• 48-in. Sphere

    The Wilco™ 48-in. sphere storage vessel can supply compressed natural gas (CNG) at up to 5,500 psi. Typical commercial systems store CNG at 4,500 psi and supply CNG to the customer vehicles’ fuel tanks at 3,000 to 3,600 psi.


    The vessel assembly is custom designed for the end users, and is designed using specifications and requirements from ASME Section VIII, Division 2, for National Board of Boiler and Pressure Vessel Inspectors registration.

    Wind and Seismic Calculations
    Wilco CNG Sphere Environment loads (seismic and wind) design strength considerations are performed on individual and stacked CNG spheres.

    Seismic shear load calculations for the CNG vessel and support structure design show that its strength exceeds the calculated ASCE/IBC earthquake load requirements. Calculations using the maximum United States of America seismic parameters were used:

    SS=2.00 (Maximum, United States of America, risk-adjusted maximum considered earthquake (MCER) ground motion parameter for conterminous United States for 0.2-s spectral response acceleration parameter (5% critical damping).

    Wind loading calculations are performed for 180-mph wind force on the spheres (maximum in the United States of America). The vessel and support structure systems have strength in excess of that required to withstand the calculated wind force.

    Seismic and Wind calculations for specific areas are made upon request.


    • High-pressure lock-out valve out with “Block and Bleed”

    • High-pressure lock-out valve out with “Block and Bleed”: A high-pressure “lock out” valve is used to close off the vessel’s relief nozzle during scheduled maintenance operations. This valve’s use in design and practice are prescribed in ASME Section VIII, Division 2. The standard unit is also supplied with block and bleed system for releasing pressure between the lock-out valve and relief valve to be bled off. The "block and bleed" system has a 1/4-in. manifold to contain the displaced, bled off gas.

    • Conventional skirt-type support structure

    • Pressure vessel has ¾- and 1-inch FNPT nozzle threaded ports which can be optionally used as fill-discharge ports

    • Pressure relief valve is available with either ¾ or 1-in. NPT connection

    • Clean-out drain manifold at bottom has a high-pressure needle valve with ½-inch NPT thread

    • Analysis of cyclic pressure loadings between 4,500 and 3,500-psi yields a vessel life of 260 years.

    • Support structure design incorporates strength requirements for maximum wind and seismic load resistance.


    Height (sphere and support skirt only)68.9 in. (1.750 m)
    Total height (with relief valve and lock-out valve)87.7-in. (2.228 m)
    Outside diameter (vessel sphere)54.5 in. (1.382 m)
    Vessel assembly weight (empty)8,060-lb (3,660-kg)
    Total weight of vessel assembly (CNG at 5,500 psi, 70° F)8,570-lb (3,890-kg)
    Storage capabilities9,436-scf at 3,500 psi, 70° F
    11,125-scf at 4,500 psi, 70° F
    12,363-scf at 5,500 psi, 70° F
    Maximum allowable working pressure5,500 psi, at 120° F (37.9 MPa, 48.9° C)
    Minimum design metal temperature0° F at 5,500 psi (-17.8° C, 37.9 MPa)