WO2004094892A2 - Inherently safe system for supplying energy to and exchanging signals with field devices in hazardous areas - Google Patents

Abstract

The control center (1) receives and processes incoming signals from and sends commands and information data to field instrumentation generally referred to by reference numeral (4 and 5). Instrumentation (4) includes devices located in a hazardous area (6). Instrumentation (4) could comprise, for example, devices of sensor, detectors, actuators, switches, petitioners, transmitters, comtroller and analyzer could perform the functions of measuring, sensing controlling positioning, calculating, communicating processing, displaying, discrete data collecting and providing an alarm function. Equipment (11) is a diaphragm actuated control valve.

Description

INHERENTLY SAFE SYSTEM FOR SUPPLYING ENERGY TO AND EXCHANGING SIGNALS WITH FIELD DEVICES IN HAZARDOUS AREAS

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority of United States Provisional Patent Application 60/464,685 filed April 22, 2003 and United States Provisional Patent Application 60/504,061 filed September 19, 2003. FIELD OF THE INVENTION The present invention relates to supplying energy to and exchanging communications signals with field instruments in hazardous atmospheres. BACKGROUND OF THE INVENTION There is a great need for and wide use instrumentation in potentially explosive atmospheres or hazardous areas. Many industries have hazardous locations. These industries include chemical industries, petrochemical processing, oil drilling, natural gas transporting pipelines, mining, pharmaceutical production, grain handling, waste water treatment and brewing, for example. For purpose of process control, a great deal of field devices must be installed within the hazardous area. These field devices include instrumentations, examples of which are sensors, actuators, switches, transmitters, controllers, and analyzers. These field devices communicate with control systems, measures and controls process parameters, uch as temperature, pressure, flow speed, or liquid level. A control system may comprise a controller in a control center. Most of these field devices need electrical power to operate and all sorts of operations must be performed in hazardous atmospheres. Using electrical field devices in hazardous areas requires special methods of protection to prevent accidental ignition of the presented explosive materials. There are three recognized classes of explosive mixtures of air. Class 1 includes air mixed with gases or vapors. Class 2 includes dust. Dust includes metal dust, flour, starch and grain. Class 3 includes fibers or flyings. Several protection techniques are used in the industries. Examples are Intrinsic Safety, Purge and Pressurization, Ihcreased Safety, Encapsulation, and Explosion Proofing. Standard ANSI/ISA/RP 12.6-1995 defines an intrinsically safe field device as "equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration." (The Instrumentation, Systems, and Automation Society, Research Triangle Park, NC, 1995). Intrinsic safety is the most widely used technique for low power devices operating in hazardous areas. , In intrinsic safety arrangements, it is common to use two conductive wires to provide electrical power to low power field devices and to use the same two wires to transfer analog DC signals between the device and the controller. This implementation saves one pair of wires compared with the early types of four-wire systems, in which one pair of wires provides operating power to the field device and one pair of wires transfers the processing signal. In typical two-wire analog applications, 4 to 20 mA loop current is used to represent a processing variable with typically 5 to 24 volts across the device. A signal of 4 mA will correspond to a lower limit (0%) of a calibrated range of a particular transducer, and 20 mA will correspond to the upper limit (100%) of the calibrated range. In more advanced applications, unidirectional or bidirectional digital communication is added on the same pair of wires along with the analog signal. One recognized system for safe operation in hazardous environments is a system utilizing the Highway Addressable Remote Transducer, or HART, Protocol. The HART Protocol provides a low current to each of a number of field devices and superimposes digital communications at a low level on top of the analog signal. Communication at 1200 bps is provided without interrupting the DC signal. Limitations in this protocol include the need to have one wire pair dedicated to interconnect each field instrument to a central control center in a safe area if analog signal transmission is used. A low data rate of 1200 bps is available in view of operating currents as low as 4 mA and as low as 40 mW power available for the device to use. In order to provide more efficient use of the wire and adapt more advanced data communication technology, the Fieldbus system has been proposed. The FF (Foundation Fieldbus) network developed by the Fieldbus Foundation and Profibus PA from Profibus international are two examples of Fieldbus systems in which the physical layer is specified by IEC61 158-2(lnternational Electro technical Commission; Geneva, Switzerland, 1996). The FF and Profibus PA systems supply a safe level of power to devices over two wires, and multiple devices can provide data over the two wires through time division multiplexing. Total current limitations on any bus line in an intrinsic safety application limit the total current draw by field devices. Therefore, only four or five devices may be actually possibly installed on one bus line, even though the data specification of the bus line may allow up to 32 devices connected on one single line. This limitation in number of devices on a bus reduces available cost saving from reduction of wiring. Detailed safety analysis and 74 documentation is needed to deploy the system.

75 Even though currently FISCO(Fieldbus intrinsic safety concept) and

76 FNICO(Fieldbus non-incentive concept) have been brought up to alleviate the

77 inconvenience of the safety analysis and documentation preparation, only a few

78 more devices could be added on a single Fieldbus, limited power available on each

79 segment of the Fieldbus is still a bottleneck to adding more devices on each bus so line.

8i For any intrinsic safety application in which wires are used to provide power to

82 the field devices in the hazardous areas, intrinsic safety barriers have to be used at

83 an interface between the safe area and the hazardous area.

84 Two conventional forms of safety barriers are the Shunt-diode safety barrier

85 and the Galvanic isolated safety barrier. Barrier products from Pepperl+Fuchs of

86 Twinsburg, Ohio, and MTL of Hampton, New Hampshire are examples. The Zener

87 diode safety barrier clamps supplied voltage to a safe level and utilizes fuses to limit

88 current levels supplied to the hazardous area. A high integrity safety ground is

89 required to ensure reliable grounding in the case of a system fault. The transformer

90 safety isolator, one popular form of safety isolator, uses primary and secondly

91 windings to provide a high degree of isolation. It needs separate power suppliers for

92 both the safe and hazardous sides.

