Rosemount Manual: Flame Photometric Detector For GC Hardware Reference Manual Rev B | Rosemount Manuals & Guides

FPD for Gas Chromatographs

Hardware Reference Manual

7R00370-H01

Revision B

October 2017

Introduction

NOTICE

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Introduction

Table of Contents

Table of Contents

1 Introduction .......................................................................... 1

1.1 Theory of operation ........................................................................................................2

1.2 Equipment description ...................................................................................................4

1.2.1

Model 500 FPD ...................................................................................................6

1.2.2

Model 700 FPD ...................................................................................................9

1.2.3

Model 700 FPD front entry ............................................................................... 12

1.2.4

Model 700XA FPD ............................................................................................ 13

1.2.5

Model 700XA FPD front entry .......................................................................... 14

1.2.6

Model 1500XA FPD .......................................................................................... 15

1.3 Glossary ...................................................................................................................... 16

2 Setup ................................................................................... 19

2.1 Gas connections .......................................................................................................... 19

2.2 Environmental Considerations ..................................................................................... 19

2.3 Utility gases ................................................................................................................. 19

2.4 Venting ....................................................................................................................... 20

3 Operation and maintenance.................................................. 23

3.1 Operation .................................................................................................................... 23

3.1.1

Igniting the flame manually ............................................................................. 24

3.2 Maintenance ............................................................................................................... 25

3.3 Troubleshooting.......................................................................................................... 26

A Appendix A: Drawings .......................................................... 29

A.1 Model 500 FPD drawings ............................................................................................. 29

A.2 Model 700 FPD drawings ............................................................................................. 30

A.3 Enclosure threaded entry details ................................................................................. 51

B Appendix B: Manufacturer’s manuals ..................................... 57

B.1 Flame Photometric Detector Operation Manual ........................................................... 58

B.2 GUB FPD 118500-3411 GUB ........................................................................................ 67

C Appendix C: Spare Parts List ................................................ 107

i

Figure

1 Introduction

The flame photometric detector (FPD) that you have received is factory-engineered to be used in
conjunction with all Rosemount gas chromatographs. The FPD can be used as a solitary detector to
measure low levels of sulfur compounds in natural gas or as a secondary detector in conjunction
with a thermal conductivity detector (TCD) that allows the GC to analyze the full range of
components present in a natural gas sample, including sulfur compounds.

1-1: Flame Photometric Detector (FPD)

Introduction

A. Flame photometric detector (FPD)
B. Photomultiplier tube
C. Flame cell
D. Electrometer board

An FPD (A) typically consists of the following major components:

The flame cell (C) - Located in the lower enclosure, the flame cell has connections for fuel gas,
hydrocarbon-free air, sample injection (process gas plus nitrogen carrier), and an exhaust pipe. It is
fitted with an RTD to monitor the temperature when running, and an ignitor to light the fuel gas.

The photomultiplier tube (B) - Located in the lower enclosure, the photomultiplier tube contains the
sensors that measure the light that is emitted from the flame cell during operation. It has one signal
lead and one high voltage wire that take the signal from the detector to the electrometer board
and provide the power for ignition. The leads are co-axial type cables.

1

Introduction

The electrometer board (D) - Located in the upper enclosure, the electrometer board amplifies and
processes the signal data from the detector, and sends it to the CPU board on the GC. It also
provides the ignition circuit, controls the re-light function, and generates the flame out alarm.

1.1 Theory of operation

NOTICE

See also Section 1.3 of this manual, for definitions of some of the terminology used in the following
explanations.

The detection system in the FPD uses the reactions of sulfur components in a hydrogen or air flame
as a source for analytical detection. The source of the FPD's signal is derived from the light
produced by an excited molecule created in the flame's combustion, which is a photochemical
process called chemiluminescence.

A thermocouple is fitted to the flame cell to ensure that the flame is present. If the flame is not
detected, the electrometer shuts off the hydrogen to the flame cell. It then supplies a voltage to
the igniter, waits five seconds and opens the hydrogen shut off valve. The electrometer will make
ten ignition attempts if necessary. If it is not successful, then the hydrogen is shut off, an alarm is
triggered on the GC and the unit awaits attention from the operator.

