FAQ

  • 1. What is LPG/Autogas?

    Liquid gas (also autogas or LPG (Liquefied petroleum gas) mentioned) one calls a mixture from propane and butane. In addition, pure propane or pure butane can concern. It is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles.  It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer.  When specifically used as a vehicle fuel, it is often referred to as autogas.

    In place of liquid gas also frequently the term "propulsion gas" is used. Liquid gas consists of easily liquefiable hydrocarbon connections (CmHn) with 3 or 4 carbon atoms. It can concern thereby around an individual connection or a mixture of several connections.

    - Non Toxic

    - Non Corrosive

    - Free to Lead

  • 2. Can anyone service an LPG System?

    NO. Only qualified and licensed LPG technicians can install service and repair LP Gas systems.

  • 3. Do Vaporizers build pressure?

    YES and NO.  There are two types of vaporizers systems – Feed-out and Feed-back.  Feed-back systems add heat to the liquid LPG and allow it to return to the storage vessel as vapor and/or liquid.  The process of adding heat to the fluid results in a pressure rise in the storage vessel.  Feed-back systems require specially configured vaporizers sometimes referred to as tank heaters or feed-back vaporizers.  Feed-out vaporizers do not build pressure – they simply add heat to convert the liquid to vapor as it passes through, but they allow the storage vessel to maintain a higher pressure that corresponds to the ambient temperature.  Without a vaporizer all storage vessels will naturally refrigerate resulting in lower pressures.

  • 4. What type of vaporization system is best – Feed-out or Feed-back?

    There are benefits to both types of systems, but the deciding factor is usually energy waste. With Feed-back systems the energy added to the LPG returns to the tank resulting in a higher storage tank pressure and temperature. The higher storage temperature results in heat loss to the atmosphere. With Feed-out systems the amount of energy used is a direct factor of the amount of LPG consumed by the downstream process. Heat is added at the rate necessary to convert the liquid LPG to vapor only as it is consumed.

    The other factor is product consistency. If LPG is used, it is comprised of butanes and propane each having distinctly different partial pressures.  Because of the different partial pressures, the butanes and propane will vaporize at different rates inside the storage vessel.  In a Feed-back system vapor for the downstream process is taken from the vapor space in the storage vessel which initially results in higher propane concentrations and gradually shifts toward greater butane concentration as the tank is emptied.  The end result is inconsistent combustion properties.  Feed-out systems send out only vaporized liquid which maintains a homogeneous form in the storage vessel.

  • 5. Do vaporizers increase combustion efficiency?

    In some cases.  When LPG comprised of butanes and propane is used, vaporization without a Feed-out vaporizer will result in early vaporization of the propane followed later by more concentrated butane-rich LPG vapor.  Combustion resulting from the varying product composition will yield changing efficiency and combustion properties.  A feed-out type vaporizer will provide consistent LPG vapor quality that will allow the combustion equipment to be optimized.

    If the LPG being used is strictly propane then a vaporizer will not yield improved combustion efficiency. It is important to note, however, that a reduction in combustion output can occur without a vaporizer if the system pressure drops because of a lack of natural vaporization.  This often happens with changes in climate such as when the temperature drops at night or as winter approaches.  A vaporizer will allow the combustion equipment to continue at full output.

  • 6. Can I put a check valve between the storage vessel and the vaporizer?

    NO.  Liquid and vapor must be allowed to return to the storage vessel.  All vaporizers operate with a flywheel effect which means they have heat (energy) available after a downturn in the use of gas.  The remaining heat is transferred into the liquid LPG left in the vaporizer.  The heat converts the liquid into vapor causing rapid expansion.  This expansion results in a pressure rise that if unable to return to the tank will force the over-pressure relief valve to vent.

  • 7. If air is mixed with propane to form a mixture suitable for replacing natural gas, is it flammable?

    NO.  The appropriate mixing ratio for using propane to replace natural gas is 46 - 48% propane and 54 - 52% air.  The limits of flammability for propane are roughly 2.5 – 9.5% propane in air.  Propane above 9.5% concentration in air will not ignite.

  • 8. What is the usable of a vaporizer?

    The question of vaporizer design life is a very popular and appropriate question which has been asked many times in the past by customers.  LP-Gas suppliers and end users like need to know what they can expect as the typical life expectancy for a particular type of vaporizer placed on site under given conditions.  The information is needed both establish the front-end economics and to establish a safe and responsible maintenance and replacement program.

