USER MANUAL OLC/OLCT 20

Gas Detector

Part Number: NPO20GB

Revision: D.0
The Fixed Gas Detection Experts
 GAS DETECTION

We are delighted that you have chosen an OLDHAM instrument and would like to thank you for your
choice.

We have taken all the necessary measures to ensure that your instrument provides total satisfaction.

Now it is important to read this document carefully.

EXTENT OF RESPONSIBILITY
* OLDHAM declines its responsibility towards any person for material damage, physical injury or death resulting
wholly or partly from inappropriate use, installation or storage of its equipment resulting from failure to observe
instructions and warnings and/or standards and regulations in force.

* OLDHAM neither supports nor authorises any company, physical or moral person to assume responsibility on
behalf of OLDHAM, even if it is involved in the sale of OLDHAM products.

* OLDHAM cannot be held responsible for direct or indirect damage or be required to pay direct or indirect
compensation resulting from the sale or use of any of its products IF THESE PRODUCTS HAVE NOT BEEN
DEFINED AND CHOSEN BY OLDHAM FOR THEIR SPECIFIC USE.

CLAUSES CONCERNING PROPERTY

* Drawings, plans, specifications and information included in this document contain confidential information that is
the property of OLDHAM.

* None of this information may be reproduced, copied, divulged or translated, by physical, electronic or any other
means, nor used as the basis for the manufacture or sale of OLDHAM equipment or for any other reasons without
prior consent from OLDHAM.

WARNINGS
* This document is not contractually binding. In the interests of its customers, OLDHAM reserves to modify the
technical specifications of its equipment without notice, in order to improve its performance.

* READ THIS MANUAL CAREFULLY BEFORE FIRST USE OF THE EQUIPMENT: this manual must be
read by any person who is or will be responsible for using, maintaining or repairing this equipment.

* This equipment will only provide the announced performance levels if it is used, maintained and repaired
according to OLDHAM directives, by OLDHAM personnel or by personnel approved by OLDHAM.

GUARANTEE
2 years guarantee in normal conditions of use on parts and technical labour, return in our workshops, excluding
consumables (sensors, filters, etc.)

2
 CONTENTS

1 Description ................................................................................................... 5
1.1 General ..........................................................................................................................5
1.2 Main characteristics of the various versions .................................................................5
1.3 Mechanical installation of the various versions ............................................................6
2 Wiring arrangements .................................................................................. 7
2.1 3-Wire version (OLC 20d, OLCT 20d) ........................................................................7
2.2 2-wire versions (OLCT 20d).........................................................................................7
2.3 2-wire Intrinsic Safety versions (OLCT 20i) ................................................................8
3 Maintenance ................................................................................................. 9
3.1 Detector OLC 20 ...........................................................................................................9
3.1.1 Calibration ...............................................................................................................9
3.1.2 Replacing a sensor on an OLC 20 .........................................................................10
3.2 Transmitters OLCT 20 ................................................................................................10
3.2.1 Calibration .............................................................................................................10
3.2.2 Calibration specifications ......................................................................................12
3.3 Replacing a sensor on OLCT 20 .................................................................................12
3.4 Disposal of OLC(T) 20 ...............................................................................................12
4 Spare Parts ................................................................................................. 13
4.1 OLC 20 flameproof gas detector ................................................................................13
4.2 OLCT 20 flameproof gas detector ..............................................................................13
4.3 OLCT 20 Intrinsic Safety detector..............................................................................14
5 Accessories ................................................................................................. 15
6 Technical characteristics of OLC 20 ....................................................... 17
7 Technical characteristics of OLCT 20..................................................... 17
8 Specific Instructions for use in Explosive Atmospheres according to
European Directive ATEX 94/9/EC ........................................................ 19
8.1 Specifications for mechanical and electrical installation in Classified Areas. ...........19
8.1.1 Flameproof detectors (d) .......................................................................................19
8.1.2 Intrinsic safety detectors (i) OLCT 20 i ................................................................19

3
 8.2 Metrological specifications for explosive gas and oxygen measurement detectors ...20
8.2.1 Technical Specifications and Special Instructions for explosive gas detectors ....21
8.2.2 Technical Specifications and Special Instructions for Oxygen detectors .............25
8.3 Markings .....................................................................................................................26
8.3.1 Flameproof certified version: OLC 20d and OLCT 20 d......................................26
8.3.2 Intrinsic safety version: OLCT 20 i ......................................................................26
9 Recommendations ..................................................................................... 27
10 EU Declaration of Conformity ................................................................. 29

4
1 Description

1.1 General

OLC 20 gas detectors are catalytic type detectors intended for the detection of combustible
gases. They are flameproof certified (OLC 20d).