93 The safety barriers must transfer analog or digital signals from the two wires.

94 This constraint can lead to complicated and costly design in signal processing

95 circuits. For all field devices connected by electrical conductor wires to the control

96 center or interconnected in same bus segment, lightning and surge protection issues

97 must be considered. As cable length from a field device to the control center or 98 distance among the field devices in one segment increases, magnitude of possible

99 transient voltages due to shifts in ground potential increase. Surges due to lightning loo or other causes can be impressed on the wires. The surge can damage the device loi instantly or cause future failure, which could cost more because the device could

102 stop the work at any time without warning. Surge protectors need to be installed on

103 both device side and the safety barrier side. Consequently, additional cost is

104 inherent in the use of wires to power instruments.

105 Purge and Pressurization techniques may be used to keep explosive

106 atmospheres out of the confines of ignition sources and allow operation at a higher

107 power lever and avoid some of the above-described shortcomings. Pressurization

108 techniques are described by various standards. European Harmonized Standard

109 EN50 016 originally issued by CENELEC in 1977 describes pressurization is "a no method of protection using the pressure of a protective gas to prevent the ingress of in explosive atmosphere to a space that may contain a source of ignition..."

112 Pressurization in accordance with this standard can be applied to a small electrical ιi3 enclosure or an entire computer room. CENELEC is the European Committee for ιi4 Electro Technical Standardization in Brussels, Belgium, and is the most influential us international standards organization for intrinsic safety, It is a recognized body,

116 competent to adopt harmonized standards pursuant to directive 94/9/EC of the

117 European Parliament and the Counsel of March 23, 1994, on the Approximation of

118 the Laws of the Member States Concerning Equipment and Protective Systems ιi9 Intended for Use in Potentially Explosive Atmospheres. In the United States, 120 Standard NFPA 496 (National Fire Protection Association; Quincy, MA, 2003) i2i addresses pressurization to prevent explosions. 122 Inherent in the design of intrinsically safe systems is the provision of a low

123 power level. Therefore the number of active devices that can be operated is limited.

124 Distributed processing possibilities are limited, and fewer processor parameters can

125 be handles by a local microprocessor. It may not be possible to provide sufficient

126 current to operate relatively high current draw devices such as solenoids and micro

127 motors. More complicated and more expensive circuit designs must be used to

128 provide functions that would otherwise be provided by simple, higher power devices.

129 For Foundation Fieldbus and Profibus PA systems, the power limitations limit the

130 number of instruments that can be utilized to provide outputs to a data bus.

131

132 SUMMARY OF THE INVENTION

133 It is therefore a particular advantage of embodiments of the present invention

134 to provide an energy source for coupling to field devices for independently powering

135 the field devices and which is capable of providing communication methods for

136 individual signals or groups of signals to be transmitted to or/and received from the

137 field devices in hazardous areas.

138 It is a more specific particular advantage of embodiments of the present

139 invention to provide a method to use compressed air energy to drive a generator

140 which is coupled and provides electrical power to field instruments in a system and i4i apparatus of the type described. The invention also allows the use or sharing of the

142 existing distributed compressed air sources which are needed to drive high power

143 equipment, such as various kinds of valves.

144 It is a further particular advantage of embodiments of the present invention to

145 provide a system and apparatus of the type described in which a pneumatic supply 146 for generators is also used for purge and positive pressurization of enclosures to

147 provide a technique of explosion protection.

148 It is another particular object of embodiments of the present invention to

149 provide a system and apparatus of the type described in which an inherently safe

150 system is provided such that safety barriers are not needed. The present invention

151 also provides a system in which lightning or surge protection devices may not

152 needed to be installed, if compressed air is delivered to the field devices using non- 153 electrical conductive pipe and fiber optic cable or wireless communication is chosen

154 to transfer data.

155 It is another particular advantage of embodiments of the present invention in

156 one form to provide methods of imbedding the data communication cables into the

157 compressed air pipe to simplify the field installation.

158 It is also a particular advantage of embodiments of the present invention to

159 provide for alignment of a turbine and a generator to enable reliable operation at

160 high speed.

161 It is a further particular advantage of embodiments of the present invention to

162 provide for monitoring of air consumption and pneumatic pressure to warn of

163 possible leakage.

164 It is also a further advantage of embodiments of the present invention to

165 provide for use of an ultracapacitor to store generated energy to facilitate a low duty

166 cycle of turbine usage.

167 It is also an advantage of embodiments of the present invention to provide for

168 selective use of different sources for pneumatic power, such as central air

169 compressor, field compressed air outlet or an air tank. 170 It is an additional advantage of embodiments of the present invention to

171 provide for control of air supplies from a control center to provide the ability to control

172 charging of energy devices may be discharged below a selected level.

173 It is also a particular advantage of embodiments of the present invention to

174 provide for illumination of field devices by remote control or by sensing of movement

175 near the field devices..

176 Briefly stated, and in accordance with embodiments of the present invention,

177 there are provided a system and apparatus in which compressed air is used as an

178 energy source and supplied from a safe area through pipes to turbine generator

179 modules in a hazardous area, each turbine generator module being attached or

180 otherwise coupled to supply a field device. Data communication cables imbedded i8i into the compressed air pipe and extend from the field instruments to provide data to

182 the safe environment. Devices with compressed air may use the pressure of the gas

183 to prevent the ingress of an explosive atmosphere to enclosures. In a turbine

184 generator module, a turbine rotor may be connected to a generator axle and be

185 supported by a generator bearing. In another form, alignment may be achieved by

186 placing the generator upstream and having the turbine stator fixed to the generator

187 for alignment.

188 Many other advantages are provided. This summary is neither exhaustive not

189 determinative of the scope of the invention.

