mtl700 series...710 10 50 200 √√√ 6v dc & 4v ac systems 85 6.0 6.9 c 50 710p 10 33 300 √√...

EUROPE (EMEA) Tel: +44 (0)1582 723633 Fax: +44 (0)1582 422283AMERICAS Tel: +1 603 926 0090 Fax: +1 603 926 1899ASIA PACIFIC Tel: +65 487 7887 Fax: +65 487 7997E-mail: [email protected] Web site: www.mtl-inst.com

April 2006

for safe measurement andcontrol in hazardous areas

MTL700 SERIES

MTL700 Series shunt-diode safety barriersare 1- or 2-channel devices which pass an electricalsignal in either direction without shunting it, but limitthe transfer of energy to a level that cannot igniteexplosive atmospheres. Connected in series with thesignal transmission lines on a process plant, theyprotect hazardous-area wiring and equipmentagainst faults occurring in the safe area, and enablea wide range of measurement and controloperations to be carried out simply andinexpensively by intrinsically safe techniques.

Applications include the protection of installationscontaining ‘simple’ uncertified devices such asthermocouples, switches, and resistive sensors, orseparately certified ‘energy storing’ or ‘voltageproducing’ apparatus, for example ac sensors,transmitters, and current-to-pneumatic (I/P)converters.

Essential features of the MTL700 Series are theself checking ‘as-you-mount-it’ earthing via two studsdirectly to nickel-plated brass or copper busbar. Theearth connection is on top of the unit, allowing easyinspection, installation and removal. The shape ofthe barrier has been designed for easy wiring, whilethe common (14.5 mm) space requirement of both1- and 2-channel units simplifies planning oralteration of installations of all sizes. The busbar isinsulated for separate earthing, to eliminate thedanger of invasion by fault currents.

MTL700P shunt-diode safety barriers delivermore power into hazardous areas. Because of thehigher power levels available, it is important whenconsidering the use of MTL700P barriers to check thecompatibility of the electrical safety parameters ofthe field equipment (such as transmitters andsolenoid valves) with those of the barriers to makesure the combination is safe. In addition, with thebarriers designed for IIB gas group applications, theoverall gas classification of the system also needschecking

References. The following documents areavailable for further information on MTL700 Seriesbarriers:

AN9007 A user’s guide to shunt-diode safety barriersINM700 The MTL700 Series Instruction Manual

◆ All models short-circuit proof

◆ Fixed tagging & cable-screen earthing accessories

◆ Certified to worldwide standards

◆ 1 or 2 channels in same package

◆ Electronic protection prevents blown fuses

◆◆ Higher-power barriers for groupIIC and IIB gases


June 2004

MTL V ΩΩ mA

702 25 200 125 √ Transmitters – – 35 See706 28 300 93 √√ Transmitters – – 35 'How707 28 300 93 √√ Switches – – 35 they

28 diode – – – – 50 work’707P† 28 164 170 √ Transmitters, switches, 35 50

15 diode – controller outputs – –708 28 300 93 √√ Solenoids, alarms, LEDs, – – 35 –

710 10 50 200 √ √ √ 6V dc & 4V ac systems 85 6.0 6.9 c 50710P 10 33 300 √ √ 8V dc systems 42 8.0 9.2 200715 15 100 150 √ √ 12V systems 155 12.0 13.0 100715P 15 50 291 √ 12V dc systems 60 12.5 13.8 200722 22 150 147 √ √ 18V dc systems 185 19.0 20.2 50722P 22 101 213 √ 18V dc systems 121 18.5 20.0 100728 28 300 93 √√ Controller outputs, solenoids 340 25.5 26.6 50

28 300 93 √ √ Transmitters 340 25.5b 26.6d 50728P 28 234 119 √ Controller outputs, solenoid valves 253 24.5 26.0 100729P† 28 164 170 √ Controller outputs, solenoid valves 184 24.5 26.0 100

751 1 10 100 √ Active dc & ac sensors 20 0.3 2.0 2501 10 100 (low impedance receivers) 20 0.3 2.0 250

755 3 10 300 √√ Resistance temperature 18.0a (0.6) 3.6 2503 10 300 detectors 18.0a (0.6) 3.6 250

758 7.5 10 750 √ √ Gas detectors 18 6.0 7.0 2007.5 10 750 18 6.0 7.0 200

761 9 90 100 √ 145 6.0 7.5 1009 90 100 145 6.0 7.5 100

761P 9 350 25 √ Strain-gauge 384 7.0 8.1 509 350 25 bridges 384 7.0 8.1 50

764 12 1k 12 √ √ √ Strain-gauge bridges 1075 10.0 10.7 e 5012 1k 12 1075 10.0 10.7 e 50

766 12 150 80 √ 185 10.0 11.2 5012 150 80 185 10.0 11.2 50

766P 12 75 157 √ Strain-gauge 93 9.8 11.3 10012 75 157 bridges 93 9.8 11.3 100

767 15 100 150 √ √ 12V dc systems 155 12.0 13.0 10015 100 150 155 12.0 13.0 100

768 22 150 147 √ √ 18V dc systems 185 19.0 20.2 5022 150 147 185 19.0 20.2 50

779 28 300 93 √ √ Controller outputs 340 25.5 26.6 5028 300 93 340 25.5 26.6 50

796 26 300 87 √ √ Vibration probes 340 23.5 24.6 5020 390 51 (MTL796 negative) 435 17.5 18.7 50

760 10 50 200 √√ Active dc & ac sensors 85 6.0 7.4 5010 50 200 Thermocouples 85 6.0 7.4 50

765 15 100 150 √ 135 12.0 13.2 5015 100 150 135 12.0 13.2 50

772 22 300 73 √ 2-wire dc & ac systems 340 18.0 19.7 5022 300 73 340 18.0 19.7 50

778 28 600 47 √ 665 24.0 25.7 5028 600 47 665 24.0 25.7 50

786 28 diode – √ √ Signal returns 2.2V+30Ω 25.5 26.6 5028 diode – 2.2V+30Ω 25.5 26.6 50

787 28 300 93 √ √ Controller outputs, 340 25.5 26.6 5028 diode – switches 2.2V+30Ω 25.5 26.6 50

787S 28 300 93 √√ Transmitters 340 25.5 26.6 5028 diode – Controller outputs, switches 0.9V+20ΩΩ 25.5 26.6 50

787SP 28 234 119 √ Transmitters, controller outputs 258 24.5 26.5 8028 diode – switches 0.9V+16Ω 24.5 26.5 80

788 28 300 93 √ √ 340 25.5 26.6 5010 50 200 85 6.0 6.9 50

Transmitters 340 25.5 26.6 50788R 28 300 93 √ √ 85 6.0 6.9 50

10 50 200

791 11 51 216 √ 31.25kbit/s fieldbus 62.6 10V (at 50µA) 10.5 10011 51 216 √ installations 62.6 –10V (at 50µA) –10.5 100

799 Dummy barrier for securing cables for future installations – takes hazardous-area circuits to earth.

}

3

4

1

2

Internalterminator

Vmax

V

SPECIFICATIONS ‘Key’ barriers shown in blueModelNo.

Safety description Polaritiesavailable

+ – ac

Basic circuit

Hazardous Safe

Fuserating

mA

Vwkg at10(1)µA

V

Max. end-to-end

resistanceΩΩ

Application

}

3

4

1

*2

(768 & 779 require channelsseparate in IIC)}

3

4

1

2

ac

3 (26V:796)

4 (20V:796)

1

*

2

3

4

1

ac

2Star connected

3

4

1

23

4

1

2

787S

3 (28V)

4 (10V)

1

2

250Ω

a: Tolerance ±0.15Ω at 20°C, channels track within 0.15Ω from –20 to +60°C. d: ac version 26.1V.b: ac version 24.5V. e: ac version 11.2V.c: ac version 7.4V. †: Gas group IIB (CENELEC), C (N America).*Diagrams show positive versions. All diodes reversed on negative versions. Additional diodes fitted on ac versions.Patents for MTL787S: UK Patent No. 2210522, USA Patent No. 4860151; Patents for MTL707P: UK Patent Nos. 2210521, 2210522; USA Patent No. 4860151; Patents for MTL787SP: UK Patent No. 2210522; USA Patent No. 4860151

3

4

1

2

Terminal 1 & 2open circuit

3

4

1

2

See 'HOW THEY WORK'and

'OVERVOLT-PROTECTED

BARRIERS'

See additionalspecification

switches


June 2004

Ambient temperature and humidity limits–20 to +60°C continuous working–40 to +80°C storage5–95% RH

Leakage currentFor ‘basic’ barriers with a working voltage of 5V or more, theleakage current decreases by at least one decade per voltreduction in applied voltage below the working voltage, over twodecades. For the MTL755 it decreases by at least one decade fora 0.4V reduction in applied voltage.