OLCT 20 gas detectors are 4-20 mA transmitters and are intended for the measurement of
combustible and toxic gases and oxygen. They are either flameproof certified (OLCT 20d)
or intrinsically safe certified (OLCT 20i).

OLC 20s and OLCT 20s are available in ¾ NPT or M25 screw fittings and are designed to
be attached on a junction box or any compatible generic transmitters.

1.2 Main characteristics of the various versions

OLC 20 OLCT 20
LEL LEL TOX/O2

Flameproof design X X X
Intrinsic safety design X
3-wire cable / Wheatstone bridge X
3-wire cable / 4-20 mA output X
2-wire cable / 4-20 mA output X
Catalytic sensor X X
Electrochemical sensor X
Replaceable sensor X
Replaceable and pre-calibrated sensor X X

5
1.3 Mechanical installation of the various versions

Please ensure you read the paragraph: Special Specifications for use in Potentially Explosive
Atmospheres in Accordance with European Directive ATEX 94/9/EC

See Appendix 1 for general installation instructions.

Figure 1 : Dimensions

Dimensions OLC/OLCT 20 Cable length 0.2 m

6
2 Wiring arrangements
Please ensure you read the paragraph: Special Specifications for use in Potentially Explosive
Atmospheres in Accordance with European Directive ATEX 94/9/EC

2.1 3-Wire version (OLC 20d, OLCT 20d)

1 1 (S) E

2 2 (-) D

3 3 (+) D

B C

Figure 2
A B C D E
OLDHAM controller OLC or OLCT 20 Grounding Power supply Signal (I)

2.2 2-wire versions (OLCT 20d)

3 3 (+) D
1 1 (-/S) E

Figure 3

A B C D E
OLDHAM controller OLC 20 or OLCT 20 Grounding Power supply Power supply
Signal

7
2.3 2-wire Intrinsic Safety versions (OLCT 20i)

Hazardous area Safe area

A
B

Figure 4
A B C
OLDHAM controller OLC 20 or OLCT 20 ZENER Barrier

8
3 Maintenance
The operations and adjustments described in this chapter must be performed
by authorized personnel only as they can affect the appliance's reliability in
detection.
It is prohibited to open the transmitter when energized

3.1 Detector OLC 20

Gas detection instruments are potential life-saving devices. Recognizing this fact, OLDHAM Corporation
recommends that a functional “bump” test be performed on every fixed gas-monitoring instruments as part of
a regular maintenance program. A functional test is defined as a brief exposure of the detector to a
concentration of gas(es) in excess of the lowest alarm set-point for each sensor for the purpose of verifying
sensor and alarm operation and is not intended to be a measure of the accuracy of the instrument.

OLDHAM further recommends that a full instrument calibration be performed using a certified
concentration(s) of calibration gas(es) quarterly, every 3 months.* Calibrations may be necessary more or
less frequently based, for example, on application, field conditions, exposure to gas, sensor technology, and
environmental conditions. The frequency of calibration is best determined by company policy or local
regulatory agencies.

If an instrument fails to operate properly during any functional “bump” test, a full instrument calibration
should be performed successfully prior to use.
These recommendations are based on safe work procedures, industry best practises, and regulatory standards
to ensure worker safety. OLDHAM is not responsible for setting safety practices and policies.

* For new installations it may be prudent to carry out bump tests frequently at first (perhaps weekly),
increasing the time intervals (to, perhaps, monthly or more) as confidence grows with experience in the
installation concerned, on the basis of the maintenance record.

3.1.1 Calibration

On the controller On the detector

Set the measuring channel to the calibration

position (alarm relays inhibited)

Apply the calibration cup and perform the

calibration in accordance with the procedure
defined during the training course provided
by OLDHAM or by an OLDHAM’s
authorized person

Proceed the zero and span

Set the measuring channel back to the

"normal" position and make sure that it is
working properly.

