MTL Instruments TP24/7 Specifications

Technical data

MTL surge protection

MTL TP24/7 range

Safeguards 4-wire process
transmitters against induced
surges and transients from
field cabling

• Specifically designed for multivariable

Transmitters and Level Transmitters

• Four wires protected, one pair at 12V to 24V

and one pair at 7V (e.g. RS485)

• Easy and direct mounting — simply screws

into spare conduit entry

• Intrinsically safe and flameproof to

CENELEC standards

• FM for US and Canada and ATEX approved

March 2016
EPS 901-102 Rev L

The TP24/7 surge protection device is a unique unit providing a level
of protection for field-mounted transmitters that is far in excess of the
optional transient protection facilities available from the transmitter
manufacturers - without involving any additional wiring, conduit
modifications or other expensive extras.

The TP24/7 protection network consists of high-power, solid-state
electronics and a gas-filled discharge tube capable of diverting 10kA
impulses. The whole unit is encased in a 316 stainless steel housing,
threaded for the common conduit entries used on process transmitters.
Versions are available for 1/2” NPT, 20mm ISO, and G1/2” (BSP 1/2
inch) threaded entries.

Installation is simple and can easily be carried out retrospectively to
existing installations. The TP24/7 is screwed into any unused conduit
entry on the transmitter case and flying leads are connected to the
terminal block (+ve, -ve), RS485 terminals and the internal earth stud.
They operate without in any way affecting normal operation - passing ac
or dc signals without attenuation while diverting surge currents safely to
earth and clamping output voltages to specific levels.

Measurement Technology Limited,
Great Marlings, Butterfield, Luton
Beds, LU2 8DL, UK.
Tel: + 44 (0)1582 723633 Fax: + 44 (0)1582 422283
E-mail: [e-mail]
www.mtl-inst.com

© 2016 MTL
All Rights Reserved
Publication No. EPS 901-102 Rev L 030316
March 2016

1

The all-important earthing connection is made to the local casing of
the transmitter with no separate earth connection or ground stake at
the transmitter being needed. In operation, the TP24/7 makes sure that
the transmitter electronics are never exposed to damaging transients
between lines or between lines and casing/earth. Any surge current
appearing as a series-mode or common-mode transient is converted
into a common-mode voltage - whereupon the transmitter electronics
are temporarily raised to some higher voltage level before ‘floating’
down automatically (and without damage) to resume normal operation.

For hazardous area use, approvals for both intrinsically safe and
flameproof (explosion-proof) operation are available, in all gas groups
and apparatus temperature classification up to T4. Where transmitters
are used in circuits suitable for Div 2/Zone 2 installations, the TP24/7
can be added without adversely affecting the level of safety.

MTL TP24/7 range

March 2016

APPROVALS

Country (Authority) Standard No. Certificate/File Approved for Product

EC (BASEEFA) EN 60079-0:2012+A11:2013

EN 60079-11:2012

BASEEFA04ATEX0251X

II 1G Ex ia IIC T4/T5/T6 Ga
II 1D Ex ia IIIC T135°C/ T100°C/ T85°C Da

TP32-N-NDI
TP32-I-NDI
TP32-G-NDI

EC (BASEEFA) EN 60079-0:2012+A11:2013

ATEX Directive 94/9/EC EN 60079-0:2012

USA (FM)

Canada (FM) C22.2 No 213 (1987), C22.2 No 142 (1987),

Global IEC 60079-0:2011, IEC 60079-11:2011 IECEx BAS 07.0045X Ex ia IIC T4/T5/T6 Ga

EN 60079-1:2015

EN 60079-15:2010

Class 3600 (1998), Class 3610 (2010),
Class 3611 (1999), Class 3615 (1989),
Class 3810 (1989) Incl Suppl #1 (1995)

ANSI/NEMA 250 (1991)
ISA-S12.0.01 (1998)
ANSI/ISA 60079-0 (2009)
ANSI/ISA 60079-11 (2009)

C22.2 No 94 (1991), C22.2 No 157 (1992),
C22.2 No 30 (1986)

ANSI/NEMA 250 (1991)
CAN/CSA-E79-0 (2002)
CAN/CSA-E79-11 (2002)

BASEEFA04ATEX0053X

TML01ATEX0048

II 2G Ex db IIC T6 Gb (T

II 3 G Ex nA IIC T6 (-40°C<T
II 3 G Ex nA IIC T5 (-40°C<T

3011208 Intrinsically Safe:

3025374 Intrinsically Safe:

I, II, III/1/A-G, I/0/IIC
Explosion-proof: I/1/A-D
Non-incendive: I/2/A-D, I/2/IIC
Dust ignition proof: II,III/1/EFG
Special protection: II/2/FG

I, II, II/1/A-G, I/O/IIC
Explosion-proof: I/1/A-D
Non-incendive: I/2/A-D, I/2/IIC
Dust ignition proof: II, III/1/EFG
Special protection: II/2/FG

