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BT-235B
VJ Series
CO2 / N20 Bulk Storage Tanks
Do not attempt to use or maintain these units until you read and understand these instructions. Refer to the TaylorWharton’s Safety First booklet (TW-202) for handling cryogenic material. Do not permit untrained persons to use or maintain this equipment. If you do not understand these instructions, contact your supplier for additional information.
9918-7827 6/18/02
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TABLE OF CONTENTS |
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SAFETY PRECAUTIONS FOR CARBON DIOXIDE ........................................................................ |
3 |
SAFETY PRECAUTIONS FOR NITROUS OXIDED......................................................................... |
4 |
INTRODUCTION.................................................................................................................................. |
5 |
PROPERTIES OF CARBON DIOXIDE ............................................................................................... |
5 |
FUNCTIONAL DESCRIPTION............................................................................................................ |
6 |
TANK CONSTRUCTION ................................................................................................................. |
6 |
PIPING AND CONTROLS ............................................................................................................... |
6 |
Fill................................................................................................................................................... |
6 |
Liquid and Vapor Connections....................................................................................................... |
6 |
Instrumentation............................................................................................................................... |
7 |
Safety Relief ................................................................................................................................... |
7 |
Refrigeration................................................................................................................................... |
7 |
INSTALLATION................................................................................................................................... |
8 |
HANDLING....................................................................................................................................... |
8 |
INSTALLATION CHECKS .............................................................................................................. |
8 |
CUSTOMER INSTALLED EQUIPMENT/PIPING ......................................................................... |
8 |
RIGGING ......................................................................................................................................... |
10 |
OPERATION ....................................................................................................................................... |
12 |
PURGE PROCEDURE .................................................................................................................... |
12 |
FILLING PROCEDURE.................................................................................................................. |
13 |
MAINTENANCE................................................................................................................................. |
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LEAK TEST..................................................................................................................................... |
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HAND VALVES.............................................................................................................................. |
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BACK PRESSURE VALVE............................................................................................................ |
14 |
RESETTING BACK PRESSURE VALVE................................................................................. |
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PRESSURE AND LIQUID LEVEL GAUGES ............................................................................... |
14 |
CASING AND VACUUM MAINTENANCE .................................................................................... |
15 |
CHECKING VACUUM................................................................................................................... |
15 |
VACUUM GAUGE TUBE.............................................................................................................. |
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ANALYZING VACUUM DETERIORATION............................................................................... |
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TESTING FOR CASING LEAKAGE............................................................................................. |
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BREAKING VACUUM................................................................................................................... |
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RE-EVACUATION PROCEDURE................................................................................................. |
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PAINTING ........................................................................................................................................... |
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SAFETY PRECAUTIONS PERTAINING TO PAINTING OPERATIONS ................................. |
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MOVING THE TANK......................................................................................................................... |
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TROUBLE-REMEDY GUILD ............................................................................................................ |
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RECOMMENDED TOOLS, EQUIPMENT AND MATERIALS ...................................................... |
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REPLACEMENT PARTS.................................................................................................................... |
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APPENDIX A: CONTENTS GAUGE CHARTS............................................................................... |
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APPENDIX B: OPTIONAL REFRIGERATION SYSTEM KIT ...................................................... |
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Introduction ...................................................................................................................................... |
33 |
Condenser Unit................................................................................................................................. |
33 |
Tank Evaporator Coil ....................................................................................................................... |
33 |
Pressure Control Switch ................................................................................................................... |
33 |
Thermostatic Expansion Valve and Bulb ......................................................................................... |
34 |
Filter / Drier and Sight-glass ............................................................................................................ |
34 |
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SAFETY PRECAUTIONS FOR CARBON DIOXIDE |
WARNING: |
Carbon Dioxide can cause asphyxiation and death in confined, poorly |
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ventilated areas. Cold Carbon Dioxide gas can cause severe frostbite to the |
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eyes or skin. Do not touch frosted pipes or valves. If accidental exposure |
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occurs, consult a physician at once. If a physician is not readily available, |
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warm the areas affected by frostbite with water that is near body temperature. |
KEEP WORK AREA WELL VENTILATED
Carbon dioxide affects the important acid-base balance in the body. Carbon dioxide is formed from normal functioning of the body, but the body can tolerate increased amounts of carbon dioxide only in limited concentration. This is recognized in OSHA standards where a Threshold Limit Value of 5,000 parts per million by volume (0.5 percent concentration) has been adopted. For safety, concentrations above this level should not be permitted; increased concentrations can cause bodily harm or death. Additionally, carbon dioxide can cause asphyxiation by displacing oxygen resulting in dizziness, unconsciousness or death.
