Carbon Dioxide Snow Cleaning systems are for the most part straightforward, they consist of a CO2 source, a nozzle with an internal orifice, an on/off valve, and the means to transport the CO2 from the source to the nozzle. A typical system, such as shown below, consists of a cylinder fitting, tubing, an on/off gun or valve and a nozzle. Most units are made with a PTFE lined flexible stainless steel hosing (we do offer all stainless steel units). Available on/off controls include solenoid, pneumatic, or manual valves, or hand guns.
The standard unit (K1-10) from Applied Surface Technologies, shown below, is supplied with two nozzles - one asymmettric venturi stainless steel on the unit and a second low velocity nozzle, an on/off gun, a 10 foot flexible stainless steel PTFE lined hose, a cylinder fitting, an optional 0.5 micron sintered stainless steel filter, and an optional 0 - 2000 psi pressure gauge. A 12, 24VDC or 120 VAC solenoid valve can be supplied in place of on/off gun.
The high purity unit (K4-10) from Applied Surface Technologies shown below has a packless electropolished stainless steel diaphragm valve to control carbon dioxide flow. Also shown is a 0.01 micron filter, a polymer nozzle, and a 10 foot flexible stainless steel PTFE lined hose. All fittings for this unit are compression fittings as opposed to NPT fittings for the standard unit shown above. Two stainless steel nozzles also comes with this unit, the asymmetric ventuir and a low velocity nozzle. For semiautomatic operation, a 24VDC or solenoid valve (with compression fittings) can be selected in place of the 90 deg. on/off valve. This unit is referred to as the K4-10S and is shown below the K4-10 unit. The high purity units can be made cleanroom ready. Further, the high purity units can be made with VCR or VCO type fittings (K4-10VCR).
The Dual Gas Unit (K6-10DG) offers a special nozzle with a nitrogen flow surrounding the carbon dioxide snow stream. This unit assists in reducing moisture condensation problems. A High Purity unit (K4-10S) is modified by using 2 solenoids (one for N2, other for CO2), and a dual foot pedal for individual control. Filters and other options can be added.
Two nozzle come with the standard and high purity units - one polymer (a fluorpolymer) and the other stainless steel. The metal nozzle is stable for either gas or liquid carbon dioxide feeds while the polymer nozzle is stable for gaseous carbon dioxide feed. Further, the polymer nozzle always has a lower flow rate than the metal nozzle although they have the same internal dimensions. The standard nozzles have a 16 mil orifice though other diameters ranging from 8 to 39.5 mils have been made and are available.
The nozzle design is by far the most important factor in performing CO2 snow cleaning. The simplest nozzles are the single expansion nozzles and are usually variations of a Venturi orifice design. The exit side is more typically a nosecone and this chamber is for dry ice nucleation. Its angle and length play an important role in determining the velocity of the stream and the snow size. Other nozzle designs are available including small diameter orifice tubes, metering leak valves or others but they nozzles violate constant enthalpy conditions. Different cleaning abilities can result from different designs.
The nozzles from Applied Surface Technologies can operate with gas or liquid CO2 while other nozzle geometries may not. This difference in operation is related to the fact that other commercial nozzles have a sudden expansion internal to the nozzle. This sudden expansion violates the need for a constant enthalpy expansion and causes the enthalpy to decrease enough to exit the mixed gas-liquid phase region shown earlier. When these nozzles are used with a liquid source, the same inefficiency is present but does not interfere with snow formation or cleaning - just wastes carbon dioxide.
The nozzles described above are point sources and clean about a 1/4 inch diameter. Layden in 1990 introduced large area double expansion nozzles and made units ranging from 1/2 inch to over 28 inches in length. The picture below shows a two inch wide large area nozzle along with the standard nozzle and an inner tube cleaning nozzle.
Our equipment can be used worldwide. In the US, we supply the CGA320 carbon dioxide cylinder fitting. In Europe, we supply the DIN 6 carbon dioxide cylinder fitting. For Japan, we supply the JIS 22R or 22L (you must specify) carbon dioxide cylinder fitting. For countries outside of US and Europe, the purchase order must specify your cylinder fitting selection; there are no extra charges for DIN or JIS fittings.
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