Certified Eaton MTL TP48-3-I-NDI 20 mm ISO Surge Protector for Three-Wire Field Transmitters in Hazardous-Area Installations

Eaton MTL TP48-3-I-NDI is a compact field-mount surge protection device intended for three-wire transmitters and instruments exposed to lightning-induced or switching transients. Rather than placing protection only at the control-room end, the TP48 can be installed close to the field instrument so damaging surge energy is diverted before it reaches sensitive transmitter electronics. The stainless-steel construction, sealed IP66 design, and certified hazardous-location options make the model suitable for demanding outdoor and process-plant environments.

Reading the TP48-3-I-NDI Order Code

Every suffix identifies a physical or certification detail. “TP48” defines the transmitter protector family. The “3” identifies the three-wire version. “I” specifies a 20 mm ISO thread, while the certified configuration is intended for use where the relevant hazardous-area approval and installation conditions are satisfied. The flying-lead arrangement provides positive, negative, signal, and earth connections. Because other TP48 versions use different threads, wire counts, or approval combinations, the complete code TP48-3-I-NDI should remain on purchase orders and maintenance records.

Protection Figures for Engineering Review

• Nominal voltage: 35 V
• Maximum continuous voltage: 58 V
• Nominal discharge current: 10 kA, 8/20 microseconds
• Lightning impulse current: 2.5 kA, 10/350 microseconds
• Voltage protection: below 76 V at 1 kV/microsecond
• Voltage protection at nominal discharge: 90 V
• Leakage current: below 1 microampere
• Signal bandwidth reference: 1 MHz

These values help engineers assess the protective level, but they do not replace a complete surge-protection design. Cable routing, bonding, earth impedance, shield termination, surge exposure, and protection at the control-system end all influence the result. Coordination with upstream and downstream protective devices should be reviewed for the actual installation.

Installation Details That Matter

The TP48-3-I-NDI uses a 20 mm ISO threaded mounting arrangement and four 18 AWG flying leads. The earth conductor must be connected through a short, low-impedance path; a long or coiled earth lead can reduce high-frequency surge performance. Check that the enclosure entry accepts the specified thread and that the final seal maintains the required ingress protection. The 316 stainless-steel body measures approximately 75 x 27 x 23 mm and weighs about 175 g, making it practical for transmitter housings and junction boxes where space is limited.

Environmental and Application Considerations

The published operating range is -40 to +60 degrees Celsius, with storage from -40 to +85 degrees Celsius. Typical uses include pressure, flow, level, and temperature transmitters in oil and gas facilities, chemical plants, water and wastewater sites, power generation, mining, marine installations, and exposed utility systems. For hazardous or classified locations, the site classification, gas group, temperature limits, and current certificate must be checked by the responsible engineer before installation.

What to Send With an Inquiry

To confirm the correct unit, provide the full MTL TP48-3-I-NDI model, quantity, transmitter type, enclosure thread, operating voltage, destination country, and delivery deadline. A clear photo of the existing protector and transmitter entry is helpful for retrofit work. Sunup-MTL can support availability checks, quotation, export packing, documentation, and international delivery for shutdown preparation, field-instrument upgrades, and long-term spare-part planning.

Other MTL product families often requested for the same projects: TP48 series surge protectors, MTL4500 isolators, MTL5500 isolators, MTL7700 barriers, MTL power supplies, interface modules, backplanes, and fieldbus protection products. Match the full order code rather than selecting only by family name.