Patent Application
20250141026
The present invention relates generally to industrial process control and monitoring systems. More particularly, the present invention relates to wireless process field devices for use in such systems.
In industrial settings, process control systems are used to monitor and control inventories and operation of industrial and chemical processes, and the like. Typically, the system that performs these functions uses field devices distributed at key locations in the industrial process coupled to control circuitry in a control room by a process control loop. The term “field device” refers to any device that performs a function in a distributed control or process monitoring system, including all devices used in the measurement, control, and monitoring of industrial processes. Usually, such field devices have a field-hardened enclosure so that they can be installed outdoors in relatively rugged environments and be able to withstand climatological extremes of temperature, humidity, vibration, and mechanical shock.
Typically, each field device also includes communication circuitry that is used for communicating with a process controller, or other field devices, or other circuitry, over the process control loop. In some installations, the process control loop is also used to deliver a regulated current and/or voltage to the field device for powering the field device. The process control loop also carries data, either in an analog or digital format.
In some installations, wireless technologies are now used to communicate with field devices. Wireless operation simplifies field device wiring and setup. Wireless installations are currently used in which the field device includes a local power source. However, because of power limitations, the functionality of such wireless field devices may be limited.
Wireless field devices may employ an intrinsically-safe local power source that may be replaceable when the energy of the power source becomes depleted or below a selected threshold. When the battery needs to be replaced, it is desirable that the battery is easily replaceable and intrinsically-safe so that it can be replaced in an explosive environment without the requirement for a hot work permit or removing the wireless transmitter from the explosive environment. Alternatively, some wireless field devices may employ a battery as a power source that is not intrinsically-safe.
Intrinsic safety is a term that refers to the ability of the field device to operate safely in potentially volatile environments. For example, the environment in which field devices operate can sometimes be so volatile that an errant spark or sufficiently high surface temperature of an electrical component could cause the environment to ignite and generate an explosion. To ensure that such situations do not occur, intrinsic safety specifications have been developed. Compliance with an intrinsic safety requirement helps ensure that even under fault conditions, the circuitry or device itself cannot ignite a volatile environment. One specification for an intrinsic safety requirement is set forth in: APPROVAL STANDARD INTRINISICALLY SAFE APPARATUS AND ASSOCIATED APPARATUS FOR USE IN CLASS I, II AND III, DIVISION 1 HAZARDOUS (CLASSIFIED) LOCATIONS, CLASS 3610, promulgated by Factory Mutual Research October 1988. Adaptations to comply with additional industrial standards such as Canadian Standards Association (CSA) and the European Cenelec standards are also contemplated.
Many wireless field devices are rated for Division 1 and Zone 0 areas. This means that explosive gases are likely to be present and that very strict criteria are applied to the electronic equipment used in these areas. If a battery does not meet certain energy limiting criteria or is not properly protected from damage when dropped, it cannot be brought into a Class 1 or Zone 0 area without obtaining a hot work permit and taking actions to temporality declassify the area. This is a time-consuming and costly process. While there are some commercially available batteries that may meet short circuit temperature rise requirements for Intrinsically-Safe certification, they are susceptible to damage when dropped from as little as 2 to 3 feet because the battery positive terminal is often sealed with a brittle glass to metal seal.
Another challenge for powering wireless field devices is securing the battery. Wireless field devices are often installed in very harsh industrial environments. Since the battery of a wireless field device may be expected to last for 10 years, the long-term reliability of the connection to the battery is very important. Fretting corrosion is a phenomenon that can occur when the mating parts of a connection move very slightly relative to each other. When this happens, protective coatings on the mating interfaces of the connector are disturbed leading to formation of corrosion that eventually causes the contact resistance to increase and the battery can no longer power the field device.
