SNO GUNTM CLEANER
Description and Operating Instructions
You have just purchased the newest dry ice snow cleaning system, the SNO GUNTM cleaner manufactured by Va-Tran Systems, Inc. These units have been used by a number of companies in a variety of applications. This system is intended to provide an environmentally and economically sound substitute for the use of CFC based cleaners in many of current applications.
These instructions present our experience in the use of dry ice snow for cleaning. You may want to try other things or call us if you have any questions. We appreciate that part of selling any new technology is helping the customer use it successfully. If we do that, everyone will be happy.
The dry ice SNO GUNTM cleaner is a new device and as such it is important that everyone using the unit understand the potential problems. The snowflakes do look pretty and there is a tendency to "play" with the system. This is not dangerous in itself but users should know what not to do. In this connection we must emphasize that Va-Tran Systems, Inc. cannot control the applications of the purchaser. Va-Tran Systems, Inc. therefore denies all responsibilities for injuries or accidents resulting from misuse of the dry ice cleaning system.
1) Carbon dioxide (CO2 CAS # 124-38-9) is an inert gas, and human beings have a very high tolerance of exposure. OSHA requirements effective March 1, 1990 specify a TWA of 10,000 ppm and a STEL of 30,000 ppm. In real English, this means that a person can be exposed to an average concentration of 10,000 ppm over an entire 8-hour workday. A person can also be exposed to a concentration of 30,000 ppm when exposure is averaged over 15 minutes. The limit of detection of CO2 is well below both of these limits. At moderate concentrations, a sharp odor or taste will be detected. If there is a concern regarding the accumulation of CO2 in the working environment, several high quality monitors are available. The SNO GUNTM should only be used in a well-ventilated area where CO2 vapor will not build up above these levels. If the SNO GUNTM is to be used in a non-ventilated, confined area, all personnel in this area must be provided with respirators that have an external breathable air supply. A common industrial respirator or fume mask will not remove CO2 from the air.
2) The dry ice snow is very cold (-109oF). Momentary contact with human skin is harmless but a buildup of the snow will cause frostbite. The blast of dry ice snowflakes should never be aimed at any person. In many applications the dry ice snow can be swept across the surface very quickly. In most cases this will preclude any condensation of water vapor or build up of snow particles on the surface. We have never heard of or seen any cracking or scratching of ceramic or glass parts from the dry ice snow. Even gold-coated telescope mirrors have been cleaned with dry ice snow quite successfully. There is, however, always the danger of cracking with a highly stressed glass or ceramic part. Users should wear appropriate eye protection to minimize the chance of injury.
3) Parts being cleaned should be firmly supported to make sure that they do not blow away while being cleaned. No one wants to get hit by a flying wafer. The usual vacuum chuck or even a simple clamp is usually sufficient.
4) The high-pressure hose that connects the tank to the nozzle is designed to withstand the high pressures of liquid CO2 at ambient temperatures (about 850psi). However, there is always a danger that a user might shut off both the tank valve and the valve on the SNO GUNTM while there is still liquid in the line. If this happens and the hose is exposed to high temperatures, the pressure within the hose will rise rapidly. For this reason, a fragmenting rupture disk is incorporated at the tank and filter attachment. The rupture disk assembly is carefully designed and precisely calibrated to protect the SNO GUNTM from damage and users from injury. Under no circumstances should this rupture disk be defeated or replaced with an assembly not supplied by Va-Tran Systems, Inc. These assemblies are stocked and available for immediate delivery.
THE PROPER PROCEDURE FOR SHUTTING OFF THE CO2 TANK valve IS TO ALWAYS ALLOW THE CONTENTS OF THE HOSE TO BE VENTED THROUGH THE SNO GUNTM NOZZLE BEFORE THE VALVE ON THE SNO GUNTM IS CLOSED.
5) The SNO GUNTM cleaner is designed to function only when supplied with liquid CO2. The use of any other type of compressed or liquefied gas may cause damage to the SNO GUNTM and/or injury to the user. In any case this will void the warranty.
DO NOT USE THIS CLEANING DEVICE WITH ANY OTHER COMPRESSED OR LIQUEFIED GAS.
All cylinders should be adequately restrained in an approved cylinder rack or securely fastened to a structural wall to avoid any possibility of the cylinder tipping over. A generous supply of stainless steel braided hose has been provided to eliminate the need to try to stretch "just a little farther". This hose is provided only to transport carbon dioxide to the gun, it should not be used as a leash to push, pull, or tie down a cylinder.
The SNO GUNTM cleaning system starts with a stainless steel nut that connects to your carbon dioxide source. Make sure that the fittings match, that the Teflon gasket is in place inside the stainless steel nut, and that the nut is wrench tight before opening the CO2 liquid supply line. Please note that there is no regulator in the line. Regulators do not work with liquefied gasses.