TerminationsTerminals accommodate conductors up to 4mm2 (12AWG)Hazardous-area terminals are identified by blue labels.

Colour coding of barrier topGrey: non-polarisedRed: positive polarityBlack: negative polarityBlack (red label for safe-area terminals):

positive supply, negative to transmitter (MTL706) White: dummy barrier, MTL799

Weight125g approx

Mounting and earthingBy two integral M4 x 9 tin-lead plated steel fixing studs andstainless steel self-locking nuts (provided).

EMC complianceEN 50 081-2/EN 50 082-2, generic emission/immunitystandards. These rtefer to appropriate IEC/CISPR standards.(MTL707P+ and MTL702+ are not CE marked)

GENERAL SPECIFICATIONHOW THEY WORKAll MTL700 Series barriers are based on the same simple principle.Each channel contains two stages of pulse-tested Zener or forward-connected diodes and an ‘infallible’ terminating resistor. In the eventof an electrical fault in the safe area, the diodes limit the voltage thatcan reach the hazardous area and the resistor limits the current. Afuse protects the diodes, and the two stages of voltage limitationensure continued safety if either stage should fail. No active output-current limiting circuits are employed. All models are certified ‘ia’ forall zones and ‘IIC’ for all explosive atmospheres (except MTL707P+and MTL729P+, 'ia' 'IIB').

1. Safety descriptionThe safety description of a barrier, eg ‘10V 50Ω 200mA’, refers tothe maximum voltage of the terminating Zener or forward diode whilethe fuse is blowing, the minimum value of the terminating resistor, andthe corresponding maximum short-circuit current. It is an indication ofthe fault energy that can be developed in the hazardous area, andnot of the working voltage or end-to-end resistance.

2. PolarityBarriers may be polarised + or –, or non-polarised (‘ac’). Polarisedbarriers accept and/or deliver safe-area voltages of the specifiedpolarity only. Non-polarised barriers support voltages of eitherpolarity applied at either end. An exception to this is the MTL791Fieldbus barrier which has one positive and one negative channel.

3. End-to-end resistanceThe resistance between the two ends of a barrier channel at 20°C, ieof the resistors and the fuse. If diodes or transistors are present, theirvoltage drop (transistors ON) is quoted in addition.

4. Working voltage (Vwkg)The greatest steady voltage, of appropriate polarity, that can beapplied between the safe-area terminal of a ‘basic’ barrier channeland earth at 20°C for the specified leakage current, with thehazardous-area terminal open circuit.

5. Maximum voltage (Vmax)The greatest steady voltage, of appropriate polarity, that can beapplied continuously between the safe-area terminal of any barrierchannel and earth at 20°C without blowing the fuse. For ‘basic’barriers, it is specified with the hazardous-area terminal open circuit;if current is drawn in the hazardous area, the maximum voltage forthese barriers is reduced. The ‘ac’ channels of ‘basic’ barriers andmost channels of overvolt-protected barriers withstand voltages of theopposite polarity also – see circuit diagrams.

6. Fuse ratingThe greatest current that can be passed continuously (for 1000 hoursat 35°C) through the fuse.

7. Star connectionIn star-connected barriers, the two channels are interlocked such thatthe voltage between them cannot exceed the working voltage, Vwkg:this allows for higher cable capacitance or inductance.

8. Maximum safe-area voltage (Um)The maximum permissible safe-area voltage (Um) for MTL700 Seriesbarriers is 250V ac/dc.

TERMINOLOGY

APPLICATION KEY BARRIERResistance temperature detectorsThermocouples, ac sensorsController outputs, one line earthedController outputs, neither line earthed

Transmitters, 2-wire, 4/20mA

Switches

Solenoids, alarms, LEDs

755ac760ac728+787S+

dc power supply26.0V 20–35V

787S+

787S+

728+

706+

707+

708+

Patents for MTL706+, 707+, 708+, 787S+

KEY MTL700 SERIES BARRIERS SUMMARISED

TYPEAnalogueinput (low-level)Analogueoutput

Analogueinput (high-level)Digital (on/off)inputDigital (on/off)output

49.2

85.093.5

9.0

25.0 11.57.5 7.5

14.2

61.5

3 4 2

12 1

Hazardous-areaterminals

DIMENSIONS (mm)

Safe-area terminals


April 2006

3

4

4/20mA

50mA

40mA max+35V max.

50mA

50mA250Ω±5%

Current limit

RegulateNegative

4/20mA

0V

1

2–

+Tx

MTL706+ for 'smart' 2-wire 4/20mA transmittersUK Patent No. 2205699USA Patent No. 4967302European Patent (Germany, France, Italy) No. EP 0 294 139 B1The MTL706+ is a 1-channel shunt-diode safety barrier, with built-inelectronic overvolt protection, for energising a 2-wire 4/20mAtransmitter in a hazardous area. It is powered from a positive supplyof 20–35V dc and delivers a 4/20mA signal into an earthed load inthe safe area. It is proof against short circuits in the field and in thesafe area and is extremely accurate. The MTL706+ will pass incomingcommunication signals up to 10kHz from a ‘smart’ transmitter, whilein the outgoing direction it will pass signals of any frequency likely tobe encountered.

Since the MTL706+ has no return channel for energising the load, theentire output of the single ‘28V’ channel is available to power thetransmitter, providing high output capability. This channel is negativelypolarised, and the safe-area signal is in fact the very current thatreturns through it from the hazardous area, the novel circuit beingenergised by a built-in floating dc supply derived from the external dcsource of power.

To prevent any leakage through the Zener diodes and maximise theoutput voltage available at 20mA, the floating supply is given a risingvoltage/current characteristic. This is achieved by monitoring the4/20mA current, an arrangement which allows all-frequencycommunication in both directions. A separate circuit limits the currentto protect the fuse in the event of a short circuit in the hazardous area.

With a 22V supply, the barrier will deliver 15V minimum at 20mA forthe transmitter and lines and consumes less than 40mA in normaloperation.

Note: the MTL706+ supercedes the MTL705+, which was similar in basicperformance but did not pass outgoing communication signals below about1kHz.

BASIC CIRCUIT

OVERVOLT-PROTECTEDBARRIERS

ADDITIONAL SPECIFICATIONSupply voltage

20 to 35V dc, positive w.r.t. earthVoltage available for transmitter and lines (at 20mA)

(Vsupply – 8V), limited at 16VVoltage available for load (at 20mA)

Vsupply – 5VLoad resistance

850Ω maximumOutput impedance to load

>1MΩCalibrated accuracy (at 20°C with 250ΩΩ load)

0.05% of maximum output, including non-linearity and hysteresis

Zero temperature drift


June 2004

OVERVOLT-PROTECTEDBARRIERS(continued)

MTL707+ for switch inputsUK Patent Nos. 2245439, 2210521European Patent No. EP 0 310 280 B1

The MTL707+ is a 2-channel shunt-diode safety barrier similar to theMTL787+ but with built-in electronic overvolt protection. It is intendedprimarily for safeguarding a hazardous-area switch controlling arelay, opto-coupler or other safe-area load from an unregulated dcsupply in the safe area.

The outgoing channel accepts supply voltages up to +35V and isprotected against reverse voltages: the return channel is unaffected byvoltages up to +250V.

In normal operation the protection circuit introduces only a smallvoltage drop and shunts less than 1mA to earth, so its overall effect isminimal. If the supply voltage exceeds about 27V, however, causingthe Zener diodes to conduct – or if the safe-area load has a very lowresistance – the supply current is limited automatically to 50mA,protecting the fuse and power supply and enabling the loop tocontinue working.