190 BRIEF DESCRIPTION OF THE DRAWINGS

191 Embodiments of the invention may be further understood by reference to the

192 following description taken in connection with the following drawings:

193 Of the drawings: 194 Figure 1 is a block diagram of a system and apparatus constructed in

195 accordance with the present invention;

196 Figure 2 is a block diagram of a field distribution centers which may distribute

197 air and/or data paths;

198 Figure 3 is a schematic illustration of a turbine generator module;

199 Figure 4 consists of Figures 4a, 4b and 4c, which are schematic illustrations

200 of arrangements for coupling the air turbine to the generator;

201 Figures 5 - 9 are cross-sectional illustrations of various embodiments of

202 combined compressed air and signal cables; and

203 Figure 10 is an illustration of a sensor controlling display illumination.

204

205 DETAILED DESCRIPTION

206 Embodiments of the present invention provide, for example, for pneumatic

207 energy supply to turbine generator modules, supply of energy to instrumentation in

208 hazardous areas from turbine generator modules, storage of energy and

209 transmission of signals between field devices and a safe area. The disclosures of 2io the above-identified provisional applications are incorporated herein by reference. In 2iι the embodiment of Figure 1 , a control center 1 is in a safe, or non-hazardous, zone

212 3. The control center 1 receives and processes incoming signals from and sends

213 commands and information data to field instrumentation generally referred to by

214 reference numeral 4 and 5. Instrumentation 4 includes devices located in a

215 hazardous area 6. Instrumentation 4 could comprise, for example, devices of

216 sensors, detectors, actuators, switches, positioners, transmitters, controllers and

217 analyzers could perform the functions of measuring, sensing, controlling, positioning, 218 calculating, communicating, processing, displaying, discrete data collecting,

219 providing an alarm function or providing remote I/O function, and could have

220 communication interfaces communicating with control intelligence with signals of

221 binary form, analog form or digital form. Instrumentation 5 is a form of

222 instrumentation 4 and is directly attached or installed not far away from equipment

223 that is pneumatically powered. Examples of pneumatically powered equipment are

224 flow control valves. And examples of the instrumentation 5 are electro-pneumatic

225 positioners and current pressure converters. Equipment 1 1 is a diaphragm

226 actuated control valve. Instrumentation 5-1 is the electro-pneumatic positioner. It

227 accepts control signal from cable 37-3. Based on a control signal, the

228 instrumentation 5-1 controls the input compressed air from line 23-2, and the output

229 air from instrumentation 5-1 connects to actuator 12 through a pipe 9. The actuator

230 drives a rod 7 to control the degree of opening of a valve 8. A feedback detector 13

231 may send back feedback signals either to the control center 1 directly through other

232 instrumentation (not shown), or to the instrumentation 5-1 , wherein the

233 instrumentation 5-1 has the function of bidirectional communication with the control

234 center 1.

235 The control center 1 may include known control means such as DCS

236 (Distributing Control System), and PLC (Programming Logic Controller) providing

237 prior art functions such as process control, display of measured parameters,

238 recording of process data, and monitoring for alarm conditions. The control center 1

239 may communicate with controlled devices in the hazardous area 6 in a well-known

240 manner. Examples are 4-20 mA analog signal communication methods; analog

241 signal with a digital signal superimposed thereon, such as HART, with or without 242 electrical power carried on the same cable; field bus systems, such as Fieldbus FF

243 or Profibus PA or other bus protocol, with or without electrical power carried on the

244 same cable; fiber optic data transmission; or wireless communication. The safe

245 zone 3 and hazardous zone 6 are separated physically in accordance with

246 applicable standards. This physical separation is schematically illustrated in Figure

247 1 by a boundary 10.

248 Electrical power is supplied to units collectively referred to as instrumentation

249 4 and 5 by pneumatically powered turbine generator modules 20 further described

250 with respect to Figure 3 below. Instrumentation 4 and 5 comprise field devices.

251 Individual instrumentation units 4-1 to 4-15 and 5-1 to 5-3 are illustrated in Figure 1.

252 The instrumentation units 5-1 through 5-3 are field devices controlling pneumatically

253 powered equipment. The turbine generator modules may be attached to or installed

254 near the field devices as in 20-2 and device 4-3, and connected through an external

255 cable 19 to provide power to and exchange signals with the devices, or may be

256 integrated in the device as in 20-1 and device 4-2 Power to the instrumentation 4 or

257 5 allows the instrumentation to perform powered operations such as parameter

258 measurement and signal transmission. Power may also be used to illuminate

259 displays, e.g., backlit LCDs (liquid crystal devices) or color LEDs (light emitting

260 diodes) in instrumentation 4 or 5. The instrumentation 4 or 5 may further comprise a

261 motion sensor, simple radio frequency wireless control system, or infrared ray

262 remote control system to activate illumination so that the illumination is activated in

263 response to the presence of or a command sent by field personnel inspecting the

264 instrumentation 4 and using an infrared or radio frequency remote controller 15 or

265 16. Field personnel may also use the remote controllers 15 or 16 to command the 266 instrumentation 4 or 5 to change display parameters or units. Compressed air used

267 to drive turbine generator modules 20 may be provided from a compressed air

268 system 22, an existing field compressed air distribute system 23, which is used to

269 provide pneumatic power to drive other field devices such as valves, or discrete

270 compressed air sources 24. While the invention is not limited to the use of air as the

271 compressed gas, air will be the preferred gas. The compressed air system 22 may

272 comprise a conventional prior art system including, for example, a well-known twin-

273 screw compressor to compress air drawn in through an air filter. Air coming out of

274 the compressor goes through an oil separator and air dryer to supply the output air.

275 Air is coupled from the compressed air system 22 by a plurality of piping lines

276 collectively referred to as piping lines 27. While it is conventional to use various

277 forms of metal pipes in compressed air distribution, non-conductive piping such as

278 plastic piping in the segment to connect to the field device along with wireless or

279 fiber optic signal communication method could bring up a unique advantage that

280 surge protection for the field device may not needed, since there are no electrical 28i conductive materials directly connecting to the device that could receive high voltage

282 transients through shift in ground potential. Using elastic and anticorrosion plastic

283 piping in the segment of connecting to the field device is also preferred for its

284 flexibility, easiness of installation and buffering of vibration. Piping could also

285 comprise tubing.

286 In embodiments incorporating wireless or fiber optic cable transmission of

287 field sensor signals, the use of safety barriers, surge protection and wire distribution

288 cabinets is avoided. Space for this equipment in the control center could be saved,

289 and energy applied for this equipment and used for environmental control for this 290 space could be saved.

291 The discrete compressed air sources comprise air tanks 24 and 25 each

292 preferably having a regulator. It is preferred to use high pressure tanks for efficiency

293 and for their energy capacity. In a preferred form, tanks housing compressed air at

294 300 Bar, or 4500 psi, are used. While liquid carbon dioxide of liquid nitrogen could

295 be used, they are much more difficult to handle than compressed air. At 300 bars,

296 one gallon of compressed air contains approximately 636 kj (kilo Joules).

