Patent Publication Number: US-11648508-B2

Title: Systems and methods for sequencing operation of compressed air dryers

Description:
BACKGROUND 
     Compressed air systems can utilize heat exchange systems to dry compressed air by condensing and removing moisture to output a dried compressed air stream. The heat exchange systems can use a cooling medium to facilitate heat transfer from the compressed air to the cooling medium. The warmed cooling medium can then be discarded or rechilled for future use. 
     SUMMARY 
     Compressed air dryer systems are described. In an aspect, a system includes, but is not limited to, a storage tank, a single cooling medium header, a plurality of dryer modules, and a controller operable to regulate a run-time of each of the plurality of dryer modules. The storage tank is configured to hold a cooling medium in a fluid state within an interior of the storage tank. The single cooling medium header is fluidically coupled with the storage tank. The plurality of dryer modules is fluidically coupled with each of the single cooling medium header and the storage tank. Each dryer module is configured to direct a portion of cooling medium received from the single cooling medium header past a stream of compressed air and back to the storage tank. Each dryer module includes a temperature sensor in thermal communication with the portion of cooling medium and a chiller configured to reduce a temperature of the portion of cooling medium when the sensed temperature exceeds a temperature set-point. The controller is communicatively coupled with the plurality of dryer modules and operable to monitor a plurality of run-times. Each run-time is associated with a corresponding dryer module. The controller is further operable to regulate each run-time by modifying the temperature set-point of corresponding the dryer module. 
     In an aspect, a system includes, but is not limited to, a plurality of dryer modules and a controller operable to regulate a run-time of each of the plurality of dryer modules. Each dryer module is configured to direct a portion of cooling medium past a stream of compressed air to condense at least a portion of moisture held in the first stream of compressed air. Each dryer module includes a temperature sensor in thermal communication with the portion of cooling medium, and a chiller configured to reduce a temperature of the portion of cooling medium based on the sensed temperature and a temperature set-point. The controller communicatively is coupled with the plurality of dryer modules and operable to monitor a plurality of run-times. Each run-time is associated with a corresponding dryer module. The controller is further operable to direct operation of each dryer module based on its run-time by modifying the temperature set-point of the dryer module. 
     In an aspect, a method for regulating the run-time of a plurality of compressed air dryer modules includes, but is not limited to, operating a first dryer module, based on a first temperature set-point, to regulate a temperature of a first portion of cooling medium being circulated through the first dryer module; operating a second dryer module, based on a second temperature set-point, to regulate a temperature of a second portion of cooling medium being circulated through the second dryer module; monitoring, via a controller, a first run-time associated with operation of the first dryer module and a second run-time associated with operation of the second dryer module; and modifying, via the controller, the first temperature set-point and the second temperature set-point to regulate the first run-time and the second run-time, respectively. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DRAWINGS 
       The Detailed Description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items. 
         FIG.  1    is a schematic illustration of a compressed air dryer system in accordance with in accordance with embodiments of the present disclosure. 
         FIG.  2 A  is a diagram illustrating an example algorithm for regulating run-time of a compressed air dryer system, such as the compressed air dryer system of  FIG.  1   , in accordance with embodiments of the present disclosure. 
         FIG.  2 B  is another diagram illustrating an example algorithm for regulating run-time of a compressed air dryer system, such as the compressed air dryer system of  FIG.  1   , in accordance with embodiments of the present disclosure. 
         FIG.  2 C  is another diagram illustrating an example algorithm for regulating run-time of a compressed air dryer system, such as the compressed air dryer system of  FIG.  1   , in accordance with embodiments of the present disclosure. 
         FIG.  3 A  is an example flow diagram illustrating an example process for regulating the run-time of a compressed air dryer system, such as the compressed air dryer system illustrated in  FIG.  1   , in accordance with an example implementation of the present disclosure. 
