Lubrication and flushing of a fluid seal used with reactive materials

A pump system includes a housing, a lubricant system, and control circuitry. The housing includes a pump chamber defined by the housing and a throat seal. The lubricant system includes a lubricant pump, a lubricant gallery defined within the housing of the main pump, and a lubricant circuit fluidly connecting the lubricant pump and the lubricant gallery. The throat seal is disposed adjacent to and between the pump chamber and the lubricant gallery. The control circuitry is configured to cause the lubricant pump to pump a purge volume of lubricant through the lubricant system, cause the lubricant pump to stop pumping for a first time period after the lubricant pump has pumped the purge volume, and cause the lubricant pump to pump the purge volume of lubricant through the lubricant system after the first time period.

BACKGROUND

The present disclosure relates to pump lubrication systems and, more particularly, to control systems for pump lubricant systems.

Positive displacement pumps, such as reciprocating pumps, are generally provided with seals to reduce leakage from the pump chamber toward the piston rod, protecting the piston rod and other pump components from degradation or corrosion. To improve seal longevity, the pump can include a lubricant gallery to store lubricant for lubricating the seal. The lubricant held in the lubricant gallery can be used to lubricate the seal during operation of the pump, reducing seal wear and thereby improving seal lifespan. Lubricant held in the lubricant gallery can become contaminated with fluid from the pump chamber. Contaminated lubricant can be circulated out of out of the lubricant gallery and replaced with fresh lubricant, extending the lifespan of the seal.

SUMMARY

According to one aspect of the present disclosure, a pump system includes a housing, a lubricant system, and control circuitry. The housing includes a pump chamber defined by the housing and a throat seal. The lubricant system includes a lubricant pump, a lubricant gallery defined within the housing of the main pump, and a lubricant circuit fluidly connecting the lubricant pump and the lubricant gallery. The throat seal is disposed adjacent to and between the pump chamber and the lubricant gallery. The control circuitry is configured to cause the lubricant pump to pump a purge volume of lubricant through the lubricant system, cause the lubricant pump to stop pumping for a first time period after the lubricant pump has pumped the purge volume, and cause the lubricant pump to pump the purge volume of lubricant through the lubricant system after the first time period.

According to another aspect of the present disclosure, a pump control system includes a main pump configured to pump a fluid and control circuitry. The main pump includes a housing, a pump chamber defined by the housing, and a throat seal. The control circuitry is configured to cause the main pump to pump a fluid through the pump chamber, cause a lubricant pump to pump a purge volume of lubricant through a lubricant system, cause the lubricant pump to stop pumping for a first time period after the lubricant pump has pumped the purge volume, and cause the lubricant pump to pump the purge volume of lubricant through the lubricant system after the first time period. The lubricant system includes the lubricant pump, a lubricant gallery defined by the housing, and a lubricant circuit fluidly connecting the lubricant pump and the lubricant gallery. The throat seal is disposed adjacent to and between the pump chamber and the lubricant gallery.

According to another aspect of the present disclosure, a method of controlling a pump system includes operating a lubricant pump to pump a purge volume of lubricant through a lubricant system, stopping operation of the lubricant pump for a first time period after the lubricant pump has pumped the purge volume, and operating the lubricant pump to pump a second purge volume of lubricant through the lubricant system after the first time period. The lubricant system includes the lubricant pump, a lubricant gallery defined by a housing of a main pump, and a lubricant circuit fluidly connecting the lubricant pump and the lubricant gallery. The main pump includes a pump chamber defined by the housing and a throat seal disposed adjacent to and between the pump chamber and the lubricant gallery.

DETAILED DESCRIPTION

The present disclosure includes lubricant systems for throat seals of fluid pumps. The present disclosure further includes control systems for controlling the operation of the lubricant systems and fluid pumps disclosed herein. The lubricant systems and control systems disclosed herein reduce the undesirable agitation of lubricant while also ensuring adequate lubricant flow to the throat seal of a fluid pump.

