CAPTURING IN AN EMERGENCY SITUATION REFRIGERANT

FROM A REFRIGERANT CHTT.T FR SYSTEM

FIELD OF THE INVENTION

This invention relates to a containment tank system which provides for the environmentally safe transfer of refrigerant from a refrigerant chiller system to a storage tank. The system is automated so that, in the event of an emergency situation in a refrigerant chiller system where the refrigerant pressure approaches a predetermined level, the refrigerant is then safely transferred to a storage tank system. BACKGROUND OF THE INVENTION

Over-pressure situations in refrigerant chiller system often occur due to faulty equipment operation, faulty operator control and faulty heating and cooling management systems in a building. In the event of over- pressurization of the refrigerant fluid in the refrigerant system, considerable damage can be done. To avoid damage to the refrigerant system, it is common practice to employ rupturable discs which are designed to break and release the pressurized refrigerant from the refrigerant system when refrigerant pressure attains a predetermined level, such as about 15 psig in low pressure refrigerant systems and about 375 to 450 psig in high pressure refrigerant systems. Should the pressure of the refrigerant in the evaporator of the refrigerator system exceed the pressure rupture value, the disc ruptures and the refrigerants are vented to the atmosphere. Such venting to atmosphere of the refrigerants is, of course, considered harmful from many different viewpoints. Some refrigerants are quite toxic and poisonous. Other refrigerants are harmful to the atmosphere. For example, chlorinated fluorinated hydrocarbon refrigerants are considered to be harmful to the ozone layer. It would therefore be important to capture the refrigerants

which can be released to the atmosphere by rupture of the rupturable disc to prevent release of the harmful refrigerants to atmosphere.

It has been very common to take steps to safely transfer refrigerant from a refrigerant system when it is decided that the system requires service Service of a refrigerant system may be periodic, may be due to automated self-diagnosis indicating a problem in the system, or may be due to the disc rupturing. Examples of refrigerant servicing systems are described, for example, in United States patent 5,024,061, 5,046,320, 5,161,385 and 5,269,148. In all of these servicing systems, it is common to transfer refrigerant either liquid, vapor or both to a storage tank. The refrigerant may then be removed from the storage tank and reused by introduction back into the refrigerant system after the system has been serviced. None of these systems, however, contemplate a sensing of the pressure in the refrigerant system to indicate an emergency situation requiring immediate handling of the refrigerant to avoid release to the environment.

United States patent 4,711,096 describes a leak detection system which will activate an alarm and/or interrupt refrigerant flow in the system in the event that ammonia, as the refrigerant, is detected. In the event of detecting ammoma refrigerant in the area of the heat exchangers due to a leak in the tubing, a three-way valve system is actuated to vent the ammonia refrigerant to atmosphere outside of the building in which the ammonia leak is occurring. It is suggested that, for larger systems, a more sophisticated disposal or collection arrangement could be provided.

Although the prior art approaches deal with problems associated with refrigerant systems and an attempt to contain refrigerant during servicing, no system is available which provides for capturing of refrigerant in the event of an emergency in the refrigerant system which normally would have the potential of releasing the refrigerant to atmosphere.

The device for opening the refrigerant valve may include a refrigerant pressure sensor connected to the evaporator, the pressure sensor generating

an open signal when sensed refrigerant pressure in the evaporator attains the set predetermined level. The refrigerant valve is a normally closed solenoid refrigerant valve. A controller opens the refrigerant valve when the pressure sensor senses the predetermined pressure and in turn transmits an "open" signal to the controlled.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a system is provided for automatically capturing pressurized refrigerant in an emergency from a refrigerant chiller system which includes an evaporator. The system comprises:

I) a sealed containment tank system capable of containing substantially all pressurized refrigerant fluid in the refrigerant chiller system; ii) a refrigerant conduit for delivering refrigerant from the evaporator to the containment tank; iii) a normally closed refrigerant valve in the conduit; and iv) controller means for opening the refrigerant valve in response to refrigerant pressure in the evaporator attaining a set predetermined level. In accordance with another aspect of the invention, the means for opening the refrigerant valve includes a refrigerant pressure sensor connected to the evaporator and a controller in communication with the pressure sensor. The pressure sensor generates an open signal when sensed refrigerant pressure in the evaporator attains the set predetermined level. The refrigerant valve is a normally closed solenoid refrigerant valve. The controller opens the refrigerant solenoid valve in response to the open signal from the refrigerant pressure sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic of the system for automatically capturing pressurized refrigerant from a refrigerant system in the event of an emergency in the refrigerant system; Figure 2 is a schematic for the controller wiring hook-up; and

Figure 3 is a schematic of the wiring diagram for the controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to liquid refrigerant transfer, containment and storage. The system can be used to transfer liquid refrigerant from the tank back into a low pressure or high pressure chiller through the drain opening. The containment tank is non-portable and is located as close as possible to the chiller. The containment tank system of this invention can be used with either low pressure or high pressure refrigerant systems. The high pressure systems tend to be more common in Europe I commercial installations. The low pressure systems commonly run with refrigerants sold under the trademark FREON R-ll, R-113 and R-123. The high pressure systems run with refrigerants sold under the trademark FREON R-12, FREON R-22 and FREON R-134a. For purposes of describing an embodiment of the invention, reference will be made to low pressure refrigerant systems. The containment system invention can prevent the loss of refrigerant venting through the rupture disk, even though the rupture disc is retained as standard equipment on the chiller system. The system includes a control package that monitors the pressure in the evaporator. The micro-processor based control is a multi-function controller. It alarms to indicate an emergency when the pressure in the evaporator is approaching an unsafe limit. If the pressure continues to increase, the controller activates the liqui refrigerant solenoid valve to start the transfer of liquid refrigerant from the chiller to the containment tank preventing contamination or continuous venting into the atmosphere.

In a first embodiment of the invention, a low-pressure liquid refrigerant storage tank. It is often desirable and even necessary to drain liquid refrigerant from low pressure chillers and store the refrigerant. The containment tank system will store liquid refrigerant safely without the need of separate containers.

With reference to the drawings, Figure 1 is a schematic view of the containment tank control system in accordance with a preferred aspect of the invention. The containment tank system 10 is interconnected to the evaporator 34 through electronic devices and fluid communication devices. The refrigeration system 30 has the condenser 32 mounted above the evaporator 34 by way of support arm 36. The evaporator has a refrigerant charging line at the base thereof with manually controlled valve 35. At the top of the evaporator 34 are the rupture disks 46 which are set to blow off at 15 pounds pressure. Connected to the conduit above the rupture disks 46 is the rupture relief valve 48. In the event that the rupture disks 46 break down due to high pressure, the rupture relief valve will also release at 15 pounds pressure, however, in the event that the rupture disks 46 are leaking, the rupture relief valve 48 retains the refrigerant within the evaporator 34 by blocking off the conduit 45 above the rupture disks. In the usual manner, the refrigeration system is mounted on base 37 and the rupture relief valve 48 is mounted by post 38.

The containment tank 10 is sized to contain refrigerant which may be transferred through line 33 to the tank 10. The tank 10 preferably has provided therein the wound water coil 12 which, in turn, may be used to cool the tank and increase its holding capacity. The water enters the tank through line 11 and is discharged through drain 14. As previously discussed, the containment tank 10 is connected through the necessary conduits with appropriate control valves to the recharge line 33 to receive refrigerant when the refrigeration system is overloading or malfunctioning. The necessary plumbing in connecting the refrigeration system to the

containment tank 10 is supplied by way of conduit 51 connected to manual valve 35. Conduit 51 has a manual charging valve 29 connected to its free end. Isolation valve 42 is provided, which along with shut off valve 20, allows replacement of the electronically controlled solenoid valve 52 when required. Line 51, as it passes through solenoid valve 52, is connected to the shut off valve 20. Also connected to the tank 10 is the tank relief valve 18 which is set to release at approximately 250 pounds pressure. Also at th base of tank 10 is a drain with valve 16, the purpose of which is to remove refrigerant from the base of the containment tank if required. It is understood that all connections for the conduits, valves and lines are provided with leak proof couplings to ensure no refrigerant leakage during operation.

