• 48-in. Stackable Sphere

    Each vessel has 48-inch inside diameter, 33.5-cf spherical CNG storage vessel is for the commercial dispensing of compressed natural gas to motor vehicles at CNG fuel stations. The vessel can supply 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.

    Description

    The vessel assembly is custom designed for the end users, and is based on specifications and requirements from ASME Section VIII, Division 2. The vessel is also designed and built for registration with the National Board of Boiler and Pressure Vessel Inspectors. Structural supports are designed to the requirements of ASCE 7-10, and for to satisfying requirements by governmental jurisdictions.


    Features/Benefits

    NOZZLES

    • ¾-in. FNPT in top hemisphere, 45° with respect to top of tank. The ball valve, pressure relief valve, and block and bleed manifold are system are installed to this port.

    • ½-in. FNPT at the bottom of the storage tank is for drain-cleanout manifold installation. A ½-in. drain line with a high-pressure needle valve is located at the bottom of the vessel for easy maintenance cleanout.

    • ¾-in. FNPT at top of tank

    • 1-in. PNPT at 45° with respect to top of tank (opposite the relief valve, etc.)

    • ¾-in. FNPT in bottom hemisphere, at 60° with respect to vertical.

    • 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.

     

    FEATURES

    Conventional skirt-type support structures for mounting to the pad and to each other

    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.

    The unit is typically used between 4,500 and 3,500 psi. Fatigue analysis of cyclic pressure loadings between 4,500 and 3,500 psi yields a vessel life of 414 years.

    Design also incorporates strength requirements for maximum wind and seismic loads based on requirements from ASCE 7-10.

     

    Specifications

    Overall height (two stacked spheres)138 in. (3.5 m)
    Total height (with relief valve and lock-out valve)144.1 in. (3.66 m)
    Outside diameter (vessel sphere)54.5 in. (1.382 m)
    Maximum width at position of relief valve and lock-out valves installation side)68.1 in. (1.73 m)
    Vessels assembly weight (empty)16,520 lb (7,490 kg)
    Empty weight (top sphere assembly)8,055 lb (3,653 kg)
    Empty weight (bottom sphere assembly)8,460 lb (3,840 kg)
    Total weight of vessel assembly (CNG at 4,500 psi, 70° F)17,450 lb (7,920 kg)
    Individual capacity11,125-scf at 4,500 psi, 70° F
    12,363-scf at 5,500 psi, 70° F
    Total capacity22,250-scf at 4,500 psi, 70° F
    27,726-scf at at 5,500. 70° F
    Maximum allowable working pressure8,460 lb (3,840 kg)
    Minimum design metal temperature0° F at 5,500 psi (-17.8° C, 37.9 MPa)