{"id":"transformer-pad-mounted","version":"0.4.0","classification":{"uniformat":"D5010"},"names":["Transformer, pad-mounted liquid-filled"],"aliases":["pad mount transformer"],"service_life":{"median_years":31,"range_years":[30,32],"range_basis":"source_spread"},"pm_tasks":[{"task":"Inspect solid insulation for discoloration","frequency":"P1Y","reference":"TM 5-692-1 Maintenance of Mechanical and Electrical Equipment at Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities: Recommended Maintenance Practices","url":"https://www.wbdg.org/FFC/ARMYCOE/COETM/tm_5_692_1.pdf","page":165,"checklist":"Table 20-5 Transformers (primary distribution)"},{"task":"Oil dielectric strength test","frequency":"P1Y","reference":"TM 5-692-1 Maintenance of Mechanical and Electrical Equipment at Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities: Recommended Maintenance Practices","url":"https://www.wbdg.org/FFC/ARMYCOE/COETM/tm_5_692_1.pdf","page":165,"checklist":"Table 20-5 Transformers (primary distribution)"},{"task":"Oil acidity test","frequency":"P1Y","reference":"TM 5-692-1 Maintenance of Mechanical and Electrical Equipment at Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities: Recommended Maintenance Practices","url":"https://www.wbdg.org/FFC/ARMYCOE/COETM/tm_5_692_1.pdf","page":165,"checklist":"Table 20-5 Transformers (primary distribution)"},{"task":"Oil color test","frequency":"P1Y","reference":"TM 5-692-1 Maintenance of Mechanical and Electrical Equipment at Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities: Recommended Maintenance Practices","url":"https://www.wbdg.org/FFC/ARMYCOE/COETM/tm_5_692_1.pdf","page":165,"checklist":"Table 20-5 Transformers (primary distribution)"},{"task":"Verify transformer alarms","frequency":"P1Y","reference":"TM 5-692-1 Maintenance of Mechanical and Electrical Equipment at Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities: Recommended Maintenance Practices","url":"https://www.wbdg.org/FFC/ARMYCOE/COETM/tm_5_692_1.pdf","page":165,"checklist":"Table 20-5 Transformers (primary distribution)"},{"task":"Inspect transformer enclosure for rust and oil leaks","frequency":"P2Y","reference":"UFM 3-550-07 Operation and Maintenance (O&M): Exterior Power Distribution Systems","url":"https://www.wbdg.org/FFC/DOD/UFC/ufm_3_550_07_2026.pdf","page":89,"checklist":"5-2.2.4.1 Time-Base Preventative Maintenance (transformers)"},{"task":"Check and record transformer gauges","frequency":"P2Y","reference":"UFM 3-550-07 Operation and Maintenance (O&M): Exterior Power Distribution Systems","url":"https://www.wbdg.org/FFC/DOD/UFC/ufm_3_550_07_2026.pdf","page":89,"checklist":"5-2.2.4.1 Time-Base Preventative Maintenance (transformers)"},{"task":"Take oil sample for dissolved gas analysis (DGA)","frequency":"P2Y","reference":"UFM 3-550-07 Operation and Maintenance (O&M): Exterior Power Distribution Systems","url":"https://www.wbdg.org/FFC/DOD/UFC/ufm_3_550_07_2026.pdf","page":90,"checklist":"5-2.2.4.2 Time-Based Predictive Maintenance (transformers)"},{"task":"Infrared scan for hot spots under load","frequency":"P2Y","reference":"UFM 3-550-07 Operation and Maintenance (O&M): Exterior Power Distribution Systems","url":"https://www.wbdg.org/FFC/DOD/UFC/ufm_3_550_07_2026.pdf","page":90,"checklist":"5-2.2.4.2 Time-Based Predictive Maintenance (transformers)"}],"basis":[{"type":"public_document","life_type":"planning","title":"CNA e-Tool Estimated Useful Life Table","by":"U.S. Department of Housing and Urban Development","url":"https://www.hud.gov/sites/documents/eul_for_cna_e_tool.pdf","page":3,"code":"HUD CNA 3.2.8.2.3","label":"Transformer","years":30,"note":"Same life for family and elderly properties. US multifamily housing. HUD's row is a site electric utility transformer."},{"type":"public_document","life_type":"planning","title":"Energy Conservation Program: Energy Conservation Standards for Distribution Transformers (final rule), 89 FR 29834, April 22, 2024","by":"U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy","url":"https://www.govinfo.gov/content/pkg/FR-2024-04-22/pdf/2024-07480.pdf","page":113,"code":"IV.F.8","label":"Transformer Service Lifetime: \"a distribution of lifetimes, with an estimated average of 32 years and a maximum of 60 years\"","years":32,"note":"Printed page 29946. Covers all distribution transformers, including low-voltage dry-type (building dry-type) and medium-voltage liquid-immersed (pad-mounted). Mean of a distribution; the maximum is 60 years. Same value also stated on p.5 (printed 29838) and in Table IV summary on p.101 (printed 29934)."}],"confidence":{"grade":"C","sample_size":null},"open_questions":["Every source here is a published planning, design or accounting life. None is observed replacement data.","Some maintenance intervals come from TM 5-692-1, an Army manual for mission-critical (C4ISR) facilities; they may be tighter than typical commercial practice."],"contributors":["unfinished.one editors"],"last_reviewed":"2026-10-22","canonical_url":"https://unfinished.one/c/transformer-pad-mounted","versioned_url":"https://unfinished.one/c/transformer-pad-mounted/v/0.4.0","licence":"CC-BY-4.0","citation":"unfinished.one (2026). Transformer, pad-mounted liquid-filled, v0.4.0. https://unfinished.one/c/transformer-pad-mounted/v/0.4.0"}