    As the manufacturer, we can anticipate a variety of site and operating conditions and incorporate that information into our design basis.  However, as the manufacturer it is not practical to calculate the life of the vaporizer under every possible set of field and site conditions.  The most appropriate approach for permanent installations is to use the formula below to establish the expected physical lifespan:

    Expected Physical Lifespan = Vaporizer Design Life X (1 – Environmental Factor + Maintenance Factor)

    Vaporizer Design Life:

    ZIMMER

    8 years

    TORREXX

    8 years

    TORREXX w/hermetic relay

    10 years

    POWER P-Series

    10 years

    POWER XP

    8 years

    Direct Fired

    8 years


    Environmental Factor (0 = best to 0.3 = worst):
        Evaluated based on the severity of the physical atmosphere where the vaporizer is placed. Considerations – salt air, acid atmosphere, flooding, etc

    Maintenance Factor (-0.5 = best to 0.5 = worst):    No maintenance over the life of the vaporizer results in the worst case and a regular maintenance program, appropriate for the type of vaporizer and one that effectively addresses and prevents problems including those related to LPG quality, results in the best case. For example, vaporizer processing HD-5 propane beginning with a new (un-used) tank and a regular periodic preventive maintenance program would use a factor of -0.5.

    Example: 
    A TORREXX vaporizer w/ hermetic relay is placed at an inland factory using propane. The installation is new beginning with a new (un-used) tank and a regular periodic preventive maintenance program is implemented. What is the expected lifespan?

    Vaporizer Design Life = 10 years
    Environmental Factor = 0
    Maintenance Factor = -0.5

    Expected Physical Lifespan = 10 years x (1 – 0 + (-0.5)) = 15 years

    Naturally the environmental and maintenance factors are subjective and require some experience to effectively predict. All of our factory authorized representatives are experts in the field of vaporizers and are capable of helping you assess these values. Keep in mind that the overall purpose of the formula is to establish an expected lifespan. It is quite common and possible for our vaporizers to operate well beyond the predicted results but one also has to be aware of the risks and flammable nature of the fluid being processed and take this into consideration when trying to determine the appropriate time for replacement. Effective use of the formula above will help establish a safe and responsible program for you and/or your customer’s LPG facility.

  • 9. What is the compressor supposed to do?

    The compressor is to transfer liquid propane from railcars into a bulk storage tank. After the liquid has been transferred, the remaining vapors will be recovered. The compressor will operate year around, emptying about 2 railcars per week.

    This compressor will be used to evacuate a vessel at the end of a batch process. It will be used in a production facility that will perform 6 batch operations in a 16 hour day.

    Many compressors operate at more than one condition. Determine why and how often the various conditions occur.

  • 10. What kinds of data will be needed in order to determine what type of compressor system will be needed to accomplish the job?

    As a minimum, a precise understanding of the following data is required:

    • Gas being handled
    • Suction and Discharge Pressure
    • Site Elevation (or Local Barometric Pressure)
    • Suction Temperature
    • Capacity

    In addition the following items are needed to help make some subjective decisions when two or more options are available or in the selection of various accessories.

    • 'Normal' operating conditions
    • Other operating conditions
    • Duty Cycle
    • Electrical characteristics and area classification
    • Availability of cooling water
  • 11. How do we select the proper compressor?

    Knowledge of the gas, required capacity, suction pressure, suction temperature, and discharge pressure will enable the proper compressor to be sized. The basics steps involved are:

    1. Calculate the compression ratio.
    2. Choose between a single-stage or two-stage compressor.
    3. Calculate the discharge temperature.
    4. Determine the volumetric efficiency.
    5. Determine the required piston displacement.
    6. Select the compressor model.
    7. Determine the minimum RPM required of the selected compressor.
    8. Select an actual RPM.
    9. Calculate the actual piston displacement.
    10. Calculate the power required.
    11. Select appropriate options.

    A computer is generally used to perform steps 1 to 10, but hand calculations are often adequate.

  • 12. Who is to supply the motor, switchgear piping, etc.?

    The term 'compressor' will have different meanings depending on your frame of reference.  As a manufacturer, Blackmer usually views a 'compressor' as meaning the compressor block only. The Blackmer catalog lists a wide variety of basic compressors and also lists configurations that include closely related compressor accessories that are common to almost every installation.

    A user generally has a plant or product that is his primary concern. Within the plant will be a process that requires a 'compressor' to accomplish its task. In this context, the 'compressor' is everything that is needed to take the gas at some point in the system and place it at another point in the system at a higher pressure. Such a 'compressor' is actually a process or system in itself and almost always consists of a number of common items or systems:

    • The compressor Driver
    • Gauges Drive System
    • Relief Devices Protective Switches
    • Cooling SystemsControl Switches
    • Vessels Motor Starter and Logic Circuits
    • Piping Capacity Control System
    • Filtration Liquid Condensate