Intrinsically safe communication and control system for use in hazardous locations including monotoring device with intrinsically safe fluorescent tube backlit

Abstract

An intrinsically safe data acquisition system is disclosed for use in hazardous locations. The system includes a driller's console that itself is intrinsically safe and includes a large LCD monitor, keypad and local CPU. The monitor includes an intrinsically safe backlighting system. The system further includes satellite data acquisition and processing boxes that are also intrinsically safe and that are located within the hazardous area. Each satellite box includes its own CPU and acquires and locally processes signals received from a number of field sensors. The satellite box converts the signals into digital form, and transmits the data via a fiber optic communication channel to a master CPU box located in an unclassified area. A high current intrinsically safe barrier distributes power from the master CPU box to the satellite box for powering all the sensors supported by that satellite box. Another such barrier distributes all the power required by the driller's console.

Claims

What is claimed is:

1. An intrinsically safe monitoring device for use in a hazardous area, comprising:

an enclosure;

a CPU board mounted in said enclosure;

a video display in said enclosure, said video display including a display screen and a fluorescent tube for illuminating said display screen;

a video driver board in said enclosure for supporting said video display;

a data input device mounted on said enclosure for providing communication with said CPU board;

wherein said CPU board, said video driver board, said video display including the display screen and the fluorescent tube, and said data input device are each intrinsically safe for class 1, division 1, group C and D areas.

2. The intrinsically safe monitoring device of claim 1, wherein said display screen comprises an LCD.

3. The intrinsically safe monitoring device of claim 1, wherein said fluorescent tube that uses less than 2.5 watts of power.

4. The intrinsically safe monitoring device of claim 1, wherein said fluorescent tube that uses less than 2.0 watts of power.

5. The intrinsically safe monitoring device of claim 1, wherein said fluorescent tube is powered by an inverter that provides approximately 2 watts of power.

6. A data acquisition system for use in a region that includes a hazardous area, said system comprising:

a master CPU box located outside the hazardous area for distributing power throughout said system;

a plurality of intrinsically safe sensing devices located within the hazardous area for sensing predetermined parameters;

an intrinsically safe satellite box located within the hazardous area for transmitting power to said sensing devices and for collecting data sensed by said sensing devices, said satellite box including:

an onboard CPU; and

a means for transmitting data collected from said sensing devices and

processed by said onboard CPU to said master CPU box on a single channel;

an intrinsically safe console located within the hazardous area for communicating with said master CPU box, said console including:

a monitor for displaying data, said monitoring including a video display screen and a fluorescent tube for illuminating said screen;

an internal CPU; and

a data entry device; and

a barrier box located outside the hazardous area for receiving power from the master CPU box and redistributing the power to said satellite box and said intrinsically safe console;

wherein said monitor including the display screen, the fluorescent tube, said internal CPU, and said data entry device are each intrinsically safe for class 1, division 1, group C and D areas.

7. The intrinsically safe monitoring device of claim 6, wherein said display screen comprises an LCD.

8. The intrinsically safe monitoring device of claim 6, wherein said fluorescent tube uses less than 2.5 watts of power.

9. The intrinsically safe monitoring device of claim 6, wherein said fluorescent tube uses less than 2.0 watts of power.

10. The intrinsically safe monitoring device of claim 6, wherein said fluorescent tube is powered by an inverter that provides at most approximately 2 watts of power at the operating voltage.

Description

FIELD OF THE INVENTION

The present invention relates generally to communication and control systems for use in monitoring and controlling various systems and equipment in industrial environments. More particularly, the invention relates to systems and apparatus for providing communications between, and a distribution of a control voltage to, equipment and devices located in areas that are classified as hazardous due to the presence of explosive vapors or dust. Still more particularly, the invention relates to intrinsically safe monitors and to an intrinsically safe backlit monitor that can be located in class 1, division 1 locations.

BACKGROUND OF THE INVENTION

At locations where oil or gas wells are being drilled, a number of flammable gases may be present, including mixtures of oxygen, methane, ethane, propane, hydrogen sulfide and others. Similar potentially dangerous environmental conditions exist in locations in which petroleum products are being recovered, refined or processed. Likewise, in industrial areas where large quantities of dust are present, such as in grain handling facilities or pulp and paper mills, hazardous environmental conditions may exist. Standardized classifications for the various types of hazardous locations have been adopted and assigned by regulatory agencies according to the nature and type of hazard that is generally present or that may occasionally be present.

Because electrical components, by their nature, may generate heat and sparks sufficient to ignite a flammable gas or other flammable mixture under even normal operating conditions, such components must be carefully selected and installed when used in an area that is classified as hazardous. More specifically, the components must exceed certain minimum standards as to such characteristics as power consumption, operating temperature, current and voltage requirements, and energy storage capabilities. These standards are also established by regulatory authorities and vary depending upon the particular hazardous environment.

Certain electrical devices are intrinsically safe. An intrinsically safe device may be generally described as a device that during normal operation, as well as operation during any fault condition, cannot cause a spark or achieve a temperature sufficient to ignite the gas or other substance that is present and that causes the area to be classified. If a device is not intrinsically safe, other means must be provided to ensure that the device cannot serve as a source of ignition. Typically where a device is not intrinsically safe, it may be made safe by housing it in an explosion proof enclosure, or by enclosing the device in some other type of enclosure and purging the enclosure with "clean" air. An explosion proof box or enclosure is one that will prevent any explosion that might occur within the box from causing the atmosphere outside the box to ignite. Purging an enclosure with a continuing source of clean air prevents the air that is laden with the hazardous substance from entering the box, such that a spark or elevated temperature of the component within the box cannot ignite the hazardous atmosphere.

