. The output signal then is routed to the external amplifier assembly, which converts the
signal from the head into digital flame on/off, analog intensity, and alarm output signals.
The UV-4 flame detector includes two major subassemblies: a head assembly and a base assembly. The
head assembly (figure 1) consists of a machined housing that contains the internal electronics of the flame
detector:
Figure 1 UV-4 Head Configuration
•The sensor tube contains an ultraviolet-sensitive gas at reduced pressure. When UV light enters the tube,
the gas ionizes, enabling current to flow between two electrodes. Signal conversion electronics on an
internal printed circuit board (PCB) transforms the resulting voltage surges into digital pulses.
•The PCB contains a voltage level converter, optical isolator, and a single shot. These components
supply the bias voltage required by the sensor tube and transform voltage transients into a well-defined
digital pulse train.
•A rotary solenoid is located next to the UV sensor tube. When the external amplifier assembly energizes
the solenoid, it moves a mechanical shutter into a position in front of the sensor. This action can be used
to blind the flame detector for a self-test cycle or to disable the system when its operation is not
required.

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•A six-position electrical connector mates with a corresponding connector in the base assembly to
facilitate installation or field replacement.
Forney offers UV-4 base assemblies having several different configurations. Figures 2 through 4 illustrate
the major physical variations. The primary functional differences are as follows:
•A base with a lens assembly. This configuration is used for front-mount configurations. The lens
assembly can be plain or magnifying glass and isolates the electronic components from furnace gases in
the sight tube. The flame detector is available with either pigtail wiring or a bulkhead connector that
provides the electrical interface with the external amplifier assembly.
Figure 2 Base Assembly with Bulkhead Connector
Figure 3 Base Assemblies with Pigtail Wiring
•A base with a fiber-optic light guide. This assembly includes a fiber-optic cable assembly instead of a
lens. The fiber-optic light guide frequently is used to transmit light through the wind box of a
tangentially fired furnace with tilting burners or in applications that lack the space for direct viewing. As
before, the flame detector is available with either pigtail wiring or a bulkhead connector.

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Figure 4 Base Assemblies with Fiber-Optics Light Guide

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1.1 Mechanical Specifications
Size Length 6 in
Width 4 by 3.5 in.
Weight 4.4 lb
Mounting-tube connection 1-in NPT female
Cooling-air connection 1-in NPT female (part of mounting tube)
Viewing angle The head has a 32° viewing angle that is restricted to
an angle between 3° and 5° when attached to the
mounting tube assembly; fiber-optic assemblies have
a 22° viewing angel from a 3-in setback in the
mounting tube.
Temperature Requirements -25° C to 60 ° C (-13° F to 140 ° F) operating;
-55° C to 125° C (-67 °F to 257° F) storage
Cooling-/Seal-Air Requirement Normally 10 SCFM at 5 inc. w.c., 120° F maximum
temperature. Refer to submittal drawings for figures
specific to this project.
Spectral Response UV mode – 190 to 260 nanometers
1.2 Electrical Specifications
Shutter Solenoid Power +14 ± 1 vdc @ 0.9 to 1.0 A nominal current
Input Power +_15 vdc @ 47 mA nominal current
Output Signal Open collector 500-µs digital pulse train
Power Consumption 12 vA maximum
I/O Cable Connector MS3116E10-6S (units with bulkhead connector only)
Bulkhead Connector MS3112E10-6P (units with bulkhead connector only)
A prefabricated four-wire, 2 –18 AWG and 2 – 20 AWG, shielded cable assembly is available from
Forney. Cable signal/connector pin assignments are as follows:
Pin A shutter voltage (green wire – 18 AWG)
Pin B common ground (black wire – 18 AWG)
Pin C +15 vdc power (red wire – 20 AWG)
Pin D output signal (white wire – 20 AWG)
Cable Shield (connected to amplifier ground plain)