9
 3.1.2 Replacing a sensor on an OLC 20

When?
- When the sensor is damaged or cannot be calibrated
- On a preventive basis

How?
- Turn off the relevant measuring channel
- Remove the sensor to be replaced
- Replace it with a new sensor
- Turn on the channel back and check that it operates correctly
(see the following page for more information)

3.2 Transmitters OLCT 20

OLCT 20 gas transmitters are equipped with a pre-calibrated sensor and do not require any
adjustment on installation.

However, as gas detectors are safety equipment, it is recommended to bump test the complete
transmitter after a sensor replacement.

3.2.1 Calibration

After removing the sensor from the transmitter, perform the calibration by using the calibrating
bench provided for that purpose (see CALIBRO’s user manual).

10
 Procedure

On the controller On the detector

Set the measuring channel to the calibration

position (alarm relays inhibited) Loosen the
locking screw

1
Rotate the sensor
module then
extract it
2

Once calibrated put the sensor back in place or

use a replacement sensor and reinstall the whole
assembly.

Set the measuring channel back to the

"normal" position and make sure that it is
working properly.

11
 3.2.2 Calibration specifications

Calibration shall be performed outside classified areas and by using suitable

equipment that is described during the training course provided by OLDHAM
or by a person authorized by OLDHAM.

item 1 - Adjustment of 0 in
clean air, using
potentiometer (item 1).
OLCT 20 sensor module - Adjustment of
(LEL/TOX/O2) sensitivity (with
standard gas), using the
potentiometer (item 2).
item 2

3.3 Replacing a sensor on OLCT 20

When?

- When the sensor is damaged or cannot be calibrated.

- On a preventive basis.

How?

- Switch off the relevant measuring channel.

- Remove the sensor to be replaced.
- Replace it with a new, precalibrated unit.
- Switch the channel back on and check that it operates correctly.

3.4 Disposal of OLC(T) 20

Concerning the conservation, of the protection and the improvement of the

quality of the environment, as well as for the protection of the health of the
persons and the careful and rational use of natural resources, OLCT 20 has to be
the object of a selective collection for the electronic equipments and cannot be
scrapped with the normal domestic waste. The user thus has the obligation to
separate the OLCT 20 of the other waste so as to guarantee that it is recycled in a
sure way at the environmental level. For more details of the existing sites of
collection, contact the local administration or the distributor of this product.

12
4 Spare Parts
Use only genuine spares, otherwise the reliability of the equipment could be adversely
affected

4.1 OLC 20 flameproof gas detector

Flameproof replacement sensors Part number

Replacement sensor (VQ1 – standard) 6313757

Replacement sensor (AP – poison resistant) 6313758

Catharometric sensor 6313759

4.2 OLCT 20 flameproof gas detector

Flameproof replacement sensors Part number

OLCT 20, 0-100% LEL (VQ1) 6313685

OLCT 20, 0-100% LEL (AP) 6313974

OLCT 20, 0-100% vol. (catharometer) 6313687

OLCT 20 CO, 0 – 100 ppm 6313690

OLCT 20 CO, 0 – 300 ppm 6313691
OLCT 20 CO, 0 - 1000 ppm 6313692

OLCT 20 H2S, 0 – 30 ppm 6313695

OLCT 20 H2S, 0 – 100 ppm 6313696
OLCT 20 H2S, 0 - 1000 ppm 6313697

OLCT 20 NO, 0 – 100 ppm 6313698

OLCT 20 NO, 0 – 300 ppm 6313699
OLCT 20 NO, 0 - 1000 ppm 6313700

OLCT 20 H2, 0 - 2000 ppm 6313706

OLCT 20 NH3, 0 – 100 ppm 6313707

OLCT 20 NH3, 0 - 1000 ppm 6313708

OLCT 20 O2, 0 - 0–30% vol. 6313710

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4.3 OLCT 20 Intrinsic Safety detector