         FIG.  3 B  is another example flow diagram illustrating an example process for regulating the run-time of a compressed air dryer system, such as the compressed air dryer system illustrated in  FIG.  1   , in accordance with an example implementation of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     Compressed air systems treat a source of air, such as environmental air, by compressing the air to provide a source of compressed air for work applications. The air may have moisture present following treatment by the compressed air system, such as due to humidity conditions in the environment supplying the source air. Moisture can be detrimental to various compressed air applications, such as by posing a risk for machines that utilize the compressed air, products treated by application of the compressed air, products produced with the compressed air, and the like. For example, moisture in compressed air can contribute to risks for rust, corrosion, contamination, bacterial growth, dilution, and the like. To reduce the amount of moisture present in compressed air, compressed air systems can include or be coupled with heat exchange systems to remove moisture through condensation of moisture and separation of the condensation from the flow of compressed air. The heat exchange systems can circulate a cooling medium, such as water, glycol, synthetic refrigerant, or the like, to cool a flow of compressed air and heat the cooling medium. The heated cooling medium can then be discarded or chilled to provide cooling for future applications. 
     Compressed air systems can incorporate multiple heat exchange systems for drying multiple flows of compressed air. For example, compressed air systems can include multiple dryer modules that share a source of cooling medium that is circulated through the modules, and/or multiple independent dryer modules. For systems that share a source of cooling medium, the cooling medium can be stored in a storage tank for transfer to the individual dryer modules by one or more pumps. As the dryer modules treat the compressed air, the cooling medium is heated during condensation of the moisture and then subsequently cooled (e.g., by a chiller) and transferred back to the storage tank. 
     The number of dryer modules in operation may vary based on a load condition of the compressed air system. The system will operate with the minimum number of dryer modules necessary to meet the total compressed air demand. At low load conditions, for example, one module (e.g., the lead module) may be sufficient to meet the compressed air demand of the system, and will operate more frequently than the other dryer modules to maintain a desired temperature of the cooling medium. As the system load increases, additional dryer modules are engaged sequentially to meet the increased compressed air demand. A large compressed air system may operate most frequently at lower load conditions (e.g., nights, weekends, etc.), operating at near full capacity less than 45 percent of the time. Because the dryer modules are engaged sequentially based on the load condition of the system, the run-time (e.g., run-hours) of each dryer module varies, with some dyer modules (e.g., the lead module) operating more frequently than other modules. This disparate run-time between dryer modules results in varied mechanical and electrical wear on the dryer modules and their components, and can decrease the operating life of modules with high run-time. 
     Accordingly, the present disclosure is directed, at least in part, to systems and methods for regulating run-time in compressed air systems operating multiple dryer modules. In an aspect, each of the dryer modules includes a temperature sensor in thermal communication with the cooling medium circulating through the dryer module; and a chiller configured to reduce a temperature of the portion of cooling medium based on the sensed temperature and a temperature set-point. A controller is operable to monitor the run-time (e.g., run hours) of each of the dryer modules. The controller regulates operation of each of the dryer modules based on its run-time by modifying the temperature set-point of the dryer modules. In some aspects, each dryer module will have a unique temperature set-point selected to match the required cooling load of the system, and the dryer modules will operate sequentially based on a hierarchy of temperature set-points. By modifying the temperature set-points, the controller is operable to adjust each dryer module&#39;s position in the sequence of operation to achieve a desired run-time for each module, for example, to achieve equivalent run-time of the dryer modules. Operating the dryer modules with run-time can facilitate uniform mechanical and electrical wear on the modules, enhancing the reliability and operating life of each module and its components, and reducing the incidence of premature module failures. 
     Example Implementations 
     Referring generally to  FIG.  1   , a compressed air dryer system  100  for regulating run-time of a plurality of dryer modules for drying a plurality of compressed air streams is described in accordance with example embodiments of the present disclosure. In some embodiments, the system  100  includes a shared cooling medium that is distributed to the plurality of drying modules. The system  100  is shown including a storage tank  102 , a circulation pump  104 , a cooling medium header  106 , a dryer module  108 , a circulation pump  204 , and a dryer module  208 . The system  100  distributes a cooling medium from the storage tank  102  to the cooling medium header  106  for supply to each dryer module fluidically coupled with the cooling medium header  106  to condense moisture carried in flows of compressed air through the dryer modules. In  FIG.  1   , each of dryer module  108  and dryer module  208  are fluidically coupled with the cooling medium header  106  to receive cooling medium flowed therethrough. While  FIG.  1    shows two dryer modules fluidically coupled with the cooling medium header  106  (e.g., dryer module  108  and dryer module  208 ), the system  100  is not limited to such configurations. For instance, the system  100  can include more than two dryer modules fluidically coupled with the cooling medium header  106 , including, but not limited to, three dryer modules, four dryer modules, five dryer modules, six dryer modules, seven dryer modules, eight dryer modules, more than eight dryer modules, or the like. 