Ten percent carbon dioxide in air can be endured for only a few minutes; twelve to fifteen percent soon causes unconsciousness; twenty five percent may cause death if exposure lasts for several hours. Carbon dioxide cannot be detected by human senses and will be inhaled like air. Carbon dioxide is heavier than air and will accumulate in low-lying areas. Carbon dioxide concentrations will be greater in these areas. If adequate ventilation is not provided, carbon dioxide may displace normal air without warning that a life-depriving atmosphere is developing.
COVER EYES AND SKIN
If released to atmosphere, liquid carbon dioxide will turn to carbon dioxide snow. Accidental contact of carbon dioxide snow or cold gas with the eyes or skin may cause severe frostbite. Handle liquid so that it will not vent or spill. Protect your eyes with safety goggles or a face shield. Cover the skin to prevent contact with snow or cold gas, or with cold pipes and equipment. Protective gloves can be quickly and easily removed and long sleeves are recommended for protection.
GROUP ALL PIPING
The rapid discharge of liquid carbon dioxide through a line, which is not electrically grounded, will result in a buildup of static electricity. Contact with this electrical charge could be startling and potentially dangerous to operating personnel. Such lines should be grounded before use.
NOTE: |
For additional information of properties of carbon dioxide and proper handling refer to |
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CGA pamphlets G-6, "Carbon Dioxide" and G-6.1, "Standard for Low Pressure Carbon |
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Dioxide Systems at Consumer Sites". These publications are available from the |
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Compressed Gas Association, 1235 Jefferson Davis Highway, Arlington, VA, 22202. |
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SAFETY PRECAUTIONS FOR NITROUS OXIDED |
WARNING: |
The following safety precautions are for your protection. Before performing |
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installation, operation, or maintenance procedures, read and follow all safety |
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precautions in this section and in reference publications. Failure to observe |
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all safety precautions can result in property damage, personal injury, or |
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possibly death. It is the responsibility of the purchaser to adequately warn |
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the user of the precautions and safe practices for the use of this equipment |
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and the cryogenic fluid stored in it. |
Nitrous oxide is a gas, which has no color, taste, and practically no odor. It is obtained by the thermal decomposition of ammonium nitrate, which yields nitrous oxide and water. Due to the toxic impurities produced in this process, the water is condensed out and the gas is passed through scrubbing towers to remove impurities.
EXTREME COLD – COVER EYES AN EXPOSED SKIN
Accidental exposure or contact with skin or eyes can cause severe frostbite. Avoid contact with cold piping and equipment. Protect eyes with goggles or shield, especially if there is a possibility of liquid ejection or if cold gas may issue forcefully from equipment. Keep skin covered at all times.
KEEP WORK AREA WELL VENTILATED
Due to the difficulty of detecting nitrous oxide's presence, there is eminent danger of loss of consciousness and physical inability to function if exposed to low levels of this gas, and death by asphyxiation if exposed to medium or high levels. Since nitrous oxide is a non-toxic gas, these hazards are created when life-supporting oxygen is displaced. The American Conference of Governmental Industrial Hygienist (ACGIH) in it's "Threshold Limit Valves & Biological Exposure Indices for 19891990" recommends a 50 ppm threshold limit value - Time Weighted Exposure Limit (TLV-TWA). It is imperative to maintain a well-ventilated work environment to minimize the danger from a leaking system or activated safety relief device.
DANGER OF EXPLOSION
Nitrous oxide is non-flammable but, as with oxygen, ignition of combustible materials may occur more readily in a nitrous oxide-enriched atmosphere. Nitrous Oxide decomposes exothermically under conditions of high temperature and pressure. If sufficient heat is added, the decomposition can be self-sustaining and, with high temperature and pressure, nitrous oxide can explode. Open flame and smoking are strictly prohibited.
NOTE: For more detailed information concerning safety precautions and safe handling of nitrous oxide, consult CGA pamphlet G-8.1, "Standard for Nitrous Oxide at Consumer Sites", and CGA pamphlet G-8.2 "Commodity specification for Nitrous Oxide". These publications are available from the Compressed Gas Association, 1235 Jefferson Davis Highway, Arlington, VA 22202.
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INTRODUCTION
This manual provides information for the user to operate and maintain Taylor-Wharton Cryogenics VJSeries Carbon Dioxide Storage Vessels. These tanks are primarily intended for liquid withdrawal at a normal operating pressure between 260 psig (18 bar/1793 kPa) and 320 psig (22 bar/2206 kPa), the maximum allowable working pressure is 350 psig (24 bar/2413 kPa). If your application requires the withdrawal of gaseous product, the flow rate must not exceed the ability of the tank to maintain a minimum pressure of 200 psig (14 bar/1379 kPa) at all times. The constant withdrawal of gaseous product at high flow rates will cause a decrease in tank pressure. This effect can be overcome by installing an electric pressure building vaporizer. Supply and return connections are provided on the tank to allow for the addition of this feature if required.