297 In the example of Figure 1 , individual piping lines 27-1 , 27-2, and 27-3 each

298 extend from the compressed air system 22 to a different location. The piping lines

299 27 may supply air-to-air distribution center 30. In the example of Figure 1 , piping

300 lines 27-1 , 27-2 and 27-3 are connected to air distribution center 30-1 , 30-2 and 30-

301 3 respectively. The air distribution center 30, further described with respect to Figure

302 2 below, supply a plurality of combined compressed air tubing - data cables 33 or

303 branch lines 34. Various embodiments of compressed air tubing - data cables 33

304 are described with respect to Figures 5 -9 below. Branch lines 34 may comprise

305 pipe or tubing. Branch lines 34-1 may be connected to couplers 35 to provide

306 further multiple lines, or may be connected to another air distribution center 30-4. In

307 the example of Figure 1 , distribution center 30-1 supplies compressed air tubing -

308 data cables 33-1. Distribution center 30-2 supplies branch line 34-1 or couplers 21

309 and 35. The coupler 35 has an air distribution function, and the coupler 21 has data 3io cable and compressed air integration and separation functions. The distribution

3iι center 30-3 supplies branch line 34-3 and another air distribution center 30-4. In

312 order to provide for redundancy, the branch line 26 is also connected to the

313 distribution center 30-2, and 36 provides an inter-compressed air distribution center 314 redundancy between 30-1 and 30-2 Different compressed air sources may be

315 easily connected to each other. Existing field compressed air distribution system 23

316 could be used to directly to drive turbine generator modules 20, such as compressed

317 air pipe 23-2 provides energy to devices 4-12, 5-1 and 23-3 for device 5-2 and 23-1

318 for device 5-3.

319 Instrumentation 4 or 5 may communicate with the control center 1 directly

320 through cables or via remote I/O. For the cable connection, all prior art of protocols

321 could be used. These include 4-20 mA scheme, or HART, such as used in device 4-

322 15 through powered cable 17, device 4-8 through remote I/O in the air distribution

323 center 30-3, or device 4-12 through standalone remote I/O 31 or Fieldbus FF or

324 Profibus PA, such as used in devices 4-5, 4-6, 4-7 and 5-2. Hybrid powering mode

325 mixture with data cable powered and compressed air powered devices could exist in

326 the same area. An example is in bus line 39. Device 4-7 is powered by the bus line

327 39, while 4-5, 4-6 and 5-2 are powered by compressed air.

328 Instrumentation 4-5, 4-6 and 5-2 may be powered by compressed air, but

329 communicate with control center 1 based on FF or Profibus PA protocol through

330 cable 39. Using existing communication protocol but powered by compressed air has

331 some advantages. In the case of FF is used, one cable can carry as many as 32

332 field devices as designed without considering the power shortage and intrinsic safety

333 issue caused by cable arrangement. Another advantage might be that the optical

334 isolator, which might consist of light emitting diode, optically transparent insulation

335 barrier and phototransistor, could be used and then surge protection might be avoid

336 for these field devices.

337 Remote I/O could be integrated with compresses air distribution center such 338 as in 30-1 , 30-3, and 30-4 or installed standalone such as 31. Remote I/O might be

339 conventional prior art system. A well-known remote I/O is MTL8000 Modular process

340 I/O of MTL.

341 In the example of Figure 1 , wireless interface 38 are also used for field

342 devices to exchange data with control center 1. Using wireless communication

343 combined with compressed air energy would realize totally wireless control system in

344 field and provide opportunity to constitute a high density control and monitoring

345 points for all manageable resources. Wireless interface 38 could be a simple

346 transmitter only, receiver only, transceiver or transceiver with routing function

347 depending on its usages. Routing function might include wireless signal repeating,

348 packet switching or gateway function between wireless interface and wire line. The

349 wireless interfaces 38 may also be provided at the control center 1 as 38-8 in Figure

350 1 , air distribution center 30-3 as 38-5 and in air distribution centers 30-2, 30-4 as

351 38-6 and 38-3 respectively, as well as other intermediate locations such as along

352 compressed air piping lines 27-1 and 27-2 at 38-9 and 38-7 respectively. In such a

353 manner, high density installations are possible. The use of high density systems

354 with selected wireless interfaces are configured with routing function will allow

355 communication over extended distances at low power and form a mesh network that

356 will provide high reliability. Many well-known protocols and techniques are available

357 for effective field networks. These include the ZigBee standard maintained by the

358 ZigBee Alliance of San Ramon, California, IEEE 802.14.5 (Institute of Electrical and

359 Electronic Engineers; New York, NY), or Bluetooth maintained by the Bluetooth

360 Special Interest Group. Free licensed frequency band such as ISM band might be

361 used. In many applications, the wireless interfaces will communicate within the 362 confines of the safe and hazardous zones 3 and 6. However, the wireless interface

363 38 may be configured have capability to communicate with a commercial wireless

364 service 40. A well-known modem card may be installed in instrumentation 4 or 5 or

365 in turbine generator modules 20 to support interaction, for example, with existing

366 wireless telephone systems such as GSM or CDMA cellular telephone systems. The

367 control center 1 can get the data through land line 41 or through similar modem

368 cards. Use of cellular phone connections is suitable for low duty cycle functions and

369 low data rate functions. These functions include monitoring of such parameters as

370 hazardous gas leakage and excursions above temperature or pressure limits. Use

371 commercial available wireless system could shorten the monitoring point installation

372 period and provide longer communication distance with larger transmit power

373 allowed.

374 In addition to provide wireless signal routing function, the wireless interface 38

375 installed on the compressed air pipe line, such as 38-7 and 38-9 , may be coupled

376 with flow meters or pressure sensors, and could provide compressed air

377 consumption statistics or compressed air pressure data to the control center 1. Air

378 flow meters and pressure sensors may also be installed in the air distribution center

379 30-1 , 30-2, 30-3 and 30-4 to get the compressed air consumption statistics or air

380 pressure status which could be reported to the control center 1 through either air

381 interface 38-6, 38-5 and 38-3 or through cables 32-1 , 32-2 and 37-1. By monitoring

382 the compressed air consumption at different point for different pipe branch on

383 regular basis, any abnormal air usage or leakage could be found in real-time or

384 predicted based on analysis of the history statistics data.

