Storage ullage

Most storage containers for ciyogens are designed for a 10 percent ullage volume. The latter permits reasonable vaporization of the contents due to heat leak without incurring too rapid a buildup of the pressure in the container. This, in turn, permits closure of the container for short periods of time to either avoid partial loss of the contents or to transport flammable or hazardous ciyogens safely from one location to another. 

Irradiated Magnox and AGR fuel is stored at the power stations in open topped skips and transported to Sellafield in shielded flasks. At Sellafield, in the Fuel Handling Plant (FHP), the fuel is placed into ullaged containers which can be stacked. Based upon an extensive research programme an optimiun water chemistry of pH 13 was identified for the containers. Under these conditions storage times of at least five years without cladding penetration are achievable. 

For a large-scale liquid hydrogen storage, tanks of spherical shape are used to minimize boiloff losses. Two spherical dewars with a capacity of 190 of LH2 plus 10 % ullage each were components at the Nuclear Rocket Development Station, Nevada, during the ROVER project starting in 1955 (see section 9.5.1.). The insulation consisted of a vacuum jacket and a 0.9 m perlite powder layer allowing an estimated boiloff rate of... 

The largest LH2 tank constructed so far is the NASA 3407 vacuum perlite-insulated spherical storage tank at the Kennedy Space Center, Florida, used in the US space shuttle program. The outer sphere is made from carbon steel with an inside diameter of 21.34 m and the inner sphere is made from austenitic stainless steel with an inside diameter of 18.75 m the ullage is about 10 %. The tank has a boiloff rate of 0.03 % or approx. 800 1 per day [51]. For comparison purposes the LH2 storage tank within the External Tank (47 m height, 8.4 m diameter) of the US Space Shuttle has a volume of almost 1600 m. ... 

The discharge of vents and pressure relief pipes should be to areas safe from both the fire and toxic hazards. It should not be within a building. Since the vent of the feedstock storage tank must discharge a similar vapour in a safe place, the feedstock tank is often a suitable catchpot for the disengagement of any liquid droplets that may be carried by vent discharges, provided that sufficient ullage in the tank is maintained at aU times. 

Diethyl ether should be inhibited against peroxide formation in storage and use with an inhibitor of which pyrogallol (0.2% w/w), hydroquinone or other phenols and diphenylamine are possible choices. Storage under nitrogen is very desirable. Samples should be stored in brown bottles with a minimum of ullage. Since all the inhibitors are very much less volatile than diethyl ether, newly distilled material will be iminhibited and should be treated without delay. 

The use of unst bilized THF will eliminate the problem of an extraneous peak, but careful precautions are necessary to avoid oxidation minimum sample filtration times, avoidance of excessive ullage in containers, and storage under an inert gas. 

In many applications, a predetermined quantity of cryogenic liquid must be transferred from a storage vessel to a point-of-use within a certain time interval. In the transfer of cryogenic liquids, two techniques have been used—pumps and ullage pressurization. 

The total gas required to pressurize the storage-tank ullage and transfer liquid could be estimated if the mass of gas condensed and the temperature-pressure-volume history of the gas were known. These data are not known, nor is a reliable estimation of them possible. Suppose, however, one were to substitute the following hypothetical model for the actual process. 

Total inflow gas is imagined to be divided into two parts one part remains as a gas at entering temperature and storage tank pressure "equivalent ullage mass" and the other part cools and condenses to a liquid at the system pressure, "equivalent condensed mass."... 

The differential pressure across the transfer test line is determined by the pressure of the fluid at the inlet to the line and by the back pressure developed at the discharge end by the receiver tank. The inlet pressure was maintained nearly constant by a control valve (CV-3—Fig. 1) whose upstream pressure was maintained through pressurization of the storage tank ullage. The outlet pressure of the test line was determined by the flow impedance of the receiver vent and the difference in elevation between the receiver and OF-2. 

As liquids are heated they expand volumetrically and this effect has to be taken into account in the storage of liquids in closed vessels. It is normal to leave an air space above the liquid, the ullage, to allow for this expansion, and to fit pressure relief valves to release any excess pressure generated. An example of what can happen if these precautions are not taken was seen at Los Alfaques Camping Site at San Carlos de la Rapita in Spain in July 1978 when a road tanker carrying 23.5 tonnes of propylene exploded killing 215 people. The circumstances of the incident were that the unlagged tanker... 

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