SF6 Handling Products
The applications which have the greatest effect of SF6 usage and recording requirements are those surrounding filling, topping up and leak management. There are a number of regulations for handling of SF6 during installation, commissioning, normal and abnormal operations, disposal at the end-of-life high-voltage switchgear and control gear. These are detailed and prescriptive procedures, regarded as minimum requirements, to ensure the safety of personnel working with SF6 and to minimise SF6 emissions to the environment.
Globally there are many standards, regulations, advisory papers and publications that are, or can be used to aid operators in the handling of SF6. Each geographical region has their own process and restrictions. To make it easier to understand EMT typically split these publications into two main categories.
The first being publications relating to the control and reporting of SF6 usage such as the European F-Gas regulation or EPA reporting requirements in the US or even geographically specific such as the CARB in California.
The second group would be that of publications and guidelines relating to the actual physical usage, handling and manipulation of SF6 during operations such as IEC62271-4. These standards tend to be much more prescriptive regarding the usage of SF6 in operations such as evacuation of SF6 from a compartment or how to take a test. Whilst different in terms of their contents, these two types of standard or reporting requirement are not mutually exclusive and so are run along side each other.
Each standard has its requirement for measuring and recording SF6 usage and loss in a variety of reporting methodologies, differing calculations and analysis means – its just picking the ones that are relevant for your local country or continent requirement.
Our EMT specialists can advise you on those regulations which apply to you, how to effectively monitor and record SF6 emissions, and how best to perform key tasks, including the use of gas carts to evacuate SF6, guidance on conducting SF6 purity analysis or even how to ship and dispose of waste SF6 gas.
At EMT our experience is that most emissions are generated during 2 key processes, these being filling assets or topping them up. Both operations have the potential for significant emission of SF6. The filling and topping up process represents a high risk for emissions as large volumes of gas are used. This also creates other potential risks as operators must decide to fill or top-up compartments with the circuit live (sometimes called hot fill) or they have to de-energise the site and then perform the task.
Either way, filling or topping up have associated risks such as the safety of the personnel performing the process, and potential human error during the fill process resulting in under or over pressurization of the equipment. In most instances topping up or filling up is still a manual engineer process and these human errors can lead to other risks such as arc flashover if the asset is being filled too quickly, also associated with this is line freezing caused by the Jouls Thompson effect of the gas reducing in pressure. This all adds time, cost, reliance on a free engineer, but also potential down time of the asset.
Fundamental to all this is the requirement to record what SF6 has passed through your network, to do this you need instrumentation to give you accurate methods for measurement. For SF6 related applications EMT recommend mass flow controllers should be used. At EMT we always recommend utilising mass flow controllers rather than meters for that added functional control over the process. This process has many benefits, most importantly it allows for accurate mass measurements, even where there are changes in temperature and pressure i.e. filling late in the day and over night.
Using a mass flow controller provides many benefits when utilised to fill an SF6 compartment in comparison to having an engineer operated procedure. For example using instrumentation containing a mass flow controller removes the need for an engineer to be onsite all day, the equipment can be setup and then left to run with the mass flow controller ensuring the right amount of gas has been installed and the compartment is at the right pressure. The instrument will even do the paperwork for you as it will log the amount of gas used. This frees up engineers for other works which are required.
By using a mass flow controller you also remove the risk of too much gas being flowed at once, by controlling the flow accurately you remove the potential for line freezing and over pressurization and even the risk of arc flash over as the gas is not stirring up contaminants in the compartment. These reductions in risk are why EMT are seeing a very sharp upward trend of live or hot filling/topping up of SF6 compartments and a move away from having to de-energise equipment prior to works commencing.
With any filling device, there are a range of accessories that help produce a more efficient fill. For example we can supply a range of heated blankets and regulators to ensure if manually filling, the chances of a line freeze are reduced. They also ensure the maximum amount of SF6 can be recovered from the cylinder. Often we see around 20-25% wastage of SF6 in cylinders due to temperatures and pressures keeping the SF6 liquified.
EMT have a range of hoses and fittings connections for our products and other manufacturers equipment to connect to your SF6 compartments:
- ensure perfect gas transmission, free of contaminants
- longer hoses for more difficult to access areas
- range of self-sealing fittings such as DN8, DN20, Malmquist etc.
- available in brass and stainless steel
We also have a wide selection of gas handling carts for the evacuation of compartments and storage of gas and specialist SF6 cryogenics plant available, designed to allow operators to clean and purify their old SF6 gas themselves, into reusable gas, within specification, for putting back on to the network.