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Section 2 Safety
Electrical power always should be removed from the flame detector amplifier before installing or
replacing a flame detector head assembly. In addition, if a flame detector head must be replaced
while the furnace is in operation, maintenance personnel should exercise case to avoid exposure to
flying particles and hot furnace gas.
WARNING
Before installing/removing a front-mount detector base,
maintenance personnel should close the ball valve attached
to the sight tube. In addition, maintenance personnel should
wear safety glasses to prevent eye injury from pressurized
gas and flying particles.
CAUTION
The detector head contains sensitive electrical components.
Ensure that all power is removed from the external amplifier
assembly before connecting or disconnecting the I/O cable.
NOTICE
Disconnect the cable from the detector by hand, but do NOT
twist the connector barrel (figure 5). Twisting could cause
the wires to become disconnected from solder connections
inside the connector barrel.
Figure 5 Cable Connections to Detector Head
(IDD Detector Head shown instead of UV-4 shown for illustration purposes)

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Section 3 Commissioning
When installing a detector head for the first time, ensure the following requirements are satisfied:
•The physical mounts are adequate to support the weight of the detector head in the position required
for operation.
•The ball valve lever of the cooling-air line moves through its entire operating range without
obstruction from any structure, cable, or hose.
•The cooling-air hose and I/O cable do not interfere with the operation of any moving components at
the boiler front. The I/O cable does not contact hot surfaces capable of melting its insulation.
After installation of external amplifiers for the flame detectors, perform an operational checkout as
follows:
1. If the system uses rack-mounted amplifier assemblies, ensure that all power supplies for the flame
detector system are adjusted to the required voltage levels.
2. Apply operating power to the external amplifier. If a dual-range amplifier assembly is being used,
ensure that the UV mode of operation is selected. Verify that the voltage outputs from the amplifier
are at the correct level.
3. Verify operation of the detector head as follows:
a. If already installed, remove the detector head and base assemblies from the furnace mounting.
b. Reassemble the flame detector and place a UV light source 1 to 4 feet from the surface of the
lens or the end of the fiber-optic light guide.
c. Use an oscilloscope to measure the signal from the flame detector head at the input terminal of
the external amplifier. The signal observed should be a series of digital pulses having a
maximum frequency between 1 and 2 kHz.
d. Blind the detector cell. Verify that the external amplifier supplies +15 vdc to energize the shutter
solenoid. Ensure that the output signal from the detector head is lost.
4. After checkout, return the system to normal configuration.
Section 4 Removal / Installation
The UV-4 flame detector is designed for front-mounted, direct-view, or fiber-optic sighting of the burner
flame. Initial installation of a new flame detector normally is accomplished with the furnace cold and
depressurized. However, failure of a flame detector during operation requires prompt replacement of the
head assembly. Major considerations for removal/installation of a flame detector head during furnace
operation are as follows:
1. Remove power from the external amplifier assembly for the flame detector being replaced.
2. Loosen the bolt securing the head assembly to the base assembly. Carefully disengage the
mating internal connectors to remove the head assembly.
3. Perform these steps in reverse order to install a replacement head.

