Cryogenic Pumps (Ebara)

This unique design allows the pump to be installed inside a storage tank in a vertical pump column, with a suction (foot) valve located at the bottom. Because the pump is installed through the top of the tank, all connections below the maximum liquid level of the tank can be eliminated. This eliminates the possibility of major tank leakage due to a pipe or connection problem. It also permits the storage vessel to be located below ground level or completely covered by mounding. The applicable codes allow the owner to minimize the land area needed to locate a liquefied gas storage tank due to the reduction of spillage potential.

The submerged pump and motor unit is designed to fit into the smallest practical column diameter by using an axial diffuser design. The column then acts as a guide to seat the pump during installation and also as the discharge pipe from the pump to the top of the tank. Each pump is fitted with an inducer, which is an axial flow impeller located at the lowest possible level of the tank to improve the NPSHR (Net Positive Suction Head Required) and allow operators to lower tank liquid levels to extremely low levels. To isolate the tank contents from the pump column, a suction valve is used, which incorporates a dual pressure sensitive seal. The valve is flanged to the lower end of the pump column and is closed by coil springs as well as by the hydrostatic pressure of the liquid in the tank.

The valve is opened by lowering the pump into the valve. The inlet feet of the pump press down against the bottom plate, forcing the valve to open using the weight of the pump. The valve can also be closed by simply lifting up on the lifting eye located at the top of the column headplate, without dis-assembly of any other components. Once the valve is closed, the column can be inerted with nitrogen gas to allow the safe removal of the pump even with liquid in the tank. The power cables used in the retraction system are a high quality armored cable, made especially for Cryodynamics. These cables are UL (Underwriter's Laboratory) listed, and were developed specifically for use in cryogenic liquids. The lifting cables used are an anti-twist, stainless steel cable, which can provide many years of use without replacement.

The entire pump and motor assembly are contained within a suction vessel built to the appropriate pressure vessel code for each application, making the installation safe, simple and reliable. The suction vessel functions as the outer pump casing. It is fabricated with a suction nozzle, welded couplings (for drain and liquid level indication), support brackets, a head plate with discharge nozzle, a conduit for electrical cables and a vent nozzle. The result is a compact, lightweight, uncomplicated installation having low noise levels and significant safety advantages over conventional pumps.

Frequently used as a multistage design for vaporizer feed service, the ECC model is also widely used as a single stage transfer pump. Flow capacities are available up to 3000 m3/h and differential heads up to more than 2500 meters (depending on flow and power). For multi-stage pumps traditionally used for vaporizer send-out applications, Cryodynamics has developed a radial, stiff shaft design in order to provide a more compact, more reliable machine. By combining the use of radial diffusers, which allows a much shorter stage length, with a much larger shaft diameter, the rotor becomes much more stable, normally operating well below the first critical speed. This new design has proven to be extremely reliable in send-out systems which require a large, multi-stage pump to perform on a continuous, 24 hour-per-day basis.

These pumps are of similar construction to the ECC type and are usually located within the refrigerated cargo tank of a marine gas carrier to transfer such fluids as LNG, LPG, Ethylene, etc. These units are available for all applications of liquefied gas carriers and are used for main cargo unloading, stripping, spray and emergency (retractable) service. The units are fixed to the bottom of the tanks using a mounting arrangement designed to minimize stresses, and are connected directly to the discharge piping, which then travels out through the tops of the tanks.

Flow capacities range from 20 to 3000 m3/h and with heads up to 200 meters on single stage pumps. A single stage design is most often used, although multi-stage pumps can also be supplied if required.

Electric power feed cables and deck penetration assemblies provided by Cryodynamics meet the requirements of all the major ship classification societies. The main in-tank power cables are Cryodynamics UL listed armored cables, and can be provided in all voltage ranges up to 8000 volts. Special designs with built-in internal filtration are available to handle cargoes that are likely to suffer particulate contamination such as LPG.