INTRINSIC SAFETY SENSORS (SI) Part number

OLCT 20 CO, 0 – 100 ppm 6313711

OLCT 20 CO, 0 – 300 ppm 6313712
OLCT 20 CO, 0 - 1000 ppm 6313713

OLCT 20 H2S, 0 – 30 ppm 6313716

OLCT 20 H2S, 0 – 100 ppm 6313717
OLCT 20 H2S, 0 - 1000 ppm 6313718

OLCT 20 NO, 0 – 100 ppm 6313719

OLCT 20 NO, 0 – 300 ppm 6313720
OLCT 20 NO, 0 - 1000 ppm 6313721

OLCT 20 NO2, 0 – 10 ppm 6313722

OLCT 20 NO2, 0 – 30 ppm 6313723

OLCT 20 SO2, 0 – 10 ppm 6313724

OLCT 20 SO2, 0 – 30 ppm 6313725
OLCT 20 SO2, 0 - 100 ppm 6313726

OLCT 20 H2, 0 – 2000 ppm 6313727

OLCT 20 NH3, 0 – 100 ppm 6313728

OLCT 20 NH3, 0 - 1000 ppm 6313729

OLCT 20 HCl, 0 – 30 ppm 6313730

OLCT 20 HCl, 0 - 100 ppm 6313731

OLCT 20 HCN, 0 – 30 ppm 6313732

OLCT 20 HCN, 0 - 100 ppm 6313733

OLCT 20 Cl2, 0 – 10 ppm 6313734

OLCT 20 O3, 0 – 1 ppm 6313735

OLCT 20 COCl2, 0 – 1 ppm 6313736

OLCT 20 PH3, 0 – 1 ppm 6313737

OLCT 20 AsH3, 0 – 1 ppm 6313738

OLCT 20 HF, 0 – 10 ppm 6313739

OLCT 20 ClO2, 0 – 3 ppm 6313740

OLCT 20 ETO, 0 – 30 ppm 6313746

OLCT 20 SiH4, 0 – 50 ppm 6313747

OLCT 20 O2, 0 – 30% vol. 6313748

14
5 Accessories

TOOL KIT 6147869

CALIBRATION CUP 6331141

BY-PASS ADAPTOR
6327910
for combustible gases, CO, H2S, O2

PLASH GUARD 6329004

PROTECTIVE FILTER, PTFE 6335975

ACTIVE CARBON FILTER 6335976

REMOTE CALIBRATION CUP

6327911
(for combustible gases only)

15
16
6 Technical characteristics of OLC 20
Power supply: voltage on detector terminals = 2.8 V max
Power consumption: 3-wire version = 400 mA max
Measurement signal: Wheatstone bridge
Line length (shielded cable): 3-wire version = 1 km as 3x 1.5 mm2
(32 ohms in loop mode)
Output signal mV bridge output, 3 wires
Ingress Protection IP66
Weight 800 g
Dimensions 60 X 120 mm

7 Technical characteristics of OLCT 20

A) Explosion-proof version

Power supply: voltage on detector terminals = 15 V to 30 V

Power consumption: 3-wire version = 100 mA
2-wire version = 25 mA
Load resistance: maximum resistance = 250 ohms
Line length (shielded cable): 3-wire version = 1 km as 3x 1.5 mm2 (32 ohms in
loop mode)
2-wire version = 4 km as 3x 1.5 mm2 (32 ohms in
loop mode)

B) Intrinsic safety version

Characteristics of ZENER barrier: 28 V - 300 ohms

Supply voltage for barrier: 19 V to 26 V
Voltage on detector terminals: 10 V to 26 V
Power consumption: 25 mA max
Load resistance: 47 ohms
Line length (shielded cable): 1 km as 3x 1.5 mm2 (32 ohms in loop mode)

Output signal

Source mode current 4-20 mA

Max. current 25 mA
Fault current <1 mA

Miscellaneous

Ingress Protection IP66

Weight 800 g
Dimensions 60 X 120 mm

17
18
8 Specific Instructions for use in Explosive Atmospheres
according to European Directive ATEX 94/9/EC
The OLC/OLCT 20 gas detectors comply with the requirements of European Directive ATEX
94/9/EC relating to explosive Dust and Gas atmospheres.

As a result of their metrological performance, as tested by the Approval Agency INERIS, the
OLC/OLCT 20 gas detectors designed to measure explosive gasses and oxygen are classified as
safety devices and may therefore contribute to limiting the risk of explosion.

The information contained in the following paragraphs should be respected and taken into
account by the manager of the site where the equipment is installed. Please refer to the provisions of
European Directive ATEX 1999/92/EC on improving health and safety conditions for workers
exposed to potentially explosive atmospheres.