FIG.1is a cross-sectional view of lubricant system10, which is a prior art system for pumping lubricant. Lubricant system10is a closed lubrication system and includes main pump12, lubricant lines14A and14B, and lubricant reservoir16. Pump12is a reciprocating pump and includes pump housing18, piston20, rod22, throat seal24, and attachment point26. Pump housing18defines pump chamber28, lubricant gallery30, and inlet32, outlet34. Lubricant gallery30includes first end36and second end38. Lubricant reservoir16includes check valves40A and40B.

Main pump12is configured to pump a process fluid through pump chamber28using reciprocation of piston20and rod22. Rod22and piston20are disposed within pump housing18, connected at attachment point26, and centered on axis P-P. In operation, an external motor attached to rod22can cause piston20and rod22to reciprocate along pump axis P-P, creating fluid flow through pump chamber28of main pump12. The process fluid pumped through pump chamber28of main pump12is generally a material other than a lubricant. The difference in diameter between piston20and rod22causes piston20to displace lubricant from lubricant gallery30as piston20and rod22reciprocate along axis P-P, generating pumping power. In this manner, the reciprocation of piston20and rod22functions both to create pump process fluid through pump chamber28and to pump lubricant through lubricant system10.

Lubricant gallery30is a substantially cylindrical chamber defined by an interior surface of pump housing18and is centered on axis P-P and extends from first end36to second end38. Lubricant gallery surrounds a portion of rod22, a portion of piston20, and attachment point26. Lubricant gallery stores lubricant that is used to lubricate throat seal24, preventing damage to throat seal24from the reciprocation of piston20. Lubricant gallery includes first end36and second end38, which define the axial ends of lubricant gallery30. First end36is formed by pump housing18and second end38is formed by throat seal24. Piston20extends through and throat seal24is disposed adjacent to second end38. Rod22extends through and throat seal24is disposed opposite first end36.

Throat seal24is an annular seal that is centered on axis P-P and surrounds a portion of piston20and reduces flow of the process fluid pumped by piston20from pump chamber28into lubricant gallery30. Lubricant gallery30is an annular chamber centered on axis P-P that holds a lubricant for lubricating throat seal24. Throat seal24mitigates but does not prevent flow of process fluid from pump chamber28into lubricant gallery30. Consequently, process fluid from pump chamber28can migrate past throat seal24and contaminate lubricant held in lubricant gallery30during operation of pump12. Contamination of lubricant in lubricant gallery30can cause degradation of throat seal24, rod22, or other components of pump12, adversely affecting the performance of pump12.

Lubricant reservoir16includes check valves40A and40B. Lubricant reservoir is generally sized such that the volume of lubricant stored in lubricant reservoir16is significantly larger than the volume of lubricant held in lubricant gallery30. This allows contaminated lubricant in lubricant gallery to be diluted in the lubricant held in lubricant reservoir16, delaying the onset of negative effects of lubricant contamination, as will be explained in more detail subsequently.

In operation, as piston20moves out of lubricant gallery30(i.e., as attachment point26moves toward second end38of lubricant gallery30), lubricant is drawn into lubricant gallery30from lubricant reservoir16through lubricant line14A. As piston20reciprocates and moves into lubricant gallery30(i.e., as attachment point26moves toward first end36of lubricant gallery30), lubricant flows from lubricant gallery30to lubricant reservoir16through lubricant line14B.

To enforce directional flow through lubricant system10, check valves40A and40B are included at lubricant reservoir16. Check valve40A is a one-way valve that is configured to allow fluid to flow from lubricant reservoir16through lubricant line14A to inlet32and prevent backward flow from inlet32of lubricant gallery30through lubricant line14A to lubricant reservoir16. Similarly, check valve40B is a one-way valve that is configured to allow fluid to flow from outlet34through lubricant line14B to lubricant reservoir16and prevent backward flow from lubricant reservoir16through lubricant line14B to outlet34. The operation of check valves40A and40B causes lubricant to flow through lubricant system10according to the direction of arrows42.