The controller 54 is shown in more detail in Figure 2 with the internal relay contacts being shown in Figure 3. Electronically connected to the controller 54, is a pressure transducer 64 in the evaporator 34 and a pressur transducer 66 sensing the pressure within the tank 10. Also connected to th controller 54 is the input through line 67 which signals whether the refrigeration system is operating or not operating. Also the refrigerant sensor 44, which is positioned above the rupture disks 46, is connected to the controller. Outputs from the controller are electronic relay switches Kl, K2, K3, K4, K5, K6 and K7. As well be described in more detail with respect to Figure 3, relay switch Kl controls the opening and closing of the normally closed solenoid valve 50. When relay switch Kl is open, solenoid valve 50 is normally closed. When switch Kl is moved to the closed position, the solenoid valve 50 is open. Correspondingly with relay switch K3, the normally closed solenoid valve 52 is opened when switch K3 is closed. Relay switch K5 controls the sounding of the 24 volt bell. Switch K5 may be closed to sound a general alarm through the bell when either CFCs are sensed in the environment by CFC sensor 44, or when dumping o the refrigerant into the containment tank occurs to also sound a general

alarm that refrigerant is being transferred. Relay switch K4 actuates the alarm signal device 58 to indicate that high pressure has been sensed in the evaporator by pressure transducer 64. Relay switch K6 controls the remote alarm signalling device 60 to actuate an alarm at the operator's station to indicate that refrigerant is being transferred. K6 relay switch may also be closed to actuate the remote alarm when switch Kl is closed. Relay switch K7 is closed to actuate alarm signal device 62 to indicate if high pressure has been sensed in the containment tank as monitored by the pressure transducer 66. The controller is designed to monitor the pressure status in the evaporator 34 regardless of whether the refrigeration system is operating or not operating. In accordance with the preferred embodiment, refrigerant is only released from the evaporator 34 when the refrigeration system is not operating. This avoids reliance on fail-safe systems within the refrigeration system to shut down the refrigeration system when refrigerant is suddenly released from the evaporator, unless provision is made in the controller to provide for a programmed shutdown of the refrigerant system. The most frequent times when pressure in the evaporator exceeds a desired upper limit, is when the system is shut down during the spring and fall periods. At that time, hot water from the heat conditioning system of the building, can find its way into the evaporator and pressurize the refrigerant to exceedingly emergency high levels, hence the provision of the rupture disks 46 to avoid damaging of the evaporator system. Alternatively, heavy loads placed on the refrigeration system can result in generating too much pressure in the evaporator. Furthermore, operator error in starting up the refrigerant system can cause an overpressure situation in the evaporator. It should be noted however, that the refrigerant containment tank 10, as connected to the refrigeration system in the manner noted, provides for additional benefits albeit during maintenance of the refrigeration system, where refrigerant can be transferred to the tank 10 to allow servicing of the evaporator and

condenser, or in situations where it is beneficial to store the refrigerant in the containment tank 10 and in essence remove all refrigerant from the refrigeration system. This can occur, for example, during the winter month when the system will not be in use and it is not necessary to have refrigerant in the system.

The process controller 54 operates the solenoid valves in a prescribed manner in accordance with its program, based on inputs from the pressure transducer 64, 66 and the refrigerant sensor 44. In the event that the refrigerant sensor 44 detects a leakage of refrigerant around the rupturable disks 46 or in the area of the refrigeration system, a signal is transmitted to the controller through input line 44 of Figure 2, which in turn sets off the alarm relay K5 to sound a 24 volt bell as shown in Figure 3.