385 Compressed air from dedicated source 22, existing source 23, or air tank 24 386 provides pneumatic energy to each turbine generator module 20. The turbine

387 generator module 20 could be attached to or installed near of the field devices as in

388 instrumentation 4-3 and connected through external cable 19 to provide power to

389 and exchange signal with the device, or the turbine generator module 20 could be

390 integrated into the device as part of the device as in 4-2 or 5-2. The turbine

391 generator module could be apply to a variety of field devices with different

392 communication protocols, such as 4-20 mA, HART, FF, Profibus-PA or devices with

393 binary signal, such as proximity switches, actuation of solenoid valves. Including a

394 turbine generator module 20 in a field device, e.g. a valve, having compressed air

395 connected thereto, will save cost of installation of a separate compressed pipe to

396 such field devices 5, for example.

397 Turbine generator modules 20 could be used to provide power only to one

398 device and the device could use the original communication method with the control

399 center, or be used to provide power and communication interface to upgrade the

400 device to more advanced protocol, such as from Binary signal to Fieldbus protocol,

401 from 4-20 mA scheme to Fieldbus. A field device with turbine generator module 20

402 attached or installed could be connected to the control center 1 though cable, as in

403 4-4, through wireless, as in 4-1 1 , through tubing-data cable, as in 4-2, or through

404 cable plus wireless as redundancy, as in 4-6 and 4-12. Using both cable and

405 wireless communication at the same time to some critical field devices could greatly

406 increase the communication reliability of the devices.

407 Figure 2 is a block diagram of an air distribution center. An air distribution

408 center 30 may include an air distributor 42 and remote I/O 49, one of the turbine

409 generator modules 20 connected thereto and wireless gateway 61. The same 410 reference numerals are used to denote elements corresponding to those in Figure 1.

4iι One of the piping lines 27 or 23 or 36 supplies an air distributor 42. The air

412 distributor 42 comprises an air tank and a regulator. Preferably, the air distributor 42

413 also includes an air filter. The air distributor 42 may supply individual branch lines

414 34 and a manifold 45. The manifold 45 supplies further branch lines 34. One

415 branch line 34 also supplies compressed air to one or more couplers 47 which

416 provide pneumatic and electrical coupling to combined compressed air tubing - data

417 cables 33. The couplers also connect electrical signals from combined compressed

418 air tubing - data cables 33 to data lines 48 connected to a remote I/O module 49.

419 The remote I/O 49 may also include interfaces with cables 37 directly connecting to

420 the field devices. Air distribution centers 30 may include compressed air flow and

421 monitoring points 60. The monitored data is sent to the control center 1 though one

422 on the wireless interfaces 38-13 or through remote l/Os 49. Gateway 38-13 may be

423 powered by one turbine generator module 20 or powered by a power supply from

424 remote I/O 49. A remote I/O, sometimes called a distributed I/O or process I/O, has

425 field device interfaces installed in one or many cabinets and it is located in the field

426 with a well-known configuration. It can provide power to the field devices and has

427 high speed backbone data communication with the control center 1. The remote I/O

428 49 connects field device signals in accordance with its configuration and

429 consolidates them to the data cables 32. It may have wireless interface 38-14 to the

430 field devices or to the control center.

431 Remote I/O 49 has high speed data link 32 provides connection from field to

432 the control center 1. Power supply line 62 may be explosion proof (Exd) or

433 Increased Safety Exe) protected for delivering high power to hazardous areas. 434 In summary, an air distribution center 30 may only provide the air distribution

435 function through branch pipe 34, such as in 30-2; may cooperate with remote I/O 49

436 with conventional field device connection cable 37, such as in 30-4; may cooperate

437 with remote I/O 49 with compressed air pipe embedded data cable 33, such as in

438 30-1 , or may be configured with a combination of all three, such as in 30-3.

439 Figure 3 is a schematic illustration of a turbine generator module 20. The

440 turbine generator module 20 is housed in an enclosure 50. The turbine generator

441 module 20 receives air input, for example, from an air branch line 34 at an air inlet

442 51. The turbine generator module 20 receives a cool air input. A coupler 35 may be

443 located intermediate the air branch line 34 and the air inlet 51 to permit the same air

444 branch line 34 to supply other turbine generator modules 20. The air inlet 51 is

445 coupled to a pneumatic circuit including a regulator 53 which supplies air input to an

446 air turbine 54. The air inlet 51 may also have an outlet 52 for positively pressurizing

447 the enclosure 50. Should there be an air source failure, the enclosure 50 would no

448 longer be positively pressurized. However, the same air pressure failure would

449 render the turbine generator module 20 inoperative. Consequently, there is not the

450 potential to create a spark in an unpressurized enclosure. Purge air out point 68 and

451 purge air exit point 69 are for enclosed purging. Two points are located at the two

452 ends of a passage in which the components have purge protection. Device 70

453 connecting to the exit valve 57 can be controlled to an on state or an off state.

454 Combining outlet 52 and device 70 and switching 70 on or off will provide another

455 method to create purge or pressurization protection of the enclosure. The regulator

456 53 is a conventional component maintaining a substantially constant air input to the

457 air turbine 54. Air supply moves energy to the air turbine 54 and air exits via an exit 458 line 56 to an on-off valve 57 connected to an air outlet 59. The air outlet may be

459 connected to an exhaust pipe 58 having an outlet displaced from the housing 50 if

460 the output of the exhaust air needs to be released to a place at a distance away

461 from the module 20. The on-off valve 57 could be connected on the input side of the

462 air turbine 54 rather than the output side. However, more reliable control of rotation

463 of the air turbine 54 is provided by placing the on-off valve 57 on the output side.

464 With the valve 57 on the output side, when the valve 57 is closed in a manner further

465 described below, pressure drop across the pneumatic circuit 51 will go to zero and

466 air flow through the air turbine 54 will stop. Were the valve 57 on the input side,

467 when the valve 57 closed, an impeller in the air turbine 57 could continue rotating for

468 a short time due to inertia of rotors of the air turbine 54 and generator 63. This

469 rotation can create a negative pressure in the enclosure 50 while safety

470 considerations require positive pressurization. As further discussed with respect to

471 Figure 4, the air turbine 54 is coupled to supply rotational power to an electrical

472 generator 63.

