Refrigeration – Storage of solidified or liquified gas – Liquified gas transferred as liquid
Reexamination Certificate
2001-04-04
2002-11-05
Doerrler, William C. (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Liquified gas transferred as liquid
C062S050700
Reexamination Certificate
active
06474078
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
The present invention generally relates to systems and methods for transferring fluids from a vessel to another location or an end user, and more particularly to a system and method for pumping cryogenic fluids from a vessel to another location or an end user.
In general, past attempts to optimize cryogenic pump systems have fallen short of providing an economical and effective means of cooling the pump and minimizing product waste. Most cryogenic pumps in service have no insulation on the inlet line or on the vapor return line. These systems have proven to be wasteful of cryogen, often venting and losing substantial product. To ensure that these systems operate without cavitating, the systems generally have a vacuum jacketed sump at the inlet of the pump that acts as a phase separator. Also, the pump must be cooled down to an appropriate level with a minimum of wasted product.
One way to reduce product losses is to insulate the inlet and/or vapor return lines. This not only helps to reduce losses, but also improves pump performance. However, there are drawbacks to insulating the piping. If the vapor return line is not insulated, there will be liquid cryogen in this line which will boil off and add to the vent losses of the system. For vacuum jacketed piping, the cost of the piping can exceed the cost of the pump itself. If insulated with foam insulation, the foam is subject to thermal cycling which damages the foam and draws in moisture. Freezing of water inside the insulation can result in higher heat leak rates than an uninsulated line.
Others have attempted to overcome these deficiencies in the prior art. Various prior art systems which have attempted to reduce product losses and/or overcome the other above-described deficiencies are discussed below.
One prior art method is to submerge the pump in a supply tank or vessel so that the pump is always cold. Losses for this type of system are primarily due to heat leak of the vessel and heat generation of the pump.
U.S. Pat. Nos. 4,472,946 (Zwick) and 4,860,545 (Zwick, et al.) disclose a cryogenic storage tank with a built-in submerged pump that is kept in a continuously cooled down state by the cryogen stored in the tank such that pumping may be commenced immediately. This approach attempts to reduce the loss of cryogen through boil-off by minimizing the heat leak path from the environment into the cryogen caused by the presence of the pump inside the tank. This is done by providing an insulated cryogenic storage vessel with a pump mounting tube extending into the vessel and immersed in the cryogen. The outer surface of the pump mounting tube within the vessel is insulated so as to minimize the heat leakage from the pump mounting tube to the cryogen surrounding the tube. However, there are several drawbacks to this design, which in general is impractical. First, there is the requirement of a special tank in which to install the pump. Second, to repair the pump, the tank pressure must be vented and the pump removed and warmed up before repairs can be made. Overall, the costs associated with this design are unacceptable.
U.S. Pat. No. 5,819,544 (Andonian) discloses a high pressure pumping system for pumping cryogenic liquid from a low pressure holding cylinder to a high pressure gas cylinder (or other high pressure utilization system). The system includes a high pressure piston pump having a unidirectional flow input and a unidirectional flow output immersed in the cryogenic liquid in a low pressure pump container that is fed cryogenic liquid from the low pressure holding cylinder. The pressure in the pump container is maintained so that driving the pump piston pumps cryogenic liquid from the bulk tank to the high pressure utilization system. Although this design is more economical than the cryogenic storage tank with built-in pump by Zwick, it has other problems. For example, the smaller tank must be filled periodically. This results in vent losses due to blowing down of the vessel and line heating. Further complications are added because of the controls needed to accomplish tank filling without the pump having to shut down.
U.S. Pat. No. 5,218,827 (Pevzner) discloses a method and apparatus for supplying liquified gas from a vessel to a pump with subcooling so as to avoid cavitation during pumping. No attempt is made to minimize product losses, only to provide a subcooled liquid to the pump. Problems associated with vent losses are largely ignored.
U.S. Pat. No. 5,537,828 (Borcuch, et aL) discloses a temperature-based cryogenic pump cooldown system wherein the suction or input conduit to the cryogenic pump and the cryogenic pump itself are sequentially cooled prior to pumping. This system also ignores problems associated with vent losses, focusing primarily on how the pump is effectively cooled down and how that cool down is monitored and controlled.
U.S. Pat. No. 5,411,374 (Gram) discloses a cryogenic fluid pump system and method of pumping cryogenic fluid. The system is intended primarily for LNG, although it discusses other cryogenic fluids. It does not discuss insulating the lines, nor does it discuss a conventional vapor return line. The pump is required to pump vapor and liquid separately out of the inlet line. Cooldown of the pump is accomplished by recirculating the cryogenic fluid back to the top of the supply tank, which is not an uncommon practice.
U.S. Pat. No. 5,353,849 (Sutton, et al.) discloses another method of operating a cryogenic pump, which is complicated by additional methodology used to meter the cryogenic fluid. The method used to cool down the pump is similar to that in U.S. Pat. No. 5,411,374 (Gram). A liquid sensor (e.g., a temperature probe) indicates when cryogenic liquid has gone through the pump. When the probe indicates liquid downstream of the pump, there is a time delay before the pump is started.
U.S. Pat. No. 5,160,769 (Garrett) discloses a method to minimize vent losses in cryogenic pump systems. This patent teaches a type of purged cryogenic pipe insulation particularly for cryogenic fluids that are less than 77 Kelvin (−321°F.).
U.S. Pat. No. 3,630,639 (Durron, et al.) also discloses a method to minimize vent losses in cryogenic pump systems. Specifically, this patent teaches the use of an automatically controlled vent valve in a vent line connected to the suction line in a cryogenic pumping system. The vent valve is in an open position during the cooldown cycle and is moved to a closed position after the system has reached desired operating conditions. Blowby gas which leaks around the piston of the pumping system provides the pressure for closing the vent valve. The vent valve contains an orifice through which the blowby gas bleeds and returns to the storage vessel for the cryogenic fluid being pumped.
It is desired to have an apparatus and a method that will minimize product losses associated with the operation of cryogenic pumps by minimizing heat leak during the pumping cycle and by more efficient means of cooling down the pump to cryogenic temperature.
It is further desired to have an apparatus and method which use an insulation for cryogenic pipe that is more durable and effective than conventional foam insulations by making use of gas vaporized during normal operation of a cryogenic tank which would otherwise be wasted.
It is still further desired to have an apparatus and a method to ensure that the cryogenic pump has a minimum net positive suction head (NPSH) at the suction without the need for elevating the cryogenic supply tank.
It also is desired to have an improved apparatus and method for transferring a fluid from a vessel to an end user which overcomes the difficulties and disadvantages of the prior art to provide better and more advantageous results.
BRIEF SUMMARY OF THE INVENTION
The invention is an apparatus and an method for transferring a fluid from a vessel. The invention also includes a method for con
Chalk David Jonathan
Farese David John
Fischl John Francis
Thompson Donald Earl
Air Products and Chemicals Inc.
Doerrler William C.
Drake Malik N.
Jones II Willard
LandOfFree
Pumping system and method for pumping fluids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pumping system and method for pumping fluids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pumping system and method for pumping fluids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2916011