     The storage tank  102  holds a volume of cooling medium suitable for distribution throughout the system  100  to condense moisture carried in flows of compressed air through the dryer modules. The capacity of the storage tank  102  can depend on the type of cooling medium utilized, the number of dryer modules, the throughput of compressed gas processed by the system  100 , and the like. In example implementations, the storage tank  102  holds a volume of approximately 70 gallons to approximately 300 gallons to support from two to eight dryer modules for an air capacity of approximately 3,500 standard cubic feet per minute (SCFM) of compressed air to approximately 25,000 SCFM of compressed air. Alternatively or additionally, the system  100  can include a plurality of storage tanks  102  to store cooling medium for the dryer modules, for example, where a first storage tank  102  can provide cooling medium to a first subset dryer modules of the system  100 , a second storage tank  102  can provide cooling medium to a second subset dryer modules of the system  100 , and so on. In implementations, the plurality of storage tanks  102  include a single common cooling medium header  106 . Alternatively, the plurality of storage tanks  102  include different cooling medium headers  106  for the individual subsets of dryer modules. 
     The storage tank  102  stores the cooling medium following refrigeration of the cooling medium by the dryer modules. In implementations, the storage tank  102  is thermally insulated to maintain the cooling medium at a cold temperature to provide a pressure dew point in the dryer modules from about 40° F. to about 32° F. The cooling medium can include, but is not limited to, a glycol-based medium (e.g., propylene glycol, ethylene glycol, etc.), water, a synthetic refrigerant, or combinations thereof. For example, the cooling medium can include a blend of glycol with water in a volumetric ratio of about 1:2. 
     A plurality of circulation pumps draws cooling medium from the storage tank  102  and supplies the cooling medium to the cooling medium header  106 . While  FIG.  1    shows two circulation pumps coupled between the storage tank  102  and the cooling medium header  106  (e.g., circulation pump  104  and circulation pump  204 ), the system  100  is not limited to such configurations. For instance, the system  100  can include more than two circulation pumps fluidically coupled between the storage tank  102  and the cooling medium header  106 , including, but not limited to, three circulation pumps, four circulation pumps, five circulation pumps, six circulation pumps, seven circulation pumps, eight circulation pumps, more than eight circulation pumps, or the like. In implementations, the system  100  includes one or more pumps for each dryer module fluidically coupled with the storage tank  102 . Multiple circulation pumps can provide redundancy of flow of cooling medium to the cooling medium header  106 , which can ensure continuous flow of cooling medium in events where one or more circulation pumps are offline or otherwise not pumping fluid (e.g., during a maintenance activity, loss of power, failure of one or more components, etc.). 
     In implementations, each circulation pump is fluidically coupled to each of the storage tank  102  and the cooling medium header  106  via individual fluid lines to supply the cooling medium to the cooling medium header  106  through each of the individual fluid lines during operation of the respective circulation pumps. For example, the circulation pump  104  is fluidically coupled with the storage tank  102  via fluid line  110  and with the cooling medium header  106  via fluid line  112 , and the circulation pump  204  is fluidically coupled with the storage tank  102  via fluid line  210  and with the cooling medium header  106  via fluid line  212 . In implementations, each of the circulation pumps is operated on a continuous basis to continuously draw cooling medium from the storage tank  102  and direct the cooling medium into the cooling medium header  106 . The system can include valves to isolate the circulation pumps during service, to control fluid direction of cooling medium, or the like. For example, the system can include valve  114  between the circulation pump  104  and the storage tank  102 , valve  116  between the circulation pump  104  and the cooling medium header  106 , valve  214  between the circulation pump  204  and the storage tank  102 , valve  216  between the circulation pump  204  and the cooling medium header  106 , or combinations thereof. 
