Starting at $442.00
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  • Working voltage: 48V dc and 32V dc maximum
  • Maximum surge current: 20kA peak current (8/20μs waveform)
  • Electrical connection: 3 flying leads (line 1, line 2 & earth)
  • Easy and direct mounting – screws into spare conduit entry on the transmitter
  • Intrinsically safe and flameproof to CENELEC standards
  • Low impedance series connection avoids signal degradation of the loop
  • ATEX and Factory Mutual (FM) approved
  • 10 year product warranty


The MTL TP-Pipe series surge protector safeguards field-mounted process transmitters where it matters, right at the unit. The TP-Pipe screws directly into the conduit entry, with no additional modification. After this simple installation, it provides high-level protection against surges and transients while normal operation remains unaffected.

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

Installation of the MTL TP-Pipe is very simple and can easily be carried out retrospectively to existing installations. The TP-Pipe screws directly into the conduit entry on the transmitter case and flying leads are connected to the terminal block and the internal earth stud. Field wiring is connected to a three position socket and then connected to the provided header. 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.

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 TP-Pipe 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 TP-P can be added without adversely affecting the level of safety.

For Fieldbus applications, use the TP-P-32 which meets the requirements of IEC61158-2:2004 and ANSI/ISA-50.02-2 1992 for 31.25kbit/s systems as used by Foundation™ fieldbus, PROFIBUS-PA and WorldFIP.