Although areas that are classified as hazardous are prevalent in many industries, the problems of powering and communicating with electrical devices in hazardous areas are particularly acute in the drilling industry. In drilling a well, a great deal of equipment is located in close proximity to the well head, including mud pumps, compressors, mud pits and other subsystems associated with drilling. Many of these areas around a drilling site are classified as hazardous, and thus special precautions are required with respect to the electrical communication and power distribution systems. To efficiently and safely control the drilling operation, the driller will require a system having sensors positioned in a number of locations in the hazardous area. These sensors will transmit needed data to a computer that can process that data and transmit important information to the driller by means of a driller's console or monitor. By viewing the information on the driller's monitor, the driller can then make whatever changes are appropriate to the system to assure safe and continuing operation.

The driller's monitor is typically required to be very close to the well head and thus is located in a hazardous area. Historically, driller consoles have varied with respect to the amount of information displayed and type of indicators used. In the past, when a simple meter or gage provided all the information that was required, the device could sometimes be made intrinsically safe. However, due to the sophistication of today's drilling practices, consoles or monitors usually must provide a driller with a tremendous amount of information concerning the location and orientation of the drill bit, the mud flow rates, downhole pressures, as well as the status of the other systems supporting the drilling operation. Additionally, the console must permit the driller to issue commands or make inquiries through the use of a keyboard or key pad, and must display all the needed information by means of a CRT or other sophisticated monitor. These modem driller's consoles or monitors have a substantial power requirement that has prevented them from being made intrinsically safe, and that requires that they be housed in an explosion proof or a purged enclosure. Due to its size and extreme weight, an explosion proof enclosure is typically not practical for large consoles. Accordingly, is has been the usual practice to house today's monitor in a purged enclosure.

There are several distinct and significant disadvantages associated with this conventional practice. First, purged air is typically supplied in a form that includes an oil mist that has been added to the system to assure proper operation of air compressors. The oil mist is both a nuisance and, over time, can have a detrimental effect on the electronic components. Additionally, and significantly, purge air has often proved to be unreliable due to various mechanical failures. When the purge air is lost, the system must automatically be shut down to avoid the possibility of ignition of flammable gases. The driller has a tremendous financial investment in the operation at the drilling site such that even a short shutdown is extremely costly.

Furthermore, purge air systems require the installation of piping from the air source to the monitor, and to other devices receiving the purged air. This investment is one that the driller would prefer not to make because it typically will be removing its equipment and personnel from the drilling site after a relatively short length of time. Thus the semi-permanent nature of installing pipe, the extra time involved in installing the piping, and the additional monitoring and backup equipment necessary to ensure the integrity of the purged air system are all costly additional investments the driller would prefer to avoid if an alternative was available.

In addition to the afore-mentioned issues, the visual displays for these driller's monitors are typically LCD's, which do not emit light and therefore depend on a separate light source for illumination. During daylight operation, there is typically enough ambient light to enable the driller to read the displayed information. At night, however, it becomes necessary to provide light from another source. This causes problems, as conventional light sources are not intrinsically safe, and intrinsically safe light sources tend to be large and cumbersome because they are purged or otherwise protected. Hence, successful nighttime use of monitoring systems in intrinsically safe environments is currently relatively impractical.

Additional drawbacks or compromises exist or are required in the conventional data acquisition systems currently used by drillers. As mentioned above, various sensors are positioned about the drilling site in hazardous locations. Electrical conductors, which provide power and a communication means to and from the sensors, are routed from each sensor to a junction box which is also located in the hazardous area. These junction boxes receive power from and communication signals to and from another box that is located outside the hazardous area and which includes an intrinsically safe barrier (ISB) for each of the sensors interconnected through that box. Conventional ISBs limit the current and voltage that is conducted to a sensor to ensure that the power reaching the sensor is not of a magnitude that might permit the device to ignite the atmosphere in the hazardous area. Using this conventional system, one ISB is required for each sensor. Accordingly, it is typical practice to interconnect each junction box with the box containing the ISBs by means of a relatively bulky and expensive multiconductor cable. Likewise, another multiconductor cable typically interconnects the box containing the ISBs to a computer or other central controller that is located outside the hazardous area.

For all of the foregoing reasons, installation of conventional monitoring equipment can be time consuming and difficult. In addition, the driller's equipment is typically used sequentially in a number of separate jobs , with the result that it is installed, dismantled and reinstalled on a fairly frequent basis. Accordingly, running piping for purge air, routing and locating bulky and heavy multiconductor cables and conduits, and handling and installing heavy explosion proof enclosures and light sources is typically not practical and, at a minimum, undesirable.

Accordingly, despite the fact that there currently exist workable data acquisition systems for use in and about hazardous environments, there remains a need for safe, less cumbersome and low cost means for acquiring and manipulating data from the various sensors. More specifically, an illuminated display that includes an intrinsically safe light source is desired. The preferred illuminated display will overcome the disadvantages associated with having to provide cumbersome external light sources for nighttime monitoring in areas requiring intrinsically safe equipment.

SUMMARY OF THE INVENTION

Accordingly, there is provided herein an intrinsically safe date acquisition system for use in areas classified as hazardous due to the presence of ignitable vapors, dust or the like. The invention generally includes a master CPU box that is located outside the hazardous area for distributing power to the other system components. An intrinsically safe satellite box is located within the hazardous area for redistributing power to, and collecting signals from various sensors that are located in the hazardous area. The invention further includes an intrinsically safe console, including monitor, that is located within the hazardous area for communicating with the master CPU box. The intrinsically safe monitor includes an intrinsically safe backlighting system that permits nighttime monitoring without requiring any external light source. A barrier box is included in the system and located outside the hazardous area for receiving power from the master CPU box and safely redistributing the power to the intrinsically safe satellite box and console.