8.1 Specifications for mechanical and electrical installation in Classified Areas.

Installation will comply with all applicable standards, and particularly with EN 60079-14 and
EN 60079-17.

8.1.1 Flameproof detectors (d)

- These detectors are intended for use in surface industries II, Category 2, zones 1 and 2
(Gas) and zones 21 and 22 (Dust) in ambient temperature from -20°C to +70°C.
- Cables will be mechanically protected.
- The transmitter casing will be earthed using the external or internal terminal, which
should be corrosion-protected. Users should clean detectors regularly in order to prevent
any external accumulation of dust.
- Mechanically, detectors will be installed such that the detection sensor points downwards.
Any variance of over 45° from the vertical will result in measurement errors.
- Where connections are located in a classified zone, they will be enclosed in approved
envelopes.
- The width of the threaded joint of cable gland is superior to the value specified in the table
of EN 60079-1 standard.

8.1.2 Intrinsic safety detectors (i) OLCT 20 i

- These detectors are intended for use in surface industries II, Category 1, zones 0, 1 and 2
(Gas) and zones 20, 21 and 22 (Dust). They are also intended for use in coal mines,
Category M1. The ambient operating temperature range is –20°C to +70°C.
- Users should clean detectors regularly in order to prevent any external accumulation of
dust.
- The person responsible for IS installation (the “System Designer”) must draw up a system
document demonstrating that every aspect of the Power Cable Detector system complies
with intrinsic safety.
- They must be powered by an intrinsic safety source: 28V - 300 ohms
- Where connections are located in a classified zone, they will be enclosed in approved
envelopes.
- The safety parameters applying to the OLCT 20i detectors are :

Ui (V) Ii (mA) Pi (mW) Ci (nF) Li (H)

28 94 658 40 15μH

19
8.2 Metrological specifications for explosive gas and oxygen measurement
detectors

In case of exposure above the measuring range, it is mandatory to bump test

the instrument with gas and/or to perform a calibration.
In the event of a change of position, it is necessary to re-calibrate the detector.

The OLC/OLCT 20 transmitter sensors intended to measure explosive gasses and oxygen are
classified as safety devices and may therefore contribute to limiting the risk of explosion.
Detectors comply with the following European standards:

Explosive gas detectors:

- OLC 20 explosive gas detectors comply with European standards EN 50054 and EN
50057 for Methane (calibration gas), Propane and Hydrogen (gasses following response
curves) where they are used with the following OLDHAM controllers SV 4B, MX 15,
MX 32, MX 42A, MX 43, MX 48 and MX 52.

- OLCT 20 explosive gas detectors comply with European standards EN 50054 and EN
50057 for Methane (calibration gas), Propane and Hydrogen (gasses following response
curves), where they are used with SV 4B, MX 15, MX 32, MX 42A, MX 43, MX 48, MX
52 and MX 62 OLDHAM controllers, or where they are connected to measurement
devices with 4-20 mA inputs in accordance with paragraph 1.5 of Appendix II of the
ATEX 94/9/EC Directive and are compatible with their characteristics (cf. transfer curve).

Oxygen detectors:
- OLCT 20 oxygen detectors comply with European Standard EN 50104 where they are
used with MX 15, MX 32, MX 42A, MX 43, MX 48, MX 52 and MX 62 OLDHAM
controllers, or where they are connected to measurement devices with 4-20 mA inputs in
accordance with paragraph 1.5 of Appendix II of the ATEX 94/9/EC Directive and are
compatible with their characteristics (cf. transfer curve).

20
 8.2.1 Technical Specifications and Special Instructions for explosive gas detectors

8.2.1.1 Transfer curves for OLCT 20 detectors

The following curve shows transmitter output current values as a function of gas
concentration. Where the user connects the transmitter to a device other than a device manufactured
by OLDHAM, he must check that the transfer curve is fully compatible with its input characteristics
to ensure that the information generated by the transmitter is correctly interpreted. Equally, the
device must supply a suitable power supply voltage, allowing for cable voltage losses.