ADDITIONAL SPECIFICATION

Supply voltage (Vs)10 to 35V dc, positive w.r.t. earth

Output current (Iout)Up to 35mA available

Maximum voltage drop (at 20°C, current not limited)Iout x 370Ω + 1.5V, terminal 1 to 3Iout x 50Ω + 2.1V, terminal 4 to 2

Supply currentIout + 1mA max, Vs 28V or low load resistance

MTL707P+ for switch inputs, IIB gasesThe MTL707P+ is a two-channel shunt-diode safety barrier similar tothe MTL787SP+, but is designed for use with group IIB gases andfeatures built-in electronic overvolt protection allowing use withunregulated power supplies up to 35V dc. It is intended primarily asa low cost solution for driving IIB certified 2-wire 4/20mAtransmitters, but can also be used with controller outputs with currentmonitoring, solenoid valves and switches. To protect the fuse andenable the loop to continue working, the supply current is limitedautomatically at 50mA should the output be short-circuited or excessvoltage applied.

ADDITIONAL SPECIFICATIONSupply voltage – channel 1 (Vs)

10 to 35V dc positive with respect to earthOutput current – channel 1 (I out)

Up to 35mA availableMaximum voltage drop (at 20°C, current not limited)

Iout x 200Ω + 0.2V, terminals 1 to 3Iout x 18Ω + 1.3V, terminals 4 to 2

Supply currentIout + 2mA max, Vs28V or low load resistance

MTL708+ for switched outputsUK Patent No. 2210521European Patent No. EP 0 310 280 B1

The MTL708+ is a 1-channel shunt-diode safety barrier similar to theMTL728+ but with built-in electronic overvolt protection. It is intendedprimarily for safeguarding solenoids, alarms, light-emitting diodes orother hazardous-area loads controlled by a safe-area switch from anunregulated dc supply in the safe area.

The barrier accepts supply voltages up to +35V and is protectedagainst reverse voltages.

In normal operation the protection circuit introduces only a smallvoltage drop and shunts less than 1mA to earth, so its overall effect isminimal. If the supply voltage exceeds about 27V, however, causingthe Zener diodes to conduct – or if the hazardous-area load has avery low resistance – the supply current is limited automatically to50mA, protecting the fuse and power supply and enabling the loopto continue working.

BASIC CIRCUIT

ADDITIONAL SPECIFICATIONSupply voltage (Vs)

10 to 35V dc, positive w.r.t. earthOutput current (Iout)

Up to 35mA availableMaximum voltage drop (at 20°C, current not limited)

Iout x 370Ω + 1.5V, terminal 1 to 3Supply current

Iout + 1mA max, Vs 28V or low load resistance

Hazardous area Safe area

Currentlimit

50mA

50mA

1 mA maxI out

+35V max1

2

3

4


BASIC CIRCUIT


BASIC CIRCUIT

Currentlimit

50mA

1 mA maxI out

3

2

+35V max1

LED,alarm,

solenoid,etc

4

Currentlimit

50mA

50mA

1 mA maxI out

+35V max1

2

3

4


June 2004

BARRIERS FOR SENSORS

Note: voltage figures shown on busbar are safety description values.

ANALOGUE INPUTS, LOW LEVELThermocouplesThe preferred barrier for thermocouples is the MTL760ac, whose 2-channel non-polarised design retains the ‘earth-free’ nature of thesignal. Provided that the receiver’s input circuit floats, the combinationrejects common-mode ac and dc interference up to at least 6V and isunaffected by earth faults on the primary element. Even if thereceiver’s circuit is tied to its ‘0V’ rail, the use of a 2-channel barriertakes the worry out of earthing. To eliminate errors due to thermalemfs, the compensating cable should be continued from the barrier tothe receiver. For moving coil or other low resistance receivers, use theMTL751 (40Ω) or the MTL755ac (36Ω) if the resistance of theMTL760 (170Ω) is unacceptable.

USA regulations permit the thermocouple to be earthed on theassumption that the barrier will not conduct, but Europe and other‘IEC countries’ assume that it may do so. In these countries either thethermocouple and its cables must be insulated to withstand 500V, Fig.1; or the earth loop must be broken by an isolating transmitter, Fig.2, or by one of the isolating interface devices in the MTL2000, 3000,4000 or 5000 Series.

Resistance temperature detectorsFor 3-wire circuits with a floating bridge, the most economical solutionis provided by the MTL755ac 2-channel barrier, Fig.4. The two leads from the bridge arms are protected by thebarrier, while the third (supply) lead is earthed at the busbar. TheMTL755ac has a low end-to-end resistance of only 18.0Ω perchannel to minimise span changes, and its channels track within0.15Ω (from –20 to +60°C) to minimise zero shift with temperature.Close tolerancing of each channel to ±0.15Ω at 20°C facilitatesbarrier substitution.

If the bridge circuit is already earthed, a third barrier channel isneeded; in practice this can be one half of another MTL755ac, Fig.5. For extreme accuracy use three channels and an earth-free bridge,since the small errors due to barrier leakage tend to cancel.

4-wire constant-current circuits do not require matched barrierresistances, and can be protected more economically by twoMTL761ac 2-channel barriers, Fig.6. If the increase in loop resistanceis too great, use two MTL755acs.

Slidewire displacement transducersThere are many solutions. Perhaps the simplest is that shown in Fig.7, where an MTL760ac supplies power and brings back a unipolarsignal. Other barriers that could be used include the MTL761ac,765ac, 772ac, 778ac. Where polarity reversal or very highaccuracy are required, use the techniques designed for strain-gaugebridges, overleaf.

Photocells, ac sensors, flowmetersSimilar arguments apply, and the MTL760ac is recommended, Fig. 3.Any other 2-channel non-polarised barrier that will handle the voltagewould be suitable. All MTL barriers of this type transmit signals up toa few kHz. At higher frequencies the self capacitance of the Zenerdiodes – around 1000pF – may attenuate the signal. No certificationis required for sensors generating less than 1.2V, 0.1A, 20µJ and25mW. In practice this includes all photocells, but some ac sensorsmay have significant inductance and require to be designed andcertified for use in hazardous areas.


MTL760ac

0VVout+7V max.

Fig. 7

34

12

10V10V

MTL760ac

3 4 2 110V

10V

Compensating cable

Insulatedfrom earth

Fig. 1

Recorder,controller,

data logger,computer

Fig. 2

Temperature transmitter

3 4 2 1

10V10V

Fig. 3

MTL760acEarth-freesignal

Photocell,microphone,

turbineflowmeter, etc

3 4 2 1

Receiver

LNE

3V3V

Fig. 4

MTL755ac

3 4 2 1

Receiver

LNE

3V3V

3V3V

Fig. 5

MTL755ac

1/2 MTL755ac

3 4 2 1

3 4 2 1

Receiver

LNE

MTL761acMTL755ac

MTL761acMTL755ac

Fig. 6

3 4 2 1

3 4 2 1


June 2004

BARRIERS FOR SENSORS(continued)

ANALOGUE INPUTS, LOW LEVEL (continued)Strain-gauge bridgesFig. 8 shows an arrangement using two or three barriers, which issafe in IIC gases (system certificate no. Ex842125). With theMTL761ac, the circuit is powered from a 12V, 290Ω source; if thebridge resistance is 290Ω, then the bridge voltage is 6V. If theMTL766ac is used, the source is 20V, 370Ω, and provides a bridgevoltage of 10V when the bridge resistance is 370Ω.

Quite frequently there is a demand to monitor three load cells, and apossible circuit is shown in Fig. 9 (system certificate no. Ex842128).The two channels of each MTL766ac barrier are connected in parallelto reduce the source resistance, and provide 8V across the three350Ω bridges. However, the higher energy present means that thesystem is safe in IIA and IIB gases only.

Weighing by load-cell is an application where the lower voltage dropof the MTL766Pac, compared to the MTL766ac, is a great advantage.In such applications, the MTL766Pac supplies power to the bridgewhile an MTL761Pac interfaces with the sensing and pick-off circuits.Using the two barriers in combination (see Fig. 10), the minimumvoltages available in 350Ω bridge systems with a ±10V supply are asfollows:-

1 bridge: 13.0V2 bridges: 9.7V3 bridges: 7.7V4 bridges: 6.4V


Gas detectors, logic systemsSome devices require a high current at a low voltage, for example,300mA at 2.3V for a typical gas detector. The low end-to-endresistance (18Ω) of the 2-channel MTL758+, and its working voltageof 6V, make this barrier ideal for energising gas detectors, 5V logicsystems, certain displays and similar equipment. The two channelscan be used separately or in parallel as required, and the systemremains safe in IIC gases if an MTL761ac is added to bring back themeasurement.