The intrinsically safe console preferably includes a monitor having a large format LCD screen and a data input device, such as a keypad or keyboard. The console includes an onboard micro-controller and communication circuitry allowing the operator using the console to communicate with the master CPU box, preferably via fiber-optic cable. Because of the low power requirements of the console, an explosion proof or purged housing or enclosure is not required. The console is intrinsically safe for Class 1, Division 1, Groups C and D, locations.

The satellite box of the present invention is an intrinsically safe data collection and processing center. The satellite box transmits power to the total of up to 10 analog and digital sensors. The box receives the signals from the sensors and converts them to digital form for transmission to the master CPU box via a single communication channel, preferably a fiber-optic conductor. The satellite box preferably includes an on-board CPU for converting the analog signals to digital, processing those signals, deriving calculated data, and transmitting that data outside the hazardous area. The box further includes signal conditioning means for the received analog and digital signals, as well as independent voltage regulating means for each sensor. The box is intrinsically safe for Class 1, Division 1, Groups C and D locations.

The present invention eliminates the need for expensive and heavy explosion proof enclosures for consoles and boxes that are to be located in hazardous areas. The invention also eliminates the need for installing permanent or semi-permanent piping for supplying purged air to such enclosures. Further, the invention permits an operator in the hazardous area to visually monitor a large amount of data and to effectively communicate with a master CPU box located outside a hazardous area. Furthermore, the local processing of data within the satellite box and transmitting that data via a single communication channel eliminates the need for bulky and expensive multi-conductor cables otherwise required for sending individual signals to the master CPU box outside the hazardous area. Additionally, the invention eliminates the previously existing problem of electrical noise being induced in the long, multiconductor cable runs, eliminates the number of intrinsically safe barriers traditionally required to safely operate a data acquisition system within a hazardous area, and further relieves the master CPU box from certain data processing duty.

Thus, the present invention comprises a combination of features and advantages which enable it to substantially advance the area of technology concerning data acquisition and communications within hazardous areas. These and various other characteristics and advantages of the present invention will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing, in schematic form, the elements comprising the data acquisition system of the present invention;

FIGS. 2 and 3 are front and side views, respectively, of the satellite box shown in FIG. 1;

FIG. 4 is a plan view of the satellite PCB housed in the satellite box shown in FIGS. 2 and 3;

FIGS. 5A-5B are an electrical diagram, in schematic form, showing the interconnection of the various components of the satellite PCB shown in FIG. 4;

FIG. 6 is a plan view of the communication module PCB that is connected to the satellite PCB shown in FIG. 4;

FIG. 7 is an electrical schematic showing the interconnections of the components mounted on the PCB shown in FIG. 6;

FIG. 8 is a front view of the barrier box shown in FIG. 1 with a portion of the cover cut away to show the intrinsically safe barriers and other internal components;

FIG. 9 is a section view of the barrier box shown in FIG. 8 taken along line 9--9;

FIG. 10 is a schematic diagram showing the components of the high current intrinsically safe barrier employed in the barrier box shown in FIGS. 8 and 9;

FIGS. 11 and 12 are front and side views, respectively, of the intrinsically safe driller's monitor shown in FIG. 1;

FIG. 13 is a section view of the driller's monitor taken along line 13--13 of FIG. 11;

FIG. 14 is an elevation view of the inside of the cover of the driller's monitor shown in FIGS. 11-13 showing the various PCBs and the interconnecting ribbon connectors;

FIG. 15 is a plan view of the monitor interface PCB that is housed in the driller's monitor shown in FIGS. 11-13;

FIG. 16 is an electrical diagram in schematic form, showing the interconnections between the various components on the monitor interface PCB shown in FIG. 15;

FIG. 17 is a plan elevation view of the CPU board housed in the driller's monitor shown in FIG. 13 and 14;

FIG. 18 is a plan view of the LCD driver board housed in the driller's monitor shown in FIGS. 13 and 14;

FIG. 19 is an electrical diagram, in schematic form, showing the interconnection of the components of the interface PCB that is housed in the CPU box shown in FIG. 1;

FIG. 20 is an electrical diagram, in schematic form, representative of eight separate circuits contained in the 8-channel breakout PCB housed in the CPU box shown in FIG. 1; and

FIG. 21 is an electrical diagram, in schematic form, representative of an intrinsically safe backlighting system according tot he present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

It is frequently necessary to monitor and control various electrical systems and subsystems that are located partially or totally within hazardous areas, such as those where explosive vapors may be present. The present invention discloses a data acquisition, communication and control system that may safely be employed in such hazardous areas, the system as a whole, and specific subsystems themselves, being intrinsically safe. The invention has particular utility when used on a drilling site to interconnect the driller's monitor, a central or master controller and various sensors that are located throughout the drilling site. Accordingly, the preferred embodiment of the present invention will be described with reference to employing the invention on a drilling site; however, it is to be understood that the invention is not limited to such applications, but instead is broadly applicable to any of a myriad of situations where computers, monitors and sensors are to be located in areas classified as hazardous.

Referring now to FIG. 1, the intrinsically safe data acquisition system (DAS) 10 of the invention is generally shown. DAS 1 generally includes a central or master CPU box 12, a barrier box 14, an intrinsically safe driller's monitor 16, and one or more intrinsically safe satellite boxes 18-20. Additionally, DAS 10 includes an intrinsically safe audible alarm, such as horn 22 and any number of intrinsically safe sensors such as sensors 31-38.

