Refrigeration – Processes – Compressing – condensing and evaporating
Reexamination Certificate
2001-04-13
2002-08-13
Tapolcal, William E. (Department: 3744)
Refrigeration
Processes
Compressing, condensing and evaporating
C062S129000, C165S011100, C236S051000
Reexamination Certificate
active
06430944
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a system and method for monitoring the performance of remote factory located chiller units, and in particular, to a system and method which enable the precognition of a refrigerant leak, or insufficiency of a refrigerant, in the refrigeration circuit of chiller units, for enabling preventative maintenance to be performed thereon.
2. Description of the Related Art
Systems for performing remote maintenance on various types of industrial equipment are known. Remote maintenance technology is a technique for monitoring operation and predicting problems of equipment located at customer sites from a monitoring and maintenance facility, thus allowing one to obtain equipment operating data. In such systems, various operational parameters of the equipment installed in remote locations are sensed and transmitted in digital form over a network to a server monitoring and maintenance facility. At the server monitoring and maintenance facility, the parameters are collected and monitored over time and, on the basis of various protocols, if one or more of the sensed parameters suggests a current or potential future malfunction in the equipment, maintenance staff can be dispatched to the remote locations where the equipment is located, in order to effect repairs, perform routine maintenance, and the like. One particular type of industrial equipment which is widely used is known as a“chiller” unit. The outer aspect of a known type of chiller unit is shown in FIG.
1
. The chiller unit
10
is basically a portable refrigeration unit having a refrigeration circuit through which a refrigerant gas medium such as R134a, R22, R404A, or the like, is circulated in a known manner. In addition to the refrigeration circuit, a cooling medium, usually water, is circulated both internally and externally of the chiller unit
10
through a cooling medium circulating circuit, wherein the cooling water undergoes thermal exchange with the refrigeration circuit for cooling the water. The cooled water is then pumped centrifugally out of the chiller unit
10
through a cooling conduit making up the external part of the cooling medium circulating circuit. More specifically, respective ends of the cooling conduit are connected to cooling medium inlet and outlet connections
20
and
30
on the chiller unit
10
, wherein the cooling medium circulating conduit is installed in a circuitous pattern throughout the location where it is necessary to maintain a predetermined cooled condition, such as in semiconductor manufacturing chambers, computer hardware installations, or any other type of equipment for which controlled cooling is required. The chiller unit
10
, as shown in
FIG. 1
, includes various controls and/or indicator lights (generally designated at
40
) thereon for controlling chiller operation. The operating temperature of the cooling medium produced from chiller unit may be displayed using a gauge
70
. Such chiller units
10
are generally portable via casters
50
and are intended to be located in close proximity to the customer facility in which the cooling conduits are installed and used, the units being fixed in place by adjustable positioning feet
60
.
A typical maintenance problem with any refrigeration circuit, including the above-described chiller units, is that of refrigerant gas leakage. In the context of chiller units, the most serious problem, of course, is when the unit fails to cool properly, and refrigerant gas leakage is one of the primary causes for failure to cool. The demands of precision manufacturing, such as in semiconductor production facilities, require precise and unfailing temperature controls. Unfortunately, it is generally difficult to effectively diagnose problems of refrigerant gas leakage.
Currently, two methods are used to detect refrigerant gas leakage in chiller units. The first is to directly trace the gas leak using a refrigerant gas leakage detector. Secondly, it is possible to diagnose gas leakage by reading the refrigerant gas pressure. Both of these methods have disadvantages. Namely, the detecting devices tend to be expensive. In addition, the devices must be used at the location of the chiller unit in order to directly detect a leak or to detect refrigerant gas pressure. Such devices are not easily capable of transmitting the detected data to other locations. Moreover, such devices, while useful for detecting the source of a refrigerant gas leak, do not enable ongoing observation of a refrigeration circuit in such a way as to enable predictive maintenance to be performed, namely, to tell when a refrigerant gas leak or insufficiency of refrigerant is likely to happen, and perform the necessary preventative maintenance to correct the problem. before it becomes serious.
The temperature in connection with the evaporator in a refrigeration circuit has been measured as a method for detecting insufficiency of the refrigerant. Prior art references which employ such methods, in various forms, shall be discussed below. Typically such systems have been proposed primarily for use in automobiles.
Japanese Laid-Open Application No. 63-32271 proposes that the evaporation temperature of a refrigerant medium should be detected before and after starting a compressor, wherein a gas leak can be detected by comparing such values.
Japanese Laid-Open Application No. 63-135761 discloses the use of an electrical expansion valve, wherein a refrigerant medium gas leak is detected from a relationship between an opening degree of the expansion valve and the evaporation temperature.
Japanese Laid-Open Application No. 63-238364 proposes sensing the evaporator outlet temperature at a time when the compressor is halted, for detecting a refrigerant medium gas leakage.
U.S. Pat. No. 5,150,584 to Tomasov et al. discloses detecting a refrigerant medium gas leak from a relationship between inlet evaporation temperature and the outlet evaporation temperature of an evaporator, and the compressor surface temperature.
U.S. Pat. No. 5,301,514 to Bessler et al. discloses detecting a refrigerant medium gas leak from a relation between an expansion pressure valve opening degree and evaporation temperature.
U.S. Pat. No. 5,713,213 to Nobuta et al. uses not only evaporation temperature but also a relationship with the halted state of the compressor for accurate detection of a refrigerant medium leak.
Finally, German Patent Document DE 3 913 521 by Hemm discloses detecting a refrigerant medium gas leak by means of a calculation using the compressor inlet refrigerant medium pressure and refrigerant medium temperature.
The above known techniques, although suggesting a relationship of evaporation temperature with a refrigerant gas leak, nevertheless possess important differences which make them impractical for use in a remote factory installed environment which is an indispensable requirement of the above-described chiller unit. In particular, since these known techniques are primarily intended for use in automobiles, a continuous time-based monitoring of parameters is not readily possible. Moreover, because an automobile encounters all kinds of environmental changes in temperature, humidity and the like, it is difficult to reliably detect an evaporation temperature that is not influenced by environmental conditions, and reliably determining temperature changes in the evaporation temperature alone, not affected by environmental conditions, is difficult if not impossible in an automotive situation.
SUMMARY OF THE INVENTION
In contrast to the prior techniques discussed above, the present invention has an object of detecting a refrigerant leak using remote maintenance technology, for chiller units that are disposed in a substantially constant temperature factory setting, where the influence of environmental temperature is largely constant and therefore can be accounted for in a predictable way. Therefore, the present invention enables a simple and low cost method of detecting or predicting a refrigerant gas leak, on the basis of a relat
Ali Mohammad M
Guss Paul A.
SMC Kabushiki Kaisha
Tapolcal William E.
LandOfFree
Remote maintenance system and method for chiller units does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Remote maintenance system and method for chiller units, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Remote maintenance system and method for chiller units will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2917526