473 To generate the sort of power needed for field instrumentation, a miniature

474 turbine 54 and generator 63 may be used. The turbine 54 and generator 63 may

475 have rotor diameters on the order of 5-50 mm. "Miniature" is defined by literature

476 references. Qualitatively, miniature is smaller than a fist. An important alternative is

477 a turbine 54 the size of a turbine used in a dental handpiece. Many different forms

478 of air turbine 54 could be provided. In a preferred form, the air turbine 54 comprises

479 a small, high speed turbine. A single stage, axial impulse turbine, also known as a

480 Laval turbine, operating at, for example 100,000 to 200,000 rpm provides good

481 efficiency. Higher speeds may be preferable for greater efficiency. However, 482 currently, the bearings in the turbine are a limiting factor in achievable rotational

483 speed. The turbine 54 is designed to use low pressure, e.g., 0.5-2.5 Bar. An

484 example of a suitable turbine is the Midwest Quiet Air turbine distributed by

485 Handpiece Parts and Products of Orange, California. The generator 63 is preferably

486 a miniature, brushless, coreless machine. Preferably the generator 63 comprises a

487 rare earth magnet providing a stronger magnetic field for its size than other magnets.

488 The generator 63 may be a small brushless dc motor used as a generator. A

489 suitable example is the Faulhaber type 1628 TO24B K312 distributed by MicroMo

490 Electronics Inc. of Clearwater, Florida.

491 The electrical generator 63 supplies power to a control circuit 65 and may

492 supply and energy storage circuit 67. An energy limiter device 72 may be provided

493 in series between the control circuit 65 and a device interface circuit 74. The energy

494 limiter device 72, which could be a conventional safety barrier, may be included in

495 modules 20 which are retrofit into existing prior art systems in the field which

496 currently interface with a barrier device. A galvanic isolator 73 may be placed

497 between the control circuit 65 and control system interface 75. The galvanic isolator

498 73 provides a function of isolation function for control system interface 75 from its

499 connecting communications line. The control system interface 75 may connect via

500 the communications to a circuit such as the control center 1 , one of the I/O remote

501 interface cards 49 or a field bus connector junction box.

502 The remote I/O 49 couples signals to and from the turbine generator module

503 20 as further described below with respect to Figure 3. In many instances, the

504 control function will be included in the control center 1. However, in accordance with

505 well-known methods, control intelligence may be distributed. Control functions could 506 be provided by known apparatus further included in the remote I/O 49, the turbine

507 generator module 20 or in instrumentation 4 or 5. Any components such as the

508 above-described component providing a control function are referred as control

509 intelligence. Therefore, the device interface circuit 74 and the control system 5io interface 75 may be described as an interface between a field device and control 5iι intelligence.

512 The control circuit 65 performs a number of functions. The control circuit 65

513 switches energy to the energy storage circuit 67, monitors stored energy available,

514 and operates the on-off valve 57. The control circuit 65 may also regulate power

515 supplied to instrumentation 4 or 5. Preferably, an air pressure monitor 76 is included

516 in the housing 50. The air pressure monitor 76 is a well-known transducer which

517 measures air pressure responsive to the air pressure supplied to the air inlet 51.

518 The air pressure monitor may be pneumatically connected to sense air pressure at

519 the output of the regulator 53. The air pressure monitor 76 provides an electrical

520 signal indicative of pressure to the power supply and control circuit 65. Monitoring

521 air pressure may serve a number of purposes. It is useful to monitor leakage. The

522 power supply and control circuit is configured to supply from the air pressure monitor

523 76 through the remote I/O 49 or wireless interface 38 to the control center 1 where a

524 history of air consumption is registered. Change in air consumption can be flagged

525 as an early warning of leakage. The output of the air pressure monitor 76 is also

526 used to provide a charging signal to indicate when air is being used to drive the

527 turbine 54. This operation is monitored at the control center 1. Charging signals are

528 monitored and control signals issued from control intelligence to prevent an

529 excessive number of turbine-generator modules from initiating charging at the same 530 time. An excessive number is one that would overload a branch 34 or other air

531 supply line. Since, as explained below, charging may be accomplished at a low duty

532 cycle. Combining the self-controlled charging time and control intelligence controlled

533 charging time will provide ability to maintain a proper charge on the ultracapacitor 67

534 and at the same time prevent overload the air supply system.

535 It is preferable to have an energy storage circuit 67 as opposed to operating

536 the instrumentation 4 or 5 directly from the generator 63. Components may be

537 selected with respect to required electrical output so that the average duty cycle of

538 the air turbine 54 may be limited to a range of 1 %-20%, increasing its life and

539 reliability. Low duty cycle minimizes heat generation by the turbine 54 and the

540 generator 63.

541 Where a system is designed with a 10 year life, if a 1% duty cycle can be

542 maintained, turbine 54 and the generator 63 will operate for a total of 1.2 months

543 over the useful life. For example, the generator 63 may run for 5 seconds at a 25

544 watt output level. This will charge the ultracapacitor 67 with 25x5, or 125 joules of

545 energy (not considering any losses). If the field device draws 250 mw of power, then

546 the energy in the ultracapacitor 67 could provide power for 500 seconds of

547 continuous operation.

548 Wearing out of components will be avoided as will very costly system

549 shutdown due to a failure. Use of the energy storage circuit 67 can provide for a

550 relatively constant load on the generator 63 when charging the energy storage circuit

551 67. When instrumentation 4 is operating directly of the generator 63, variable

552 electrical load on the generator 63 creates a variable load a variable resistance that

553 the turbine 54 must overcome to rotate the generator 63. In turn, variable input 554 pressure requirements are imposed on the air input for the branch line 34. Due to

555 the time lag in input air pressure in tracking load, when mechanical load drops, a

556 relatively high pressure applied to the air inlet 51 does not drop immediately.

