Installing oil lines with flexible hoses - OPT100

OPT100 Installation Guide

Document code
Document type
User guide
  • 14‑mm wrench (2 pcs)
  • 19‑mm wrench
  • 22‑mm wrench
  • Flex hose kit, 2 x 10 m (Vaisala item ASM214666SP)
  • Adapter kit, ½" NPT (Vaisala item ASM214667SP)
  • Adapter kit, 1" NPT (Vaisala item ASM214668SP)
  • Adapter kit, 2" NPT (Vaisala item ASM214669SP)
  • Optional pipeline valve kit, 10‑mm (Vaisala item ASM214670SP)
  • Pressurized air, either a bottle or a compressor
  • Container for waste oil with at least 5 liter (1.3 gallon) capacity
  • Oil pipe insulation, for example ArmaFlex tubing (min. 20-mm (0.787 in) wall thickness) (recommended in cold climates, especially for devices using synthetic ester liquid)
  • Trace heating, self-regulating, 10 W/m (recommended in cold climates, especially for devices using synthetic ester liquid)
  • Transformer valve tag (2 pcs)

Follow these instructions to install oil lines with flexible hoses. The flex hose kit and adapters are not delivered with the standard DGA monitor delivery.


When working with oil pipes, hoses, fittings, and adapters:

  • Keep parts and tools clean and off the ground. Dirty parts may contaminate the transformer oil or cause connections to leak.
  • Oil pipes, hoses and connection adapters must be dry, without any free water residue inside. Water inside the oil lines can cause issues with the OPT100 measurement and water may be carried with the oil to the connected transformer.
  • Use new Swagelok® adapters (nuts and ferrules) when making new connections. Do not use third party adapters or used parts from a different connection. Opening and retightening existing oil line connections without changing the nuts and ferrules is OK as long as the parts appear intact and you can verify the connections do not leak.
  • If you are unsure about the proper use of fittings and adapters, refer to their manufacturer's instructions online.
Wear protective eyewear and gloves.

If the DGA monitor is mounted using the wall mounting set, the power supply unit will be attached by a mounting cradle. Make sure you are not routing the oil lines so that they will obstruct the power supply unit attachment.

Before starting to install the oil lines, see installation site requirements and recommended locations of oil connections for important information.

Minimum bending radius from center line for the flexible hoses is 3.05 cm (1.20 inches).
Do not bend flexible hoses close to the fitting connection to avoid strain.
  1. Inspect and prepare the selected inlet and outlet oil valves on the transformer:
    1. Remove any previously installed flow direction control valves. The DGA monitor needs to pump oil in both directions during initialization, and will not work if there are flow direction controllers in the oil lines.
    2. Clean any loose dirt from the outside and inside of the oil valves on the transformer.
    3. Drain some oil from the selected valves into the waste oil container. Verify that the oil is clean and there is no sludge coming out with the oil. If there is sludge, do not use that valve to connect the DGA monitor.
  2. Install the adapters to the inlet and outlet valves on the transformer to match them to the size of the flexible hose connectors.
  3. Measure the distance from the oil valves to the DGA monitor, and plan the shape of the oil line installation.
    1. Use pipe supports every 1 meters (3 feet).
    2. Do not coil excess flexible hoses. Loop the hoses away from the DGA monitor along the cable guides or other protection structures. Mind the minimum bending radius.
    3. Make sure the flexible tubing is parallel to the ground to avoid air traps during bleeding.
    4. Make sure the flexible hoses are not under constant strain after installation.

    Make sure that both oil connections on the transformer are below oil level. There must be no risk of drawing gas into the oil lines even when the flow is reversed.

  4. Build the oil lines between the valves and the oil connections on the DGA monitor marked Oil In and Oil Out.
  5. Remove the plugs from the pipe fittings on the DGA monitor and store them for possible later use. Check that the fittings are clean.
  6. Connect both oil lines to the fittings on the DGA monitor. Use the supplied Swagelok® adapters (delivered in a separate bag). See Installing oil lines, 10 and manufacturer's instructions for more information on tightening the fittings.
  7. Install trace heating for the pipes if you are using the device with synthetic ester liquid or if it is necessary due to a cold climate for a device with mineral oil. The heating cable must touch the pipes for optimal heat transfer.
  8. Install insulation over the whole length of the inlet and outlet pipes and the pipe connectors if you are using the device with synthetic ester liquid or if it is necessary due to a cold climate for a device with mineral oil.
    Protect the insulation from potential damages caused by animals.
  9. Install pipe supports for the flexible hose. Do not leave the flexible hose on the ground where it can be stepped over.
  10. Ground the flexible tubing and the support materials according to local regulations.
  11. Add the transformer valve tags to the transformer intake and return valves.
To verify that the oil connections are tight, check for leaks during commissioning when the DGA monitor is pumping oil. Ideally, check the connections again after the DGA monitor has been running for some time (for example, the next day).