Fig. 11Gas detector

MTL758+

MTL761ac0V

9V9V

7.5V7.5V +6V

Output

34

12

34

12

MTL766Pac

MTL761Pac

350ΩBridge

Fig. 10

12V12V

+– Sense

MTL761Pac

Output, mV

9V9V

9V9V

+10V

0V

–10V

350ΩBridge

350ΩBridge

supply34

12

34

12

34

12

Fig. 8

Bridge

MTL761acMTL766ac

MTL764ac

MTL761ac

0V

+– Sense

12V12V

9V9V

+10V (MTL766)+6V (MTL761)

–6V (MTL761)–10V (MTL766)

Optional

Output, mV

34

12

34

12

34

12

MTL764ac

MTL766ac

MTL766ac

Bridge

Bridge

Bridge

Fig. 9

12V12V

+– Sense

MTL764ac

Output, mV

12V12V

12V12V

12V12V

+10V

–10V0V

34

12

34

12

34

12

34

12


June 2004

BARRIERS FORTRANSMITTERS ANDSWITCHES

ANALOGUE INPUTS, HIGH LEVEL2-wire 4/20mA transmittersIf several transmitters are to be operated from a common dc supply,and this can be closely regulated (at 26V max), the MTL787S+ nowbeats the previously recommended MTL788+ by nearly half a volt,providing up to 12.9V at 20mA for a transmitter and its lines, as wellas the usual 5V for the load, Fig. 12. Its return channel is moretolerant of errors during installation and fault finding, and it is safewith cables of much higher inductance. If the load requirement canbe reduced, the voltage available for the transmitter will be greater.

If the supply can be closely regulated, and the transmitter iscompatible with the higher power levels available from this barrier inIIC gas groups, the 2-channel MTL787SP+ is recommended. With a26V supply it provides 14.6V at 20mA for a transmitter and lines aswell as the usual 5V for the load, beating the MTL787S+ by 1.7V, Fig.12.

The voltage available for the transmitter and its lines can be increasedby converting the return current into a 1–5V signal before it passesthrough an MTL788+ barrier. The MTL788R+ contains a 250Ωprecision resistor for this purpose and makes 14.2V available, Fig.13.

If greater voltage capability is required for the transmitter or the load,or the supply is not closely regulated, then the MTL702+ is a provengood solution, Fig. 14. This overvolt-protected barrier delivers 14V at20mA for the transmitter and lines from a 22–35V supply, plus a quiteexceptional 17V for the load, both voltages being increased by 2V ifthe supply is at least 24V. It will pass incoming communication signalsof any frequency from a ‘smart’ transmitter but inherently cannot passsignals in the outgoing direction. Accuracy is high and currentconsumption is less than 60mA.

Where 2-way communication with ‘smart’ transmitters is required,there are two solutions. If the supply is closely regulated, choose theMTL787S+ (above). If it cannot be closely regulated, choose theMTL706+, Fig. 15. This overvolt-protected barrier – derived from thepreviously recommended MTL705+ – provides 15V at 20mA for thetransmitter and lines from a 22–35V supply, plus 5V for the load. It islower in cost than the MTL702+, is extremely accurate, has a standardsafety description and consumes only 35mA. Note that the loadresistor must be 250Ω ±5% and that terminal 3 is negative.

If the supply is poorly regulated, the 2-channel MTL707P+ provides alow cost solution for IIB applications, where its low end-to-endresistance makes 13V available for the transmitter and field cablingplus 5V for the load when powered from 24V dc, and its overvoltprotection allows supply variations up to 35V dc, Fig. 16.

Fire and gas detectionDesigned primarily for fire and gas detection systems, the lowermaximum end-to-end resistance of the MTL722P+ (121Ω) comparedto the MTL722+ (185Ω) can be an advantage (see Fig. 17). Inaddition, it may prove useful in other 18V dc systems.

MTL707P+*28VDiode15V

+35V max.1–5V

0VFig. 16

4/20mA

34

12

* CENELEC gas group IIB (C & D N. America)

IIB


+18V0V

MTL722P+22VEarth

18V dcsystems

Fig. 17

34

12

MTL787S+ MTL787SP+

28VDiode

Fig. 12

4/20mA 250Ω

+26V max.1–5V

0V

34

12

MTL788R+28V10V

Fig. 13

4/20mA

+26V max.1–5V

0V

34

12

MTL702+25V

E+35V max.1–5V

0VFig. 144/20/mA 250Ω

34

12

MTL706+28V

E+35V max.1–5V

0VFig. 15

Negative

4/20/mA 250Ω

34

12


June 2004

DIGITAL (ON/OFF) INPUTSSwitchesFor switch-status transfer, Fig. 18, the MTL707+ is preferred for tworeasons. First, the circuit fails safe if there is an earth fault on either line– ie the safe-area load de-energises. Second, the MTL707+ accepts upto 35V from poorly regulated power supplies without blowing its fuse:if the supply is well regulated, the MTL787S+ can be used, see Fig. 19.

In both cases, optimum power transfer with relays is achieved if theresistance of the load is made about equal to the combined resistanceof the two channels. The relay coil should then be rated at about halfthe supply voltage.

Switches, data-loggers, logic systemsThe MTL710P+ can be used for supplying power to low-voltageequipment in hazardous areas, such as data-loggers, switches andlogic systems. Its low maximum end-to-end resistance of 42Ω,compared to 85Ω for the MTL710+, means it can typically supplymore than 65mA current at 5V from an 8V supply (see Fig. 20). It alsohas the advantage of a higher working voltage (8V compared to 6Vfor the MTL710+).

The MTL715P+ functions similarly for 12V dc systems and can also beapplied to multiple-switch and logic circuits where the additionalpower proves useful, Fig. 21.


28VDiode

+35V max.Logic signal

0VFig. 18

MTL707+34

12

28VDiode

+26V max.Logic signal

0VFig. 19

MTL787S+34

12

+8V0V

MTL710P+10VEarth

8V dcsystems

Fig. 20

34

12

+12V0V

MTL715P+15VEarth

12V dcsystems

Fig. 21

34

12

ANALOGUE OUTPUTSController outputs – 4 to 20mAIn most cases the output current of a controller flows directly to its ‘0V’rail and the rail can be earthed at the busbar, Fig.22. Occasionally theoutput circuit may be fully floating. In either event the 1-channelMTL728+ or half an MTL779+ provides the solution. Overvoltprotection is not required, since current limiting in the controller protectsthe fuse in the barrier. The voltage drop introduced by the barrier is6.8V at 20mA.

The maximum voltage drop introduced by the MTL728P+ is only 5.1Vat 20mA (compared to 6.8V for the MTL728+).

For IIB applications, the MTL728P+ can be replaced with the similarlydesigned 1-channel MTL729P+.

If the output circuit of the controller is separated from the ‘0V’ rail by thecontrol transistor, Fig.23, a 2-channel barrier is necessary. TheMTL787S+ is recommended, since its return channel can handle up to25.5V, allowing the control signal to be turned off completely. Thevoltage drop introduced by the barrier is 8.1V at 20mA.

The maximum voltage drop introduced by the MTL787SP+ is only6.4V at 20mA (compared to 8.1V for the MTL787S+). The barrierreturn channel can handle up to 24.5V, allowing the control signal tobe turned off completely.

BARRIERS FOR CONTROL ELEMENTS


MTL728+MTL728P+MTL729P+

+

0V rail28V

EI/P

Fig. 22

4/20mA34

12

+4/20mA

0V rail

MTL787S+MTL787SP+

28VDiodeI/P

Fig. 23

34

12

Controller


June 2004


MTL787S+ MTL787SP+

Monitor

0V rail

+

28VDiode

I/P4/20mA

Fig. 24

34

12

Controller

The MTL787S+ and MTL787SP+ are also suitable for controllerscontaining a resistor which enables the return current to be monitoredfor high-integrity operation, Fig.24.

For IIB applications where a 2-channel barrier is needed (see above),the MTL707P+ can be used as, although the overvolt protectionprovided by this barrier is not necessary, the diode return channel andlow voltage drop makes this an ideal replacement for the MTL787S+or MTL787SP+ for IIB gas groups, Fig.25.

DIGITAL (ON/OFF) OUTPUTSSolenoids, alarms, LEDsIf the supply is well regulated, an MTL728+ (or half an MTL779+) canbe used.