If the system pressure as sensed by transducer 64 is greater than 3 pounds (that is, above normal operating levels), this input is received by the controller CPU 70 through line 64, which in turn actuates relay Kl to open solenoid valve 50. This allows water to pass through the water coil 12 and commence cooling the tank in preparation for receiving refrigerant from the unit. However, as already noted, if the refrigeration unit is in operation, refrigerant will not flow to the tank. If the system pressure is less than 1 pound, then the water solenoid 50 is deactuated by the controller 73 relay Kl being opened. Furthermore, in the event that Kl is closed, to open the solenoid valve for water to flow through the cooling coil, a remote general alarm may be sounded through K6 to alert the operator that a problem exists and that the refrigerant system may have to be shut down if pressure continues to rise.

If the system pressure as detected by transducer 64, is greater than 7 pounds and there is no signal on line 67 to indicate that the refrigeration system, chiller is in operation, then solenoid valve 52 is opened by closure of relay K3. This commences dumping of the refrigerant into the containment tank 10 through valves 35 and 42 and 20 which are all open to

receive refrigerant within the tank 10. Once the system pressure drops below 6 pounds, solenoid 52 is shut off to stop any further flow of refrigerant into tank 10. At the same time as closure of relay K3, contacts K5, K4 and K6 are closed to set off the appropriate audible alarm, high pressure evaporator alarm and a remote alarm to a pick-up station where appropriate repair people are notified. In addition, through pressure transducer 66,, controller CPU 70 can open and close flow of water through the wound coil 12, should the pressure in the containment tank exceed some predetermined level. For example, when pressure in the tank exceeds 15 pounds, the water flows through the tank to decrease pressure to a desirable level of less than 7 pounds, at which time water flow is cut off. Should the water pressure in the containment tank exceed 20 pounds, an alarm condition is actuated and relay K7 is closed to indicate high containment tank pressure. Hence, a form of control may also be provided to only supply cooling water to the tank on an "as needed" basis.

As already noted, in accordance with the preferred embodiment the central processing unit 70 can continue to sense all aspects of the operation of the refrigeration unit and status of pressure in the evaporator and in the containment tank, but it will not open solenoid valve 52 until the refrigeration unit is shut down. Hence, when the appropriate alarms are sounded, an attendant can arrive at the scene, assess the situation and shut down the refrigeration unit. At that instant, the central processing unit opens and closes the necessary relays to commence dumping of refrigerant into the containment tank 10. Although an embodiment of this invention has been described with respect to the Figures concerning a low pressure refrigerant chiller system, it is understood that the containment tank system may also be used in high pressure refrigerant chiller systems. The containment tank selection of valves, conduits, and other components of the system are designed to handle the pressures of the high pressure refrigerant systems. Usually such high

pressure refrigerant systems operate at considerably higher pressures normally in excess of 300 psig. Such high pressure systems normally use high pressure refrigerants such as R-12, R-22 and R-134a. The rupture dis or other relief devices for the high pressure system are normally designed t relieve excessively high pressures from the evaporator in the range of 375 t 400 psig. The controller 54 is set up to close relay switch Kl to in turn open solenoid valve 50 and commence cooling of the tank when the sensed pressure in the evaporator by transducer 64 is about 70% of the pressure at which the chiller relief valve would normally release. Similarly with respec to relay switch K3, it is closed by the controller to open solenoid valve 52 when the refrigerant pressure in the evaporator obtains a value of about 90 of the pressure at which the chiller relief device would normally release refrigerant from the evaporator. The transducer 66 on the containment tank is also set to signal high pressure in the tank at a valve of about 90% of the pressure at which the chiller relief device would normally rupture. This ensures that the containment tank is capable of handling high pressure refrigerants from the high pressure refrigerant system.

During the voluntary stages of maintaining the system or the desire to store refrigerant in the tank, it is understood that in order to drive all refrigerant from the evaporator, hot or warm water can be introduced to the coils of the evaporator to increase the pressure of the refrigerant in the evaporator so that it flows into the containment tank. Conversely when it i desired to introduce refrigerant from the containment tank back into the evaporator, hot water can be run through the coil within the containment tank to increase pressure of the refrigerant so that it flows back into the evaporator. It is understood of course that some refrigerant should be left i the containment tank to avoid potential corrosion problems and the like because of the presence of the inert refrigerant.