The drilling site includes an unclassified or nonhazardous area 1 and a hazardous area 2, the dividing line between such areas being generally depicted in FIG. 1 by dashed line 3. Areas are classified according to the presence or likely presence of explosive vapors. The standards for such areas are established by the American Petroleum Institute (API) and are published in the API "Recommended Practices for Classification of Locations for Electrical Installations at Petroleum Facilities," API Recommended Practice 500 (RP500), First Edition, Jun. 1, 1991, specifically incorporated herein by this reference. In a typical drilling site, hazardous area 2 typically may be classified as a Class 1, Division 1, Groups C and D hazardous location due to the likely presence of hydrogen sulfide. Other Group D gases may also be present. Other gases in Group D include benzene, butane, ethane, gasoline, methane, propane and others. A complete listing of Group C and D gases is included in Article 500 of the National Electric Code Handbook, Sixth Edition, based on the 1993 Edition of the National Electric Code, published by the National Fire Protection Association, the entire disclosure of Article 500 being hereby specifically incorporated by this reference. As shown in FIG. 1, sensors 31-38, satellite boxes 18-20, horn 22 and driller's monitor 16 are all physically located within the hazardous area 2. Accordingly, driller's monitor 16, satellite boxes 18-20, sensors 31-38 and horn 22 are all intrinsically safe. By contrast, master CPU box 12 and barrier box 14 are located in unclassified area 1 and therefore are not required to be intrinsically safe. Optional displays or monitors 24, 25 and optional circular recorders such as recorder 26 shown in FIG. 1 are also located in unclassified area 1 and thus likewise need not be intrinsically safe.

The driller's monitor 16, satellite boxes 18-20 and the 15 volt, 5 ohm high current ISBs 62 (described in detail below and which assist in distributing power from the master CPU box 12) have each been certified as intrinsically safe and non-incendive for use in hazardous locations in accordance with Canadian Standards Association ("CSA") Standard No. C22.2 No. 157-M1987. The ISBs 62, driller's monitor 16 and satellite boxes 18-20 have received the certification by the CSA for class 1, division 1, group C and D locations. The CSA certifications are acceptable by all United States and Canadian regulatory bodies, including for example, the U.S. NFPA and the U.S. Coast Guard. The standards for electrical equipment being certified intrinsically safe and non-incendive are set out in the standards as published in May 1987 by the CSA, 178 Rexdale Boulevard, Rexdale, (Toronto) Canada M9W1R3. The standard is entitled "C22.2 No. 157-M1987 Intrinsically Safe and Non-Incendive Equipment for Use in Hazardous Locations, Consumer and Commercial Products forming part of Canadian Electrical Code, Part II Safety Standards for Electrical Equipment, ISSN0317-5669," the entire disclosure of which is incorporated herein by this reference. The CSA has also published additional standards relating to non-incendive equipment for use in class 1, division 2 hazardous locations. Such standards include various charts and tables showing ignition temperatures and currents and voltages that may ignite explosive vapors of various types and which relate to Standards C22.2 No. 157-M1987 regarding Intrinsically Safe and Non-Incendive Equipment. Accordingly, also incorporated herein by this reference is the CSA's standard C22.2 No. 213-AM1987 entitled "Non-Incendive Electrical Equipment for Use in Class 1, Division 2 Hazardous Locations--Industrial Products Forming Part of Canadian Electrical Code, Part II Safety Standards and Electrical Equipment" published in March 1987 by the Canadian Standards Association.

System Overview

Before describing the various apparatus, subsystems and features of the present invention in greater detail, a general overview of the system is provided. In general, to monitor and control modem, sophisticated drilling equipment, a variety of sensors 31-38 are employed to detect and communicate various parameters to master CPU box 12. Such sensors are typically located in or near the various pumps, compressors, drilling fluid (mud) pits and tanks. Such sensors are interconnected with intrinsically safe satellite box 18. Although not shown, a number of other sensors would likewise each be interconnected with satellite box 19 or 20.

The signals generated by the various field sensors must be communicated to master CPU box 12. The signals from each group of sensors are collected by their respective satellite box 18-20. Each satellite box 18-20, which may collect both analog and digital signals from its respective sensors, converts all the received analog signals to digital, and then transmits those digital signals and any calculated data through barrier box 14 to master CPU box 12 via fiber optic cables. Each barrier box 18-20 includes a CPU for data processing and thus relieves master CPU box 12 of some of the data processing burden.

The barrier box 14 includes intrinsically safe barriers (ISBs), sometimes referred to as "current barriers" or "zener barriers." Barrier box 14 includes a separate intrinsically safe barrier for driller's box 16, horn 22 and each satellite box 18-20. The intrinsically safe barriers ensure that the power distributed to each of these peripherals is at a current level and voltage level that will not ignite the hazardous vapors.

The power to operate all the components of DAS 10 is supplied from master CPU box 12. That power is then distributed to driller's monitor 16, horn 22 and satellite boxes 18-20 through barrier box 14. Master CPU box 12 also distributes power to the optional displays 24-26; however, such power distribution need not pass through barrier box 14 since these monitors are located in unclassified area 1.

Driller's monitor 16 includes an LCD display, keypad and local CPU for use in communicating with master CPU box 12. Communications between intrinsically safe monitor 16 and master CPU box 12 likewise are conducted through barrier box 14 via fiber optic cables as described more fully below.

Sensors

Typical sensors for use in the DAS 10 of the present invention include up to eight mud pit probes, two trip tank probes, a flow paddle and three pump stroke rate detectors, all of which are intrinsically safe. If all the above-identified devices are employed in the DAS 10, the system will require two satellite boxes 18 and 19 as shown in FIG. 1. Any analog sensor may be connected to any analog channel in any satellite box. Likewise, any digital sensor can be connected to any digital channel of any satellite box.

In other applications, a variety of additional sensors may be desirable. Thus, depending upon the total number of sensors, a third satellite box 20 may be required. Particularly desirable additional sensors include sensors indicating tool depth, rotary RPM, hookload, pump pressure, casing pressure, hydraulic rotary torque and electric rotary torque. With these seven additional sensors, a myriad of other calculated parameters can be locally derived within satellite boxes 18-20 and then transmitted to master CPU box 12.

