Vol: 4 and d LP SNG an LPG G Systems Over Overv view A Hand andbook from the SNG Academy ™
Tulsa, Oklahoma, USA
LPG and SNG Systems Overview Table of Contents C ontents History & Abstract Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 General Business Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Te Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Purpose of the handbook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 SNG System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 SNG System Owner Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 LPG Cylinder Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 LPG Storage anks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 LPG Pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 LPG Vaporizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 SNG Blenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Venturi SNG Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Proportional SNG Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Old Fashioned Piston ype Mixers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 SNG to NG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Properties of LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Codes & Standards (USA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 LPG Safety Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Combustion Characteristics of LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 SNG System Operation, Maintenance and Malfunctions . . . . . . . . . . . . . . . . . . . . . 34 Emergency Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Disclaimer of Responsibility: Ely Energy Inc. does not warrant or assume any legal liability or responsibility for the accuracy, completeness, completeness, or usefulness of any information, apparatus, product, or process described herein. Ely Energy Inc. assumes no liability for the misuse, abuse, or incorrect application of data presented. This Handbook does not purport to cover all details or varia tions in equipment nor to provide for every possible conti ngency to be met in connection with installation, operation, maintenance or training. Should further information be desired or should particular problems arise which are not covered sufficiently for the readers purposes the matter should be referred to Ely Energy Inc.
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LPG and SNG Systems Overview Table of Contents C ontents History & Abstract Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 General Business Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Te Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Purpose of the handbook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 SNG System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 SNG System Owner Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 LPG Cylinder Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 LPG Storage anks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 LPG Pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 LPG Vaporizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 SNG Blenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Venturi SNG Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Proportional SNG Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Old Fashioned Piston ype Mixers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 SNG to NG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Properties of LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Codes & Standards (USA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 LPG Safety Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Combustion Characteristics of LPG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 SNG System Operation, Maintenance and Malfunctions . . . . . . . . . . . . . . . . . . . . . 34 Emergency Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Disclaimer of Responsibility: Ely Energy Inc. does not warrant or assume any legal liability or responsibility for the accuracy, completeness, completeness, or usefulness of any information, apparatus, product, or process described herein. Ely Energy Inc. assumes no liability for the misuse, abuse, or incorrect application of data presented. This Handbook does not purport to cover all details or varia tions in equipment nor to provide for every possible conti ngency to be met in connection with installation, operation, maintenance or training. Should further information be desired or should particular problems arise which are not covered sufficiently for the readers purposes the matter should be referred to Ely Energy Inc.
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LPG and SNG Systems Overview
History & Abstract Synthetic Natural Natura l Gas (SNG), (SNG), plays a niche role, yet a critical role in meeting the t he energy needs of nations around the world. SNG is a term that describes a variety variet y of “manufac “manufactured tured gases”. In our language, SNG is a blend of Liquefied Petroleum Gas (LPG) and air that provides a direct replacement for natural gas.
Tis handbook ha ndbook provides basic information and describes describe s concepts and equipment common to the SNG industry. Our presentation is intended to assist personnel who are involved with SNG SNG systems systems and equipm equipmen ent. t.
History of Ely Energy, Inc. From 1898 1898 to the 21st-Century… 21st-Century…
In 1898, 1898, Energy Systems, Inc. (ESI) began bega n as a mechanical mechanica l contractor located in southern Minnesota (USA). By the 1950’ 1950’ss ESI had branched out into associated as sociated mechanical mechanica l engineering activities that grew to include design and manufacture of Synthetic Natural Gas (SNG) systems. Teir applications included peak shaving for natural gas utilities and industry, industry, backup fuel systems s ystems and CityGas CityGa s distributed gas systems. s ystems. Around 1980, 1980, ESI was acquired by the RJ Ely Company of ulsa, Oklahoma (USA) and began operations as Ely Energy Systems, and later as Ely Energy Inc. — a subsidiary of the RJ Ely Company. In 1998, under a corporate c orporate consolidation, the corporation formally formal ly changed to Ely Energy, Inc. (EEI).