     As shown in  FIG.  1   , the system  100  can include a single cooling medium header (e.g., cooling medium header  106 ) during circulation of the cooling medium throughout the system  100 . For example, in implementations, the cooling medium made available to the dryer modules and received from the dryer modules is combined in two regions of the system  100 . First, the cooling medium is stored and mixed in the storage tank  102 . Second, the cooling medium is stored and mixed in the cooling medium header  106  to be made available to each of the dryer module  108  and the dryer module  208 . Other regions of the system  100  separate the cooling medium within confined flow paths (e.g., fluid lines  110  and  112 , fluid lines  210  and  212 , within the dryer module  108 , within the dryer module  208 , transferred from the dryer module  108  to the storage tank  102 , transferred from the dryer module  208  to the storage tank  102 ). The cooling medium header  106  receives cooling medium from each of the circulation pump  104  and the circulation pump  204 , where the cooling medium is permitted to span the length of the cooling medium header  106  to be available to each of the dryer module  108  and the dryer module  208  at the same inlet temperature. The system  100  permits mixture of the cooling medium in the storage tank  102  following receipt from the dryer modules  108  and  208  to provide an initial mixing of streams of cooling medium that may be at different temperatures dependent on the duty experienced by the dryer modules  108  and  208  (e.g., proportional to the flow of compressed air through the respective dryer modules). The cooling medium can again mix in the cooling medium header  106  prior to transfer to the dryer module  108  or the dryer module  208 . The cooling medium header  106  can be dimensioned based on the volumetric flow of cooling medium through the system  100 , based on the number of dryer modules serviced by the storage tank  102 , or the like. In implementations, the cooling medium header  106  includes a capped conduit having an inner diameter from about two inches to about twelve inches, however the system  100  is not limited to such dimensions and can have larger or smaller diameters for the cooling medium header  106  dependent on system throughput. 
     The dryer modules of the system  100  receive cooling medium from the cooling medium header  106  through individual fluid lines for each dryer module and output used cooling medium to the storage tank  102  through individual fluid lines for each dryer module. For example, dryer module  108  receives cooling medium from the cooling medium header  106  via fluid line  118  and transfers cooling medium (e.g., cooling medium having been heated by heat exchange with compressed air within the dryer module  108 ) to the storage tank  102  via fluid line  120 , whereas dryer module  208  receives cooling medium from the cooling medium header  106  via fluid line  218  and transfers cooling medium (e.g., cooling medium having been heated by heat exchange with compressed air within the dryer module  208 ) to the storage tank  102  via fluid line  220 . 
     In implementations, the dryer modules first direct the cooling medium received from the cooling medium header  106  into one or more heat exchangers to transfer heat from a stream of compressed air to the cooling medium to cool the compressed air, condense moisture held by the compressed air, and warm the cooling medium. For example, the dryer module  108  directs cooling medium from fluid line  118  into a heat exchanger  122  having an input stream  124  of compressed air that passes by a separated flow of cooling medium to condense moisture held in the compressed air and dry the compressed air for output at  126 . Similarly, the dryer module  208  directs cooling medium from fluid line  218  into a heat exchanger  222  having an input stream  224  of compressed air that passes by a separated flow of cooling medium to condense moisture held in the compressed air and dry the compressed air for output at  226 . The condensation separated from the compressed air is then removed from the dryer module, such as through an air/moisture separator, water trap, or other separation system. 
     Warmed cooling medium (or chilled cooling medium if no flow of compressed air is circulated within the dryer module) is transferred from the heat exchanger to a chiller that cools cooling medium in preparation for transfer back to the storage tank  102 . For example, the dryer module  108  directs cooling medium from the heat exchanger  122  to a chiller  128  via fluid line  130 , and the dryer module  208  directs cooling medium from the heat exchanger  222  to a chiller  228  via fluid line  230 . The chillers  128  and  228  can include compressors, condensers, thermal expansions valves, or the like, or combinations thereof, to chill the cooling medium for output to the storage tank  102  via fluid lines  120  and  220 , respectively. 
