SF6_Gas_Recovery_Cart.pdf

SF6 Gas Recovery Cart Specifications

GENERAL

The unit shall be capable of recovering 99.9+% of SF6 gas from circuit breakers or similar equipment, without any oil lubricated or refrigeration components. The unit will be designed to perform its intended functions while operating over the ambient range of 0°F to 113°F, in humidity as high as 100%. The cart will be designed in such a way that no operator error can result in damage to the cart.

Self-Evacuation/Recovery

Prior to removing the SF6 from gas-insulated equipment (GIE), the unit shall have the ability to evacuate air and moisture, or recover residual gas and moisture, from its own storage vessel, associated piping, and fixtures. The “blank-off pressure”, or final vacuum, in the unit will be no greater than 1 mbar (0.75 torr)

Removal of SF6 from Electrical Equipment (Recovery)

The unit shall be capable of removing an indefinite amount of SF6 from electrical equipment. This process shall remove 99.9+% of the SF6 without any oil contamination by utilizing a system with a compression ratio of 10,000:1 or greater. The final pressure within the electrical equipment after removing the SF6 will be no greater than 5 mbar (3.5 torr). This process shall also be capable of removing contaminant concentrations that fall within the limits specified under the Cigre Recycling Guide, Section 4, subsection 4.3.

Evacuation of Air from Electrical Equipment

The unit shall be capable of evacuating air and moisture from electrical equipment. The final pressure within the electrical equipment, after removing air, will be no greater than 1 mbar (0.75 torr).

Charging the Electrical Equipment

The unit shall be capable of returning the SF6 originally removed from the electrical equipment back into the breaker without ANY oil or air contamination. This process shall be capable of removing contaminant concentrations that fall within the limits specified under the Cigre Recycling Guide, Section 4, and subsection 4.3.

Transfer SF6 from Cylinders

The unit shall be capable of transferring SF6 from cylinders to internal or external storage. The unit shall also be capable of transferring SF6 from the storage unit to any SF6 cylinders. The unit shall be able to compress gaseous SF6 into liquid form, through compression only. This process shall also be capable of removing contaminant concentrations that fall within the limits specified under the Cigre Recycling Guide, Section 4, subsection 4.3.

Storage Connection & Vessel(s)

To remain legal under all DOT transport conditions, the storage vessel(s) shall comply with either 49CFR173.304a(2) or ISO 9809-1 standards. The gas service cart shall have a manifold with both integrated and external cylinder connections

Vacuum Pump

The vacuum pump shall have a minimum performance rating of 8 cfm. The vacuum pump shall have a final vacuum pressure of less than 1 mbar (0.75 torr). The vacuum pump shall be designed to extract only air and moisture. A solenoid valve shall be placed in the input line of the vacuum pump, and serve as an anti-suck back valve in the event of power failure.

Vacuum Compressor

To guarantee a 10,000:1 overall recovery compression ratio, an oil-less, hermetically sealed dry running vacuum compressor will be mandatory. The vacuum compressor must be placed in-line with the main compressor. It shall include automatic by-pass valves and automatic on/off operation using pressure sensitive sensors. The blank-off pressure shall be no higher than 5 mbar (3.5 torr).

SF6 Compressor

The main gas compressor must be 100% oil-less and hermetically sealed. It shall be capable of generating an unassisted 100:1 compression ratio. Together with the vacuum compressor, it will be capable of generating 10,000:1. There must be absolutely no oil in the compressor, crankcase, compression chambers, motor, gears, or any other part of the compression system. Crankcase heaters are not permitted. The compressor(s) shall have a discharge pressure of at least 725 psi, while simultaneously pulling down to atmosphere (0 PSIG) at the input. The liquefying compressor shall be self-sufficient in liquefying the SF6 without the assistance of any thermodynamic system (i.e.

refrigeration and heat exchangers). The compressor must have no oil seals, and be gas tight under positive or negative pressure, when power is turned off. The entire compressor unit (motor, pistons, and all moving parts) must be enclosed in a singular pressure sealed housing (hermetically sealed). Because crankshaft seals of compressors can develop leaks (air/moisture intrusion, and/or SF6 leakage), under no circumstances shall non-hermetically sealed or belt-driven compressors be permitted.