General Business Description EEI specializes in specific niche market opportunities opportunities that typically t ypically involve LPG (liq (liquid uid fired petroleum gases) ga ses) or NH3 (ammonia). (ammonia). Te cornersto cornerstone ne of EEI’s EEI’s business is i s the so-called so-ca lled synthetic natural natura l gas (SN (SNG) G) group group that offers solutions solutions to assist in i n natural natura l gas ga s management. Most people have have heard of natural natura l gas. Some have heard of liquefied petroleum gas (LPG). (LP G). Few outside the energy energ y sector, however, however, understand SNG. We create SNG by blending LPG with air to a specific specific ratio ratio that results results in a fuel with with comb combustio ustion n characteri characteristics stics essen essentially tially identical identical to natural natura l gas. Tis T is precise and controlled controlled mixing of LPG and air allows it to be used as a s an alternative alternative to natural gas for “backup” use, ‘peak shaving’, shaving’, and CityGas CityG as supply in regions where natural gas is not yet available. No orifice changes, pressure changes or any other changes are required to the natural gas consuming equipment! SNG is a direct replacement for natural gas (NG)! Te technology of blending LPG and Air to simulate natural gas is not new — SNG extends back to the 1950’s. What is new is our ability to provide much higher degrees of control, control, gas quality qua lity consistency consistency and a nd safety to the t he process. Our SNG solutions solutions assist in natural natu ral gas ga s energy management mana gement for for private industry, the federal government, the U.S. military militar y, municipalities, educational and correctional correctional institutions i nstitutions and the medical-health care sector. We offer solutions in various forms, typically involving the installation of an on-site SNG system for either ‘standby’ or ‘base load’ use. With With ancestral roots that trace trace to 1898, 1898, EEI is easily one one of of the most most respected respected SNG SNG 2
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Ely Energy, Inc.
equipment and service providers in the world. Our commitment is to optimize our available resource base to make every project successful. We provide a variety of SNG energy services including: ■
SNG Backup Systems: Allow Systems: Allow the industrial natural gas customer to change from a FIRM FIR M to an INERRUPIBLE INERRUP IBLE Natural Natural Gas Ga s rate structure. Te savings will often pay for an installation within 6 mo. or less, up to 4 years.
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SNG Peak Shaving Systems of NG: SNG NG: SNG is used by both NG Companies and Industrial Clients to augment their NG demand during peak demand periods.
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SNG Base-Load Systems: Provide Systems: Provide SNG in regions where NG NG is currently cur rently not available. SNG provides a bridge fuel or a long-term solution solution for an energy energ y need.
The Company We We can be contacted contacted at fax (9 (918) 254-54 54-5412 12 (USA) (USA) or at our e-mail: e-mail: sales@elyen sales@elyenergy ergy.co .com. m. Our telephone telephone switchboard sw itchboard is at (91 (918) 250-6601. 250-6601. ouch ouch ‘0’ for the Operator to direct direc t your call. ca ll. Or visit us on the Internet at ww at www w.elyenergy .elyenergy.com .com.. Our physical physica l address is 1138 11385 5 East 60th Place South, ulsa, ulsa , Oklahoma Ok lahoma 741 74146 (U.S.A.). ( U.S.A.).
AQUA-GAS AQUA- GAS ® under manufacture at Ely Energy.