     In implementations, the dryer modules include temperature sensors (e.g., thermistors, thermocouple, etc.) to determine a temperature of cooling medium to control operation of the chillers. For example, the dryer module  108 ,  208  can include a temperature sensor in thermal communication with the cooling medium to determine a temperature of cooling medium leaving the heat exchanger  122 ,  222 , where a controller (e.g., module controller  132 ,  232 ) of the dryer module  108 ,  208  directs operation of the chiller  128 ,  228  to cool the cooling medium if the temperature meets a threshold temperature (e.g., a temperature set-point) for the module  108 ,  208 . It is to be understood that terminology “meeting a threshold temperature” is meant to include meeting or exceeding the temperature set-point. In a specific implementation, the module controller  132 ,  232  monitors the temperature of the cooling medium that is being circulated to the heat exchanger  122 ,  222  and will then activate operation of the chiller  128 ,  228  as the temperature rises above the desired temperature set-point for each module  108 ,  208 . Once the temperature of the cooling medium returns to the temperature set-point, the module controller  132 ,  232  deactivates operation of the chiller  128 ,  228 . 
     In some implementations, each dryer module  108 ,  208  will have a unique temperature set-point selected to match the required cooling load of the system  100 , and the dryer modules  108 ,  208  will operate sequentially based on a hierarchy of temperature set-points. For example, operation of dryer module  108  is directed based on a first temperature set-point (e.g., a base temperature set-point), and operation of dryer module  208  is directed based on a second temperature set-point that is offset from the base temperature set-point. Dryer module  108  will be activated first when the temperature of the cooling medium reaches (or exceeds) the base temperature set-point, and dryer module  208  will be subsequently activated when the temperature of the cooling medium meets (or exceeds) the second temperature set-point. In such implementations, the dryer module with the lowest temperature set-point (e.g., the lead module) will have the highest operating frequency, while the dryer module with the highest temperature set-point will have the lowest operating frequency. 
     In some implementations, the offset temperature set-point(s) are determined based on a temperature differential between each module. For example, there may be an operating temperature differential of 0.5° F., 1.0° F., 1.5° F., 2.0° F., 2.5° F., 3.0° F., 3.5° F., 4.0° F., 4.5° F., 5.0° F., or the like, between each dryer module. In a specific embodiment, the first dryer module  108  has a base temperature set-point, and the second dryer module  208  has a temperature set-point of the base temperature set-point plus the operating temperature differential. Depending on the number of dryer modules and the load requirements of the system  100 , the operating temperature differential may be a fixed temperature differential, an incremental temperature differential, or an exponential temperature differential. As the load of the system  100  increases, dryer modules are sequentially activated based on the next-lowest temperature set-point to meet the total compressed air demand. It is to be understood that while the dyer modules are generally activated sequentially as the load of the system  100  increases, the total compressed air demand may necessitate that two or more dryer modules be activated simultaneously. Such simultaneous activation can be achieved by assigning the same temperature set-point to the dryer modules. 
     Alternatively or additionally, the storage tank  102  or another portion of the system  100  can include one or more temperature sensors to control operation of the chillers  128 ,  228 . 
     In implementations, the system  100  includes a controller  134  that is operable to regulate the run-time of each of the dryer modules  108 ,  208 . For example, the system can include a selected run-time threshold (e.g., operating hour set-point) for the dryer modules  108 ,  208 . In implementations, the run-time threshold can be selected by an operator of the system  100  or preconfigured by a manufacturer. In a specific implementation, the run-time threshold is in the range of 500 hours to 1,000 hours. The controller  134  is operable to monitor a plurality of run-times (e.g., run-hours), each associated with one of the dryer modules  108 ,  208 , and determine when the run-time threshold is met. For example, the controller  134  can compare the run-time of each dryer module  108 ,  208  to the run-time threshold and determine if the run-time threshold has been met or exceeded. When the controller  134  determines that the dyer module  108 ,  208  run-time meets the run-time threshold, the controller  134  directs deactivation of the module  108 ,  208 , for example by deactivating the respective chiller  128 ,  228 . It is to be understood that the terminology “determining when the run-time threshold is met” and “meeting the run-time threshold” are meant to include meeting or exceeding the run-time threshold. 
     In a specific implementation, the system  100  utilizes the techniques described herein to direct operation of the dryer modules  108 ,  208  such that the run-time for the modules  108 ,  208  is substantially equivalent. Operating the dryer modules  108 ,  208  with an equivalent number of run-hours can facilitate uniform mechanical and electrical wear on the modules  108 ,  208 , enhancing the reliability and operating life of each module  108 ,  208  and its components, and reducing the incidence of premature module failures. 