NOTICE

To ignite the flame manually, see Section 3.1.1.

The signal is sent from the PMT to the electrometer to be amplified. The electrometer also provides
the PMT with the high voltage it requires to operate the auto re-light circuits.1.3

2

Introduction

Figure

1-2: Elution of Components

1.

2.

3.

4.

5.

Carrier gas only at the detector

First component begins to elute from the columns and is sensed by the detector.

Peak concentration of first component.

The second component begins to elute from the columns and is sensed by the detector.

Peak concentration of the second component.

3

Introduction

The signal is then sent to the preamplifier board for further amplification. In addition, the
preamplifier converts each voltage signal to a value that is proportional to the concentration of the
component detected in the gas sample. The preamplifier provides four different gain channels as well
as compensation for baseline drift. The signals are sent to the GC for computation or for viewing on
a PC monitor or local operator interface (LOI).

While the GC is in Idle mode, prior to injecting a sample, the detector is exposed to pure carrier gas.
In this condition, the output from the detector is electrically nulled. The detector output is set to 1
mV DC. This is measured on the red and black terminals on the preamplifier board, and adjusted
using the potentiometer (R38) on the electrometer PCB.

1.2 Equipment description

FPDs are available in the following configurations:

• Model 500 FPD

• Model 700 FPD

• Model 700 FPD Front Entry

• 700XA FPD

• 700XA FPD Front Entry

• 1500XA FPD

NOTICE

The Front Entry configurations include an additional frame to allow all the FPD enclosures to be
mounted on the front of the unit. This allows the unit to be located close to a wall because no rear
access is required for installation or maintenance.

All configurations are ATEX-certified. The differences between the configurations are detailed in
later sections of this chapter.

4

Introduction

The FPD used with the Model 500, 700, and 700XA gas chromatographs has the following
hazardous area certification markings:

5

Introduction

Figure

1.2.1

Model 500 FPD

1-3: Model 500 FPD

The Model 500 FPD module consists of three Exd GUB enclosures mounted on a frame, plus an Exd
solenoid that acts as a hydrogen shut-off valve. The enclosures contain the following:

• Electrometer assembly in GUB 5 enclosure

• Flame cell and photometric detector tube in GUB 5 enclosure

• Transformer (either 230/110 Vac or 110/110 Vac) in GUB 4 enclosure

• Hydrogen shut-off valve

6

Introduction

Figure

1-4: Model 500 FPD Enclosures

A. Electrometer assembly
B. Flame cell and FP tube

shut off valve

C. H

2

D. Transformer

Place the FPD module as close as possible to its partner GC to minimize the length of sample tubing
between them, and therefore to keep the cycle time as short as possible.

The tubing required to operate the FPD flame cell is 1/16 in. OD 0.010 in. ID. All tubing enters the
GUB enclosure containing the flame cell via a specially designed tubing gland. All internal fittings
are Swagelok double ferrule type compression fittings.

7

Introduction

Figure

1-5: Specialized Tubing Gland

8

Introduction

Figure

1.2.2

Model 700 FPD

1-6: Model 700 FPD

The Model 700 FPD module consists of four Exd GUB enclosures mounted on a frame, plus an Exd
solenoid valve that acts as a hydrogen shut-off valve. The Model 700 FPD requires an additional
enclosure to house temperature control equipment that on a Module 500 GC is available internally.

9

Introduction

Figure

The enclosures contain the following:

• Electrometer assembly in GUB 5 enclosure

• Flame cell and photometric detector tube in GUB 5 enclosure

• PID Temperature controller and relay

• Transformer (either 230/110 Vac or 110/110 Vac) in GUB 4 enclosure

• Hydrogen shut-off valve

1-7: PID Temperature Controller and Relay

Place the FPD module as close as possible to its partner GC to minimize the length of sample tubing
between them, and therefore to keep the cycle time as short as possible.

The tubing required to operate the FPD flame cell is 1/16 in. OD 0.010 in. ID. All tubing enters the
GUB enclosure containing the flame cell via a specially designed tubing gland. All internal fittings are
Swagelok double ferrule type compression fittings.