Circulation of lubrication through lubrication system10reduces the effects of contamination of lubricant gallery30by washing contaminated lubricant away from throat seal24and diluting the contaminated lubricant in lubricant reservoir16. The volume of lubricant stored in lubricant reservoir16is generally significantly larger than the volume of lubricant held in lubricant gallery30, such that circulation of lubricant through lubricant system10dilutes contaminated lubricant from lubricant gallery30in the larger volume of lubricant held in lubricant reservoir16, thereby delaying onset of adverse effects caused by lubricant contamination.

FIG.2is a cross-sectional view of lubricant system110, which is similar to lubricant system10and includes main pump112, lubricant pump113, lubricant lines114A-C, lubricant reservoir16, and controller117. Main pump112is substantially the same as pump12and includes pump housing118, throat seal124, and rod22. Pump housing118defines pump chamber128(shown inFIG.3), lubricant gallery130, inlet132, and outlet134. To improve clarity ofFIG.2, piston20and attachment point26are not shown inFIG.2.

Unlike lubricant system10, lubricant system110does not use the differential area of piston20and rod22to pump lubricant through lubricant system110. Rather, lubricant system110uses lubricant pump113to pump lubricant, decoupling the flow of lubricant from the pumping action of main pump112.

Main pump112is configured to pump a process fluid through pump chamber128using reciprocation of piston20and rod22. In operation, an external motor attached to rod22can cause piston20and rod22to reciprocate along pump axis P-P, creating fluid flow through pump chamber28of main pump112. Main pump112can be used in combination with another main pump to pump one material component of plural component spray material, as discussed in more detail with respect toFIG.3.

Lubricant gallery130is substantially similar to lubricant gallery30, as described previously with respect toFIG.1. Lubricant gallery130stores lubricant for lubricating throat seal124, is a substantially cylindrical chamber defined by an interior surface of pump housing118, and is centered on axis P′-P′. Unlike lubricant gallery30, lubricant gallery130only surrounds a portion of rod22. Further, Throat seal124is substantially similar to throat seal24, as described previously with respect toFIG.1, but surrounds a portion of rod22rather than a portion of piston20. Throat seal124is an annular seal that is centered on axis P-P and functions to reduce flow of the process fluid pumped by piston20from pump chamber128into lubricant gallery130.

As piston20is not required to reciprocate through lubricant gallery30to create pumping action through lubricant system110, positioning throat seal124to surround a portion of rod22rather than a portion of piston20functions to prevent additional, unwanted pumping action that could be created by the reciprocation of piston20through lubricant gallery30. Flow of lubricant through lubricant system110is consequently controlled entirely by operation of lubricant pump113, as will be explained in more detail subsequently. Disposing throat seal124about a portion of rod22rather than a portion of piston20also allows lubricant gallery130to have a reduced volume as compared to lubricant gallery30, as the flow rate of lubricant through lubricant system110is driven by a standalone lubricant pump113rather than displacement of lubricant in lubricant gallery130by piston20.

Lubricant pump113creates pumping action and causes lubricant to flow from lubricant reservoir16to lubricant gallery130and from lubricant gallery130to lubricant reservoir16. In the depicted example, lubricant pump113is a peristaltic pump and suitable for being driven by a fixed-speed electric motor. However, lubricant pump113can be any suitable pump for pumping fluid through lubricant system110. Similarly, lubricant pump113can also be driven by a variable-speed motor. Advantageously, inclusion of separate lubricant pump113allows for control of the flow of lubricant independent of the operation of main pump12.