     In implementations, the controller  134  includes a sequencer operable to regulate the run-time of the dryer modules  108 ,  208  by modifying the temperature set-point of each module  108 ,  208 . For example, when the run-time of a dryer module  108 ,  208  meets the run-time threshold, the controller  134  directs operation of the dyer modules  108 ,  208  by increasing the temperature set-point of the module  108 ,  208  such that the respective chiller  128 ,  228  is deactivated. In implementations, when the run-time for a dryer module meets the run-time threshold the sequencer is operable to modify the temperature set-points for each of the dryer modules based on the run-time for each module. For example, when the lead module reaches the run-time threshold, the sequencer is operable to reset the temperature set-point of the lead module to the bottom of the temperature hierarchy (e.g., by increasing the temperature set-point to the highest temperature set-point of the group of modules). The sequencer is further operable to reset the temperature set-points of the remaining dryer modules, moving each temperature set-point upwards in the temperature hierarchy (e.g., by decreasing the temperature set-point for the respective module) such that the module with next-highest run-time becomes the new lead module. Once a lead module(s) reaches the run-time threshold and is deactivated, the run-time for that module is reset (e.g., to 0 hours). In such implementations, the controller  134  directs operation of the dryer modules such that the module with the highest run-time operates at the highest frequency until the run-time threshold is met. 
     In some implementations, the sequencer can regulate operation of the dryer modules  108 ,  208  based on other system load considerations. For example, the controller  134  can direct operation of the dryer modules  108 ,  208  by modifying the temperature set-point based on time-of-day or other load monitoring parameters to reduce run-time during low load periods. 
     While  FIG.  1    shows controller  134  as an independent control separate from the individual module controllers  132 ,  232 , the system  100  is not limited to such configurations. Alternatively, part or all of the functionality of controller  134  may be integrated into one or more of the module controllers  132 ,  232 . Likewise, part or all of the functionality of the module controllers  132 ,  232  may be integrated into one or more independent controllers. The controller  134  and/or the module controllers  132 ,  232  can control the components and functions of systems  100  described herein using software, firmware, hardware (e.g., fixed logic circuitry), manual processing, or a combination thereof. The terms “controller,” “functionality,” “service,” and “logic” as used herein generally represent software, firmware, hardware, or a combination of software, firmware, or hardware in conjunction with controlling the systems  100 . In the case of a software implementation, the module, functionality, or logic represents program code that performs specified tasks when executed on a processor (e.g., central processing unit (CPU) or CPUs). The program code can be stored in one or more computer-readable memory devices (e.g., internal memory and/or one or more tangible media), and so on. The structures, functions, approaches, and techniques described herein can be implemented on a variety of commercial computing platforms having a variety of processors. It is to be understood the that the controller  134  and/or the module controllers  132 ,  232  can include any number of microcontrollers, processors, and/or resident or external memory. 
     In configurations where controller  134  functions as an independent controller in communication with module controllers  132 ,  232 , controller  134  can be operable to monitor additional operating parameters associated with the individual controllers  132 ,  232 . For example, the controller  134  can monitor a fault condition associated with module controller  132 ,  232  to identify a defective dryer module. Similarly, the controller  134  can monitor a maintenance condition (e.g., a filter wear condition, drain condition, etc.) associated with module controller  132 ,  232  to identify a dryer module requiring maintenance. Based on identification of a fault condition and/or a maintenance, the controller  134  may be operable to deactivate the corresponding dryer module and/or its components (e.g., chillers), for example, by directing operation of a switch (e.g., electrical switch, pneumatic switch, etc.), valve, or the like of the dyer module. In a specific implementation, the controller  134  directs operation of an electrical switch output or a low voltage communications interface to deactivate the dryer module. Alternatively or additionally, the controller  134  can direct operation of an electrical or pneumatic switch to energize a shut-off air isolation valve, thereby preventing compressed airflow through the dryer module. 
