MA-005 - MINITRANS Installation Manual - Rev 3.1
29-Sep-15
Page 20 of 85
Ensure that the valve chosen to return oil is not internally piped to another
location within the transformer, such as the headspace or the internal
windings.
8.1.4
Cooling Loop Valves
The product should only be supplied with oil from a cooling loop valve if there are no
other valves available.
Note: Oil should not be taken from a forced oil cooling loop.
Do not
return oil to the cooling loop unless it is absolutely clear that the cooling
is not directed flow and that there are no other alternative valves in which to
connect the product.
8.2
Supply & Return Valves
All transformers have different valve configurations. The supply and return valves on the
transformer will need to be adapted to a ¼ in. female NPT fitting to properly fit the ¼ in.
NPT male fitting on the product. When choosing how to prepare the oil supply and return
valves, consider these points:
8.2.1
Oil Supply
Oil is typically taken from a valve midway up on the transformer or from an active
cooling loop.
Note: Oil should not be taken from a forced oil cooling loop.
It is necessary to
ensure that the oil is taken from a location where the oil is well mixed and in the
active flow of transformer oil. The oil temperature at this location should not exceed
100 °C or be lower than −10 °C.
The distance between the oil supply valve and oil return valve should be at least 30
cm (12 in.) to prevent mixing of the de-gassed oil with the transformer oil being
sampled.
Fittings must be provided to adapt the oil supply valve to a ¼ in. female NPT fitting
using fittings and adaptors made from stainless steel, brass or black iron.
Do not
use galvanised steel, copper or plastic fittings as these materials can
negatively affect the gas concentrations in the sample line.
If the oil supply valve is located more than 1.82 m (6 ft) above the base of the
transformer, it is recommended that an additional ¼ in. ball valve be placed in the
oil supply line within easy reach while standing, and in an easily accessible and
visible location. This valve can be used to conveniently shut off the oil supply, if
required.
