A guide to drying out and salvaging flood damaged equipment: Part 1

18 March 2019


The destructive power of water continually shapes our world, from changing natural landscapes to flooding our communities.  Whether the flooding is caused by a major storm, like a hurricane, melting snow and ice after a nor’easter strikes, or a pipe bursting, its aftermath can have devastating results.

Water and electricity don’t mix, but for electrical equipment that gets caught in its crosshairs, there is a possibility that it can be salvaged if it is dried properly. 


Register for our flood recovery webinar


Drying out windings

There are several procedures that need to be adhered to when attempting to dry out different classes of electrical equipment. But no matter what class of equipment you are trying to dry out, the regulations of temperatures used on windings should be carefully controlled. 

The maximum drying temperature on windings should not exceed 194°F. This prevents rapid thermal deterioration of the equipment’s insulation, as well as stops damage from high vapor pressures should steam be produced during the drying process.

Different drying methods

There are several methods that can be used to dry windings; however the best is placing them in an oven with suitable temperature control and proper air circulation.  Windings can also be dried out by setting up banks of infrared lamps to help them dry out.  Steam coils or electric resistance type units can also be used as a heat and drying source as long as a housing is constructed around the water damaged equipment with openings in the structure so that air can circulate. Blowers can be used to help increase movement.

Vacuum drying is another method that can be performed; however, certain precautions need to be taken and should only be performed by experienced personnel. 

Use an insulation tester before applying current

Another frequently used method is to circulate low-voltage current through the windings.  This method cannot be performed until the insulation resistance reaches at least 100 kohm.

It is important to have an insulation tester to perform this check before application of current.  You must look for a tester that has kilohm ranges.  Measurement during the test is only performed at 5 V, so it will not damage even the worst insulation. Welding sets can provide current.  The flow of current should only be a fraction of nameplate amperes and a careful check must be maintained on maximum temperatures on the insulated parts.

Keep drying the equipment

When insulation resistance values are used as an indicator of the suitability of windings for service or for application of test potential, the drying must continue for a bit of time to ensure that the values are reliable. 

The resistance curve will often take one or more sharp dips before leveling off or continuing to increase in a positive direction. This is because moisture is working its way out of the windings.

Once the machine appears to be completely dried out, further work is required to remove any remaining dust.  This can be accomplished by using dry compressed air at a pressure not exceeding 40 psi. 

Salvaging other equipment

Guidance on how to dry out specific classes of electrical equipment, including rotating electrical machines, switchboards and electrical controls, transformers, cables and wiring, as well as electrical tools after being damaged by flood waters will follow in part 2 on, as well as the full guide in NETA World.