     In implementations, the controller  134  can be communicatively coupled with the dryer modules  108 ,  208  over a communication network. It is further contemplated that dryer module  108  is can be communicatively coupled with dryer module  208  over the communications network. The communication network may comprise a variety of different types of networks and connections that are contemplated, including, but not limited to: wired and/or wireless connections; the Internet; an intranet; a satellite network; a cellular network; a mobile data network; and so forth. Wired communications are contemplated through universal serial bus (USB), RS-485, Ethernet, BACnet, Profibus, serial connections, and so forth. Wireless communications are also contemplated through wireless networks including, but are not limited to: networks configured for communications according to: one or more standard of the Institute of Electrical and Electronics Engineers (IEEE), such as 802.11 or 802.16 (Wi-Max) standards; Wi-Fi standards promulgated by the Wi-Fi Alliance; Bluetooth standards promulgated by the Bluetooth Special Interest Group; and so on. In a specific implementation, the controller  134  can monitor each dryer module  108 ,  208  via a wired communications network that is wired in sequence between each of the modules  108 ,  208 . 
     In implementations, the controller  134  and/or the module controllers  132 ,  232  can include a user interface for receiving operator input and displaying information to the operator. For example, the user interface may include a display such as an LCD (Liquid Crystal Diode) display, a TFT (Thin Film Transistor) LCD display, an LEP (Light Emitting Polymer) or PLED (Polymer Light Emitting Diode) display, and so forth, configured to display text and/or graphical information such as a graphical user interface. The user interface can also include one or more input/output (I/O) devices (e.g., a keypad, buttons, a wireless input device, a thumbwheel input device, a touchscreen, and so on). The I/O devices may include one or more audio I/O devices, such as a microphone, speakers, and so on. 
     It is to be understood that while  FIG.  1    shows multiple dryer modules  108 ,  208  with a shared storage tank  102  of cooling medium, the system  100  is not limited to such configurations. Alternatively or additionally, the system  100  can include multiple independent dryer modules that do not share a common store of cooling medium. 
       FIGS.  2 A through  2 C  illustrate example algorithms that are executable by the controller  134  (e.g., via the sequencer) for determining the temperature set-points for the plurality of dryer modules. The sequencer is operable to execute one or more algorithms or commands to determine a temperature set-point for each dryer module based on the selected base temperature set-point, the selected temperature differential, and the selected number of dryer modules (e.g., as described with reference to  FIG.  2 A ). Based on the number of modules selected, the sequencer determines the temperature set-point for each module by applying an offset from the base temperature set-point that is based on the temperature differential. For example, when two dryer modules are selected, the first module is directed to become operational at the base temperature set-point (SP), and the second dryer module is directed to become operational at an offset temperature set-point based on the selected temperature differential (SP+3*Diff). The sequencer is further operable to execute one or more algorithms or commands to determine a temperature vector ordering the modules in an operating hierarchy based on the temperature set-points (e.g., as described with reference to  FIG.  2 B ). For example, the dryer modules may be arranged in a hierarchy of ascending temperatures such that the lead dryer module (e.g., module  1 ) is activated at the base temperature set-point, and the other dryer modules are activated in order of ascending temperature set-point. The sequencer is further operable to monitor the run-time (e.g., run hours) of each dryer module and execute one or more algorithms or commands to modify the temperature set-point of each module such that the modules are rotated through the operating hierarchy based on run-time (e.g., as described with reference to  FIG.  2 C ). For example, when module  1  reaches or exceeds the run-time threshold, the sequencer modifies the temperature set-points of the dryer modules such that module is moved to the bottom of the operating hierarchy. In such implementations, the temperature set-point of the lead module (e.g., module  1 ) is reset to the highest temperature set-point of the temperature vector. The temperature set-points of the other dryer modules are reset such that these modules are moved up the operating hierarchy and the module with the next-highest run-time (e.g., module  2 ) becomes the lead module with the lowest temperature set-point (e.g., the base temperature set-point). As described above, the total compressed air demand of the system  100  may necessitate that two or more dryer modules be activated simultaneously. As shown in  FIGS.  2 A through  2 C , the sequencer may assign the same temperature set-point to two or more dryer modules to achieve such simultaneous activation needs. 
       FIGS.  3 A and  3 B  illustrate an example process  300  for regulating the run-time of a plurality dryer modules utilizing a compressed air dryer system, such as the compressed air dryer system  100  described above. As shown in  FIG.  3 A , a selection of a desired number of dryer modules is received (Block  302 ). In implementations, the desired number of dryer modules can be based on the required cooling-load of the system. For example, under low-load conditions (e.g., evenings, weekends), it may be desirable to utilize fewer dryer modules. The selection of the number of modules can be received as operator input (e.g., via the user interface), and/or as a preconfigured manufacturer setting. 