Output Current in
mA
Fault
23.2 mA
20.0 mA

4.0 mA
1 mA
Fault
Concentration
in % LEL
0% 100 % 120%

Please note: Detectors can generate ambiguous measurements at high gas concentrations, i.e. the
current output for a > 20% concentration of gas by volume is the same as for a concentration of < 5%
by volume (bell curve). It is therefore essential that the measuring device memorises the fact that the
value has exceeded the scale and that resetting is manual rather than automatic, and follows the safety
regulations specific to the site.

21
8.2.1.2 Metrological data

Type VQ1

Maximum concentration 100% LEL

Principle Catalytic

Estimated service life > 36 months

Away from air -10°C < T < 35°C

Storage
10% < RH < 60%. Maximum 6 months
Continuous temperature range -20°C to +55°C
Humidity range 0% RH to 95% RH
Pressure range 1 bar ± 10%
Between 0% and 70% LEL:  1% LEL
Linearity variance (methane scale)
Between 70% and 100% LEL:  7% LEL

± 2% of the value measured, or ± 1 LEL

Measurement reproducibility
(or ± 0.05% CH4)

Long-term drift Zero point: < 5% methane LEL per year

in normal Sensitivity: Typical drift values
operating Methane < 20% of the value measured per year
conditions Propane/Butane < 10% of the value measured per year
Effect of humidity (10% to 90% RH) at
± 5% of relative sensitivity
40°C
Maximum recommended interval between
6 months
calibrations (normal operating conditions)
Calibration concentration 30– 80% LEL
Response time gas and Methane Hydrogen Pentane Styrene
(may vary ± 10% concentration (50% LEL) (50% LEL) (52% LEL) (45% LEL)
between sensors) injected
t25 4 sec 3 sec 8 sec 12 sec
t50 8 sec 6 sec 12 sec 40 sec
t90 15 sec 10 sec 27 sec 60 sec

22
 8.2.1.3 Special precautions for explosive gas detectors

 Sensors are sensitive to certain poisons, which can reduce their sensitivity: emission of
silicone-containing vapours at concentrations > 10 ppm and chlorinated or sulphurous
products at concentrations > 100 ppm.

 A lack of oxygen (< 15% O2) or over-oxygenation (> 23% O2) may cause under-measurement
(in the former case) or over-measurement (in the latter case).

 Sensors must be located head downwards at installation or during maintenance work.

8.2.1.4 Response to other explosive gasses

It is recommended that the detector is calibrated using the gas to be measured. Users wishing to
calibrate the detector using a gas other that detected and factory-programmed should refer to the
following table, and use the recommended gas and corresponding coefficient.

Table 1 : Calibration Coefficients

- -
Gas Chemical LEL LSE Flash Vapor Coefficient Coefficient Coefficient Coefficient
Formula (%) (%) point density Calibration gas Calibration gas - Calibration gas - Calibration gas
CH4 (methane) H2 (Hydrogen) C4H10 (Butane) C5H12
(°C)
(Pentane)

Ethyl acetate C4H8O2 2,10 11,50 -4 3,0 1,65 1,35 0,90 0,80
Acetone C3H6O 2,15 13,00 -18 2,1 1,65 1,35 0,90 0,80
Acetylene C2H2 1,50 100 -18 0,9 2,35 1,90 1,25 1,15
Acrylic acid C3H4O2 2,40 8,00 54 2,5 5,00 4,00 2,65 2,40
Butyl acrylate C7H12O2 1,20 8,00 37 4,4 3,50 2,80 1,85 1,70
Ethyl acrylate C5H8O2 1,70 13,00 -2 3,5 3,05 2,45 1,65 1,50
Acrylonitrile C3H3N 2,80 28,00 -1 1,8 1,45 1,20 0,80 0,70
Ammoniac NH3 15,00 30,20 < -100 0,6 0,90 0,75 0,50 0,45
Benzene C6H6 1,20 8,00 -11 2,7 4,00 3,20 2,15 1,90
1.3-
C4H6 1,40 16,30 -85 1,9 2,55 2,05 1,35 1,25
Butadiene
Butane C4H10 1,50 8,50 -60 2,0 1,90 1,55 1,00 0,90
Butanol
C4H10O 1,4 11,3 29 2,6 1,95 1,60 1,05 0,95
(Butyl Alcool)
2 - Butanone
C4H8O 1,80 11,50 -4 2,5 3,90 3,15 2,10 1,90
(MEK)
Cyclohexane C6H12 1,20 8,30 -17 2,9 2,00 1,60 1,10 1,00
Dimethylether C2H6O 3,00 27,00 -41 1,6 1,80 1,45 0,95 0,90
Dodecane C12H26 0,60 ~6,0 74 5,9 4,00 3,20 2,15 1,90
Ethane C2H6 3,00 15,50 135 1,0 1,50 1,20 0,80 0,75
Ethanol C2H6O 3,30 19,00 13 1,6 2,15 1,75 1,15 1,05
Ether
(C2H5)2O 1,70 36,00 -45 2,6 1,90 1,55 1,00 0,90
(Diethylether)
Ethylene C2H4 2,70 34,00 - 135 1,0 1,65 1,35 0,90 0,80
LPG Prop+But 1,65 ~9,0 < -50 1,9 1,90 1,55 1,00 0,90
Diesel Melange 0,60 ~6,0 55 >4 3,20 2,60 1,70 1,55
Natural Gas CH4 5,00 15,00 -188 0,6 1,05
Heptane C7H16 1,10 6,70 -4 3,5 2,20 1,80 1,20 1,05