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LPG and SNG Systems Overview
Purpose of the Handbook Te purpose of this handbook is to provide information on the properties of LPG and basic operation of an SNG system. Tis includes basic safety and operational information. Any training must be conduc conducted ted by a techni technician cian trained trained in the prope properties rties of LPG and the application of LPG equipment to “real life” scenarios. Handbook Includes: • •
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An overview overview of LPG and SNG SNG systems systems An introductio introduction n to the the basic basic properties properties of of LPG and and how how those properties properties impact impact the operation of an SNG system An introduction introduction to to applicabl applicablee codes and standards used to to design, design, manufacture, and maintain safe operation of an SNG system Teory of operation of major subsystems of an SNG system Basic maintenance requirements How to recognize non-standard operating and emergency situations
Handbook Does Not Include: • • •
Details of combustion or “plant specific” burner applications Review of all code requirements requirements Knowledge or training necessary necessar y to make design changes to an LPG or SNG system
SNG System Overview Purpose of an SNG System:
o provide a substitute synthetic natural gas g as (SNG) to to replace or augment natural gas. ga s. SNG burns burns with similar characteristics char acteristics as natural gas. ga s. SNG requires no changes to pressure regulators or burner orifices. SNG is introduced introduced at the same pressure as natural gas. g as. SNG provides provides a similar similar “energy value” to natural natura l gas (wobbe index) at the burner tip. tip. • • • •
SNG systems utilize five basic subsystems: Truck Transfer Unloading facility (U) to receive liquid LPG from a transport •
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(~ 9,000 US gal gallons/load). lons/load). LPG Storage Tanks to store the liquid LPG. An LPG pump system to transfer and elevate the pressure of the liquid LPG from the tanks tank s to the vaporizer. An LPG vaporizer vapori zer to heat the liquid LPG and change it into the vapor (gaseous) phase. An LPG/ LPG/Air blender to blend the necessary air with the LPG vapor to create SNG.
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“tie-in” point to the existing natural gas piping is another subsystem. Almost always, this point is just downstream of the existing service regulator/meter at the natural gas entrance to the plant. Five Key Subsystems of an SNG system TTU/cylinder filling LPG Storage LPG Pump System LPG Vaporizer SNG Blender
DISCUSSION TOPICS
1. 2. 3. 4. 5.
Typical small capacity SNG System Layout
Optional components may also be associated with an SNG system (examples include): Methanol injector system located at the U to inject methanol into the storage tanks •
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to remove water which may be in the LPG. SNG metering system usually located at the outlet of the SNG blender to provide an accurate measurement of the SNG used. A ‘Gas Quality Instrument’ to ensure the SNG has the proper energy content to replicate the energy valve of the natural gas. Flare Stack allows testing the LPG air system at any time without running it into the plant or to ensure the SNG mix is good prior to sending it into the plant. Natural Gas peak shaving configurations allow SNG to augment the flow rate of natural gas either by pressure or ratio control. Remote monitoring system to provide annunciation of key safety limits and the ability to adjust flow rates from a remote location.
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LPG and SNG Systems Overview
TTU (Truck Transport Unloading Facility) A normal U off-loads a 9000 gallon (34m3) transport in about 1 hr and 15 minutes. Tis rate of off-loading is based on using a 2 liquid line and 1 ¼ vapor line with valving sized for the pipe. Liquid is extracted from the transport via the larger diameter line. Te smaller diameter line prevents a vacuum forming in the truck by allowing the pressures to equalize between the truck and the storage tank. A common cause of accidental spills of LPG is a pull-away at an LPG transfer area. Te term “pull-away” refers to an accident caused by a bulk truck moving away from the transfer point with the transfer hoses still connected to the U. A pull-away could break a hose, or in a severe case, pull out the piping network. In either case, a pull-away would create a large LPG spill and possibly result in a fire. o avoid these problems the U design incorporates a robust steel bulkhead set in a massive concrete foundation. Te U utilizes shear fittings that “break away” in a designed fashion in the event of an accidental truck pull-away. Te U is protected by large steel or concrete posts to prevent vehicles from colliding with the critical piping. Industry studies prove a point of failure can be predicted and that a specific pull-away force can be determined at which the piping will rupture in a “clean break.” Tese studies have resulted in designs and connections using Schedule 80 pipe nipples and couplings. An example of a U bulkhead is shown on the opposite page. "
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The key components of the TTU include: • • • • •
Steel bulkhead configured to meet code, including risers and concrete. “Acme” fittings to connect to hoses which normally come with the transport. Back Check Valve on the liquid line. Hand-operated back check valve on the vapor line. Emergency Safety Shutdown system (ESS Station).