For IIC applications, the lower end-to-end resistance of the MTL728P+can make a big difference to the overall loop design when drivinghigher-power solenoid valves, provided the power supply is wellregulated, Fig.26.

Should greater power be required for heavy-duty solenoids in IIB or IIAgases only (‘IEC countries’; C & D in USA and Canada), use the twochannels of the MTL779+ connected in parallel or consider theMTL3022 or MTL5022.

Similarly the MTL729P+ is ideal for powering high-power heavy-dutysolenoid valves, in IIB gas group applications, providing a maximumusable output power of 0.78W at 24V, Fig.26.

Most solenoid valves, alarms, light-emitting diodes (LEDs) and otheron/off hazardous-area loads are best driven via an MTL708+ 1-channel barrier, with built-in overvolt protection, Fig.27. The circuit failssafe with an earth fault on the live line and is unaffected by an earthfault on the earth return, while the barrier will accept up to 35V withoutblowing its fuse.

If the control switch is on earth, then a 2-channel barrier has to be used,Fig.28, but be aware that an earth fault on the return line will energisethe solenoid, whereas one on the live line does the opposite. If thesupply is poorly regulated use the MTL707+ (or MTL707P+ for IIBgases). If it is well regulated use the MTL787S+ (or MTL787SP+).

Alternatively, for operational safety, use an MTL2000, 3000, 4000 or5000 Series isolating interface unit.

Fieldbus applicationsThe MTL791 (Fig.29) is a 2-channel barrier designed specifically for31.25kbit/s fieldbus applications. Used with a suitable floatingfieldbus power supply of up to 20V (such as that provided by theMTL5995 unit) it extends the range of fieldbus applications intohazardous areas. It is provided with an internal integral safe-areaterminator*.

* ‘Terminators’ are used to terminate a fieldbus.

MTL707P+

0V rail

+

28VDiode

I/P4/20mA

Fig. 25Controller

34

12

*


MTL708+28VEarth

+35V max

0V

Fig. 27

34

12

28VDiode

+26.6Vmax (MTL787S+)+26.5Vmax (MTL787SP+)+35V max (MTL707+)+35Vmax (MTL707P+)

0VFig. 28

MTL787S+MTL787SP+MTL707+MTL707P+

34

12


*

+11V–11V

T

Fig. 29

MTL791+

–

*FBT1Fieldbusterminator

Fieldbus devices Fieldbus devicesFieldbuspowersupply

34

12

MTL728+MTL728P+MTL729P+*

28VEarth

+26.6Vmax (MTL728+)+26V max (MTL728P+)+26Vmax (MTL729P+)

0V

Fig. 26

34

12



June 2004

702+ 1 Yes 0.110 2.39 47 0.17 2.2 0.782706+ 1 Yes 0.083 3.05 56 0.12 4.0 0.65707+ Both Yes 0.083 3.05 56 0.12 4.0 0.65708+ 1 Yes 0.083 3.05 56 0.12 4.0 0.65710 1 Yes 3.0 0.91 74 3.0 1.0 0.50710P 1 Yes 3.0 0.38 44 4.89 0.22 0.75715 1 Yes 0.580 1.45 66 0.7 1.4 0.56715P 1 Yes 0.580 0.33 28 1.04 0.23 1.09722 1 Yes 0.165 1.45 45 0.2 1.4 0.81722P 1 Yes 0.165 0.30 32 0.33 0.53 1.18728 1 Yes 0.083 3.05 56 0.12 4.0 0.65728P 1 Yes 0.083 1.82 44 0.16 2.86 0.83751ac 1 Yes 100 3.72 1464 1000 4.5 0.025

2 Yes 100 0.96 558 1000 1.2 0.05No 100 3.72 732 1000 4.5 0.05

755ac 1 Yes 100 0.46 145 1000 0.4 0.2252 Yes 100 0.13 69 150 0.1 0.45

No 40 0.41 73 150 0.1 0.453 No 40 0.125 48 – – 0.684 Yes 40 0.035 31.25 – – 0.92

No 40 0.06 42 – – 0.92758 1 Yes 11.1 0.070 26 6.0 0.05 1.40

2 Yes 11.1 0.02 10 6.0 0.02 2.80760ac 1 Yes 3.0 0.91 74 3.0 0.9 0.50

2 Yes 3.0 0.20 27 3.0 0.2 1.00761ac 1 Yes 4.9 3.72 163 3.1 3.5 0.225

2 Yes 4.9 0.91 62 0.4 1.0 0.45No 0.31 3.72 81 0.4 1.0 0.45

4 Yes 0.42 0.20 26.39 – – 0.90No 0.42 0.37 37.78 – – 0.90

6 Yes 0.42 0.085 14.39 – – 1.35No 0.42 0.13 18.67 – – 1.35

761Pac 2 Yes 0.31 56 306 0.43 14.4 0.115764± 1 Yes 1.41 240 1000 1.5 200 0.036

2 Yes 1.41 61 360 1.0 60 0.072764ac 1 Yes 1.41 240 1000 1.5 200 0.036

2 Yes 1.41 61 360 0.18 60 0.072No 0.125 240 500 0.18 60 0.072

765ac 1 Yes 0.58 1.45 66 0.7 1.3 0.562 Yes 0.58 0.32 22 0.7 1.4 1.125

766ac 1 Yes 1.41 5.8 151 1.5 5.6 0.242 Yes 1.41 1.47 58 0.18 1.5 0.48

No 0.125 5.8 75 0.18 1.5 0.48766Pac 2 Yes 1.41 0.34 29 0.22 0.20 0.942

767 1 Yes 0.58 1.45 66 0.7 1.7 0.562 Yes 0.58 0.32 22 0.5 0.4 1.125

768 1 Yes 0.165 1.45 45 0.2 1.7 0.81772ac 1 Yes 0.165 6.77 89 0.2 6.0 0.404

2 Yes 0.165 1.45 34 0.2 1.8 0.808778ac 1 Yes 0.083 16 107 0.12 14 0.327

2 Yes 0.083 3.05 42 0.12 4.2 0.654779 1 Yes 0.083 3.05 56 0.12 4.0 0.65786 1 or 2 Yes 0.083 – – 0.11 500 –

787 & 787S Both Yes 0.083 3.05 56 0.11 4.0 0.65787SP 2 Yes 0.083 1.82 44 0.13 2.70 0.835

788 & 788R Both Yes 0.083 0.33 25 0.11 0.5 0.92791 Both No 0.165 0.30 32 0.24 0.31* 1.18796 Both Yes 0.10 1.94 34 0.13 2.0 0.81

707P 2 Yes 0.65 5.65 127 0.45 6.21 1.19729P 1 Yes 0.65 5.65 127 0.49 6.25 1.19

Number ofsingle channelsinterconnected

withinhazardous area

CABLE PARAMETERS AND PERMITTED COMBINATIONSBarriermodel

numberMTL

Earth 1

return used?

Maximum permissible cable parameters

CapacitanceµF

InductancemH

L/R ratioµH/ΩΩ

CapacitanceµF

Matched 2

powerW

(BASEEFA)Inductance

mHor

* L/R = 31µH/Ω

BASEEFA (ATEX) (group IIC) FM (groups A&B)

BASEEFA (group IIB) FM (group C)

1x715P Ex92C2425 Yes 0.135 0.23 39.3 0.914x764ac2 x 761ac channels Ex842125 Yes 0.2 0.24 11.6 1.012 x 764ac channels2 x 766ac channels4 x 761ac channels Ex842125 Yes 0.2 0.2 12.7 0.982 x 764ac channels4x761Pac channels2x766Pac channels Ex92C2424 Yes 0.18 0.17 18.4 1.172 x 764ac channels Ex842128 Yes 0.2 0.28 11 1.044 x 766ac channels758 + 761ac Ex872392 Yes 0.42 0.013 10.5 3.27

4 x 764ac channels Ex842128 Yes 0.6 1.1 32.6 1.124 x 766ac channels2 x 768 channels Ex842114 Yes 0.78 1.8 70 1.622 x 768 channels Ex842114 Yes 0.39 1.8 46.6 1.62Any number of 786 channels2 x 779 channels Ex842114 Yes 0.39 4.3 83 1.32 x 779 channels Ex842114 Yes 0.39 4.3 55.6 1.3Any number of 786 channels

The tables give the maximum permitted cable parameters (including cable and load) for hazardous-area circuits in group IIC and IIB gases. However, the tables are by no means exhaustive and for fulldetails of other safe combinations, consult either BASEEFA system certificates Ex832469, Ex92C2374 or Ex92C2376 or MTL. The MTL702 is covered by BASEEFA system certificate Ex842308, andthe MTL706 by Ex872513.In practice cable parameters rarely present a problem, as all cables normally used for instrument interconnection have L/R ratios below 25µH/Ω and capacitance below 200pF per metre.Note 1 If values are not quoted for when an earth return is not used, those for an earth return (‘Yes’ in the table) can be used.Note 2 The maximum power that can be drawn from the barrier combination under fault conditions. Used for assessing the temperature classification of ‘simple’ hazardous-area apparatus.Note 3 The values of the parameters for Groups IIA and IIB can be found in certificate numbers BAS01ATEX7202 and BAS01ATEX7203.For FM permitted combinations, refer to MTL document SCI-88 (via FM ref 1H8A1.AX).