Satellite Box

Referring again to FIG. 1, the satellite box 18-20 is an intrinsically safe, microprocessor controlled, data acquisition module having a temperature code T3C for Class 1, Division I, Groups C and D, hazardous locations as set out in Table 2 in CSA standard C22.2 No. 157-M1987. Because of its intrinsically safe certification, including the requisite spark ignition and thermal ignition testing set out in C22.2 No. 157-M1987, neither the satellite box nor any of its components are capable of igniting a Group C or D gas in normal use, or under any conditions of fault likely to occur in practice. At an ambient temperature of 40.degree. C., the maximum surface temperature of components in satellite box 18-20 under fault conditions is 160.degree. C.

Each satellite box 18-20 is capable of supporting eight analog channels (either voltage or current transmitter) and two digital channels. Effectively then, each satellite box can transmit power and communication signals to and from up to ten different sensors 31-38. The satellite box is sensor unspecific in that it has the ability to utilize any presently available and commonly employed sensors. All analog channels include a two point calibration means. All digital channels are high end calibratable.

As previously mentioned, the satellite box 18-20 is interconnected and communicates with the master CPU box 12 through the barrier box 14. This communication is accomplished by means of composite cables 41-43 comprising three electrical conductors, two fiber optic conductors, a drain and a shield.

Each satellite box is rated intrinsically safe by the Canadian Standards Association and contains a stand-alone CPU. The satellite box receives power via ISBs housed in the barrier box 14. The power is conditioned onboard to maintain the intrinsically safe characteristics, as well as to remove any electrical contamination (noise) that may have been introduced in transmission from the master CPU box to the satellite box.

The parameters sensed by sensors 31-38 are communicated electrically from the sensors to the satellite box CPU. All conversion of signals from analog to digital is done in the satellite box. Rates and accumulation of digital inputs are processed within the satellite box. The satellite box's onboard CPU microcontroller converts the sensed values into a digital data stream and, upon being polled by the master CPU box 12, transmits the acquired and converted data serially from the hazardous area to the master CPU box via the barrier box 14 and fiber optic conductors in cables 41-43.

The details regarding satellite boxes 18-20 are best understood with reference to FIGS. 2-5 and associated Table 5. Because boxes 18-20 are identical, a description of box 18 will describe all such boxes.

Referring to FIGS. 2 and 3, box 18 generally includes a hinged enclosure 50. The enclosure 50, and the enclosures for master CPU box 12, barrier box 14, intrinsically safe monitor 16, are all preferably made of blown fiberglass and are EMI shielded by an internal nickel-based coating. Such enclosures may be supplied by Carlon, A Lamson & Sessions Company, and are all NEMA 4.times. rated.

The satellite box enclosure 50 houses satellite PCB 52 (sometimes referred to as a data acquisition board) which is mounted by four standoffs 53 from the enclosure's mounting plate 54 which is located in the rear portion of the box. The lower end of the box includes ten cable connectors 56 which provide means for receiving and connecting the electrical cables that are routed between satellite box 18 and field sensors 31-38.

Satellite PCB 52 is best shown in FIG. 4 which shows the physical layout of the components supported by the board which are shown and identified more particularly in FIG. 5 and the associated Table 5. These components are particularly situated on board 52 to ensure that satellite box 18 is intrinsically safe. More specifically, the board 52 includes no large capacity capacitors or inductors. Further, the various components are selected such that none are capable of igniting vapors that may be present in the hazardous area 2, either by virtue of either temperature or sparking at either normal or fault conditions.

Referring now to FIG. 5 and its associated Table 5, satellite PCB 52 will be described in more detail.