About the TTU
Te U is designed to cause a predictable shear failure by utilizing forged steel pipe couplings welded vertically into a reinforced steel channel member and mounted onto two legs. Te U is set into a hole approximately 4ft by 4ft filled with concrete. Tis design protects the structural integrity of plant piping and equipment should a pull-away occur from any angle or position. Force applied to the vertical pipe nipples above the horizontal bulkheads channel results in deformation of the pipe nipple threads. Te threads continue to deform as more force is applied until the pipe nipple pulls out of the coupling. Automatic valves on the tank side of the U will then immediately shutdown the flow of LPG from the piping system. A pull-away force can be selected that would be greater than any force expected in normal operations and smaller than that which might cause hose rupture or which could pull out 6
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Typical TTU (Truck Transport Unloading) Station with Emergenc y Pull Cable. Refer to the current or appropriate version of NFPA 58 for requirements.
the valves from the vehicle tank. esting indicates a 2-inch hose requires almost 8000 lb. to break (or pull off certain fittings); a 3-inch hose requires about 11,000 lb. to failure. Tere are several additional desirable features of this vertical coupling breakaway system. ests show that nipples pulled out completely will result in sudden release of LPG. Tis will cause slugging of the system’s excess flow valves. Additionally, if the pullout nipple is mounted above the coupling, the released LPG will go straight up. Tis is the most desirable direction for safe dissipation of the LPG. Te most important attribute of this system is that the pulling force can come from any direction without compromising the design.
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LPG and SNG Systems Overview
SNG System Owner Responsibilities: LPG Transfer According to NFPA 58, during the LPG transfer process, at least one qualified and trained person must remain in attendance from the time connections are made from the truck to the U, until the valves are closed and the transfer hoses are disconnected. Without direct control as provided by the person delivering LPG, it is difficult to insure all steps are properly and safely completed. Often SNG system owners leave all transfer responsibility with the LPG supplier. Since most accidents happen during LPG transfer, a greater role should be taken by the SNG system owner. At a minimum, SNG system owners should: •
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Keep a log of tank volumes and make their own calculations to confirm that the tank(s) can accept the volume of LPG ordered. When the SNG system has more than one tank, provide a plant person during the transfer to insure the LPG goes into the correct tank(s). If your LPG supplier handles more products than LPG, make your own confirmation that the delivered product is LPG. ake any additional steps necessary to improve the reliability and safety of LPG delivery. Confirm that the tank(s) are not over filled.
The LPG vendor making delivery of LPG should: • • • • • • • • • • •
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Inspect the general area for hazards and access for their truck. Position the truck correctly and chock the wheels. Inspect the truck for damage. Check the contents of the truck to confirm the product is LPG. Perform a ‘sniff’ test to confirm an odorant is present. Record the pressure and temperature readings of the LPG tank. Determine the maximum amount of LPG which can be added to each tank. Connect the transfer hoses. ransfer the LPG. Disconnect the transfer hoses. Prepare the truck for departure.
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LPG Cylinder Filling Filling Cylinders
Tis brief training overview does not include sufficient detail to instruct the readers to become fully competent to perform full inspections of cylinders prior to filling. However, all operators are expected to follow the procedures and set aside all suspect cylinders for further inspection by your LPG supplier or cylinder supplier. Inspect the Cylinder Filling Area
LPG filling or dispensing stations should be kept clear of trash and debris. An accumulation of leaves and other combustible materials pose a significant fire hazard and may interfere with operation of the transfer equipment. During transfer operations, remove all sources of ignition within 25 feet of a point of transfer. Shut down internal combustion engines within 15 feet of a point of transfer when a transfer operation is in progress.