Operation of lubricant pump113is controlled by controller117, which can be used to start, stop, or adjust the operation of lubricant pump113and the flow of lubricant as required for a given application. Controller117can also be used to detect fault conditions and determine a maintenance cycle based on the usage of lubricant pump113. Controller117can be connected to one or more temperature sensors (not shown) disposed at one or more locations in lubricant system110and can be configured to monitor the temperature of lubricant as it is pumped by lubricant113. Similarly, controller117can be connected to one or more pressure sensors (not shown) disposed at one or more locations in lubricant system110and can be configured to monitor the pressure of lubricant as it is pumped by lubricant113. Controller117can be further configured to detect leaks or blockages within lubricant system110based on the measured pressure and to alert an operator when lubrication system110has a leak or when leaked process fluid from pump chamber128has created a blockage. For example, controller117can be configured to compare the measured pressure to a baseline or reference pressure to determine if there is a leak or blockage within lubricant system110.

Operation of main pump112causes flow of process fluid through pump chamber128and does not affect flow of lubricant through lubricant gallery130. Operation of lubricant pump113causes lubricant to flow from lubricant reservoir through lubricant line114A to lubricant pump113, from lubricant pump113through lubricant line114B to inlet132of lubricant gallery130, and from outlet134of lubricant gallery though lubricant line114C to lubricant reservoir16. To this extent, operation of lubricant pump113allows for dilution of contaminated lubricant from lubricant gallery130to lubricant reservoir.

In lubricant system110, operation of lubricant pump113enforces directional flow. To this extent, lubricant system110does not require check valves40A and40B. Check valves40A and40B can fail during operation of lubricant system10, allowing backward flow through lubricant system10. To this extent, use of lubricant pump113improves the reliability of lubricant system110over conventional systems, such as lubricant system10, that rely on check valves to create directional flow.

Although lubricant system110has been discussed as relating to lubricant pumps for throat seals, lubricant system110can be adapted for any pump or valve seal. Similarly, lubricant system110is not limited to seals of reciprocating or positive-displacement pumps, and can be adapted to provide lubrication to seals of any pump systems.

Lubricant system110provides a number of advantages over the lubricant system10described previously with respect toFIG.1. Particularly, lubricant system110uncouples and allows for independent control of the flow of process fluid through pump chamber128and the flow of lubricant through lubricant gallery130. Independent control of lubricant pump113allows, for example, lubricant to be pumped when main pump112is inactive. Lubricant system110thereby allows for finer-tuned and more granular control of the flow of lubricant, relative to conventional systems.

FIG.3is a perspective view of proportioner system200, which is an example of a plural component dispensing system. Proportioner system200includes lubricant system110including (main pump112, lubricant pump113, lubricant lines114A-C, lubricant reservoir16, and controller117), main pump212, and proportioner housing218.

Main pump212has substantially the same components and operates in substantially the same manner as main pump112. In proportioner system200, main pumps112and212are disposed on opposite sides of proportioner housing218and are configured to pump a first component material and a second component material, respectively. Main pump112and main pump212pump the first component material and the second component material, respectively, to an applicator (not depicted) to form a spray material. Further, main pump112and main pump212increase the pressure of the first and second component materials, respectively, to a spray pressure. The first and second components are different materials that are selected to combine to form a plural component spray material having desired material properties, such as a spray foam. Generally, mixing the first and second components causes a reaction that forms a plural component spray material that can be sprayed by the applicator. The first and second components are mixed at the applicator rather than an upstream location of proportioner system200to prevent unwanted reactions that can damage components of proportioner system200.

The first component material can be a catalyst, such as isocyanate, and the second component material can be a resin material, such as a polyol resin. In examples where isocyanate and polyol resin are used as the first and second component materials, respectively, the plural component spray material is a polyurethane foam. Other components can be used as a resin material based on the needs of the application. For example, the resin material can be a urethane or silicone material for some applications. Similarly, other catalyst materials can be selected based on application needs.