BASEEFAMaximum permissible cable parameters for group IIC (hydrogen)System

combinationBASEEFAsystem

Cert. No.Capacitance

µF

Earth 1

return used?

InductancemH

L/R ratioµH/ΩΩ

Matched 2power

W(BASEEFA)

or

BASEEFAMaximum permissible cable parameters for group IIB (not safe for group IIC)


June 2004

Reg

ion

Arg

entina

Aus

tralia

Aus

tralia

Aus

tralia

Bra

zil

Cana

da

Chin

aCI

SCz

ech

Rep

Hun

gary

Japan

Kor

eaK

orea

(Aut

hori

ty)

(QM

D)

(NSW

M)

(SA

)(C

SA)

(NEP

SI)

(ISC

VE)

(FTZ

U)

(BK

I)(T

IIS)

(KRS)

(KIS

CO)

(A -

M)

Stand

ard

IAP

CA

CM

A 1

925-

CM

RAA

S238

0.7-

1987

NBR

844

7/84

C22

.2, N

o 15

7G

B383

6.1-

83G

OST

C

SN 3

3 03

80M

SZ 4

814/

7-77

New

4.01

198

919

8167

/198

2A

S238

0.1-

1989

GB3

836.

4-83

2278

2.5-

78G

ijyut

ukijy

unEN

500

20IE

C 7

9-11

Appro

ved

[EX

ia]

IICM

inin

gC

oal a

nd

Ex [

ia]

I / II

CBR

-Ex

ia /

ib II

CC

lass

I, II

, III,

Ex(ia

) IIC

T6

[EEx

ia] I

IC[E

Ex ib

] IIC

[EEx

ib] I

ICEx

ia II

C[E

Ex ia

] IIC

[E

x ia

]IIC

for

shal

e m

ines

Div.

1✝ ,

A -

G¥

IIBTa

mb=

60°C

‡ C

- G

# [E

Ex ia

] IIB

Mod

el n

o.Ce

rtific

ate

/file

no.

* T6

for s

witc

hes

or if

the

haza

rdou

s-are

a de

vice

is s

uita

bly

certi

fied

✝M

TL79

1 C

anad

a (C

SA) a

nd U

SA (F

M) D

iv2,

Gps

A-D

onl

yM

TL702+

INTI

CIT

EI 9

2A00

1Q

MD

85

6124

XU

MD

A E

x. ia

141

1Ex

692

XLR

3663

7-16

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

706+

INTI

CIT

EI 9

2A00

1M

DA

Ex.

ia 1

321

Ex 2

130X

pend

ing

LR36

637-

26G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42M

TL707+

INTI

CIT

EI 9

2A00

1M

DA

Ex.

ia 1

321

Ex 2

129X

pend

ing

LR36

637-

20G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42M

TL707P+

LR36

637-

58‡

GYJ

9920

5¥LN

D03

065-

EL00

1#M

TL708+

INTI

CIT

EI 9

2A00

1M

DA

Ex.

ia 1

321

Ex 2

129X

pend

ing

LR36

637-

20G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42M

TL710+-a

cIN

TIC

ITEI

92A

001

QM

D 8

5 60

01 X

SUM

DA

Ex.

ia 1

321

Ex 5

62X

pend

ing

LR36

637-

14G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1519

1 (a

c)LN

D03

065-

EL00

1M

TL710P+

LR36

637-

58G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42LN

D03

065-

EL00

1M

TL715+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1pe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

168

LND

0306

5-EL

001

MTL

715P+

LR36

637-

58G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1345

1LN

D03

065-

EL00

1M

TL722+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

722P+

LR36

637-

58G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42LN

D03

065-

EL00

1M

TL728+

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gG

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42LN

D03

065-

EL00

198

-204

7-Q

1M

TL728-a

cEx

562

XG

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1318

5LN

D03

065-

EL00

1M

TL728P+

LR36

637-

58G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1323

1LN

D03

065-

EL00

1M

TL729P+

LR36

637-

58‡

GYJ

9920

5¥LN

D03

065-

EL00

1#M

TL751ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

755ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

229

LND

0306

5-EL

001

98-2

042-

Q1

MTL

758+-

Ex 5

62X

pend

ing

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

760ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

230

LND

0306

5-EL

001

98-2

043-

Q1

MTL

761ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

286

LND

0306

5-EL

001

98-2

044-

Q1

MTL

761Pa

cLR

3663

7-58

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

356

LND

0306

5-EL

001

98-2

216-

Q1

MTL

764+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

764ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

355

LND

0306

5-EL

001

98-2

045-

Q1

MTL

765ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1pe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

167

LND

0306

5-EL

001

MTL

766ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gG

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1331

1LN

D03

065-

EL00

198

-204

6-Q

1M

TL766Pa

cLR

3663

7-58

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

357

LND

0306

5-EL

001

98-2

215-

Q1

MTL

767+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1pe

ndin

gG

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1481

2LN

D03

065-

EL00

1M

TL768+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gG

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42LN

D03

065-

EL00

1M

TL772ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1pe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

778ac

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1pe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

779+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

786+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

787+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

787S+

INTI

CIT

EI 9

2A00

1M

DA

Ex.

ia 1

321

Ex 5

62X

pend

ing

LR36

637-

20G

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42C

1322

8M

TL787SP

+LR

3663

7-58

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C15

398

LND

0306

5-EL

001

98-2

048-

Q1

MTL

788+

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

LND

0306

5-EL

001

MTL

788R+-

INTI

CIT

EI 9

2A00

1Ex

562

XG

YJ99

205

D.9

8C.3

07FT

ZU 9

8 Ex

000

6Ex

-98.

C.5

42LN

D03

065-

EL00

1M

TL791

LR36

637-

118

✝

MTL

796+-

INTI

CIT

EI 9

2A00

1Q

MD

85

6001

XSU

MD

A E

x. ia

132

1Ex

562

Xpe

ndin

gLR

3663

7-14

GYJ

9920

5D

.98C

.307

FTZU

98

Ex 0

006

Ex-9

8.C

.542

C13

161

LND

0306

5-EL

001

MTL

799

APPRO

VA

LS-

for

the

late

st c

ertifi

cation info

rmation v

isit w

ww

.mtl-i

nst

.com

/cer

ts_1

.nsf


June 200413

Reg

ion

Pola

nd

Rom

ani

aU

KU

KU

KU

KU

KU

KU

SAU

SAU

SA(A

utho

rity

)(K

DB)

(ISM

)(B

ASE

EFA

)(B

ASE

EFA

)(B

ASE

EFA

)(B

ASE

EFA

(HSE

[M

])(L

loyd

s)(F

M)

(MSH

A)

(UL)

(N -

Z)

Syst

ems

India

vn)

Stand

ard

PN-8

4/E-

0810

7ST

AS

EN 5

0014

EN 5

0039

BS 4

683:

Pt3

EN 5

0014

EN 5

0014

Lloyd

s Re

giste

r36

10 E

ntity

Cla

ssifi

edU

L913

6877

/4-8

7EN

500

20EN

500

20EN

500

20Ty

pe A

ppro

val

Syste

m, 1

996

Appro

ved

[Ex

ia]

IIC[E

x ia

] IIC

[EEx

ia]

IICEE

x ia

IIC

Ex N

II T

6 in

[E

x ia

] IIC

[EEx

ia]

I -En

viro

nmen

tal

Cla

ss I,

II, I

II,M

inin

g Sy

stem

sC

lass

I, II

, III,

for

♦[E

Ex ia

] IIB

† EE

x ia

IIB

an e

nclo

sure

type

coal

min

ing

cate

gorie

sD

iv.1,

A-G

Div.