UFM Filling machine Modern LPG c ylinder filling machine using a small PLC and weight based filling.
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LPG and SNG Systems Overview
LPG Cylinder Filling Inspect the Containers and Valves
Check the retest date on each cylinder and be aware of the inspection periods and type of retests required for various DO cylinders. Note that relief valves in forklift cylinders must be replaced 12 years after manufacturer and every 10 years thereafter. You must also confirm that all cylinders are fitted with an OPD (overfill prevention device). Check containers to be filled for visual evidence of damage to valving or to the container walls from any of the following: Fire damage. If there is evidence that the protective coating has been burned off any portion of the cylinder surface, or the cylinder body is warped or distorted, it must be assumed that the cylinder has been overheated and must be removed from service. Check with your cylinder supplier. Dents. Dents are deformations caused by the cylinder coming in contact with a blunt object in such a way that the thickness of the metal is not materially impaired. Some dents which do not include a weld or are not sharp or defined may be tolerated. Check with your cylinder supplier. Cuts, Gouges and Digs. Cuts, gouges, and digs are deformation caused by contact with a sharp object in such a way as to cut into or upset the metal of the cylinder, decreasing the wall thickness at that point and raising the stresses in the material. Refer all gouged cylinders to your cylinder supplier. Corrosion. Corrosion or pitting involves the loss of wall thickness by corrosive action. Refer these cylinders to your supplier. Leaks. Permanently remove ALL cylinders with leaks, other than leaks at fittings which can be tightened, from service. Neck Flange or Foot Ring Defects. Check both areas for damage along with damage to valves or gauges. Markings. Code requires labels on each cylinder, indicating LPG as the contents. •
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When filling by volume, open then close the fixed liquid level gauge to be sure vapor vents
from the bleeder orifice. If no vapor escapes, the orifice may be blocked and must be reopened before the gauge will operate properly. Do not attempt to fill a cylinder by volume if the fixed level gauge is damaged or inoperable. Connect the filler hose and follow your written instructions to operate your filling equipment. Open the fixed liquid level gauge and fill until a white mist appears. When filling by weight set the container on the scale and set the scale for the tare weight of the cylinder plus the weight of the LPG plus the weight of the hose and fittings. When finished filling, verify weight to insure cylinder is not overfilled.
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LPG Storage Tanks Capacity of Storage Tanks
Te amount of LPG storage to have on site is based on the maximum time desired between LPG fills. Since LPG liquid (propane) contains 91,500 Btu/Gallon, there are about 11 gallons required for every one million BU’s (1 MMBU) required by the facility. Note also that one MMBU = 1 decatherm as 10 therms x 100,000 BU/therm = 1,000,000 BU. EXAM PLE: A factory uses a maximum of 800 Decatherms, or 800 MMBTU per day. The equivalent LPG consumption would be 800 x 11 or 8,800 gallons/day. When selecting the appropriate size of your storage tanks, consider: Average daily consumption of LPG. The logistics of LPG deliveries. LPG tanks cannot be filled completely; assume 85% usable. Larger standard size tanks come in 18,000 US gallons [67m3], 30,000 [112m3] and 60,000 [224m3] sizes. According to code, LPG storage tanks are required to have specific fittings. These fittings include : Relief valve(s) Excess flow and shutoff valves on vapor opening Back check and shutoff valves on liquid inlet openings Internal valve Fixed liquid level gauge Variable liquid level gauge Pressure gauge Temperature gauge •
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Simplified depiction of a typical LPG storage vessel with appropriate trim components.