An intrinsically-safe battery assembly for field devices, the intrinsically-safe battery assembly includes an intrinsically-safe battery and polymeric chassis. In an example, the polymeric chassis is removably coupled to the intrinsically-safe battery and has at least one retention mechanism configured to engage the intrinsically-safe battery. In another example, the polymeric structure has at least one battery ejection mechanism configured to eject the intrinsically-safe battery. A field device is also provided.
Embodiments described herein generally provide an intrinsically-safe, easily replaceable, single cell, low cost, compact battery assembly for wireless field devices. The battery assembly is suitable for an industrial application and provides a reliable electrical connection that is resistant to vibration, shock, and other environmental stresses. In some embodiments, the battery assembly meets all industry intrinsically-safe requirements allowing it to be removed and replaced in a hazardous location without the need for declassifying the area or obtaining a hot work permit. For example, in some embodiments, the battery assembly may meet all Division 1 and Zone 0 requirements to facilitate such operations in the hazardous environment. Alternatively, in some embodiments, the battery assembly may not have to be intrinsically-safe.
Batteries/power modules are used across many wireless field devices and can be replaced several times over the life of a given field device. Due to this replacement routine, current solutions are limited in terms of efficiency and commissioning time. Embodiments described below provide an intrinsically-safe battery assembly with more efficient battery retention and ejection mechanisms. In some embodiments, both retention features and ejection features are provided in a single polymeric component. The polymeric chassis contains built-in snap retention features which wrap slightly around the power module. Embodiments also provide a rear-mounted battery ejector features that, when squeezed together, push forward and eject the battery by overcoming the retaining force of the retention snaps. The squeeze displacement moves the battery assembly beyond the retention/capture features to obtain a clean ejection. Some embodiments also feature one or more directional guides at the base of the chassis to eliminate rotational and axial movement. These guides interface with corresponding grooves in the battery assembly to lock the battery assembly in place once inserted. These guides also allow the battery assembly to eject without binding.
Controller 156 may be any suitable circuitry or combination of circuitry that executes programmatic steps to generate a process variable output based upon signals received from measurement circuitry 154. In one example, controller 156 is a microprocessor. Controller 156 is also coupled to communication circuitry 158 which can receive the process variable output information from controller 156 and provide wireless industry standard process communication signals based thereon. Preferably, communication circuitry 158 allows bidirectional wireless communication utilizing wireless antenna 160. As shown diagrammatically at reference numeral 162, this bidirectional wireless communication generally communicates with the industrial process control system 164. An example of a suitable wireless process communication protocol is set forth in IEC 62591. However, other examples instead of or in addition to IEC 62591 are also contemplated.
As shown in
Wireless field device 100 also preferably includes battery identification circuitry 167 that is coupled to, or part of, controller 156. As will be described in greater detail below, embodiments disclosed herein may generally use different battery form factors (e.g., D-cell and C-cell) for powering wireless field device 100. Since different battery form factors generally provide batteries with different energy storage, battery identification logic 167 allows wireless field device 100 to determine the type of battery assembly 166 used. This allows controller 156 to modify operation of wireless field device 100 based on the type of battery detected by battery identification logic 167. Examples of such modification of operation include, without limitation, limiting or inhibiting available features and/or functions, limiting performance, and limiting a measurement interval. An example of limiting or inhibiting available features and or functions can include selectively enabling/disabling a local display of the field device based on available power from the identified type of battery assembly used. Another example includes reducing radio-frequency power of the communication circuitry 158 based on the type of battery assembly used. An example of reducing performance of the wireless field device may include selecting a lower power mode of controller 158 or reducing the set of functions it performs and/or when it performs them. An example of limiting a measurement interval includes changing the measurement interval from 10 times per second to one measurement per minute.
Battery identification logic 167 is coupled, either electrically or mechanically, to battery assembly 166, as indicated by dashed line 168. By virtue of coupling 168, battery identification logic 167 is able to determine a form factor of the battery cell within battery 166. This determination may be done using an electrical aspect of battery 166 or a mechanical aspect of battery 166.
As can be seen in
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
