FAQ

Service equipment

What is a portable SF6 gas transfer unit used for?

A portable SF6 gas transfer unit is used for the transfer and liquefaction of SF6 gas.

What is the difference between a vacuum pump and vacuum compressor?

A vacuum pump is used to evacuate a gas compartment from air. In contrast, a vacuum compressor in the SF6 recovery process ensures an initial pressure of greater than 1 bar at the SF6 compressor and thus enables a residual pressure in the gas tank of down to 1 mbar.

Why must special equipment be used for SF6 gas?

SF6 gas is a climate-damaging greenhouse gas. 1 kg of SF6 gas corresponds to approx. 23 tonnes of CO2. For this reason, leakage into the atmosphere must be avoided and the use of special equipment is mandatory. Due to the design and the special self-closing valves installed in WIKA SF6 handling equipment, gas loss can be reduced to a minimum.

What can be filled with a portable SF6 transfer unit?

Due to the maximum output pressure of 50 bar abs., you can use the portable SF6 transfer unit both for filling gas cylinders and other vessels. At this pressure, the SF6 gas has already passed into the liquid phase, thus enabling space-saving storage. With the help of the second outlet, which contains a pressure reducer, a controllable filling of up to 16 bar abs. is possible. This is mainly used when filling switchgear or other equipment.

Is evacuation of plants and vessels possible with a portable SF6 transfer unit?

For complete evacuation of plant and vessels, a second unit, a vacuum compressor for SF6, is required, since, on the input side, a portable SF6 transfer unit only allows a final pressure of slightly less than 1 bar abs..

What is the difference between “oil-free” and “oil-less”?

With oil-free, the compressor still contains small amounts of lubricant that could come into the circuit under various circumstances. “Oil-less” refers to compressors that work completely without lubricant.

Why are “oil-less” compressors recommended?

“Oil-less” compressors are recommended to prevent lubricant particles etc. from entering the SF6 circuit, which in some applications, even in small amounts, can cause technical problems. All WIKA gas handling equipment uses only “oil-less” compressors.

What should one watch out for when connecting a portable SF6 transfer unit?

In order to connect a portable SF6 transfer unit, connection hoses suitable for SF6 are recommended. Care should be taken that they are fitted with self-closing valves and are already filled with SF6 gas or fully evacuated before the first application. Otherwise, air, humidity, etc. can enter the circuit and the equipment to be filled.

Which service tasks can be performed with handling equipment?

The gas handling equipment is an SF6 handling unit, which can be used to recover and fill SF6 gas compartments as well as to filter the extracted gas. Commissioning of SF6 gas cylinders is also no problem with the gas handling equipment.

What are the special features of the safety concept of the of the GPU-S-x000?

Among the special features is the separation in two autonomously operating controllers. The process controller controls all processes and communicates with the operator via the input display (also called the HMI “Human Machine Interface”). The safety controller, which is based on SIL 2 components, monitors critical conditions of the system. The SIL 2-certified components we are referring to are the pressure sensors, a load cell for measuring tank contents and the SF6 gas detector (IR technology). The latter detects emissions in a range from 0 ... 2,000 ppmv. When the workplace limits are exceeded (1,000 ppmv), the detector automatically places the system into a safe condition and alerts the operator. The emission of SF6 gas during handling is thus reduced to a minimum. WIKA is the only provider of SF6 gas handling equipment with a safety control in accordance with SIL 2.

Is it possible to dispense with a pre-filter when recovering SF6 gas with handling equipment?

Although two filter systems are installed in the WIKA handling equipment (particle filter and SF6 filter), in the event of heavily contaminated SF6, a pre-filter (e. g. GPF-10) should be used to protect the system.

Why cannot the SF6 compressor capacity be used directly to compare process velocities?

Although the capacity of the SF6 compressor can be an indication of the process velocity, other factors such as
  • the pipe diameter in the SF6 handling unit
  • the construction of the pipeline (number of constrictions, etc.)
  • the software-based optimisation of the processes
  • the general conditions (hose length and diameter used, etc.)
can also be very crucial.