Main pumps112and212receive the first component material and second component material, respectively, from feed pumps (not shown) that pump the first and second component materials from reservoirs (not shown) of each component. Main pumps112and212are mechanically linked such that the ratio of the first and second component materials is fixed. Main pump112and main pump212can be driven by separate motors or a single motor can be used to drive both main pump112and main pump212. InFIG.3, main pump112and main pump212are both depicted as reciprocating pumps, but main pumps112,212can be any suitable type of pump for dispensing a fluid component material.

In proportioner system200, controller117also controls the operation of main pump112and main pump212. Controller117can be further configured to measure and control the temperature and/or pressure of the first component material, the second component material, or the spray material.

In the depicted example, lubricant pump113and lubricant reservoir16are disposed adjacent and are attached to the exterior of proportioner housing218above main pump112. In other examples, lubricant pump113and lubricant reservoir16can be disposed elsewhere on proportioner housing218or can be disposed at other suitable locations such that lubricant pump113and/or lubricant reservoir16are not attached to proportioner housing218. Controller117is depicted inFIG.3as mounted within proportioner housing218. In other examples, controller117can be disposed at other locations, including locations outside of proportioner housing218. Other components used for the operation of proportioner system200can also be disposed within proportioner housing218. For example, one or more motors for driving the operation of main pumps112and212can be disposed within proportioner housing218.

Advantageously, proportioner system200allows for reactive component materials to be pumped separately and combined downstream of main pumps112and212to form a plural component spray material. To this extent, proportioner system200allows control of the ratios, temperatures, and pressures of the fluid components pumped by main pumps112and212. As proportioner system200includes lubricant system110, proportioner system200also has the advantages outlined previously with respect to the discussion ofFIG.2.

FIG.4is a schematic depiction of control system400, which includes controller117, lubricant pump113, lubricant reservoir16, lubricant lines114A-C, and main pump112. Controller117includes control circuitry420, memory424, and user interface428.

Control circuitry420is configured to control the operation of lubricant pump113and main pump112by executing instructions stored on memory424. Control circuitry420can include one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other equivalent discrete or integrated logic circuitry. Control circuitry420can be entirely or partially mounted on one or more boards. Control circuitry420can be of any type suitable for operating in accordance with the techniques described herein. In some examples, control circuitry420can be implemented as a plurality of discrete circuitry subassemblies.

Memory424is configured to store instructions and/or programs that are executable by control circuitry420for controlling the operation of main pump112and lubricant pump113, including the selective operation of main pump112or lubricant pump113. Memory424, in some examples, can be described as a computer-readable storage medium. In some examples, a computer-readable storage medium can include a non-transitory medium. The term “nontransitory” can indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium can store data that can, over time, change (e.g., in RAM or cache). In some examples, memory424can include temporary memory, meaning that a primary purpose of the computer-readable memory is not long-term storage. Memory424, in some examples, can be described as a volatile memory, meaning that the memory does not maintain stored contents when electrical power to the controller is removed. Examples of volatile memories can include random access memories (RAM), dynamic random-access memories (DRAM), static random-access memories (SRAM), and other forms of volatile memories. In some examples, memory424can be used to store program instructions for execution by one or more processors of the controller. For instance, memory424can be used by software or applications executed by the control circuitry420to temporarily store information during program execution. In some examples, memory424includes non-volatile storage elements. Examples of such non-volatile storage elements can include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

An operator can interact with controller117through user interface428to control the operation of main pump112and/or lubricant pump113. User interface428can be an input/output device configured to provide and/or receive information from an operator. User interface428can be of any form that enables operator interaction with control circuitry420. For example, control system400can implement a graphical user interface displayed at a display device of user interface428for presenting information to and/or receiving input from an operator. User interface428can include graphical navigation and control elements, such as graphical buttons or other graphical control elements presented at the display device. User interface428, in some examples, includes physical navigation and control elements, such as physically actuated buttons or other physical navigation and control elements.

