MA-001 – TRANSFIX-family Installation Manual – Rev 3.0
18-Jan-16
Page 17 of 55
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: If oil has to be taken from an oil-forced cooling loop, the oil supply valve
must be located on the high pressure side of the oil pump.
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 transformer supply and return
valves should be assessed for durability to ensure that a reliable connection can be
made. The valve size should measure at least 15 mm (½ in.) in diameter. These valves will
need to be adapted to ¼ in. female NPT fittings to properly fit the ¼ in. NPT male fittings
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: If oil has to be taken from an oil-forced cooling loop, the oil supply valve
must be located on the high pressure side of the oil pump.
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 120 °C or
be lower than −20 °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
