Sampling Guide

Obtaining a sample of your transformer's dielectric fluid is an important step in understanding and managing the health and reliability of these valuable assets.  However, you cannot simply "crack the valve" and fill any container. 

SDM Sampling


Obtaining a representative sample begins with understanding a few key points:

Safety - What PPE is required to safely sample this transformer?

Equipment - What tools will I need to sample this transformer?

Procedures - What are the proper steps to obtaining the sample?

Containers - What are the industry approved containers?

Storage & Shipping - How do I safely store, pack and ship the samples to my laboratory and ensure a representative sample arrives intact?

Taking care to follow industry standards, such as ASTM D923-15 Standard Practices for Sampling Electrical Insulating Liquids, and guidelines set by industry leaders can help to ensure you answer the questions listed above.  SDMyers are experts in the transformer industry and over the past half-century have developed guidelines and training courses to ensure asset safety & reliability through proper sampling techniques.  

Click below to download: Sampling Guide for Transformers reference sheet.


Infraspection Institute 

IR Inspection of Liquid-filled Transformers

A thorough infrared inspection of an electrical transformer can point our symptoms of loose connections as well as other possible problems.  When performing an infrared inspection of a liquid-filled transformer, be certain to include not only the primary and secondary connections but also the following items as well:

    • Inspect neutral and ground connections for hot spots
    • For transformers with separate tanks for each phase, compare phase tanks to each other.  Transformers with balanced loads should exhibit similar temperatures between tanks.
    • Qualitatively inspect radiator sections.  Radiator tubes should be uniform in temperature and, in most cases, should operate above ambient temperature.

IR Inspection of Liquid-filled Transformers

    • Compare transformer operating temperature to nameplate rating.  For long tern service, transformers should not operate above their maximum rated temperature.
    • Compare tap changer tank to main body of transformer.  For properly operating tap changers, tap changer tank should not appear warmer than main body of transformer. 

In conjunction with the infrared inspection, cooling fans and/or pumps should be checked for proper settings and operation.  Finally, transformers require proper air circulation for cooling.  to help ensure maximum airflow, transformer radiators should be unobstructed and free from dirt and debris.

Infrared inspection of power distribution systems is one of the many topics covered in all Infraspection Institiute Level I training courses.  For information on course locations and dates or Distance Learning Courses, visit Infraspection Institute online or call 609-239-4788.


Click below to download: IR Inspection of Liquid-filled Transformers.