CAUTION: To avoid irreparable damage to the structure of the tank, an internal pressure of no less than 200 PSIG (14 bar/1379 kPa) must be maintained at all times.
These instructions are for experienced operators only. If you are not fully familiar with the principles of operations and safe practices for cryogenic equipment and supply systems, we urge you to read and fully understand the SAFETY PRECAUTIONS and REFERENCE PUBLICATIONS listed in this manual.
Tank specifications, flow diagram and an elevation with bottom view of the tank showing controls and piping may be found on the General Arrangement Drawings located in the back of this manual. Additional copies of these drawings may be obtained from the factory. Please include information on the tank model number and part number in making drawing requests. Tank Specifications, Rigging Details and Vacuum System Components are also shown in this manual.
PROPERTIES OF CARBON DIOXIDE
Under normal atmospheric conditions, Carbon Dioxide exists as a colorless, odorless gas, which is about 1.5 times heavier than air.
When confined to a storage tank, depending upon the pressure carbon dioxide can exist in any three states of matter; SOLID, LIQUID and GAS. The point at which all three states may exist is 75 psia [60.4 psig (4 bar)]. This is the triple point. At temperatures and pressure below these values, carbon dioxide may either be a solid or a gas, depending on the conditions.
At temperatures and pressures above the triple point, carbon dioxide liquid with overlaying gas may exist in equilibrium within a closed vessel.
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FUNCTIONAL DESCRIPTION
TANK CONSTRUCTION
The pressure vessel is suspended inside the vacuum jacket and insulated with perlite powder. The liquid and gas phase lines to the pressure vessel pass through the lower head of the vacuum jacket. All piping is designed to withstand the stresses caused by expansion and contraction of the pressure vessel, its support system, and the piping itself.
The pressure vessel is designed and constructed in accordance with the ASME Boiler and Pressure Vessel Code Section VIII, Division 1. The inner vessel is constructed of SA-612 normalized carbon steel and the piping is stainless steel. The vacuum jacket and support legs are made of structural grade carbon steel.
The insulation space between the pressure vessel and the vacuum jacket is filled with perlite powder and evacuated to a high vacuum through an EVACUATION VALVE (V-4) that is sealed at the factory. Insulation space vacuum is measured in the field by connecting a vacuum gauge to the VACUUM GAUGE TUBE (VR-1) located on the lower head of the tank. The VACUUM GAUGE TUBE (VR-1) is isolated from the vacuum jacket by a VACUUM GAUGE VALVE (V-3).
PIPING AND CONTROLS
The following paragraphs describe the operation of the main circuits of the VJ-CO2 bulk tanks. The descriptions refer to the main components of each circuit and are grouped by function. These component and circuit descriptions are pertinent to any of the tanks and should be read before attempting operation.
Fill
LIQUID FILL CONNECTION (CN-1) is a connector through which the tank is filled with liquid. It is connected to a line that connects to the bottom of the inner vessel.
LIQUID FILL VALVE (V-1) regulates flow of liquid through LIQUID FILL CONNECTION (CN-1) during a filling operation.
VAPOR EQUALIZATION CONNECTION (CN-2) is a connection where a hose is connected to the transport trailer during fill to allow equalization of tank and trailer pressures throughout the pump transfer. Presence of liquid product in this line indicates a full tank.
VAPOR EQUALIZATION VALVE (V-2) isolates VAPOR EQUALIZATION CONNECTION (CN- 2) from the transport.
DRAIN VALVES (V-9A, V-9B) are provided to relieve transport hose pressure.
Liquid and Vapor Connections
Two liquid and two vapor connection are provided on the VJ-6, VJ-14, and VJ-26 tanks. Three liquid and two vapor connections are provided on the VJ-35 and VJ-50 tanks.
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Instrumentation
LIQUID LEVEL GAUGE (LI-1) is a differential pressure gauge that indicates tank liquid level and is calibrated for lbs/tons of CO2.
PRESSURE GAUGE (PI) is a 0-600 psi gauge with 4-1/2" face. It is mounted beside the liquid level gauge.
INSTRUMENT EQUALIZATION VALVE (V-7) is used to equalize the pressure between the high and low-pressure sides of the contents gauge.
LIQUID PHASE ISOLATION VALVE (V-6) isolates contents and pressure gauges from the tank liquid (bottom) phase.
VAPOR PHASE ISOLATION VALVE (V-5) isolates contents and pressure gauges from the tank gas (top) phase.
Safety Relief
OUTER JACKET LIFT PLATE (R-1) protects the tank vacuum jacket from overpressure.
SAFETY RELIEF VALVES (SV-1A, SV-1B) provide overpressure protection for the pressure vessel. They will relieve excess tank pressure in the event that the maximum allowable working pressure of the tank is exceeded. Once activated, the valve will close when the pressure falls below 350 psig (24 bar/2413 kPa).