Ex ia IIIC T135°C/ T100°C/T85°C Da

= -40°C TO +70°C)

amb

<+60°C)

amb

<+85°C)

amb

ORDERING INFORMATION

Model TP24/7

Nominal voltage U

Rated voltage (MCOV ) U

Nominal current I

Nominal discharge current (8/20µs) i

Max discharge current (8 /20µs) I

Lightning impulse current (10/350µs) I

Residual voltage @ i

sn

Voltage protection level @ 1kV/µs U

Bandwidth f

n

c

n

sn

max

imp
U

p

p

G

Capacitance C 100pF

Series resistance R n/a

Operating temperature range -40°C to +60°C

Category tested A2, B2, C1, C2, C3, D1

Overstressed fault mode in=3kA 12k A

Impulse durability (8/20µs) 10k A

Degree of protection IP66

AC durability 1A

Service conditions 80kPa - 160kPa 5% - 95% RH

24V/7V

34V/7V

n/a

3kA

10kA

2.5kA

43V/19V

<36V/<12V

1MHz

, 5T

rms

TP32-N-NDI
TP32-I-NDI
TP32-G-NDI

TP32-N
TP32-I
TP32-G

TP32-N-NDI
TP32-I-NDI
TP32-G-NDI

TP32 All

TP32-X-NDI
TP32-T-X-NDI

2

MTL TP24/7 range

March 2016

SPECIFICATION

All figures typical at 25°C (77°F) unless
otherwise stated

Maximum surge current

10kA peak (8/20µs waveform)

Leakage current

Less than 10 µA at ma x. working voltage

Working voltage

12V to 24V dc power

Bandwidth

1MHz

Resistance

No resistance introduced into loop

Ambient temperature limits

-4 0°C to + 60°C
(-40°F to +140°F) (working)

-4 0°C to + 85°C
(-40°F to +185°F) (storage)

Humidity

5% to 95% RH (non -condensing)

Electrical connections

4 flying leads
Wire size 32 /0.2 (1.0mm
Lead length 250mm (9.85”) minimum

Casing

316 stainless steel suitable for harsh
environments

Threads

TP24 /7-N: 1/2” NPT
TP24 /7-I: 20mm ISO (M20 x 1.5)
TP24 /7-G: G 1/2” (BSP 1/2 inch)

Weight

175g (6.2oz.)

Dimensions

See figure 1

EMC compliance

To Generic Immunity Standards
BS EN 61326 -1:2013 for industrial
environments

Hazardous Area

Ex ia IIC T4, Ceq=O, Leq=0; the unit can
be connected without further certification
into any intrinsically safe loop with open
circuit voltage <6 0V and input power
<1.2 W.

Ex d IIC T4; the unit is apparatus
approved to flameproof (explosion­proof) standards, and can be fitted into a
similarly approved housing.

Electrical Safety

To BS EN 61643 -21:20 01 for surge
protection devices

2

, 18AW G)

SIL INFORMATION

Failure rates according to IEC 61508

l

SD

TP24/7 0 FIT 43 FIT 11 FIT 6 FIT

The user of the TP range can utilize these failure rates in a probabilistic model of a safety
instrumented function (SIF) to determine the suitability in part for safety instrumented system
(SIS) usage in a particular safety integrity level. A full table of failure rates in presented in the
EXIDA report (section 4.4) along with all assumptions.

*The Residual Effect failures are included in the Safe Undetected failure categor y according to
IEC 61508. Note that these failures alone will not affect system reliability or safety and should
therefore not be included in spurious trip calculations.

Safe Failure Fraction needs to be calculated on (sub)system level.

A complete copy of the EXIDA report can be downloaded at www.mtl-inst.com.

Figure 2 Connection detail
for a typical process
transmitter

l

SU

l

DD

l

DU

Figure 1 Dimensions

TO ORDER SPECIFY -

TP24/7-N-NDI Certified process transmitter surge protection device - 1/2” NPT thread

TP24/7-I-NDI Certified process transmitter surge protection device - 20mm ISO thread

TP24/7-G-NDI Certified process transmitter surge protection device - G 1/2” (BSP 1/2”)

TP24/7-N Non-certified process transmitter surge protection device - 1/2” NPT thread

TP24/7-I Non-certified process transmitter surge protection device - 20mm ISO thread

Measurement Technology Limited,
Great Marlings, Butterfield, Luton
Beds, LU2 8DL, UK.
Tel: + 44 (0)1582 723633 Fax: + 44 (0)1582 422283
E-mail: [e-mail]
www.mtl-inst.com

© 2016 MTL
All Rights Reserved
Publication No. EPS 901-102 Rev L 030316
March 2016

EUROPE (EMEA):

[phone]
[e-mail]

THE AMERICAS:

[phone]
[e-mail]

ASIA-PACIFIC:

[phone]
[e-mail]

The given d ata is only intended as a p roduct
descrip tion and sho uld not be reg arded as a leg al
warrant y of properties or gu arantee. In th e interest
of further technical developments, we reserve the
right to make de sign changes.

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