               TABLE 5
                                           MATL
              DESIGNATOR             QTY    NO.  PART NO.      DESCRIPTION
                                           REQD
                                      1     50   LSS00017      BAG STATIC
     SHIELDING 10 .times. 12 ANT-STATIC FOAM       1
                                      5     49   YML00020      TERMNL UNINS
     TEST PT. .090                               5
                                      1     48   YKH99020      JUMPER BERG
     STICK 65474-001                              1
                                      1     47   TMP00032      SOCKET IC 8 PIN
                                             1
                                      2     46   YMP00010      SOCKET IC 14 PIN
                                             2
                                      1     45   YMP00011      SOCKET IC 16 PIN
                                             1
                                      2     44   YMP00076      SOCKET IC 20 PIN
                                             2
                                      1     43   YMPO0080      SOCKET IC 28 PIN
                                             1
                                      1     42   68-65-075     SOCKET IC 68 PIN
     SQUARE PLCC                             1
                                      8     41   65-90-506     TERMNL BLOCK PCB
     CONN 5 PIN                              8
                                      3     40   65-90-497     TERMNL BLOCK PCB
     CONN PLUGGABLE 4 PIN                    3
                                      1     39   YKH99030      BERG STICK 3
     POSITION                                    1
                P5-12                 8     38   65-05-025     CONNECTOR 5 PIN
     HEADER SHROUDED PCB MNT                  8
              P2, P3, P4              3     37   65-04-015     CONNECTOR 4 PIN
     HEADER SHROUDED PCB MNT                  3
                  P1                  1     36   65-25-010     TERMNL BLOCK
     CONNECTOR 25 PIN D PCB MNT MALE             1
               VR6-VR13               8     35   67-23-367     IC LM2950ACZ
     VOLTAGE REGULATOR 5 V LOW POWER             8
                 VR5                  1     34   67-23-336     IC LM78M15CT
     VOLTAGE REGULATOR 15 V                      1
               VR3, VR4               2     33   67-95-025     IC TK1168
     VOLTAGE REGULATOR 8 V LOW DROPOUT              2
                 VR2                  1     32   67-23-366     IC LM2940
     VOLTAGE REGULATOR 5 V LOW DROPOUT              1
                 VR1                  1     31   67-23-355     IC LM117L
     VOLTAGE REG ADJ                                1
                  U8                  1     30   YJE0000B      IC MC1449OP HEX
     BOUNCE ELEMINATOR 4490                   1
                  U7                  1     29   67-95-513     IC RS232 LINE
     DRIVER/RECEIVER SP233                      1
                  U5                  1     28   67-95-795     IC 80C552 MICRO
     CONTROLLER 10 BIT A/D                    1
                U4, U5                2     27   UJA00040      IC LM324N QUAD
     OP-AMP LOW PWR                            2
                  U3                  1     26   96-65-030     SOFTWARE J-BOX
     SATELLITE                                 1
                  U2                  1     25   67-95-780     IC TRANSPARENT
     LATCH 74HCT373                            1
                  U1                  1     24   67-05-700     IC REF-02
     VOLTAGE REFERENCE                              1
                S2, S4                2     23   YSL11101      SWTCH DIP ROCKER
     8 PST 200 V MDRR-4-185                  2
                  S2                  1     22   75-79-020     SWITCH DPDT PCB
     MNT 300 MA 125 V                         1
                  S1                  1     21   75-78-060     SWITCH SPST
     ROTARY PCB MNT 500 MA 125 V                  1
                  X1                  1     20   YBA11050      CRYSTL 11.0592
     MHZ E1105                                 1
                  D1                  1     19   YDE04020      DIODE IN5817
     SCHOTTKY 1 AMP 20 V                         1
                 LD1                  1     18   68-15-010     LED GREEN RECT
                                             1
                  O1                  1     17   74-78-833     XSISTR 2N3904
     MOTOROLA                                   1
                 C14                  1     16   W05001157     CAPCTR 2.2 MFD
     50 V KEMET                                1
                 C13                  1     15   YCG31004      CAPCTR .001 MFD
     FILM .+-. 10% 18F2246                    1
               C8, C10                2     14   YCC33305      CAPCTR 33 PF 50
     V RECT CERAMIC                           2
    C2, C3, C5, C6, C11, C12, C15-C23   15     13   61-50-007     CAPCTR .10
     MFD 100 V                                    15
       C1, C4, C7, C9, C24-C31       12     12   YCA30100      CAPCTR 1 MFD 35
     V TANT 47F404                           12
               R25, R26               2     11   YRA14122      RESIST 1/4 W
     1200 OHM 5%                                 2
               R17-R24                8     10   72-05-139     RESIST 1/4 W 1M
     OHM 1% RN55D A/B                         8
               R15, R16               2      9   72-06-576     RESIST 1/4 W
     1.8k OHM 5% CARBON                          2
                R7-R14                8      8   72-03-059     RESIST 1/8 W 249
     OHM 1% METAL FILM                       8
                  R5                  1      7   72-04-073     RESIST 1/4 W
     1000 OHM .1% METAL FILM                     1
                  R6                  1      6   72-04-058     RESIST 1/4 W 240
     OHM .1% METAL FILM                      1
                  R4                  1      5   YRG82013      RESIST 1/8 W
     1000 OHM 1%                                 1
                  R3                  1      4   YRG82392      RESIST 1/8 W
     3920 OHM 1%                                 1
                  R2                  1      3   YRA14103      RESIST 1/4 W
     10000 OHM 5%                                1
                  R1                  1      2   YRA14471      RESIST 1/4 W 470
     OHM 5%                                  1
                                      1      1   96-52-105     PCB BLANK
                                             1

       TABLE 7
                           MATL
     DESIGNATOR    QTY   QTY   NO.   PART NO.   DESCRIPTION
                           REQD
                    1     1    17    LSS00016   BAG STATIC SHIELDING 8 .times.
     12 FOAM/MACKPAC
         U5         1          16    70-80-065  RECEIVER FIBER OPTIC PCB MNT
     HORIZ 49K BD PLASTIC
         U4         1          15    70-65-065  XMITER FIBER OPTIC PCB MNT
     HORIZ 40K BD PLASTIC
                          1    14    65-90-506  TERMNL BLOCK PCB CONNECTOR
     PLUGGABLE 5 PIN
         R2         1          13    YRA14472   RESIST 4700 OHM 1/4 W 5%
                               12
         C1         1     1    11    YCA30100   CAPCTR 1 MFD 35 V TANT 47F404
        C2-C5       4     4    10    61-50-007  CAPCTR 100 V .1 MFD KEMET
     C330CTD4MICUICA
         VR1        1     1     9    67-23-367  IC LM2950ACZ VOLTAGE REGULATOR
     5 V LOW POWER
         O1         1           8    74-78-833  X5i5TR 2N3904 MOTOROLA
         U1               1     7    70-65-020  XMITER CURRENT LOOP OPTICALLY
     COUPLED 20 MA
         U2               1     6    70-60-020  RECIVR CURRENT LOOP OPTICALLY
     COUPLED 20 MA
         U3         1     1     5    87-95-513  IC RS232 LINE DRIVER/RECEIVER
         P3               1     4    65-60-025  CONCTR 5 PIN HEADER SHROUDED
     PCB MNT
         P2         1     1     3    65-01-001  CONCTR 1 PIN PCB RA MICRO-D JAX
                    1     1     2    65-25-015  CONCTR 25 PIN D FEM W/WIRE WRAP
     TAXS
                    1     1     1    96-52-123  PCB BLANK D-CONN COM MDO