557 Consequently, pneumatic energy will be wasted.

558 The energy storage medium in the energy storage circuit is preferably an

559 ultracapacitor, also known as a supercapacitor. An ultracapacitor is a component

560 having a capacitance on the order of magnitude of a farad. Ultracapacitors can be

561 charged many thousands of times. Ultracapacitors have a wide temperature

562 operating range, nominally -40°C to +70°C. Charging times needed to charge

563 ultracapacitors are consistent with the need to provide a low duty cycle. The very

564 high value of an ultracapacitor provides for a very long time constant, which further

565 reduces the possibility of production of sparks. A battery could be used as the

566 storage medium in the energy storage circuit 67 but is not preferred. Rechargeable

567 batteries, e.g., nickel-cadmium batteries, have a limited maximum number of

568 recharge cycles, one the order of one thousand. Generally batteries need to be at a

569 temperature above 0° C for charging. In many applications, ambient temperature

570 will be below this level for significant parts of the year. Use and replacement of non- 571 chargeable, primary batteries is expensive. Batteries can release large amounts of

572 energy in the event of a short circuit or other fault. Appropriate explosion protection

573 needs to be provided.

574 The ultracapacitor 67 may be encapsulated with an energy release limiter

575 circuit for explosion protection in case of the sudden loss of the compressed air

576 while the ultracapacitor 67 is charged with high energy.

577 Figure 4 consists of Figures 4a, 4b and 4c, which are schematic illustrations 578 arrangements for coupling the air turbine 54 to the generator 63. The generator has

579 stator coils 92 and 93 and a rotor 95 including a permanent magnet 94. Bearings 90

580 and 91 support the rotor. The air turbine 54 is supplied from the compressed air

581 system over piping 27. The input air to the air turbine 54 will be at substantially

582 ambient temperatures. Air temperatures will not be elevated as in the case of output

583 air from combustion turbines. Consequently the air turbine 54 can be connected to

584 the generator 63 at a short distance therefore without concern for damage to the

585 generator 63 from hot air turbine output. In the embodiments of Figure 4a, 4b and

586 4c, the air turbine 54 and generator are coaxially mounted in a housing 80 having an

587 air intake 83 receiving air from the regulator 53. Air exits the housing 80 at an outlet

588 84. A turbine rotor 86 is directly mounted on the axle 95 of the generator 63.

589 Bearings 90 and 91 support the turbine rotor 86. In this arrangement, there is no

590 need to provide separate bearings for the turbine rotor 86. In this structure with the

591 turbine rotor on the generator axle, coupling loss is held to a lowest level.

592 In figure 4, the air turbine 54 comprises a stator 85 and a rotor 86. The stator

593 85 comprises circumferentially spaced nozzles which expand the air and direct air

594 input to vanes of the rotor 86. In the embodiment of Figure 4a, the turbine stator 85

595 is adjacent the air intake 83 and directs air to the turbine rotor 86. The generator 64

596 is downstream from the turbine rotor 86. In the embodiment of Figure 4b the

597 generator is adjacent the air intake 83. In the embodiment of Figure 4c, inlet 83 and

598 outlet 84 are located at a side rather than an axial end of the housing 80. In the

599 embodiments of Figure 4b and Figure 4c, a stator of the turbine 54 is connected to a

600 housing of the generator 63 for reliable alignment and space saving. In one form, the

601 inlet 83 may be located to blow directly to a nozzle tangentially directed at radial 602 turbine blades.

603 Figures 5 -9 illustrate different forms of combined compressed air tubing -

604 data cables 33. In these figures, the same reference numerals are used to denote

605 corresponding components. In the embodiment of Figure 5, an air pipe 100

606 comprises a central air conduit 102 having a central air passage 105. The central air

607 conduit 102 is surrounded by concentric first and second conductive layers 104 and

608 106. The conductive layers 104 and 106 are insulated from each other by an

609 insulation layer 103. Insulating layer 107 is between the conductive layer 104 and 6io the conduit 102. Insulating layer 101 is intermediate the conductive layer 106 and a 6iι protective layer 110. The protective layer 10 may include a braided radio frequency

612 interference shield and a plastic outer layer. The central air conduit 102 is preferably

613 of insulating material. Figures 6-9 are cross sectional views. In Figure 6, a coaxial

614 combined compressed air tubing - data cable 120 comprises an air conduit 123

615 disposed in parallel to a conductor conduit 124 joined in a cable structure 126 by

616 packing material 127. The conductor conduit 124 carries a plurality of conductors

617 130. In Figure 7, a combined compressed air tubing - data cable 140 includes a

618 wall 142 having conductors 130 embedded therein. Thus a communications line is

619 coaxial with a compressed air line. In the embodiment of Figure 8, conductors 130

620 are carried in the air passage 105 of a conduit 103. In the embodiment of Figure 9,

621 the conductors 103 are integrated with the conduit 102 on an outer diameter thereof.

622 The number of the cables 130 in the embodiments Figures 6, 7, 8, and 9 may

623 be one or more than one. The cable 130 may be pair twisted, shielded or unshielded

624 copper. The cable 130 may be optical fiber.

625 Overall efficiency of the system in nominal embodiment is 7% to 15%, which 626 compares quite favorable with other generation systems used to power field devices.

627 The efficiency of the turbine generator module 20 is between 15% and 30%. A

628 nominal efficiency of converting electrical power supplying the compressed air

629 system 22 is 50%, yielding the above-stated result. Efficiency of the discrete air

630 source 24 is enhanced by the ambient atmosphere. When air is exhausted from the

631 tank included in the source 24 to an included intermediate tank 25, its temperature

632 significantly decreases due to the Joule-Thompson effect. As stated above, one

633 gallon of compressed air at 300 bars has about 636 kj of energy. Approximately

634 94% thermal energy recovery may be gained from heat exchange with the ambient

635 atmosphere. A nominal 10% may be recovered from solar heating. Assuming these

636 recoveries and the above-stated 15-30% efficiency of the turbine generator module

637 20, the module will produce 203 to 407 kj. The best and highest capacity primary

638 battery currently on the market is the 1 kg LiSoCI2 (lithium thionyl chloride) battery

639 having 1080 kj of deliverable energy. An AA size LiSoCI2 battery will provide about

640 26 kj. Then one gallon discrete source 24 will provide energy roughly approximating 64i that of eight to 16 such batteries.