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Section 5 Operation
The Forney UV-4 detector normally is sighted on the primary combustion zone of a burner, and light from
the burner flame passes through a sight tube or a fiber-optic light guide to an opening in the base assembly
housing. Because the sensor tube is positioned directly behind this opening, essentially all light enters the
tube. IF the intensity of the UV light is great enough to ionize the gas in the tube, the flame detector head
generates a continuous pulse train.
5.1 Normal Operation
Electronic components in the UV-4 flame detector PCB include a dc-dc voltage converter, RC biasing
network, optocoupler, and single-shot. The external amplifier provides +14 vdc power, which is applied to
all active components on the PCB. The dc-dc voltage converter boosts the input power to produce a large
potential difference between the anode and cathode inside the UV sensor tube. The sensor tube contains a
gas that can be ionized by absorbing energy directly from UV radiation. If the rate of ionization exceeds the
rate of recombination, a surge of current passes through the tube, producing a high-voltage transient. The
tube operates with a nominal 350-vdc bias voltage and requires a threshold flux of UV radiation to start
conducting. Each time the tube enters the conducting state, a capacitor in the anode circuitry discharges
through the cathode circuit, dropping the bias below 350 vdc. This drop in bias voltage causes the tube to
stop conducting almost immediately, and the power supply begins recharging the capacitor in the anode
circuit. Since the RC time constants for the anode and cathode circuits are fixed, the interval between
successive discharges is directly proportional to the magnitude of UV flux incident on the tube.
Each discharge through the sensor tube produces a high-voltage pulse having a duration of no more than a
few microseconds. Since the magnitude of the voltage pulse is far too great for logic circuitry, the
optocoupler performs level conversion and also inverts the signal to produce a low-active trigger pulse. The
leading edge of each trigger pulse then causes the single-shot to generate a digital output pulse having a
fixed pulse width of 500 µs. When considered as a function of time, the frequency of the output signal from
the head is directly proportional to the intensity of UV radiant energy striking the tube.
5.2 Self-Test Operation
The external amplifier normally runs a self-test cycle at regular intervals under program control. At the start
of each self-test cycle, the amplifier enables +15 vdc to energize the shutter solenoid, blocking the light path
mechanically. The amplifier then monitors the input signal from the detector head to verify that a flame-out
condition is detected. If the input signal continues to indicate flame presence for the entire test interval, the
amplifier activates an alarm to indicate test failure.
Section 6 Maintenance
The only maintenance needed by the UV-4 detector head is periodic cleaning of the glass lens (direct-view
configuration only). The appropriate cleaning schedule is determined by the quality and cleanliness of the
cooling-/seal-air source. Forney recommends the use of a non-oily cleaning solution and a soft lint-free cloth
for lens cleaning.

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Section 7 Troubleshooting
If the detector head malfunctions, ensure that the procedures described in the commissioning section have
been performed successfully.
Refer to Table 1 for troubleshooting information.
Table 1 UV-4 Flame Detector Troubleshooting
Symptom Probable Cause Remedy
Signal weak or unreliable 1. Power source voltages out
of adjustment.
2. Glass lens dirty.
3. UV sensor tube or
electronics defective.
1. Adjust power supply
voltage levels as required
(units with rack-mounted
amplifier assemblies only)
2. Clean glass lens. Use a
non-oily lens cleaner and soft
cloth to avoid scratching the
glass.
3. Replace detector head.
Return unit for repair or
replacement.
No signal output 1. Supply voltage to head not
present
2. Detector head assembly
not functional.
3. Overheated detector head.
1. Verify that external
amplifier is supplying the
correct voltages for the
selected operating mode.
2. Replace detector.
3. Check the surface
temperature of the detector. If
the temperature is greater
than 160°F, check for
inadequate cooling-air flow.
Check alarm Noise on output signal 1. Ensure that I/O cable wires
are securely attached to
terminals on the external
amplifier.
2. Check for broken cable
wire.
3. Reroute cable if not in a
shielded cable tray.
4. Replace detector.
Section 8 Storage
Store the UV-4 Detector in its shipping box until used. See the mechanical specifications for storage
temperature ranges.

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Section 9 Return or Repair Service
Forney Corporation warrants this product to be free of defective material and workmanship. Forney will
repair or replace this equipment if it is found to be defective upon receipt, but not later than 90 days from the
date of shipment.
Prior to returning any material to Forney, please contact your Forney customer service representative and
provide the contract number or the customer purchase order number.
Contact Forney’s Aftermarket Department via any one of the following methods and furnish the following
information.
E-mail Phone Fax
[e-mail]
972-458-6100 or
972-458-6142 or
1-800-356-7740 (24-hour direct line)
972-458-6600
1. Contract number
2. Customer purchase order number
3. For each part, provide the following information:
a. Part number
b. Part description
c. Quantity