23
 - -
Gas Chemical LEL LSE Flash Vapor Coefficient Coefficient Coefficient Coefficient
Formula (%) (%) point density Calibration gas Calibration gas - Calibration gas - Calibration gas
CH4 (methane) H2 (Hydrogen) C4H10 (Butane) C5H12
(°C)
(Pentane)

Hexane C6H14 1,20 7,40 -23 3,0 2,10 1,70 1,15 1,00
Hydrogen H2 4,00 75,60 - 0,069 1,00
Isobutane C4H10 1,50 8,40 -83 2,0 1,50 1,20 0,80 0,75
Isobutene C4H8 1,60 10,00 <-10 1,9 2,20 1,80 1,20 1,05
Isopropanol C3H8O 2,15 13,50 11,7 2,1 1,60 1,30 0,85 0,80
Kerosene C10 -
0,70 5,00 > 50 >4 5,00 4,00 2,65 2,40
(JP4) C16
Methyl
C5H8O2 2,10 12,50 2 3,5 2,25 1,80 1,20 1,10
Methacrylate
Methane CH4 5,00 15,00 -188 0,55 1,00
Methanol CH3OH 5,50 44,00 11 1,1 1,40 1,15 0,75 0,70
melange
Naphta 0,90 5,90 > 44 >4 3,50 2,80 1,85 1,70
(Mixture)
Nonane C9H20 0,70 5,60 31 4,4 4,40 3,55 2,35 2,10
Octane C8H18 1,00 6,00 12 3,9 2,70 2,20 1,45 1,30
Ethylene
C2H4O 2,60 100 -20 1,5 2,10 1,70 1,15 1,00
Oxyde
Propylene
C3H6O 1,90 37,00 70 2,0 2,35 1,90 1,25 1,15
oxide
Pentane C5H12 1,40 8,00 -49 2,5 1,00
Propane C3H8 2,00 9,5 -104 1,6 1,55 1,25 0,85 0,75
Propylene C3H6 2,00 11,70 -107,8 1,5 1,65 1,35 0,90 0,80
Styrene C8H8 1,1 8,00 31 3,6 6,30 5,05 3,35 3,00
Gasoline lead
/ 1,10 ~6,0 21 3à4 1,80 1,45 0,95 0,90
free
Toluene C7H8 1,20 7 5 3,1 4,00 3,20 2,15 1,90
Turpentine
- 0,8 6,0 35 4,7 3,50 2,80 1,85 1,70
Oil
Triethyl
C6H15N 1,20 8 -15 3,5 2,05 1,65 1,10 1,00
amine
melange
White Spirit 1,10 6,50 >30 >4 3,50 2,80 1,85 1,70
(Mixture)
Xylene C8H10 1,00 7,60 25 3,7 4,00 3,20 2,15 1,90
Sensors with a grey background: gases recommended for calibrating the detector (VQ1)

Example (second row of table): calibration of an Acetone detector using 1% butane (by volume) as
the calibrating gas.