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LPG and SNG Systems Overview
LPG Storage Tanks Te available storage of LPG is about 85% of the total water gallon capacity of a tank. Tis filling technique provides for approximately 15% vapor space to allow for liquid expansion and “boil off” of the LPG. anks are typically, but not always, rated for a maximum operating pressure of 250 psig. If rated at 250 psig, the “burst” or “design” pressure is 4 times the operating pressure or 1000 psig. Te point is, they do not break apart for any reason except for fire or similar catastrophic events. Pressure in an LPG storage tank is related to temperature. Tat temperature is normally at or near the ambient temperature of the outside air. The corresponding •
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For propane at 0 oF, the pressure is 24 psig. At 110 oF, the pressure is 197 psig. Te tanks pressure relief valves are generally designed to relieve at 250 psig. Te release valves are located on the top of the storage tanks. anks are required to be painted silver or white — only . Tese colors reflect sunlight and keep the tank as cool as possible. In most parts of the world, it is rare that the ambient temperature ever gets high enough to cause the relief valves to discharge. However, regions such as the Middle East and Southeast Asia are exceptions. anks are normally installed to provide at least 3 feet from the belly of the tank to the ground. Tis allows the tank to provide enough hydraulic head to the feed the LPG to the pumps. Pressure in the tank is generated by the LPG boiling off in the same way that water boils at 212oF. When water boils steam is created and if the steam is contained, as with a tea kettle, pressure builds. With our tea kettle, the pitch increases as the temperature climbs (above the 212 oF due to the confining pressure) and this increase in pressure is heard as a higher pitch. In the same way, propane creates higher and higher pressures as its temperature rises above its boiling point of -44°F.
Note: The boiling point of propane is –44oF! Tus, if the outside air temperature was say,
-45°F (very cold), propane would simply flow onto the ground and remain as a liquid — no vapor. We could carry propane with an open bucket. At 100oF, if liquid propane leaks out of the pipe, it will immediately boil and become vapor and dissipate into the atmosphere. A cooling effect occurs when LPG vaporizes and this is the reason why a storage tank cannot normally be used as a vaporizer. If you continually remove vapor via a vapor line on the top of a storage tank, you are relieving pressure from the tank. But the tank will stay at equilibrium, so this results in LPG boiling (vaporizing) to restore the tank back into equilibrium. Obviously, this boiling requires heat and this heat comes from the available ambient temperature of the LPG. Te result is the tem12
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perature of the LPG will be reduced as heat, or energy is extracted. Tis result in a lower vapor pressure in the tank which also reduces the rate at which the LPG can boil or vaporize. Over time, the LPG temperature continues to drop so low that there is little vapor available to be fed to the vapor consuming process. Te solution to this problem, of course, is to have an LPG vaporizer installed. It should be noted that any significant leak in an LPG system usually results in ice formation at the point of the leak. Te ice is created because of the cooling effect of the LPG vapor as it hits the atmosphere which contains moisture. Another way to find leaks is to see if there are any flies hovering around the tank or piping. For some reason flies love the stuff! Liquid Level in a Storage Tank
Te level of the liquid LPG in a tank is usually measured by one of two available devices. A “Magnetel” gauge consists of a float on a long arm installed internal to the storage tank. Te float rides up and down on the surface of the liquid LPG as the level changes. A pointer on the face of the gauge indicates the percentage of liquid LPG in the tank. Another type is a “rotary” gauge or so called “Spit Gage”. Tis is a long tube inside the liquid you can manually rotate through the LPG liquid surface. A small hole on the face of this gauge allows the LPG to “spit” out when the end of the arm inside the tank hits the surface. At this point you simply look at the indicator dial to estimate the % full of the tank. •
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An 85% outage gauge should be mounted on every tank at the 85% full level. Normally, during the filling process this needle type valve is opened by the person filling the tank to ensure the tank isn’t over filled. If liquid LPG gets to this level, there is a small release of liquid indicating that the tank is full. Moving the pointer on the Rotary dial causes the end of the tube to rotate until it contacts liquid in the tank. At that point, discharge from the bleed orifice turns from LPG vapor to liquid. The rotary gauge dial provides the volume percentage of liquid in the tank.
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