      TABLE 16
                           MATL
     DESIGNATOR    QTY   NO.   PART NO.   DESCRIPTION
                           REQD
                    1    49    LSS00017   BAG STATIC SHIELDING 8 .times. 12
     FOAM/MACKPAC                1
                    1    48    65-02-017  CNECTR 2 PIN FEM 12 AWG 5 MM SPACING
                             1
         P1         1    47    65-02-015  CNECTR 2 PIN HEADER PCB MNT VERT
     SHROUDED                     1
      CR1, CR2      2    46    74-17-170  DIODE IN5341 A ZENER 6.2 V 5W +/- 10%
                             2
      R23, R20      2    45    72-06-121  RESIST 100 K 1/4 W 5% C4 CORNING
     RL0S104S                     2
         X1         1    44    80-06-573  CRYSTAL 4 MHZ HC-33/U
                             1
         L1         1    43    80-51-169  INDUCTOR 1.2 MHENRY AXIAL LEAD
                             1
         U6         1    42    72-03-285  RESIST, 3.3K OHM NETWORK DIP
                             1
    R6, R14, R16    3    41    72-06-042  RESIST, 3.3K OHM NETWORK DIP
                             1
    R9, R21, R22    3    40    YRA14472   RESIST 1/4 W 4700 OHM 5%
                             3
         R5         1    39    YRA14331   RESIST 1/4 W 330 OHM 5%
                             3
         R4         1    38    YRA14302   RESIST 1/4 W 3000 OHM 5%
                             1
                    1    37    YMP00076   SOCKET IC 20 PIN
                             1
                    1    36    YMP00052   SOCKET IC 40 PIN TIN LEADS
                             1
                    2    35    YMP00011   SOCKET IC 16 PIN
                             2
                    2    34    YMP00020   TERMNL UNINS TEST
                             2
         P7         1    33    YKM39020   CNECTR MALE HEADER 2-PIN 1 IN. PIN
     SPACE W/LOC                1
      C10, C11      2    32    YCM74706   CAPCTR 47PF MICA 44F6991
                             2
         C1         1    31    YCB22200   CAPCTR 22 MFD 25 V
                             1
     C3, C7, C8     3    30    61-50-007  CAPCTR 100 V .1 MFD KEMET
     C330C104MIVICA                      3
         C9         1    29    YCA30100   CAPCTR 1 MD 35 V TANT 47F404
                             1
         P4         1    28    96-27-050  CABLE ASSY LCD DRIVE PCB INTERFACE
     SMART SYSTEM               1
         P2         1    27    96-27-049  CABLE ASSY KEYPOARD/PWR PCB INTERFACE
     SMART SYSTEM            1
         P3         1    26    96-27-048  CABLE ASSY COMMUNICATION SERIAL PCB
     INTRFC SMART              1
                                          SYSTEM
         P5         1    25    96-27-046  CABLE ASSY LCD PANEL PCB INTERFACE
     SMART SYSTEM               1
         O1         1    24    74-80-795  XSISTR MJE172 POWER 3 AMP
                             1
         O2         1    23    74-78-833  XSISTR 2N3904 MOTOROLA
                             1
         D1         1    22    74-60-410  RECTFR MUR410 POWER 4 AMP 100 V
                             1
        D2-D5       4    21    74-09-363  DIODE IN914
                             4
         R2         1    20    73-74-164  POT TRIMMER 100K 3/4W 20 TURN PCB MNT
     HORZ ADJ                1
         R3         1    19    73-74-080  POT TRIMMER 50K 1/2W 1 TURN PCB MNT
     VERT ADJ                  1
         R8         1    18    72-12-392  RESIST 1W .2 OHMS 5% WIREBOUND
                             1
         R1         1    17    72-12-280  RESIST 1W 2000 OHM 5% CARBON
                             1
         R7         1    16    72-06-603  RESIST 1/4 W 24000 OHM 5% CARBON
                             1
      R24, R25      2    15    72-06-582  RFSIST 1/4 W 3300 OHM 5% CARBON
                             2
    R19, R17, R18   3    14    72-06-177  RESIST 1/4 W 22K OHM 5% CORN C-4
                             3
         R11        1    13    72-06-169  RESIST 1/4 W 10 MEG 5% FC
                             1
         R12        1    12    72-06-097  RESIST 1/4 W 10K OHM 5% C-4
                             1
      R13, R15      2    11    72-06-081  RESIST 1/4 W 2.2K OHM 5% C-4
                             2
         PW1        1    10    70-74-065  POWER SUPPLY 7-40 VDC IN/5 VDC OUT 3K
     MA PCB MNT LO PR        1
         U3         1     9    70-65-065  TRANSMITTER FIBER OPTIC HORIZ PLSTIC
     40K BD PCB               1
         U4         1     8    70-60-065  RECEIVER FIBER OPTIC HORIZ PLASTIC
     40K BD PCB                 1
         U5        1      7    67-95-880  IC ENCODER KEYBOARD
                             1
         U2         1     6    67-95-513  IC RS232 LINE DRIVER/RECEIVER
                             1
         U1         1     5    67-20-069  IC 78S40 UNIVERSAL SWITCHING
     REGULATOR                        1
         P6         1     4    65-10-056  CNECTR 10 PIN HEADER PCB MNT RA
     POLARIZED .1 CEN              1
         C4         1     3    61-55-523  cAPCTR 680 PFD 200 V CERAMIC
     MONOLITHIC                       1
       C5, C6       2     2    61-55-505  CAPCTR 22 PFD 200 V CERAMIC
     MONOLITHIC                        2
                    1     1    96-52-135  PCB BLANK MONITOR INTERFACE BOARD
                             1