Connect the SNO GUNTM to a room temperature CO2 cylinder capable of delivering liquid CO2. A cylinder marked "Liquid Carbon Dioxide" or "Siphon" is the correct type. This cylinder will have a pressure of 800 to 1200psi depending upon the ambient temperature.
The quality of CO2 is of some concern but there is no simple answer regarding which grade is correct for you. A good way to start is to locate a room temperature cylinder of 99.99% pure CO2. This is usually available in cylinders holding 20 or 50 pounds. Pricing varies depending on where you are located but is typically less than $5.00 per pound. You may be able to find it for less than $2.00 per pound if you shop around. Do not use "Welding Grade" CO2 which has too much contamination to use for cleaning purposes.
There is no simple way to determine the level of contamination in a cylinder without cleaning a test surface. If your test results show a deposit of oil, contact your CO2 supplier and purchase a better grade of CO2 or contact Va-Tran Systems for information on CO2 purification equipment. We can provide you with 99.999999% pure CO2 from contaminated sources that cost as little as 5 cents per pound.
In addition to lowering the operating cost of the SNO GUNTM, a Purifier provides more dry ice per pound of CO2 resulting in additional cleaning power. Purification equipment is priced according to flow rate requirements but $5,000.00 is typical for single cleaning station. Please contact Va-Tran Systems for additional information.
If you are using a Va-Tran Purifier, it must be attached to a source of CO2 vapor and never to liquid from a siphon cylinder. Please read the instructions provided with the Purifier before connecting the SNO GUNTM to a Purifier.
All wetted parts of the SNO GUNTM cleaner are Stainless Steel or Teflon. The specially designed and manufactured cleaning nozzle is fitted for an acrylic extension tube that can be used if very large, soft flakes are desired. Without this extension, the SNO GUNTM will generate small, hard pellets of dry ice.
Make sure the SNO GUNTM valve is closed, point the SNO GUNTM in a safe direction. Open the valve on the cylinder, then slowly open the SNO GUNTM valve. There will be an initial flow of gas through the system for purging the line. Once the system is purged, you will begin to get a mixture of CO2 vapor and dry ice flakes.
Changing the rate of flow and slipping some insulation on the outside of the acrylic tube will change the flake size. Lengthening the tube will result in larger flakes.
WATCH OUT FOR A BUILD UP OF DRY ICE PLUGS IN THE TUBE. THEY CAN BREAK LOOSE AND FLOW OUT AT A HIGH VELOCITY. BE CAREFUL WHERE THE SNO GUNTM CLEANER IS POINTED TO AVOID INJURY.
If the acrylic tube is not used, the SNO GUNTM cleaner will generate very small, hard pellets that are useful in many cases. Determining the best configuration is generally best done with brief experimentation. When you find that you are just getting a cool gas and no snow or dry ice, this is the indication that your liquid CO2 source is exhausted. It is time for another tank.
Experiment with a clean, smooth, and dry glass or stainless steel surface. Contaminate the surface with dust particles, turn on the SNO GUNTM cleaner until you get the soft flakes and let the flakes slide across the surface. Aiming the SNO GUNTM nozzle almost parallel to the surface is most effective for dust. If you aim the nozzle vertically, it will remove light oil deposits, such as fingerprints. This process involves localized melting of dry ice particles as they impact the substrate. Liquid CO2 is an excellent solvent for organics.
If you have a problem with condensation, an infrared heat lamp or hot plate should be used to warm the surface to be cleaned. Heating the substrate to about 20oC above ambient before and after cleaning will preclude any condensation after cleaning.
You can check for dust deposition and removal using a sharply focused bright light aimed at an angle to the surface. Dust particles 5 microns and larger will show up very nicely. Fluorescent dust is very easy to detect with an UV lamp of the type sold to mineral hunters by hobby shops.
Don't make the mistake of thinking that the longer you clean the better you clean. If you can't get the dust off with 5 second bursts, the SNO GUNTM cleaner may not be suited for that application. If you do get condensation of water, the surface will become very hard to clean. The best solution is to warm up the surface with a small heat source (an industrial heat gun, hot plate, or infrared lamp) and try again.
If you are in a very humid area, you may want to flood the cleaning site with a dry gas. Usually CO2 gas is lower in cost than dry air or Nitrogen. In this case you need a CO2 tank without a siphon. For this application where you want a dry gas, the usual CO2, or Nitrogen regulator should be used.
OBSERVE ALL SAFETY PRECAUTIONS DISCUSSED ABOVE WHENEVER LARGE QUANTITIES OF NITROGEN OR CO2 GAS ARE VENTED INTO A CLOSED AREA.
Feel free to call upon Va-Tran Systems if you have problems. Part of the selling price of this unit includes technical assistance. Va-Tran Systems has experience with special systems and we can fabricate nearly anything that you need for the proper application of this equipment.
677 ANITA STREET, SUITE A, CHULA
VISTA, CALIFORNIA 91911
phone: 619/423-4555 toll free 800/379-4231 fax: 619/423-4604
Copyright 1998, Va-Tran Systems