User interface428can be used to manually control the operation of main pump112and/or lubricant pump113. Controller117can also be configured to automatically cause lubricant pump113to flow lubricant through lubricant system110. Memory424can be encoded with instructions that allow controller117to automatically control the operation of main pump112and/or lubricant pump113.

In some examples, controller117is two separate controllers two that each control one of main pump112and lubricant pump113.FIG.5is a schematic depiction of control system450, which is substantially similar to and includes the same components as control system400but also includes a separate controller467for controlling the operation of lubricant pump113. Controller467is can perform substantially the same functions as controller117, and includes control circuitry470, memory474, and user interface478, which are substantially similar to control circuitry420, memory424, and user interface428described with respect toFIG.4.

In control system450, controller117only controls operation of main pump112. Similarly, controller467only controls operation of lubricant pump113. Using separate controllers117and467to control lubricant pump113and main pump12allows for lubrication system110to be installed on existing pumping systems without reconfiguring the controller operating the main pump, allowing lubrication system110to be used on a wide variety of existing pumping systems. In some of these examples, controller467lacks memory474and control circuitry470is a timer circuit lacking a microprocessor. Using a simple timing circuit to control the operation of lubricant pump decreases the cost associated with installation of lubrication system110on an existing device. In these examples, user interface478can be one or more physical switches, buttons, knobs, or dials.

Control system400has been described with reference to lubrication system110and pump112. However, it should be understood that control system400or450can also be used to control the operation of other fluid pump systems not described herein.

Advantageously, both control system400and control system450allow for independent control of main pump112and lubricant pump113, and thereby allow for independent control of main pump112and lubricant pump113. Further, control systems400,450allow for main pump112and lubricant pump113to be controlled via operator input at user interfaces428,478, via pre-programmed instructions stored on memory424,474, or via a combination of operator input and pre-programmed instructions.

As described previously with respect toFIG.3, main pump112can pump a catalyst that reacts with a resin material pumped by main pump212to form a plural component spray foam. Some catalyst materials are moisture-sensitive and can form crystals, granules, and other hard byproducts when exposed to moisture. For example, isocyanate is known to form hard and crystalline byproducts when exposed to moisture. While lubricant circulating through lubricant system110is generally an oil or another hydrocarbon, sufficient moisture can be present in the lubricant to cause moisture-sensitive materials that flow past throat seal124into lubricant gallery130to form hard byproducts.

The hard byproducts formed by moisture-sensitive materials can damage throat seal124and other components of main pump112. Operation of lubricant pump113can remove hard byproducts and moisture-sensitive materials from lubricant gallery130and dilute them in lubricant reservoir16. However, operation of lubricant pump113also causes agitation of lubricant flowing through lubricant system110, introducing air into lubricant flowing through lubricant system110. Moisture in the air can accelerate the rate at which the moisture-sensitive materials form hard, damaging byproducts.

Advantageously, lubricant pump113can be operated intermittently to remove moisture sensitive-materials from lubricant gallery130while reducing agitation of the lubricant and thereby reducing the rate at which moisture-sensitive materials suspended in lubricant form undesirable hard byproducts.FIG.6is a schematic diagram of pump operation schedule500, which can be used by control circuitry420,470to minimize formation of undesirable hard byproducts by operating lubricant pump113intermittently. Pump operation schedule500includes bars510, bars520, bars530, and time axis540.

Pump operation schedule500describes an operation schedule of main pump112, and lubricant pump113of proportioner system200. Specifically, bars510represent time when proportioner system200is powered, bars520represent operation time of main pump112, and bars530represent operation time of lubricant pump113. The length of bars510,520,530along time axis540represent the relative operation time of proportioner system200, main pump112, and lubricant pump113, respectively. As shown by bars520, main pump112has a continuous operation period. Conversely, bars530shown that lubricant pump113has several intermittent operational periods.