      TABLE 19
     DESIGNATOR    QTY   NO.   PART NO.   DESCRIPTION
                      MATL REQD
                    1    24    LSS00017   BAG STATIC SHIELDING 10 .times. 12
     ANTI-STATIC FOAM        1
                    4    23    YML00020   TERMNL UNINS TEST PT. .090
                          4
       C1, C3       2    22    YCA31002   CAPCTR .10 MFD 50V DIP EPOXY
                          2
       C2, C4       2    21    YCA30100   CAPCTR 1 MFD 35V TANT 47F404
                          2
      PTC1-PTC4     4    20    75-18-808  FUSE .45 AMP TRIP .30 AMP HOLD
     RESETABLE PCB MNT           4
       R12-R15      4    19    73-74-069  POT TRIMMER 10K 1/2W 25 TURN PCB MNT
     VERT ADJ              4
     PWR2, PWR3     2    18    70-74-081  PWRSPY 5 VDC IN +/- 12 VDC OUT
                          2
        PWR1        1    17    70-74-073  PWRSPY 9-27 VDC IN/12 VDC OUT 1%
                          1
         P12        1    15    65-37-005  CNECTR 37 PIN D-SUB MALE PCB MNT
                          1
         P2         1    15    65-40-056  HEADER 40 PIN PCB MNT .1 SPAN
                          1
                    1    14    65-16-017  CNECTR 16 PIN FEM 12 AWG 5 MM SPACING
     PLUGGABLE            1
         P16        1    13    65-16-015  CNECTR 16 PIN HEADER PCB MNT VERT
     SHROUDED                 1
                    1    12    65-15-017  CNECTR 15 PIN FEM 12 AWG 5 MM SPACING
     PLUGGABLE            1
         P15        1    11    65-15-015  CNECTR 15 PIN HEADER PCB MNT VERT
     SHROUDED                 1
                    1    10    65-08-017  CNECTR 8 PIN FEM 12 AWG 5 MM SPACING
     PLUGGABLE             1
         P11        1     9    65-08-015  CNECTR 8 PIN HEADER PCB MNT VERT
     SHROUDED                  1
                    1     8    65-90-506  TERMNL BLOCK PCB CONN 5 PIN
                          1
         P13        1     7    65-05-025  HEADER PCB VERT 5 PIN
                          1
                    1     6    65-90-497  TERMNL BLOCK PCB CONNECTOR PLUGGABLE
     4 PIN                 1
         P14        1     5    65-04-015  CNECTR 4 PIN HEADER PCB MNT VERT
     SPACING                   1
                    8     4    65-02-017  CNECTR 2 PIN FEM 12 AWG 5 MM SPACING
     PLUGGABLE             8
       P3-P10       8     3    65-02-015  CNECTR 2 PIN HEADER PCB MNT VERT
     SHROUDED                  8
         P1         1     2    65-04-025  CNECTR 4 PIN HEADER PCB MNT VERT
     DETENT .2 CENT            1
                    1     1    96-52-137  PCB BLANK J-BOX INTERFACE
                          1

                 TABLE 20
                                           MATL
                DESIGNATOR               QTY   NO.   PART NO.   DESCRIPTION
                                           REQD
                                          1    16    LSS00017   BAG STATIC
     SHIELDING 8 .times. 12 FOAM/MACKPAC          1
                                          8    15    65-02-017  CNECTR 2 PIN
     FEM 12 AWG 5 MM SPACING PLUGGABLE          8
                                          8    14    YKH99020   JUMPER BERG
     STICK 65474-001                             8
                                          3    13    YML00020   TERMNL UNINS
     TEST PT. .090                              3
                  C2, C4                  2    12    YCA30100   CAPCTR 1MFD 35V
     TANT 47F704                             2
                  C1, C3                  2    11    61-50-007  CAPCTR 100V .1
     MFD KEMET C330C104M1CU1CA                2
             R3, R6, R9, R12,             8    10    72-06-011  RESIST 1/4 W
     2.7 OHM 5% LITTLE DEVIL OMITE              8
                   B1-B8                  8     9    YKH99030   BERG STICK 3
     POSITION                                   8
            LD2, LD4, LD6, LD8            8     8    68-15-013  lED RED RECT
                                             8
          LD10, LD12, LD14, LD16
          LD1, LD3, LD5, LD7, LD9         8     7    68-15-010  LED GREEN RECT
                                             8
             LD11, LD13, LD15
    R1, R2, R4, R5, R7, R8, R10, R11, R13  16     6    72-06-059  RESIST 1/4 W
     270 OHM 5% CORNING C4                     16
     R14, R16, R17, R19, R20, R22, R23
    P2, P4, P6, P8, P10, P12, P14, P16    8     5    65-02-015  CNECT 2 PIN
     HEADER PCB MNT VERT SHROUDED                8
     P1, P3, P5, P7, P9, P11, P13, P15    8     4    65-25-010  CNCTR 25 PIN
     D-SUB MALE PCB MNT                         8
                    P17                   1     3    65-04-025  CNECTR 4 PIN
     HEADER PCB MNT VERT DETENT .2 CENT         1
                    P18                   1     2    65-48-101  CNECTR 48 PIN
     HEADER PCB MNT RA MODULAR 8 POS           1
                                          1     1    96-52-125  PCB BLANK 8
     CHANNEL BREAKOUT                            1

• Inventors
  Burkhard, Alan W.;
• Assignee
  M-I L.L.C. (Houston, TX)
• Published
  Jun-3-2003
• Current US Classes:
  361/111
  700/286
  702/1
  702/2
  702/9
  718/1
• Application #
  193774
• International Classes
  G06F 017/00
• Field of Search
  700/286 702/1 702/2 702/9 361/111 209/1
• Examiner
  El-Hady; Nabil
• Agent
  Conley Rose, P.C.
• US Patent References:
  4330813
  4410949
  4652851
  4747060
  4959642
  5070431
  5272601
  5381309
  5583764
  5838589
  5841648