Value to be displayed:
1% (butane injected) x 100 x 0.90 (Butane/Acetone coefficient) = 60% LEL
1.5% (butane LEL)

N.B.:
- LELs vary depending on the source. Those values shown here are taken from European
Standard EN 50054
- Coefficients are accurate to  15%

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 8.2.2 Technical Specifications and Special Instructions for Oxygen detectors

8.2.2.1 Transfer curves for OLCT 20 detectors

The following curve shows the transmitter output current value as a function of gas
concentration. Where the user connects the transmitter to a device other than a device manufactured
by OLDHAM, he must check that the transfer curve is fully compatible with its input characteristics
to ensure that the information generated by the transmitter is correctly interpreted. Equally, the
device must supply a suitable power supply voltage, allowing for cable voltage losses.

Output Current in mA

Fault
23.2 mA
20.0 mA

4.0 mA
1 mA
Fault % O2 concentration
by volume
0% 30.0 % 36.0%

8.2.2.2 Metrological data

Maximum concentration 30% O2

Type and number CT5020 CELL
Principle 2-electrode electrochemical
(Measurement of oxygen
concentration by volume)
Estimated service life 30 months
Storage 4°C < T < 12°C
10% < RH < 60%
Temperature range -20°C to +45°C
Humidity range 20% RH to 95% RH
Pressure range 1 bar ± 10%
Accuracy at 20°C 15 to 21% O2 ± 0.5% vol O2
1 to 14% O2 ± 0.6% vol O2
Repeatability < 2% of signal
T90 response time < 15 seconds
Effect of temperature (0 to 40°C) < 0.5% vol O2
Effect of humidity (10% to 90% RH) The measurement is lower as a
result of the air being diluted by
water vapour
Sensitivity drift over time < 2% per month
Zero stabilisation time following 30 to 60 minutes
power-up

25
 8.2.2.3 Characteristics and Special precautions for oxygen detectors
 When the transmitter is powered up or the measurement sensor is replaced, it takes between
30 and 60 minutes for the measurement to stabilise at 20.9% v/v in pure ambient air.
 The use of an oxygen-rich atmosphere (> 25%) can compromise safety.

8.3 Markings

8.3.1 Flameproof certified version: OLC 20d and OLCT 20 d

OLDHAM
F – 62027 Arras
0080
OLC 20d or OLCT 20d
II 2GD
Ex d IIC T6 Gb
Ex tb IIIC T85°C Db IP66
Tamb : -20°C to 70°C
INERIS 01ATEX0004X
Read instruction manual
WARNING: Do not open when energized
Serial number, year of manufacture

8.3.2 Intrinsic safety version: OLCT 20 i

OLDHAM
F – 62027 Arras
0080
OLCT 20i
II 1 GD
Ex ia IIC T4 Ga
Ex ia IIIC T135°C Da IP66
I M1 Ex ia I Ma
Tamb : -20°C to 70°C
INERIS 01ATEX0004X
Read instruction manual
WARNING: Do not open when energized
Serial number, year of manufacture

26
9 Recommendations

The measuring sensor shall be positioned facing downwards. The physical location of the
TRANSMITTER depends on the type of gas to be detected:

 at the high point if the gas is lighter than air,

 at the low point if the gas is heavier than air,
 near outlet vents in the case of mechanical ventilation,
 or, more generally, in locations where the gas is likely to accumulate.

Despite its high degree of protection (IP66), it may be necessary to protect the TRANSMITTER
against adverse weather conditions (rain, dust, direct sunlight, etc.) and from direct spraying with
cleaning or maintenance products (causing soiling of the detection sensor).

The TRANSMITTER must also be positioned so as to allow access to the measuring sensor so that
it can be replaced.

Detectors must be positioned so as to optimize the detection of accumulations of gas emitted in the
air.

Factors to be considered in determining optimal detector positioning:

 potential sources of gas and vapour emissions

 chemical and physical data on gases and vapours which may be present

 liquids with low volatility  detectors as near as possible to the leak risk area

 type and concentration of gas leaks (high-pressure jet, slow leak, etc.)

 air movements

- indoors: natural and mechanical ventilation

- outdoors: wind speed and direction

 effect of temperature

 installation so as to avoid mechanical damage or deterioration caused by water in summer

 positioning to allow easy maintenance, if possible

 avoiding direct sunlight on the readout area as this would lead to maintenance problems

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28
10 EU Declaration of Conformity

29
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 The Fixed Gas Detection Experts

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