SAFETY RELIEF VALVE SELECTOR (V-10) permits the operation of one safety valve while the other is isolated. This arrangement prevents both valves from being isolated from the tank at the same time and permits maintenance of a valve without the need to vent tank pressure. To activate one valve while isolating the other move the selector valve handle all the way to the end of its travel toward the valve to be activated
BACK PRESSURE REGULATOR (PCV) automatically closes on falling tank pressure and opens on rising tank pressure to allow the tank to maintain a set pressure during periods of little or no usage. This valve is factory set at 325 psig (22 bar/2241 kPa).
ISOLATION VALVE (V-8) must be opened to activate the Back Pressure Regulator (PCV-1).
Refrigeration
An internal refrigeration coil is supplied as standard equipment on the VJ-6 ton and VJ-14 ton tanks. It has been sized to condense gaseous product produced by normal heat leakage into the tank. An optional one-half horsepower refrigeration condenser unit is available for these two sizes (see Appendix B).
The VJ-26, VJ-35, and VJ-50 ton tanks may be ordered with an optional internal refrigeration coil. It is suitable for connection to a one horsepower refrigeration condenser unit.
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INSTALLATION
HANDLING
Tank installation is the customer's responsibility. The tank is shipped in the horizontal position and secured on wooden cradles. These cradles must be removed prior to erection of the tank. Make certain the foundation used for the tank is designed for the conditions at the installation site, and that it is suitable for the tank weight. Refer to local codes for recommended foundation specifications. Employ experienced personnel to move and install the tank. Ensure that rigging equipment has adequate rated capacity to handle the tank weight listed in the specifications. This tank must be shipped and lifted empty, and with a warm inner vessel.
CAUTION: To prevent possible tip over, do not leave the tank standing upright unless it is on a specified foundation or other hard surface capable of supporting its weight. Loading on the tank legs is great enough to cause them to sink into most surfaces other than reinforced concrete.
INSTALLATION CHECKS
Before erecting the tank, inspect it carefully for possible shipping damage. Report any damage to the carrier and the factory. In addition, check tank pressure and vacuum as follows:
1.Tanks are shipped pressurized with nitrogen gas at 20 psig (1.4 bar/138 kPa). Open the gauge ISOLATION VALVE (V-5) and read tank pressure indicated on the PRESSURE GAUGE (PI). Record the "as received" tank pressure. Close the ISOLATION VALVE (V-5). Tank pressure may change due to temperature variations, accidental opening of valves, packing leaks, or minor leaks at the fill connections. If a positive pressure is not indicated on the PRESSURE GAUGE (PI) and no repairable leaks are found, contact the factory in accordance with conditions specified in the tank warranty.
2.Check insulation space vacuum by connecting a Hasting-Raydist Model TV-4A or VT-6 vacuum gauge to the tank VACUUM GAUGE TUBE. Open the tank VACUUM GAUGE VALVE (V-3), wait 30 minutes, and take a reading. If the "as received" vacuum (tank at ambient temperature) is greater than 100 microns (0.10 mm Hg) absolute, contact the factory
3.Remove shipping screws from all LIQUID LEVEL GAUGES that are equipped with adjustable level switches.
4.Attach a tag to the tank PRESSURE GAUGE (PI) indicating the normal operating pressure range of the tank. This information enables an operator to monitor tank pressure during a tank fill, and to prevent pressure upsets caused by improper fill procedures.
CUSTOMER INSTALLED EQUIPMENT/PIPING
External piping may employ carbon steel or stainless steel pipe. Liquid lines should be insulated with several inches of polyurethane insulation.
When installing vaporizing and control equipment, be sure to follow accepted design practices for your gas service. Be sure to include pressure relief valves in piping where liquid product could be trapped between closed valves, regulators, etc.
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Designing safe and effective systems for handling liquefied gases requires extensive knowledge and experience. Persons lacking the necessary skills are urged to seek help from the manufacturer. Design and consultation services are available from the Customer Service Department.
WARNING: To protect the purity of the pressure vessel, all tanks are shipped with a charge of nitrogen at 20 PSIG (1.4 bar/138 kPa). Before removing the pipe plugs for attachment of customer piping, the pressure vessel must be relieved to prevent personal injury to installation personnel.
To relieve shipping pressure for piping, open the LIQUID FILL VALVE (V-1) and VAPOR EQUALIZATION VALVE (V-2) until the PRESSURE GAUGE (PI) indicates zero psig. The close (V-1) and (V-2).
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RIGGING
Note: Refer to General Arrangement Drawing for Critical Weight and Dimensional Data
Rigging VJ-6 TON & VJ-14 TON
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Note: Refer to General Arrangement Drawing for Critical Weight and Dimensional Data Rigging VJ-26 TON, VJ-35 TON & VJ-50 TON
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