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D.6
Tubing Material
Stainless steel is the only material that should be used. The use of any other
tubing material will cause reliability issues or inaccurate results and void the
warranty of the product. GE does not support the use of copper tubing for the
installation of its transformer analysis products. The reasons for this are
outlined below.
D.6.1
Flow rate
The solid seamless stainless-steel tubing that GE specifies is 316 Stainless Steel, 1/4 in.
OD with a 0.035 in. thick wall. Most 1/4 in. copper tubing has a greater wall thickness
which reduces the flow rate rendering it too fragile to place in the field. Bends in
standard soft copper tubing crush and deform more easily, which can reduce the flow
rate than would otherwise be the case with properly bent stainless steel tubing.
D.6.2
Connection reliability and physical damage
The primary design and installation principles are to never let:
oil escape from the transformer during operation.
air enter the transformer during operation.
In general, copper tubing is too soft to create a reliable long-term seal in the vibratory
environment of a transformer — the connections eventually leak. The softness of copper
tubing also makes it prone to damage post installation — maintenance and service
activities near the transformer could potentially kink, pinch or tear connections.
D.6.3
Compounds in the transformer oil that react with copper
Transformer oils contain compounds that can react with copper. One notable compound
is Acetylene which reacts with copper to form copper acetylide. This creates two related
problems:
Copper acetylide is a highly explosive compound and for regulatory and health
and safety reasons, our equipment or installations cannot create these
compounds.
The reaction changes the chemical makeup of the oil before it reaches the
sensor in the product. This causes the product to measure acetylene and
possibly other gasses inaccurately.
Although a transformer already contains copper, GE monitoring and diagnostic
equipment is designed to accurately measure the gasses in the oil of the transformer
without affecting the oil.
GE will not guarantee or perform warranty work on a product that has been
installed using copper tubing or any other tubing, other than stainless steel,
as specified above.
MA-005 - Minitrans Installation Manual - Rev 4.5
13-Aug-20
Page 42 of 86
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