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SF6 Gas Servicing Cart
All Cryoquip gas recycling carts are designed to carry out the same operations. Models differ in recycling technology, transfer time, frame configuration, storage capacity, compressor and vacuum pump capacity and option packages available. Upgrades are available to improve transfer time and performance to meet particular process requirements. Selection of the correct design of cart for a particular application depends on several factors and will affect recycling efficiency and equipment flexibility. A general discussion of the key factors which normally enter into the equipment selection decision follows.
Tank size selected should have the capacity to hold the gas contained in the largest circuit breaker to be serviced. In the case of a gas insulated substation the largest gas room plus the two adjacent gas rooms reduced to atmospheric pressure is the governing capacity. In order to eliminate the handling of 115 lb (52 kg) SF6 cylinders and to ensure the gas recycling cart is available for emergency service, it is recommended that the capacity chosen include some inventory.
Transfer time is a very important consideration in the equipment selection formula. Apart from the cart, other factors associated with the specific circuit breaker and/or gas insulated substation to be serviced, significantly affect overall transfer time. The most important of these is the size of connection provided and the distance from the gas recycling cart. The graph illustrates approximate overall transfer times for various amounts of gas recycled.
Recycling technologies affect the speed at which SF6 gas can be reclaimed and liquefied. Low pressure assisted cooling units are much faster than comparable high pressure units. The amount of gas to be recovered should be considered carefully when selecting the recycling technology.
Carts are available in various configurations for indoor or outdoor use: Hand Carts, which are compact, lightweight and easily transported, designed specifically for processing small gas volumes; Skid Mounted units for permanent installation in manufacturing facilities and substations; and Castor Mounted units for mobile use: optional weatherproof enclosures are available for outdoor use; Trailer Mounted carts for total mobility, completely weatherproof ICC and DOT approved.
Consideration should be given to the operating capacities of cart components, notably the vacuum pump and compressor and boost compressor if applicable. These capacities directly affect the rate of gas recovery and overall transfer time. Capacities should be appropriate to the volume of gas being handled.
- Gas recycling cart has been evacuated and charged with SF6 gas before the start of processing.
- Use of 12 ft. (4m) standard hose connected to a standard 37° jic gas removal tap on electrical equipment.
- Evacuation of an enclosure originally at 80 psig (5.5 bar) SF6 gas pressure to vacuum on removal of SF6 gas.
- Evacuation of an enclosure to deep vacuum (500µ) on withdrawal of air prior to return of SF6 gas.
- Purification and drying of SF6 gas simultaneous with above step.
- Power Source: Single phase 230 volt; three phase 460 volt or dual voltage; 60 or 50 hertz designs.
- Power Cable: Standard 20 ft. (6m). Non standard lengths and connectors per customer specification. Available cable reel for ease of handling and storage.
- Vacuum Pump: Larger capacities are offered as standard options. Available oil-free or with filter system.
- Compressor: Larger capacities are offered as standard options. Available oil-free or lubricated with filter system.
- Liquid Transfer Hose: Standard 12 ft (4m) 3/4 inch (19mm) diameter transfer hose with swivel connections. Special lengths and/or diameters and self-sealing couplings are available.
- Paint: Customer specified color and/or paint and logos.
- Automatic Instrumentation: Pressure and temperature indicators with contacts for remote control operation. Available PLC control and automatic valves.
- Back-Flow Prevention Valve: An electrically operated valve (solenoid type) to prevent backflow of oil from vacuum pump to the electrical switchgear being serviced. Activated in the case of power failure or valving error.
- Tank Contents: Accurate tank contents weighing system with digital indicator.
- Towing Provisions: 5,000 or 10,000 pound (2500 or 5000 kg) ball couplers. Trailers with single, tandem or triple axles. Air, hydraulic or electric brakes. Available air suspension.
- Gas Transfer Hose: Standard 12 ft (4m) length, 1 1/4 inch (32mm). Larger diameters and longer lengths and self-sealing couplings are available.
- Alarms: Visual and audible alarms for critical equipment malfunction.
- Valve Position: A valve position display panel with open/closed indication. LED valve status display on the operator's panel door. Valves mounted on the control panel in a circuit mimic.
- Inlet Gas Scrubber - Model F25/F3: A complete inlet gas scrubbing system with desiccant dryer, three stage gas scrubber and particle filter, stand alone or mounted on the gas recycling cart trailer.
- Analytical Instrumentation: Analyzers for measuring moisture content and decomposition products.