When making a vacuum system/lifting device there are several different methods to increase safety and reliability. To give efficient operation and good economy it is important that the designed system is made for a specific application. In addition to the choice of suction cups with attachments, the type and size of vacuum pumps, accessories, safety level and type of system must also be decided upon.
For sealed systems the capacity of the pump is determined by how fast the system can be evacuated to a certain vacuum level. This capacity is called the evacuation time of the pump and is normally specified in s/l. This value is multiplied by the volume of the system in order to obtain the evacuation time to the desired vacuum level.
With non-sealed systems (lifting of porous materials) the case is different. To maintain the desired vacuum level the pump must have the capacity to pump away the air leaking in. Leakage can be due to, for example, porous material or that one is forced to lift over holes. By establishing the leaking flow, it is possible, by reading the pump data, to find the right pump for the application in question.
If the leakage occurs via a known aperture, the flow can be established according to the adjoining diagram. The diagram gives values for leakage flow when the leakage area is known. The leakage flow is valid when there is an opening of 1 mm2 (normal atmospheric pressure at sea level). To obtain the total flow, the value is multiplied by the total leakage area.
When the leakage occurs through a porous material or in an unknown way, the flow can be established by a test with a vacuum pump. The pump is connected to the system and the obtained vacuum level is read. (It should be at least 20 -kPa.) The flow that is pumped away at this vacuum level can be seen on the page of the particular pump. This flow roughly corresponds to the leaking flow.
Electrically driven, mechanical vacuum pumps normally work during the whole operating cycle and the vacuum requirements are controlled by a valve on the vacuum side. In systems with compressed air-driven vacuum pumps it is often possible to save a lot of energy. As these pumps have a faster reaction time (fast start-up and stop time) the pump can be shut off when the vacuum is no longer needed. The principles of a simple energy-saving system are shown to the right. Many pumps can be delivered with an energy-saving system as standard.
Vacuum systems for material handling can be decentralized or centralized. A decentralized vacuum system is designed so that each suction cup has a dedicated, independent vacuum source. A centralized vacuum system is designed to have one vacuum source for multiple suction cups. Handling sheet metal is an example of a sealed system and handling cardboard is an example of a leaking system. The examples are calculated using the following general assumptions: Initial flow required are for the sealed system examples is 0.7 Nl/s per suction cup FC75P, and the corresponding value is 1.2 Nl/s for the leaking system examples using the suction cup BX75P. CO2-emission, world index: 0.019 kg CO2 per produced m3 of compressed air and 0.19 kg CO2 per kWh. Machine operating hours per year: 3.000 h.
Sealed systems/handling non-porous material
Decentralized vacuum system using: Vacuum Gripper System VGS™3010 with suction cup FC75P and COAX® cartridge Xi10 2-stage vacuum pump with non-return valve, AQR Atmospheric Quick Release, Vacustat and 3/2 on/off-valve.
Annual cost of ownership: 188 €
Annual CO2 emission: 13 kg
Annual energy usage: 17 kWh
Centralized vacuum system using: P5010 with AVM™ – Automatic Vacuum Management control, COAX® cartridge Xi40 3-stage vacuum pump with non-return valve and suction cup FC75P.
Annual cost of ownership: 301 €
Annual CO2 emission: 171 kg
Annual energy usage: 900 kWh
Centralized vacuum system using: 550 W electromechanical vacuum pump with suction cup FC75P and vacuum on/off-valve.
Annual cost of ownership: 722 €
Annual CO2 emission: 443 kg
Annual energy usage: 1656 kWh
- Electric vane vacuum pumps are running constantly.
- Energy cost: 1.5 Euro-cent per produced 1 m3 compressed air and 12 Euro-cent per kWh.
- Annual cost of ownership include: energy costs, purchase price, annual cost, service and CO2 emission tax 0.025 Euro per kg. Suction cups excluded.
- Capital interest rate: 5%
- Pump life time: 5 years
Calculating carbon footprint:
Based on the world average of power generation, 1 Nl of compressed air will result in a 19 mg CO2 emission footprint. To calculate your specific footprint, just multiply your air consumption (Nl/s) by 19. The result is your CO2 emission footprint per second.
Red tubing = Compressed air
Blue tubing = Vacuum
Leaking systems/handling porous material
Decentralized vacuum system using: Vacuum Gripper System VGS™3010 with suction cup BX75P and COAX® cartridge Si08 3-stage vacuum pump and 3/2 on/off-valve.
Annual cost of ownership: 249 €
Annual CO2 emission: 145 kg
Annual energy usage: 762 kW/h
Centralized vacuum system using: P5010 with COAX® cartridge Si32 3-stage vacuum pump, suction cup BX75P and 3/2 on/off valve.
Annual cost of ownership: 227 €
Annual CO2 emission: 203 kg
Annual energy usage: 1067 kW/h
Centralized vacuum system using: 750 W electromechanical vacuum pump with suction cup BX75P and vacuum on/off-valve.
Annual cost of ownership: 808 €
Annual CO2 emission: 429 kg
Annual energy usage: 2258 kW/h