10

Introduction

Figure

1-8: Specialized Tubing Gland

11

Introduction

Figure

1.2.3

Model 700 FPD front entry

1-9: Model 700 FPD Front Entry

12

The Model 700 FPD front entry is comprised of the same components as the standard Model 700
FPD with an additional frame added to allow all the enclosures to be mounted on the front of the
unit. This allows the unit to be located close to a wall because no rear access is required for
installation or maintenance.

Introduction

Figure

1.2.4

Model 700XA FPD

1-10: Model 700XA FPD

The Model 700XA FPD consists of four explosion-proof enclosures mounted on a frame plus an
explosion-proof solenoid valve that acts as a hydrogen shut-off valve.

13

Introduction

Figure

The enclosures contain the following components:

• Electrometer assembly

• Flame cell and photometric detector tube

• Transformer, either a 230/110 Vac or a 110/110 Vac

• PID temperature controller and relay

• Hydrogen shut-off valve

Place the FPD as close as possible to its partner GC to minimize the length of sample tubing
between them, and keep the cycle time as short as possible.

The tubing size required to operate the FPD flame cell is 1/16 in. OD 0.010 in. ID. All tubing enters
the flame cell’s enclosure through a specially designed tubing gland. All internal fittings are
Swagelok double ferrule compression fittings.

1-11: Specialized Tubing Gland

1.2.5

14

Model 700XA FPD front entry

The Model 700XA FPD front entry is comprised of the same components as the standard Model
700XA FPD with an additional frame added to allow all the enclosures to be mounted on the front
of the unit. This allows the unit to be located close to a wall, because no rear access is required for
installation or maintenance.

Introduction

Figure

1.2.6

Model 1500XA FPD

1-12: Model 1500XA FPD

The Model 1500XA FPD consists of four explosion-proof enclosures mounted on a frame plus an
explosion-proof solenoid valve that acts as a hydrogen shut-off valve. The enclosures contain the
following components:

• Electrometer assembly

• Flame cell and photometric detector tube

• Transformer, either a 230/110 Vac or a 110/110 Vac

• PID temperature controller and relay

• Hydrogen shut-off valve

15

Introduction

Figure

Place the FPD as close as possible to its partner GC in order to minimize the length of sample tubing
between them, and therefore to keep the cycle time as short as possible.

The tubing size required to operate the FPD flame cell is 1/16 in. OD 0.010 in. ID. All tubing enters
the flame cell’s enclosure through a specially designed tubing gland. All internal fittings are
Swagelok double ferrule compression fittings.

1-13: Specialized Tubing Gland

1.3 Glossary

Auto Zero

Automatic zeroing of the preamplifier. May be entered into the controller to take place at any time
during the analysis when either the component is not eluting or the baseline is steady (not
normally used).

Chromatogram

A permanent record of the detector output. A chromatograph is obtained from a PC interfaced with
the detector output through the GC controller. A typical chromatogram displays all component peaks
and gain changes. It may be viewed in color as it is processed on a PC VGA display. Tick marks
recorded on the chromatogram by the GC Controller indicate where timed events take place.

Component

Any one of several different gases that may appear in a sample mixture. For example, sample gas
usually contains the following components: ethyl mercaptan, t-butyl mercaptan, methyl ethyl
sulphide, diethyl sulphide, hydrogen sulphide, and carbonyl sulphide.

16

Introduction

Response Factor

Correction factor for each component as determined by the calibration. It is defined by the
equation:

where

= Area response factor for component n in area per mole percent (%)

ARF

n

= Height response factor for component n

HRF

n

= Area associated with component n in calibration gas

Area

n

= Height associated with component n in mole % in calibration gas

Ht

n

= Amount of component n in mole % in calibration gas

Cal

n

Retention time

The time in seconds that elapses between the start of analysis ( 0 seconds) and the sensing of the
maximum concentration of each component by the analyser detector.