642 Figure 10 consists Figure 10a, 10b and 10c, which illustrates the way to

643 trigger selected field device 4 or 5 to illuminate displays, such as backlit LCDs (liquid

644 crystal devices) or color LEDs (light emitting diodes), and remotely reading the

645 display parameters under illumination. In Figure 10a, the instrumentation 4

646 comprises a motion sensor 150, so that the illumination is activated in response to

647 the presence personnel inspecting the instrumentation 4, or in response to enclosure

648 opening if the instrument 4 is installed into an enclosure.

649 In Figure 10b, the instrumentation 5 comprises infrared ray sensor 151 , so 650 that the illumination is activated in response to the command sending from the

651 remote controller 15 by field personnel inspecting the instrumentation 5. Both

652 infrared ray receiver 151 and remote controller 15 are preprogrammed such that

653 only one specific remote controller 15 activates the illumination and send some

654 simple instructions to the instrument 5 for some simple action such as change

655 reading parameters or reading units.

656 In Figure 10c, the instrumentation 4 comprises a wireless receiver 153, so

657 that the illumination is activated in response to the command sending from the

658 remote wireless transmitter 16 by field personnel inspecting the instrumentation 4. A

659 simple wireless device and protocol, such as Zigbee, could be used to perform this

660 action. Both remote wireless transmitter 153 and remote transmitter 16 are 66i preprogrammed to a predefined frequency channel and use predefined

662 communication protocol that only specific wireless transmitter activate the

663 illumination and send some simple instructions to the instrument 4 for some simple

664 action such as change reading parameters or reading units.

665 Many modifications may be made to the particular embodiments disclosed

666 above to provide forms of the present invention.

Claims

What is claimed is:

1. A system to provide energy to field devices remote from a control center comprising: a pneumatic line; at least one gas turbine receiving an input from said pneumatic line; a generator coupled to each said at least one turbine, said generator providing power for field device use in a hazardous atmosphere.

2. A system according to claim 1 wherein said generator and turbine are in a turbine generator module included in a housing.

3. A system according to claim 2 wherein said pneumatic line provides purge and pressurization to said housing.

4. A system according to claim 3 wherein said turbine is a miniature turbine.

5. A system according to claim 3 wherein said turbine is a dental turbine.

6. A system according to claim 4 wherein said generator comprises a brushless motor.

7. A system according to claim 6 wherein a stator of said turbine is attached to said generator to align said turbine and said generator.

8. A system according to claim 6 wherein said turbine rotor is fixed to an axle of said generator.

9. A system according to claim 2 wherein said turbine generator module further comprises an interface for communication between control intelligence and a field device.

10. A system according to claim 9 further comprising a communication line to couple signals between a field device and the control intelligence.

11. A system according to claim 10 wherein said communication line comprises analog transmission cable.

12. A system according to claim 10 wherein said communication line comprises a wireless link.

13. A system according to claim 10 wherein said communication line comprises a digital communication line.

14. A system according to claim 10 further comprising at least one field device coupled to one said turbine generator module.

15. A system according to claim 14 wherein said field device comprises a transducer providing a dc current as a function of sensed level within a range.

16. A system according to claim 14 wherein said field device a binary state device.

17. A system according to claim 10 wherein said field device and said communication line comprise a plurality of devices and cables connected in a field bus system.

18. A system according to claim 10 further comprising a plurality of turbine generator modules each receiving an input from a pneumatic line and providing power to a field device.

19. A system according to claim 18 further comprising a compressed air source coupled to each said pneumatic line.

20. A system according to claim 19 wherein said compressed air source comprises a compressed air pump.

21. A system according to claim 19 wherein said compressed air source comprises a compressed air tank.

22. A system according to claim 21 where said compressed air tank is pressurized to substantially at least 300 bar.

23. A system according to claim 21 comprising air regulators to operate said turbine at a pressure having an order of magnitude of 1 bar.

24. A system according to claim 23 further comprising a buffer tank coupled between said compressed air tank and said turbine, said buffer tank being lowered in temperature and response to expansion of air thereto supplied from said compressed air tank and said buffer tank being adapted to recover ambient heat.

25. A system according to claim 19 wherein said compressed air source comprises a local supply of compressed air provided for field equipment operation.

26. A system according to claim 19 wherein said compressed air source comprises a compressed air pump and a compressed air tank and a local supply of compressed air provided for field equipment operation.

27. A system according to claim 18 further comprises sensors for monitoring compressed air consumption and compressed air pressure.

28. A system according to claim 18 wherein communication lines are combined with compressed air lines.

29. A system according to claim 28 further comprising compressed air distribution centers each having an input from said compressed air pump and a plurality of outputs to turbines.

30. A system according to claim 29 wherein said compressed air distribution centers comprise remote input/output, each remote input/output coupling a plurality of communication lines to the control center.

31. A system according to claim 14 wherein said field device comprises sensing means to change a state in response to sensing of a condition.

32. A system according to claim 31 wherein the state comprises illumination or non-illumination and the condition is proximity sensing.

33. A system according to claim 31 wherein the state comprises illumination or non-illumination and the condition is activation by a remote controller.

34. A system according to claim 14 wherein said turbine generator module and a field device are integrated.

35. A system according to claim 15 wherein an ultracapacitor is provided in an energy storage circuit coupled to said generator, said energy storage circuit being couple to power said field device, the capacity of said energy storage circuit being selected to provide for a low duty cycle of said turbine generator module.

36. A system according to claim 35 wherein said duty cycle is up to 20%.

37. A system according to claim 35 wherein said turbine generator module comprises a circuit to respond to a signal from the control center to control charging time of said ultracapacitor.

38. A system according to claim 28 wherein at least one said combined communications line and compressed air line comprises a communications line coaxially formed with a compressed air line.

39. A system according to claim 28 wherein at least one said combined communications line and compressed air line comprises a communications line located in a compressed air line.

40. A system according to claim 28 wherein at least one said combined communications line and compressed air line comprises a communications line formed in a cable substantially parallel with a compressed air line.

41. A system according to claim 2 further comprising a field device including said turbine generator module.

42. A system according to claim 41 wherein said field device comprises an interface to control intelligence.

43. A turbine generator module comprising a miniature turbine and a miniature generator having a stator of said turbine connected to a housing of the generator.

44. A turbine generator module wherein said generator is located upstream of said turbine and wherein a rotor of said turbine is supported to a rotational bearing in said generator.