1, A

-GM

T20N

ENV1

, EN

V2‡

C-G

Mod

el n

o.Ce

rtific

ate

/file

no.

* T6

for s

witc

hes

or if

the

haza

rdou

s-are

a de

vice

is s

uita

bly

certi

fied

MTL

702+

Nr.9

1.01

0WIS

M N

r.90.

2821

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

86 /

001

02J.I

.1K4

A1.

AX

1320

10E1

2005

8M

TL706+

Nr.9

1.01

1WIS

M N

r.90.

2822

BAS0

1ATE

X720

2EX

01E2

204

Ex89

C23

4786

/ 0

0102

J.I.0

R6A

4.A

XE1

2005

8M

TL707+

Nr.9

1.01

2WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.2P0

A4.

AX

E120

058

MTL

707P+

BAS0

1ATE

X720

3♦Ex

01E2

205†

HSE

(M) 8

5700

0686

/ 0

0102

J.I.0

W2A

5.A

X‡M

TL708+

Nr.9

1.01

2WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.2P0

A4.

AX

E120

058

MTL

710+-a

cN

r.91.

009W

ISM

Nr.9

0.28

20BA

S01A

TEX7

202

EX01

E220

4Ex

8345

3Ex

89C

2346

HSE

(M) 8

5700

0686

/ 0

0102

J.I.1

H8A

1.A

X13

2011

E120

058

MTL

710P+

BAS0

1ATE

X720

2EX

01E2

204

86 /

001

02J.I

.0W

2A5.

AX

MTL

715+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

40E1

2005

8M

TL715P+

BAS0

1ATE

X720

2EX

01E2

204

86 /

001

02J.I

.0W

2A5.

AX

MTL

722+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

13E1

2005

8M

TL722P+

BAS0

1ATE

X720

2EX

01E2

204

86 /

001

02J.I

.0W

2A5.

AX

MTL

728+

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

14E1

2005

8M

TL728-a

cN

r.91.

009W

BAS0

1ATE

X720

2Ex

8345

386

/ 0

0102

J.I.1

H8A

1.A

X13

2014

E120

058

MTL

728P+

BAS0

1ATE

X720

2EX

01E2

204

86 /

001

02J.I

.0W

2A5.

AX

MTL

729P+

BAS0

1ATE

X720

3♦Ex

01E2

205†

86 /

001

02J.I

.0W

2A5.

AX‡

MTL

751ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

15E1

2005

8M

TL755ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

16E1

2005

8M

TL758+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2Ex

8345

3Ex

89C

2346

HSE

(M) 8

5700

0686

/ 0

0102

J.I.2

P0A

4.A

XE1

2005

8M

TL760ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

17E1

2005

8M

TL761ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

41E1

2005

8M

TL761Pa

cBA

S01A

TEX7

202

EX01

E220

486

/ 0

0102

J.I.5

W0A

3.A

XM

TL764+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

42E1

2005

8M

TL764ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

43E1

2005

8M

TL765ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

20E1

2005

8M

TL766ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

44E1

2005

8M

TL766Pa

cBA

S01A

TEX7

202

EX01

E220

486

/ 0

0102

J.I.5

W0A

3.A

XM

TL767+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

23E1

2005

8M

TL768+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

22E1

2005

8M

TL772ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

24E1

2005

8M

TL778ac

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

25E1

2005

8M

TL779+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

26E1

2005

8M

TL786+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

27E1

2005

8M

TL787+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

28E1

2005

8M

TL787S+

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2Ex

8345

3Ex

89C

2346

HSE

(M) 8

5700

0686

/ 0

0102

J.I.2

P0A

4.A

XE1

2005

8M

TL787SP

+BA

S01A

TEX7

202

EX01

E220

4J.I

.5W

0A3.

AX

MTL

788+

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

29E1

2005

8M

TL788R+-

Nr.9

1.00

9WBA

S01A

TEX7

202

Ex89

C23

4686

/ 0

0102

J.I.1

H8A

1.A

X13

2030

E120

058

MTL

791

BAS0

1ATE

X720

2J.I

.4X0

A4.

AX

✝

MTL

796+-

Nr.9

1.00

9WIS

M N

r.90.

2820

BAS0

1ATE

X720

2EX

01E2

204

Ex83

453

Ex89

C23

46H

SE (M

) 857

0006

86 /

001

02J.I

.1H

8A1.

AX

1320

31E1

2005

8M

TL799

APPRO

VA

LS(c

ontinued

)- f

or

the

late

st c

ertifi

cation info

rmation v

isit w

ww

.mtl-i

nst

.com

/cer

ts_1

.nsf


June 2004

MK05, MK12, MK20 Assembly diagramNote: MK5 has no earth rail/but does have terminal clamps on earth rail mounting brackets

Taggingstrip seal

Tagging stripwith label

Earth railclamp

Terminal clamps

Terminalclamps

Earth busbar

Earthrail

Earth railmountingbrackets

Insulatingmountingblock

MTL700 SERIESACCESSORIES

DO-IT-YOURSELF MOUNTING ARRANGEMENTBarriers are carried on lightweight plated busbar, which can bemounted on ‘top hat’ or G-profile rail or any flat surface with thebusbar insulated for separate earthing. It is recommended that twinearth cables should be used for maximum security and easy testing.Each barrier is clamped to the busbar and thereby earthed in a singleoperation, making it virtually impossible to forget the earthconnection, so easily left untightened or untested if there are scores ofindividual earth wires. Robust soft-plated double fixing studs on thetop of each barrier ensure permanent ‘gas-tight’ joints, which areimmune to vibration and corrosion yet allow barriers to be installed,inspected and removed easily.

The accessories system also provides a convenient row of terminals forterminating earth returns and cable screens, which remains in placeto keep these safely earthed should any barrier be extracted: adummy barrier is available as an alternative for the same purpose.With similar attention to users’ needs, a unique lift-up tagging facilityprovides permanent identification of circuits and barrier types to guideinstallation, fault-finding and inspection, and to ensure correctreplacement of any barrier for long-term safety.

ACCESSORIESEBB7 earth busbar, nickel-plated brass and ready drilled in onemetre lengths.IMB7 & SMB7 insulating mounting blocks are a convenientmethod of supporting the busbar. They are supplied complete withfixing screws and are ready for mounting on any flat surface. IMB7will also mount on top hat or G-profile DIN-rail. T-section DIN-railTHR2 is available in 1 metre lengths.TAG7 tagging strips clip onto the mounting blocks to positivelyidentify each location and provide space for the user to note detailsof barrier type, loop identification etc. Access to barrier mountingstuds is not impaired; just unclip one edge and swing the strip ‘open’or, if the optional plastic seal (TGS7) has not been fitted, unclip bothedges and lift it right off. TGL7 replacement labels for the taggingstrips are also available.ERL7 earth rail is a nickel-plated 3 x 10mm rail that attaches to themounting blocks via an ERB7 earth rail mounting bracket. It willaccommodate up to 2.5 ETM7 earth terminals per barrier location forterminating earth returns and cable screens from the hazardous area.ERB7 earth rail mounting bracket mounts directly over eithertype of mounting block; for a rigid earth rail an ERB7 on eachmounting block is recommended. One end carries a bolt-down fittingfor the rail – enabling easy removal for adding extra ETM7 terminals– the other end carries a 16mm2 terminal. When installed these16mm2 terminals provide connections for the high-integrity IS earth,for linking between sections of busbar, and for a common earth returnfrom the safe area.Other accessories available are the TQS7 torque spanner forsafe tightening of the vibration-proof self-locking nuts on the barrierearthing studs; SMC7 surface mounting clips for mounting a singlebarrier on a flat surface; and ISL3 or ISL7 self adhesive ‘Take Care’intrinsic safety warning labels.

MOUNTING KITSMounting kits provide all the necessary parts for installing up to aspecific number of MTL700 or MTL700P Series barriers. The kitsavailable are the MK02 (2 barriers), MK05 (5 barriers), MK12 (12barriers), and MK20 (20 barriers). Each kit provides facilities formounting and earthing the barriers, connecting the IS earth cable,terminating cable screens and noting tagging information (exceptthe MK02 kit which does not provide tagging facilities). InstructionSheet INS701 includes full assembly instructions.