17

Introduction

18

2 Setup

2.1 Gas connections

Use Silcosteel® or equivalent tubing for all calibration gas and process gas connections on all FPDs
that are used to measure low range sulfur components. If you use Grade 316 or other stainless steel
piping, the sulfur components will adhere to the internal surface of the pipe, and will continue to
do so until the entire internal surface of the tubing is coated or conditioned, which will result in
lower than expected levels of sulfur components reaching the detector for measurement.
Conditioning may take one week or longer, depending on the levels of sulfur components and the
length of the tubing.

2.2 Environmental Considerations

FPDs are sensitive to changes in temperature and pressure; therefore, place them in shelters that
have stable temperature and pressure. Do not use positive pressurization for shelters.

2.3 Utility gases

FPDs require the following utility gases:

• Hydrogen - 99.995% purity

Setup

• Hydrocarbon-free air

• Nitrogen - 99.995% purity (carrier gas)

• Helium - 99.995% purity (optional second carrier gas)

19

Setup

Figure

Make all utility and process gas connections with Swagelok
fittings. Metric conversion kits are available; contact your Rosemount sales representative for more
information.

These are typical values supplied for information only. Actual values are application specific.

2-1: Typical Pressure and Flow Rate Information

2.4 Venting

All Rosemount FPD modules have a vent from the flame cell that exits the GUB enclosure via a
proprietary Exd breather/drain/ flame arrestor assembly. The exhaust from the flame cell emits
water vapor as a result of burning hydrogen as fuel. This vapor condenses in the exhaust tubing
outside the GUB enclosure, and can be seen as drips of water.

®

1/8-inch double ferrule compression

Vent the FPD exhaust to atmosphere. Do not subject the vent to any back pressure because this will
have a detrimental effect on the detector, and may cause the flame to extinguish.

20

Setup

WARNING

Hydrogen-air mixtures can ignite with very low energy input. For reference, an invisible spark or a
static spark from a person can cause ignition. Although the auto- ignition temperature of hydrogen
is higher than those for most hydrocarbons, hydrogen's lower ignition energy makes the ignition of
hydrogen–air mixtures more likely.

Use a container with the FPD module to collect the condensed water from the FPD vent. Do not
pipe the vent away unless you can guarantee a continuous downward slope on the pipe and no
back pressure or obstruction by water.

21

Setup

22

3 Operation and maintenance

3.1 Operation

The FPD operates as a separate detector. It is controlled by and reports to the GC. The flow rates for
the utility gases and the carrier gas are factory set, and are specific to each FPD. These should only
be adjusted by fully trained and authorized personnel.

The FPD is identified as Detector #1 on the Detector screen, which is viewable with MON2000,
MON2020, and the LOI. When used in conjunction with a TCD, the FPD is Detector #1, and the TCD
is Detector #2.

NOTICE

The electrometer switch (A), which has three positions—up for Reset, centered for Normal, and
down for Override—should not be left in Override.

Operation and maintenance

A. Electrometer switch

3 - 1

23

Operation and maintenance

3.1.1

Igniting the flame manually

1.

Connect air to the inlet and slowly bring the inlet pressure to 60 psig.

2.

Connect hydrogen to the inlet and slowly bring the inlet pressure to 60 psig.

3.

Remove tubing from flame cell exhaust and use a digital flow meter to adjust the air control
valve until a reading of 160 cc/ min is obtained.

4.

Turn off the air supply.

5.

Set the auto relight switch (S1) on the electrometer PCB to the OVERRIDE position.

6.

Use the digital flow meter to adjust the hydrogen control valve until a reading of 100
cc/min is obtained.

7.

Turn on the air supply.

8.

Set the auto relight switch (S1) on the electrometer PCB to the RUN position. The auto
relight sequence starts as follows:

a. The LED on the electrometer comes on after 10 seconds, and the glow plug fitted to the

side of the flame cell is now supplied a voltage.

b. After another 5 seconds, the hydrogen shut off valve operates.
c. The gas mixture is ignited.
d. If the flame does not light in 5 seconds, the electrometer de-energizes the hydrogen

shut off valve to stop the flow into the flame cell.

e. The flame cell is then purged with air and nitrogen carrier.
f. The process starts again—up to 10 times—until the flame stays lit.

24