Field of the Invention

The present invention is directed to monitoring the performance of a recirculation control system or valve, particularly from a remote location. It is intended to measure critical valve and system performance parameters and, preferably, transmit these measurements to a remote monitoring location. The invention comprises an independent data collection and transmission system that can send valve and system performance results anywhere a telephone communications link can be established. Background of the Invention

Recirculation control systems are frequently used in centrifugal pump applications to prevent overheating of the pump. The recirculation control system will automatically recirculate fluid back to a reservoir during periods of low system demand. A recirculation control system may comprise a combination of several valves or a single recirculation control valve. One such valve, disclosed in U.S. Patent No. 4,967,783 to Loos which is hereby incorporated by reference, is totally self-contained and includes a flow sensing element, a bypass control valve, and a multistage pressure letdown valve all within one body. Other recirculation control valves are disclosed in U.S. Patent Nos. 4,779,639 and 4,941,502 which are also hereby incorporated by reference.

One disadvantage of a recirculation control system or valve is that it is difficult for plant operating personnel to confirm that it is performing correctly. Unnecessary disassembly and inspection is often performed to inspect specific components. However, even this does not confirm that a valve is actually- operating properly under all system conditions. In addition, valve inspection and repair is normally performed by trained factory representatives. This presents additional cost and scheduling problems. The critical nature of the recirculation system or valve requires that it perform properly at all times. Therefore, an object of this invention is to monitor valve performance while the valve is in operation. Another object of the invention is to permit the transmission of performance data to a remote monitoring location. There, persons skilled in assessing the condition of the valve can analyze the data and report to the user on the valve operation. The valve user thus avoids shutdowns due to both unnecessary maintenance and unexpected valve failure. Summary of the Invention

A method and apparatus for monitoring the performance of a recirculation control system are disclosed. According to the invention, the pressure of the liquid passing through the control system is measured directly by pressure and differential pressure transducers at the main inlet, main outlet and recirculation outlet of the control system. Where the means for regulating the

flow of liquid to the recirculation outlet comprises a piston within a piston chamber, the pressure of the liquid within the piston chamber may also be measured. The pressure data may be stored and displayed or transmitted to a remote location for analysis.

The present invention comprises a method for monitoring the performance of a recirculation control system through which a liquid is directed where the control system has a main inlet, a main outlet and a recirculation outlet. The method of the invention comprises obtaining data on the pressure of the liquid passing through the system at the main inlet of the system, obtaining data on the pressure of the liquid passing through the system at the main outlet of the system, obtaining data on the pressure of the liquid passing through the system at the recirculation outlet of the system, and storing the obtained data for analysis or display. Where the recirculation control system has a means for regulating the flow of liquid into the recirculation outlet comprising a piston within a piston chamber, the method may further comprise the step of obtaining pressure data of the liquid within the piston chamber during the operation of the system.

The present invention also comprises an apparatus for monitoring the performance of a recirculation control system. The apparatus comprises a means for obtaining data on the pressure of the liquid passing through the system at the main inlet of the system, a means for obtaining data on the pressure

of the liquid passing through the system at the main outlet of the system, a means for obtaining data on the pressure of the liquid passing through the system at the recirculation outlet of the system, a means for storing the obtained data for analysis or display connected to each of said means for obtaining pressure data. Where the recirculation control system has a means for regulating the flow of liquid into the recirculation outlet comprising a piston within a piston chamber, the apparatus may further comprise a means for obtaining data on the pressure of the liquid within the piston chamber during the operation of the system connected to the means for storing the obtained data.

Brief Description of the Drawings The foregoing summary, as well as the following detailed description, will be better understood when read in conjunction with the drawings appended hereto. For the purpose of illustrating the invention, there is shown in the drawings an embodiment which is presently preferred, it being understood however, that this invention is not limited to the precise arrangement and instrumentalities shown. FIG. 1 is a schematic and section view of the preferred embodiment applied to a recirculation control valve having a pilot valve actuated piston bypass valve.

FIG. 2 is a section view of the recirculation valve along line 2—2 of FIG. 1 showing the recirculation outlet and position of the pressure sensor therein.

FIG. 3 is a schematic of another preferred embodiment.

Description of the Preferred Embodiments The process of the present invention comprises monitoring critical parameters of recirculation control system performance over a period of time. These parameters are the pressure of the liquid flowing through the main inlet of the system, the pressure of the liquid flowing through the main outlet of the system or the differential between the inlet and outlet pressures, and the pressure of the liquid flowing through the recirculation outlet of the system. In the case of a recirculation control valve having a pilot valve and piston arrangement for regulating the flow of fluid through the recirculation outlet, such as the one disclosed in U.S. Patent No. 4,967,783, it is also desirable to measure and monitor the pressure of the liquid in the piston chamber. The data on the pressure of the liquid is preferably collected directly by pressure and differential pressure transducers. The data may be stored or displayed in analog or digital form by a variety of means such analog displays, strip chart recorders, digital displays, electronic buffer memory, printers, plotters, magnetic recording media, optical recording media, and the like. The means for obtaining the data and storing or displaying the data are preferably interconnected by suitable wiring.