Filtration System

The cart shall be equipped with two field replaceable filter units. The filtering medium will consist of an aluminum oxide and molecular sieve core.. Switching of filter cores will be possible without opening and re-tightening tube unions. Because all filters are by nature more efficient at higher pressures, they shall be pressure rated and operated up to a minimum of 50 bar (725 psig). Under no circumstances shall the filter be positioned after the storage tank. The filters must be capable of drying SF6 to -50°C (41 PPMv) dewpoint during regular operating conditions

Pressure Regulator

A pressure regulator, adjustable between 0 and 145 PSIG, will be integrated into the gas service cart to allow full control of filling from the storage end of the device. This prevents over-pressurizing the electrical equipment during the refilling process..

Shut-Off and Control Valves

All manual control valves should be one-quarter turn in operation and pressure rated for 725 psi or higher. There must be no more than two (2) manual valves per unit. Solenoids which are used to replace manually operated valves must be hermetically sealed to prevent moisture/air intrusion and SF6 leakage. These solenoids must also be designed to be normally closed, meaning closed when not in operation or if a loss of power should suddenly occur

Sealing System

Manufacturer must guarantee, for the life of the cart, that fittings will not develop leaks. Fittings MUST NOT require periodic re-tightening.

Internal Plumbing

Only copper tubing, stainless steel tubing, SAE 100R1 hydraulic rubber hose, and PTFE-lined stainless steel braided hose should be used. No internal component will be supported by its associated plumbing.

Any tubing longer than one (1) foot must be securely mounted to the frame of the cart to prevent fatigue over time. Fittings with potential to leak naturally over time, such as National Pipe Thread (NPT), parallel thread, or 37° flare (JIC), must not be used.

Service Hose

Service hose shall be 20 feet in length enough so that connection to gas-insulated equipment (GIE) and/or cylinders can be made from a safe operating distance. Service hose must have DILO self-sealing couplings on each end to properly connect with the external ports on the cart and to prevent air intrusion. The hose shall be no smaller than 0.4 inch I.D. Hose material must only be constructed of either hydraulic rubber, such as SAE 100R1, or PTFE-lined stainless steel braid.

Operation

A PLC automatic process control shall be be integrated into all standard and special functions. The PLC shall be able to detect inlet/outlet pressures, component operating hours, and storage weight.

The cart must be designed so that once an operation has been selected and started there would be no need for operator interaction until completion. To prevent damage to any component during unattended operation, the following automatic protection features shall be included:

• Pressure and temperature protection of compressors

• Oil back-flow prevention for vacuum pump

• Solenoid valves which automatically close with loss of power

ELECTRICAL SYSTEM

The operating voltage must be 1Φ 208-240VAC @ 60Hz. The electrical system shall be protected by a main circuit breaker. All motor circuits shall be protected by thermal overload devices.

FRAME & BODY ASSEMBLY

The frame must be designed in a way that allows ease in mobility for a single person and be able to be loaded onto and operated from a transport vehicle with minimal effort. It will include four (4) wheels, with at least two (2) being steerable and lockable. At least two (2) wheels will be large enough to handle standard outdoor aggregate surfaces and all four capable of easily moving on smoother surfaces.

QUALITY CONTROL, WARRANTY, & MONEY-BACK-GUARANTEE

All exterior metal surfaces shall be thoroughly cleaned of rust, scale, weld splatter, and all oil and grease prior to applying the paint priming coat.

The cart shall be provided with a one year full warranty on all parts and labor.

LEAK TEST

Extensive leak testing must be performed on the unit prior to shipment. Positive pressure testing will include an initial leak test with 50 bar (725 psi) of nitrogen. After the nitrogen, 3 bar (43.5 psi) of SF6 will be pressurized throughout the entire plumbing system and it will be checked with a leak testing device capable of detecting leaks as small as 10-7 ml/s. Once the unit has passed this test, it will be re-tested with the same or better leak checking method. The unit can only be considered adequate when a rate of less the 4 PPMV is observed throughout the leak testing process. When pressure testing is complete, a final vacuum leak test will be performed. The unit will be evacuated with the vacuum pump for two (2) hours reaching a final vacuum of less than 1 mbar (0.75 torr). After one (1) hour, the vacuum reading must not rise more than 5 mbar (3.75 torr) from the original blank-off pressure.

When testing is complete the cart shall remain under a vacuum and packaged for shipping.

INSTRUCTION BOOKS

An instruction book and compact disc (CD) shall be provided with the gas service cart. The printed and digital manuals shall provide instruction for operating and servicing the unit. PDF copies of this manual must be made available upon request.

DRAWINGS

A complete functional diagram and full electrical schematics, both with associated parts lists, must be provided within the included manuals.

Spare Parts

Manufacturer shall provide a spare parts list.