     A selection of a run-time threshold is received (Block  304 ). As described above with reference to  FIG.  1   , the run-time threshold is a desired run-time limit (e.g., operating hour set-point) for each of the dryer modules  108 ,  208 . In a specific implementation, the run-time threshold is in the range of 500 hours to 1,000 hours. In some implementations, the run-time threshold is selected based operating requirements of the system  100  including, but not limited to system load requirements, compressed air demand, mechanical specifications of the dryer modules, and so forth. The selection of the run-time threshold can be received as operator input (e.g., via the user interface), and/or as a preconfigured manufacturer setting. 
     A selection of a base temperature set-point and a temperature differential is received (Block  306 ). As described with reference to  FIG.  1   , each dryer module  108 ,  208  will have a unique temperature set-point selected to match the required cooling load of the system  100 , and the dryer modules  108 ,  208  will operate sequentially based on a hierarchy of temperature set-points. For example, operation of dryer module  108  is directed based on a first temperature set-point (e.g., a base temperature set-point). Operation of dryer module  208  is directed based on a second temperature set-point that is offset from the base temperature set-point based on a selected temperature differential. For example, dryer module  208  can have a temperature set-point of the base temperature set-point plus the operating temperature differential. As described above, depending on the number of dryer modules and the load requirements of the system  100 , the operating temperature differential may be a fixed temperature differential, an incremental temperature differential, or an exponential temperature differential. The selection of the base temperature set-point and the temperature differential can be received as operator input (e.g., via the user interface), and/or as preconfigured manufacturer settings. 
     A temperature set-point for each of a plurality of dryer modules is determined based on the base temperature set-point, the temperature differential, and the selected number of dryer modules (Block  308 ). As described above, based on the number of modules selected, a sequencer determines the temperature set-point for each module by applying an offset from the base temperature set-point that is based on the temperature differential (e.g., as described with reference to  FIG.  2 A ). A temperature order vector is determined based on the temperature set-points and the selected number of dryer modules (Block  310 ). As described above, the dryer modules can be arranged in a hierarchy of ascending temperatures such that the lead dryer module (e.g., module  1 ) is activated at the base temperature set-point, and the other dryer modules are activated in order of ascending temperature set-point (e.g., as described with reference to  FIG.  2 B ). 
     In some implementations, the temperature set-point for each dryer module is transmitted to the respective dryer module (Block  312 ). As described above with reference to  FIG.  1   , the sequencer can be included in an independent controller  134  that is operable to transmit the temperature set-point for each dryer module  108 ,  208  to the module controller  132 ,  232  corresponding to the module  108 ,  208  via the communication network (e.g., a wired and/or wireless network). In other embodiments, the sequencer may be integrated into one or more of the module controllers  132 ,  232 . 
     The run-time for each dryer module is monitored (Block  314 ). As described above with reference to  FIG.  1   , the controller  134  is operable to monitor a plurality of run-times (e.g., run-hours), each associated with one of the dryer modules  108 ,  208 . The system can determine when the run-time for a dryer module meets the run-time threshold (Block  316 ). As described above with reference to  FIG.  1   , the controller  134  is operable to compare the run-time of each dryer module  108 ,  208  to the run-time threshold and determine if the run-time threshold has been met or exceeded. 
     When a dryer module meets the run-time threshold, the temperature set-points for the dryer modules are modified based on the temperature order vector (Block  318 ). As described above, when a dryer module (e.g., the lead module) reaches or exceeds the run-time threshold, the sequencer is operable to modify the temperature set-points of the dryer modules such that lead module is moved to the bottom of the operating hierarchy (e.g., as described with reference to  FIG.  2 C ). In such implementations, the temperature set-point of the lead module (e.g., module  1 ) is reset to the highest temperature set-point of the temperature vector. The temperature set-points of the other dryer modules are reset such that these modules are moved up the operating hierarchy and the module with the next-highest run-time (e.g., module  2 ) becomes the lead module with the lowest temperature set-point (e.g., the base temperature set-point). In some implementations, the new temperature set-point for each dryer module is transmitted to the respective dryer module (Block  320 ). 
     Although the subject matter has been described in language specific to structural features and/or process operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.