The length of the operational period of lubricant pump113, as represented by bars530, is the length of time required for lubricant pump113to pump a purge volume of lubricant at a given pump rate. The purge volume is equal to the volume of lubricant gallery130, inlet132, outlet134, and lubricant line114B, such that pumping the purge volume completely replaces contaminated lubricant in lubricant gallery130with fresh lubricant from lubricant reservoir16. Advantageously, operating lubricant pump113for only the time required to pump a purge volume of lubricant minimizes agitation of lubricant in lubricant gallery130while still allowing lubricant pump113to completely flush contaminated lubricant out of lubricant gallery130. However, in other examples, the operational period of lubricant pump113may be sufficiently long that lubricant pump113can pump multiple purge volumes of lubricant during the operational period. For example, the operational period of lubricant pump113can be selected such that lubricant pump113pumps 1.5, 2, or 3 purge volumes during the operational period.

Between operational periods, lubricant pump113is inactive. The length of the inactive period between operational periods is selected such that lubricant pump113operates sufficiently frequently to reduce accumulation of undesirable contaminants in lubricant gallery and sufficiently infrequently to minimize lubricant agitation and thereby prevent formation of undesirable hard byproducts. To this extent, the length of the inactive period is dependent both on the rate of flow of the first component material across throat seal124and the rate of formation of undesirable hard byproducts in lubricant gallery130, among other relevant parameters. Where the first material component is isocyanate, the length of the inactive period can be, for example, 30 minutes. The length of the inactive period can be constant or can vary based on operational needs.

In the example of pump operation schedule500shown inFIG.6, lubricant pump113is active during one operational period before main pump112is operated. This initial operational period functions to as an initial purge of lubricant gallery130and removes contaminating particles (e.g., dust, the first component material, etc.) that has accumulated in lubricant gallery130while proportioner system200was inactive. As main pump112is operated, lubricant pump113is operated intermittently for operational periods offset by inactive periods. After main pump112has stopped operating, lubricant pump113is active during another operational period before proportioner system200is powered off. This final operational period functions as a final purge of lubricant gallery130before proportioner system200is set to an inactive state.

Operation schedule500can be preprogrammed and stored on memory424,474for use by control circuitry420,470. Alternatively, control circuitry420,470can be configured to automatically create operation schedule500during the operation of proportioner system200based on the volume of the lubricant gallery, the pump rate, the desired inactive period length, and operator or application preferences regarding initial and final lubricant purges.

An operator can interact with user interface428,478to program or adjust one or more elements of operation schedule500. Control circuitry420,470can be configured to automatically adjust other elements of operation schedule500based on the operator input. For example, control circuitry420,470can be configured to automatically cause lubricant pump113to perform an initial purge of lubricant gallery130after proportioner system200is powered on. Control circuitry420,470can be configured to idle main pump112and lubricant pump113until operator input is received at user interface428indicating that main pump112should be operated. Control circuitry420,470can then operate main pump112and lubricant pump113according to operation schedule500until input is received at user interface428indicating that main pump112should be idled. Control circuitry420,470can then automatically cause lubricant pump113to perform a final purge of lubricant gallery130before proportioner system200is powered off.

Operation schedule500provides significant advantages. Specifically, operation schedule500can be used by control circuitry420,470to intermittently operate lubricant pump113. As described previously, intermittent operation of lubricant pump113allows for optimal reduction both of lubricant agitation and contaminant accumulation in lubricant gallery130. Reducing lubricant agitation is particularly advantageous where main pump112is used to pump a moisture-sensitive material, such as isocyanate. Operation schedule500can further be used by control circuitry420,470to cause lubricant pump113to perform an initial lubricant purge before main pump112is operated and a final lubricant purge after main pump112is idled.

FIG.7is a flow chart depicting method600, which can be used to operate a lubricant pump113intermittently. Method600has sequential steps602-612, including pumping an initial purge volume of lubricant with a lubricant pump (step602), pumping a process fluid with a main pump (step604), pumping a purge volume of lubricant with the lubricant pump (step606), idling the lubricant pump for an inactive period (step608), determining whether the main pump is still operating (step610), pumping a final purge volume of lubricant with the lubricant pump (step612).