An example of a particular system in respect of the low pressure refrigerant system described with respect to the Figures is provided as

follows. The containment tank system consists of a 24 inch diameter by 5 feet in height steel construction tank, ASME rated at 300 psig, capable of containing 1,200 pounds R-ll (low pressure). 60 linear feet of wound 3/4 inch copper is mounted inside the tank to provide sub-cooling of the refrigerant being transferred and stored. The cooling media may be city water. Two 3/4 inch connections are mounted to the exterior of the tank to provide the means to connect the city water to the tank. One 3/4 inch pressure relief valve rated at 250 psig is located on the top of the tank. One 3/4 inch, 24 volt solenoid valve controls the flow of water from a set point value produced by the micro-processor controller. The controller also provides control to 1 inch liquid refrigerant solenoid valve in the refrigerant conduit line based on a pressure set point value. Two 0-30 psig electronic pressure transducers provide the controller with system pressure inputs. One of the transducers is mounted on the low pressure chiller evaporator, and the other is on a 3/4 inch opening located at the top of the tank. The controller requires 120 volt supply voltage. A twenty gauge two conductor wire is used to make the low voltage connections from the pressure transducers to the controller.

The sequence of operation produced by the controller, begins by receiving an input signal from the pressure transducer located on the evaporator of the low pressure chiller. If the pressure exceeds 3 psig set point value, the controller provides the voltage to open the city water solenoid valve and sounds an audible alarm. If the pressure continues to increase in the evaporator, the controller provides voltage to open the liquid refrigerant solenoid valve to start the transfer of liquid refrigerant to the tank. The controller continues to monitor the pressure in the evaporator and the containment tank. When the pressure in the evaporator is below 2 psig, the controller then turns off the liquid refrigerant solenoid valve. The city water solenoid valve remains on until the pressure in the tank is at 0 psig,

that is, until the tank is subsequently drained of contained refrigerant. The controller can also be connected to a building automation system.

One inch copper tubing or conduit is used to connect the chiller evaporator to the containment tank system. Two 1 inch manual isolation valves provide the means to transfer the liquid refrigerant from the containment tank back into the evaporator. The 1 inch copper line is first connected to the existing refrigerant fill valve located on the chiller evaporator. Next the copper tubing is connected to (In) side of the 1 inch refrigerant solenoid valve, from the (Out) side of the solenoid valve connect copper tubing to the (In) side of the 1 inch refrigerant isolation valve, from the (out) side of refrigerant isolation valve connect the 1 inch copper tubing to the 1 inch opening located at the top of the containment tank.

Located at the bottom of the containment tank is a 1 inch refrigerant isolation valve, connect 1 inch copper tubing to the refrigerant isolation valve and then to the chiller evaporator fill valve.

In summary, in accordance with an aspect of the invention, a process and apparatus is provided to receive refrigerant from the evaporator of a refrigerant system in the event that pressure within the evaporator exceeds a predetermined value. A process controller is provided, which in sensing pressure within the evaporator, actuates the necessary valves to transfer the refrigerant to the containment tank. The containment tank may be water- cooled to ensure that the maximum amount of refrigerant can be stored in the tank for the tank size. It is appreciated that the process controller may be a software programmable electronic controller system, with the program stored in an E-PROM which directs the operation of the CPU or it can be a series of relay switches operated by direct DC volt signals. It is also appreciated that the system may be designed to dump refrigerant from the evaporator in emergency situations into the tank regardless of whether the refrigeration system is operating or not. In this situation, it is understood that the controller may be programmed to provide for a controlled shut down

of the refrigerant system in conjunction with contained removal of refrigerant from the system. It is also understood that the size of the containment tank may be considerably larger if water is not available to cool the tank before introduction of the refrigerant. Although preferred embodiments of the invention are described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.