Sulfur hexafluoride is widely used as an insulating gas and arc quencher in electrical equipment. However, to maintain its effectiveness, SF6 needs regular cleaning to get rid of harmful impurities. Handling also needs to be done with care, as SF6 is a greenhouse gas. WIKA’s GPU-2000 all-in-one solution allows safe and efficient SF6 gas handling – including filling, cleaning, and replacing – in electrical switchgear and other SF6-insulated equipment.
Pure sulfur hexafluoride (SF6) gas has excellent heat transferring and dielectric properties. That’s why it is the insulator of choice for transmission and distribution (T&D) switchgear, particle accelerators, and other industrial applications.
To maintain its potency as an insulating gas, however, users have to make sure it remains pure. Even a small amount of moisture in the gas reduces its effectiveness. Normally, during an electrical arc, the six fluorine atoms break away from the sulfur atom to grab free electrons. When water enters a gas-insulated switchgear, the split sulfur and fluorine atoms grab the oxygen and/or hydrogen atoms instead, and the results are a range of toxic and corrosive byproducts.
Leaks let in moisture, but they also allow SF6 – a powerful greenhouse gas – to escape into the atmosphere. And in high enough concentrations, SF6 can cause asphyxiation in closed spaces because this heavier gas displaces air (oxygen).
For these reasons, SF6-insulated equipment must be closely monitored to prevent leaks and to keep humidity within safe levels. Filling, recovering, cleaning, evacuating, venting, and replacing SF6 gas are essential processes for the health and safety of power plants, technicians, and the planet.
All-in-One Solution from WIKA
WIKA’s answer to the challenges of SF6 gas handling is the GPU-2000. Portable, cost-effective, and low maintenance, this unit covers the entire process, from filling to storage. It has oil-free compressors and vacuum compressors, consolidated SF6 gas cylinders or tanks, and extensive storage capabilities. The built-in 10” touchscreen HMI is intuitive and easy to use.
Powerful cleaning abilities
The GPU-2000 measures humidity during SF6 gas handling via the GDHT-20, a multi-parameter sensor, available also as a stand-alone product, that provides pressure, temperature, density, and humidity information with a digital output that allows easy online data processing. The system alerts the operator when the humidity level gets close to a customer-preset value. The operator can then replace the wet gas or start a recirculation process to dry it.
The GPU-2000, with WIKA’s 3-in-1 GPF-10 filters, removes 1) humidity from the SF6gas, 2) particles up to 1 μm, and 3) SF6 byproducts, including hydrogen fluoride (HF), sulfur dioxide (SO₂), thionyl fluoride (SOF₂), sulfuryl fluoride (SO₂F₂), and sulfur tetrafluoride (SF₄).
The GPU-2000 is designed to withstand up to 145 psi absolute (10 bars abs.) at the process connection and up to 72.5 psi absolute (50 bars abs.) at the two connections to the gas cylinders. Hoses are made of stainless steel – the recommended material to avoid humidity permeation – but are also available in rubber upon request.
The GPU-2000 is fast, thanks to its ability to be configured with several different types of compressors and pumps. This customized choice allows maximum efficiency for a particular volume of SF6. As an example, these curves illustrate the performance of a standard handling unit with a 300-liter tank.
Low-maintenance SF6 gas handling
The GPU-2000 is robust and requires little maintenance, able to run for thousands of hours without needing a checkup. The maintenance schedule, however, depends heavily on operating conditions. For optimum performance, it is important to adjust maintenance intervals for each particular application. The tables below illustrate some standard maintenance intervals.
Maximum safety when working with SF6
Although the gas itself is nontoxic and nonflammable, SF6 leaks can have serious consequences for human and planet health. That’s why the GPU-2000 has built-in safety controls based on Safety Integrity Level 2 (SIL 2) components. With this configuration, there are two fail-safe layers of control systems. The safety control system is on top of the command structure and independent from the process control. In case of a leak, the safety control stops the machine when, for example, the concentration of SF6 reaches 1000ppm – the maximum concentration allowed in workplaces.
Thanks to the SIL 2 safety control, the risks of incorrect use, emissions into the environment, and overfilling the storage tank can be virtually ruled out.
A cost-effective SF6 solution
The GPU-200 is an economical all-in-one unit for SF6 gas handling. Several factors will influence a users’ return on investment, including:
- Number of hours spent on gas handling services
- Employees’ hourly rate
- Amount of SF6 used in the installation
- Maintenance frequency
The table below provides some information regarding maintenance periodicity, useful when comparing WIKA’s GPU-2000 to other available products in the market.
WIKA has put decades of laboratory and field experience into designing a unit specifically for handling the entire SF6 lifecycle. The result is the GPU-2000, one of the fastest, most efficient, and most cost-effective service equipment of its class. Contact WIKA USA for more information about this and other proven solutions for SF6 gas applications.