In step602, an initial purge volume of lubricant is pumped with a lubricant pump. The lubricant pump is configured to pump the purge volume of lubricant to purge and replace lubricant stored in a lubricant gallery of a main pump. The lubricant pump and main pump are separate pumps and can be, for example lubricant pump113and main pump112, respectively. The main pump can be a positive-displacement pump, such as a reciprocating pump. The lubricant pump can also be a positive-displacement pump, such as a peristaltic pump. The lubricant gallery is formed within the housing of the main pump and is separated from the pump chamber of the main pump by a throat seal. The throat seal reduces undesirable flow of process fluid or material from the pump chamber of the main pump toward, for example, a piston rod or other pump components. The lubricant gallery stores lubricant for lubricating the throat seal. The lubricant gallery can be, for example, lubricant gallery130, and the throat seal can be, for example, throat seal124.

The lubricant pump, lubricant gallery, and a lubricant reservoir form a lubricant system for circulating lubricant. Fresh lubricant is pumped from a lubricant reservoir and lubricant from the lubricant gallery flows to and is diluted in the lubricant reservoir. Dilution of lubricant from the lubricant gallery in the lubricant reservoir delays the onset of negative effects from contamination of lubricant with materials or process fluids pumped by the main pump. The lubricant pump, lubricant reservoir, and lubricant gallery are fluidly connected such that pumping action of the lubricant pump causes lubricant to flow in a circuit from the lubricant reservoir to the lubricant gallery and from the lubricant gallery to the lubricant reservoir. The purge volume is at least equal to the volume of the lubricant gallery. Advantageously, selecting a purge volume that is equal to the lubricant gallery minimizes unnecessary lubricant agitation, as described previously.

The initial purge volume pumped in step602functions to remove lubricant that may be contaminated by, for example, dust or the material pumped by the main pump that has accumulated while the main pump was inactive.

In step604, a process fluid is pumped with the main pump. Step604is generally performed after the initial purge performed in step602is complete, such that lubricant in the lubricant gallery has been completely replaced prior to operation of the main pump. The process fluid pumped by the main pump can be, for example, a moisture-sensitive material that forms undesirable hard byproducts when agitated or exposed to moisture.

In step606, the lubricant pump is operated to pump a purge volume of lubricant. Method600can proceed to step606immediately after step604or after a period of time equal to the inactive period (discussed with respect to step608) after step602was performed. In step608, the lubricant pump is idled for an inactive period. The length of the inactive period is dependent both on the rate of flow of the process fluid or material pumped by the main pump across the throat seal and the rate of formation of undesirable hard byproducts in the lubricant gallery, among other relevant parameters.

After the pump is idled for the inactive period in step608, method600proceeds to step610. In step610, control circuitry determines whether the main pump is still operating. If the pump is still operating, control circuitry proceeds to step606. In this manner, method600repeats steps606and608while the main pump is operating, ensuring that lubricant in lubricant pump is periodically purged during the operational period of the main pump. If the main pump is not operating, method600proceeds to step612. In step612, the lubricant pump pumps another purge volume of lubricant through the lubricant system, purging any contaminated lubricant from the lubricant gallery following the previous iteration of step606.

Advantageously, method600can be performed by control circuitry to intermittently operate a lubricant pump. As described previously, intermittent operation of a lubricant pump allows for optimal reduction both of lubricant agitation and contaminant accumulation in a lubricant gallery of a main pump. Also as described previously, reducing lubricant agitation is particularly advantageous where the main pump is used to pump a moisture-sensitive material. Method600can further be used by control circuitry to cause a lubricant pump to perform an initial lubricant purge before the main pump is operated and a final lubricant purge after the main pump is idled.