DIN rail

◆ Mounting kits for up to 20 barriers

◆ Busbar, earth terminals and insulating mountingblocks for separate connection to IS earth

◆ Earth terminal rail for cable screens and earthreturns

◆ Integral tagging system to display barrier loopdata

End elevations with recommended spacing. Shaded portions show areas swept by barrier during installation and removal.

MK02 Assembly diagram

1076

45

Terminal clamp

Insulating block

Mounting bracket

85


June 2004

14.5

95

4.2

DIMENSIONS (mm)

TGS7 tagging strip seal –sold in bags of 10

SMC7 surface mounting clip – sold in bags of 10. Twoclips needed per barrier

ETM7 earth terminal – sold inbags of 50. For cable 4mm2. Also available as ‘ZB4’ from Klippon Electricals Ltd.

TQS7 torque spanner – set to 2.3Nm torque. Complete with 7mm A/F socket.

ISL3 or ISL7 ‘Take Care’ intrinsic safety label –ISL3 adhesive back, metal *ISL7 adhesive front, plastic

TGL7 tagging strip label only – packs of 10 x 0.5 metrelengths

ERL7 earth rail – sold in 1 metre lengths. Unplated rail available as ‘SSch 10 x 3mm brass busbar', from Klippon Electricals Ltd

IMB7 insulating mounting block mounts on a flat surface ortop hat rail (to EN 50 022 – 35 x 7.5; BS 5584; 35 x 27 x 7.3DIN 46277) or G-profile rail (to EN 50 035 – G32; BS 5825; 32DIN 46277). Recommended maximum number of barriers betweenblocks is 25.

SMB7 insulating mounting block mounts on a flat surface andprovides minimum overall installation height. Recommendedmaximum number of barriers between blocks is 25.

126

70

85 21.1

M4 x 20fixing screw

M4

97

70

85 14.1

M4

M4 x 25fixing screw

TAG7 tagging strip with label and 6 ‘clic’ rivets – 1 metre lengths

64

ERB7 earth rail mounting bracket – with earth rail bolt-downfitting and terminal for cable 16mm2

EBB7 earth busbar – 1 metre lengths. Mounts up to 64 barriers.

3

10

58 72 10

11.5 253

14.5ø4.4 3

11.5 25

25

175

140 (65*)

100 (40*)

DRK700 adaptor kit allows MTL700 Series barriers tobe mounted directly on DIN-Rail.


June 2004

The MT Series of enclosures provides a simple, effective meansof mounting and protecting MTL700 Series barriers in safe areas orlow-risk hazardous areas. Three lightweight polycarbonate enclosureswith see-through lids accommodate up to 2, 5 or 12 barriers in a safearea, and a Type N approved steel enclosure holds up to 20 barriersin Zone 2. All the enclosures are supplied ready fitted with a nickel-plated brass busbar mount, so barriers can be installed and wired upimmediately without special tools; the 20-barrier enclosure is alsoprovided with cable trunking to segregate the safe- and hazardous-area wiring neatly. The polycarbonate enclosures are impact resistant,flame retardant, and dustproof to IEC529:IP65, and the steelenclosure is dustproof and waterproof to IEC529:IP67.

Tagging. All the enclosures, except the 2-barrier model, are fittedwith removable tagging strips for positive identification of barrier typeand loop number. The tagging strips are mounted above the barriersand can be hinged in either direction to give access to the barriers.Each carries a label, protected by a slide-in transparent plastic cover,upon which the user can write his barrier and loop details. Inaddition, all the enclosures carry a ‘Take Care’ intrinsic safetywarning label on the lid.

Earthing. All the enclosures except the 2-barrier model are fittedwith three large terminals: two for making a high-integrity connectionto the essential IS earth, and one to accept a cable from the ‘earthy’end of a common power supply, or system 0V rail, in the safe area.

In addition each enclosure is provided with one or two rows of smallerterminals for terminating and earthing hazardous-area earth returnsand cable screens. Except in the 2 and 5 barrier models, theseterminals are mounted on earth rail running conveniently parallel tothe busbar and attached to it by brackets. Further terminals can beadded easily by the user if needed, up to 2.5 terminals per barrierspace.

The entire earth system is insulated from any nearby metal, and theearth cable itself should also be insulated, mechanically protected andidentified so as to eliminate all danger of invasion by fault currentsfrom high-power electrical equipment.

MTL700 SERIESENCLOSURESFor marshalling barriers in safeareas or Zone 2

◆ Three polycarbonate enclosures hold up to 12barriers in safe area

◆ Type N approved steel enclosure holds up to20 barriers in Zone 2

Although it is not mandatory, MTL recommends using two cablesconnected to the busbar via two terminals on separate brackets, sothat the resistance of the whole earth loop can be checkedperiodically without breaking the connection to earth. Severalenclosures can be included in the loop if necessary.

Mounting of the three larger polycarbonate enclosures is normallyby rear-fixing screws or screw-on plastic fixing lugs, using the pre-tapped brass bushes moulded into the enclosure’s base. The lugs canbe set horizontally, vertically, or at 45°, and are supplied as standardwith each enclosure together with the necessary screws. Alternatively,if the enclosures are to be front mounted and close packed, a plasticmembrane covering the inside of each tapped hole can be knockedout, allowing the passage of other screws. Plastic plugs are suppliedto seal the knockout apertures and preserve the IP65 integrity of theenclosures if this method of fixing is used. The 2- and 5-barrierenclosures are mounted by horizontal or vertical plastic fixing lugsheld on by screws self tapped into blind holes in the base, or by otherscrews passed through holes in the base moulding walls outside thelid gasket. The steel enclosure for 20 barriers has permanent fixinglugs, and provides the additional facility that its lid can be padlockedto prevent unauthorised interference.

Glanding. All the enclosures except the 2- and 5-barrier modelshave detachable top and bottom gland plates for convenient drillingby the user, while the 2- and 5-barrier enclosures each have four20mm holes pre-drilled through the top and bottom sides of the base.All cables entering or leaving any enclosure must be suitably glandedto preserve its IP integrity.

Note: to ensure safe carriage, MTL despatches the enclosures with barriers notmounted.


June 2004

No No Yes

Plastic lugs screwed to base, pluggedknockout holes, or rear-fixing screws

4 lugs + attaching screws4 plugs

Adhesive back, on lid

Tagging strip(s) with label(s) and seal(s)

Adhesive front, inside lid

Safe area

4 captive screws

2 5 12 20MT5MT2SPECIFICATION

Maximum barrier capacityConstructionFinishLid fixing

Protection: dust-tight/waterproofGland fixing

Permitted locationCertification

Mounting (see illustration)

Mounting Kit provided

Tagging facility providedCable trunking provided?'Take care ' IS label providedEarth terminals provided:Large (


June 2004

EnclosuresMT2 Enclosure for 2 barriersMT5 Enclosure for 5 barriersMT12 Enclosure for 12 barriersMT20N Type ‘N’ enclosure for 20 barriers

LiteratureINM700 MTL700 Series instruction manualAN9007 MTL700 Series application noteCD70... MTL700 Series customer drawings

Shunt-diode safety barriersEnter barrier product code plus polarity, e.g. MTL728+

Barrier accessoriesEBB7 Earth busbar, 1m lengthERL7 Earth rail, plated, 1m lengthETM7 Earth terminal, bag of 50ERB7 Earth rail mounting bracketTHR2 DIN rail 35 x 7.5mm, 1m lengthIMB7 Insulating mounting blockSMB7 Short insulating mounting blockSMC7 Surface-mounting clip, pack of 10

TAG7 Tagging strip + label, 1m lengthTGL7 Tagging strip label, ten 0.5m lengthsTGS7 Tagging strip seal, bag of 10

TQS7 Torque spannerISL3 'Take care' intrinsic safety label, adhesive back,

metalISL7 ‘Take care’ intrinsic safety label, adhesive front,

plasticDRK700 DIN Rail mounting kit

MK2 Mounting kit for 2 barriersMK5 Mounting kit for 5 barriersMK12 Mounting kit for 12 barriersMK20 Mounting kit for 20 barriers

MTL700 SERIES ORDERING INFORMATION

TO ORDER,State the part number (bold) and any part description shown below.

mtl700 series...710 10 50 200 √√√ 6v dc & 4v ac systems 85 6.0 6.9 c 50 710p 10 33 300 √√...

Documents