Referring to Figures 1 and 2, a recirculation control valve monitoring apparatus of the present invention is shown. The valve assembly 10 includes a main housing 11 having a main inlet

12 and a main outlet 14. The main inlet 12 is connected to the recirculation system via a recirculation conduit 20.

Recirculation conduit 20 communicates with sleeve 22 housing slidable piston 26 which in turn communicates with recirculation outlet 16 via recirculation port 15. When downstream demand is present, i.e., corresponding to a decrease in outlet pressure, the pilot valve assembly 28 is actuated causing piston chamber 24 to fill with liquid. As piston chamber 24 fills with liquid, slidable piston 26 is thrust upward towards seats on sleeve 22 thereby regulating the flow of liquid to the recirculation outlet 16.

Pressure transducer 30 senses the pressure of the liquid at the main inlet 12 and converts and transmits this data as an electronic signal. Similarly, pressure transducers 34 and 36 sense the pressure of the liquid at the recirculation outlet 16 and piston chamber 24, respectively. Differential pressure transducer 32 at main outlet 14 measures the difference between the pressures of the liquid at main inlet 12 and main outlet 14. Any suitable pressure transducer or differential pressure transducer may be used such Models 1151HP and 1151DP available from Rosemount, Inc. of Eden Prairie, Missouri.

In a preferred embodiment, the invention comprises pressure and differential pressure instrumentation to measure the four critical performance parameters in a recirculation control valve, a digital data logger to convert these readings into digital numbers, a buffer memory to store these readings and a modem to

transmit these values by phone link to a remote location. In addition, a field instrument enclosure includes a strip chart recorder for on-site hardcopy backup information and power supplies to operate the pressure and differential pressure transducers.

Figure 3 illustrates a schematic of a preferred embodiment of the invention in connection with a recirculation control system having a control means for regulating the flow of liquid into the recirculation outlet comprising a pilot valve and piston, such as the recirculation control valve disclosed in U.S. Patent No. 4,967,783. With reference to Figure 3, the specifications for the preferred instrumentation are as follows: Pressure and Differential Pressure Instruments: Four high performance transducers using capacitance cell technology, ± 0.25% full scale accuracy, and with 4-20 mADC or 1-5 vDC output. Digital Data Logger: Stand alone instrument capable of measuring at least four 4-20 mADC or 1-5 vDC signals and converting them to digital format. Input impedance greater than 20 Meg Ohm in parallel with 47 nF. Common mode noise rejection greater than 140dB. Capable of scanning at 4 channels per second using a 12 bit integrating converter. Equipped with RS-232 interface and switch selectable baud rates.

Electronic Buffer Memory: Digital data storage device capable of storing a minimum of 8000 readings. Equipped with RS- 232 interface and independently selectable serial communications for both input and output ports.

Modem: External stand-alone device capable of asynchronous data transmission at 300 to 2400 bps. Interface with RJ-11 phone jack. 100% Hayes compatible ("AT" command set) and compatible with the Bell 103 and 212 A plus CCITT V.22 and V.22 bis standards. Equipped with automatic dial and automatic answer capability.

Power Supplies: Regulated DC voltage with a sufficient output current capability to operate the transmitter. An individual _, power supply is pre erred for each of the four transmitters.

Strip Chart Recorder: 100 mm wide chart recorder with a minimum of 3 channels. Chart speed selectable to 1 cm/hr or less with chart roll take up and disposable marking pens. Accuracy of 0.1% full scale with full scale response of less than 0.5 seconds. Minimum input range of 5 vDC with input impedance greater than 20 meg ohms. Common mode noise rejection of 120 db and normal mode noise rejection of 60 db.

Field Instrument Enclosure: NEMA type 12 oil and dust tight electrical enclosure to protect sophisticated control and instrumentation systems in industrial environments. CSA certified LR21001 and LL21312.

The field instrument enclosure is preferably located near the recirculation control valve to be monitored. The pressure and differential pressure transmitters are connected to four specific valve locations to measure particular valve and system operating values. These measured values are converted from

analog to digital form by a data logger. These same values are measured and recorded as a hard copy display by a strip chart recorder. Digitized data readings from the data logger are stored by an electronic buffer memory until it is requested to download this information. When it becomes necessary to transmit performance data to a remote site, a communications link is first established by telephone from the remote monitoring site to the modem. After this link is established, a "data transmit" signal is sent through the modem to the electronic buffer memory. This causes the stored data to be downloaded out of the electronic buffer memory and to be transmitted through the modem to the telephone link and to the remote monitoring site.

It will be recognized by those skilled in the art that changes may be made to the above described embodiment of the invention without departing from the broad inventive concepts thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but it is intended to cover all modifications which are within the scope and spirit of the invention as defined by the appended claims.