In-line measurement of nitrite content in metalworking fluids

Abstract

An apparatus for in-line monitoring of nitrite content in a metalworking fluid is provided, the apparatus comprising a sample inlet for receiving a sample of the metalworking fluid, a dilution inlet for receiving a dilution fluid, a reagent inlet for receiving a photoactive reagent, a reaction volume for containing a sample mixture in fluid communication with the sample inlet, the dilution and reagent inlets, a photometer for monitoring the sample mixture, and a flow control system for controlling fluid flow within the apparatus, and for selectively introducing the sample by introducing the photoactive reagent and / or dilution fluid from the respective inlets into the reaction volume to form a sample mixture, retaining the sample mixture in the reaction volume, and discharging the sample mixture from the reaction volume.

Description

[Technical field]

[0001] The present invention relates to an in-line measurement of nitrite content in metalworking fluids. In particular, the present invention relates to an apparatus and method for measuring the nitrite content of metalworking fluids by photometry. [Background technology]

[0002] Metalworking fluids are used in factories around the world for cutting and shaping metals. Their primary uses are to cool and lubricate tools, workpieces, and machines, inhibit corrosion, and aid in chip removal, cutting, grinding, and cleaning metals. There are a variety of different types of metalworking fluids. Metalworking fluids, particularly aqueous metalworking fluids, often contain nitrites, and in some cases it is necessary to measure the nitrite content of such fluids, for example to meet regulatory requirements.

[0003] Monitoring the levels of nitrite in metalworking fluids can be done by taking fluid samples from the system to be monitored and evaluating the nitrite content in a laboratory. For example, nitrite content can be monitored in a laboratory using test strips. However, such manual methods are labor intensive and therefore inefficient when regular testing is required.

[0004] There is a need for a system that can measure nitrite content in a more efficient manner and that can provide regular, real-time measurement of the nitrite content of metalworking fluids without the need to extract and transport samples to a laboratory. Summary of the Invention [Problem to be solved by the invention]

[0005] One aspect of the invention provides an apparatus for in-line monitoring of nitrite content in a metalworking fluid, the apparatus comprising: a sample inlet for receiving a sample of the metalworking fluid; a diluent inlet for receiving a diluent fluid; a reagent inlet for receiving a photoactive reagent; a reaction volume for containing a sample mixture in fluid communication with the sample inlet, the diluent inlet, and the reagent inlet; a photometer for monitoring the sample mixture; and a flow control system for controlling fluid flow within the device, comprising: (a) selectively introducing a sample, a diluent fluid, and / or a photoactive reagent into a reaction vessel through respective inlets to form a sample mixture; (b) retaining the sample mixture within a reaction volume; (c) discharging the sample mixture from the reaction volume; Includes:

[0006] The apparatus can be used to provide in-line monitoring of metalworking fluids. It is understood that in-line monitoring can include obtaining information regarding a sample obtained from a metalworking fluid that is supplied simultaneously or subsequently to a metalworking process, a used metalworking fluid stream, or a combination thereof. For example, the apparatus can be used for automated monitoring of nitrite content in a metalworking fluid supply. In-line monitoring can include diverting a sample of the metalworking fluid from the process flow to a sample inlet of the apparatus, e.g., during use, the apparatus can be positioned such that the sample inlet is in fluid communication with the metalworking fluid process flow. Diverting a sample of the metalworking fluid process flow can include obtaining a sample from a metalworking fluid process flow that is actively being used in the metalworking process, or can include obtaining a sample from a source of the metalworking fluid used in the metalworking process, e.g., a source of the metalworking fluid from which the metalworking fluid process flow is drawn.

[0007] The metalworking fluid sample may be obtained directly from the metalworking fluid process flow, or may be obtained indirectly from a previously collected volume or flow of metalworking fluid, for example, to provide a metalworking fluid sample to one or more other monitoring devices in addition to the present apparatus.

[0008] In some examples, the device may be configured to receive a sample of the metalworking fluid at a sample inlet and return the flow of the metalworking fluid through an outlet. For example, the sample inlet may include a sampling loop through which the flow of the metalworking fluid may be passed, where a sampling volume of the metalworking fluid may be contained, for example, between two valves. The sampling volume may include a defined volume, and a sample comprising the entire sampling volume is provided within the reaction volume. Alternatively, the sampling volume may be larger than the volume of the sample provided within the reaction volume.

[0009] The sample inlet can include one or more filters to remove components of the sample, such as particulate matter that may be damaging to the device. The sample inlet can include, for example, a 5-30 μm filter, such as a 10 μm filter.

[0010] The metalworking fluid can be any type of metalworking fluid known in the art, such as: (1) non-water miscible oils, (2) water miscible oils, and (3) fully synthetic oil-free products. Thus, the metalworking fluid may be oil-based, water-based, a water-in-oil emulsion, or an oil-in-water emulsion. If the metalworking fluid is an oil-in-water emulsion or a water-in-oil emulsion, the metalworking fluid may include an emulsifier to aid in the formation of the oil-in-water emulsion or the water-in-oil emulsion.

[0011] The metalworking fluid may suitably further comprise one or more additives as typically included in metalworking fluids. Such additives are known and familiar to those skilled in the art. Typical additives for use in metalworking fluids include corrosion inhibitors, pH adjusting additives, biocides, surfactants, antioxidants, yellow metal inhibitors, extreme pressure (EP) additives, antiwear (AW) additives, interface lubricity additives, and combinations thereof.

[0012] The metalworking fluid may be used as a grinding fluid in grinding and honing applications, as a cutting fluid or broaching fluid in deformation metalworking applications such as evaporative stamping fluids. The metalworking fluid may be used as a water-miscible metalworking fluid.

[0013] The dilution inlet is suitably connected to a dilution fluid source. The source of dilution fluid may be an external source, for example, where an external source is connected to the dilution inlet during use. In some examples, the source of dilution fluid may comprise an internal source of dilution fluid, for example, where the apparatus comprises a dilution fluid reservoir for storing dilution fluid. The dilution fluid may be any suitable fluid, and the particular dilution fluid may be suitably selected based on the metalworking fluid being monitored. In particular, the dilution fluid may be water.

[0014] The reagent inlets may be suitably connected to one or more external or internal sources of photoactive reagent, where the photoactive reagent may comprise a mixture of one or more components. The reagent inlets may include two or more separate inlets for providing the photoactive reagent separately. The device may include one or more reservoirs for storing the photoactive reagent, or one or more components thereof, and / or one or more components of the photoactive material during use may be provided from an external source.

[0015] The photoactive reagent may include any suitable reagent for reacting with nitrite ions in the sample to provide a species that can be observed using a photometer. The reaction of the photoactive reagent with nitrite ions may result in a color change that can be measured using a photometer. By way of example, the photoactive reagent may include sulfanilamide and N(1-naphthyl)ethylenediamine (Griess reagent), which may be combined with the sample in an acidic medium, and the nitrite content of the sample mixture may be monitored by measuring the absorption at a wavelength of 525 nm using a photometer and calculating the nitrite concentration in the sample using a set calibration function. The reagent may include sulfanilamide and N-(1-naphthyl)ethylenediamine in an acidic medium, e.g., an acidic aqueous solution such as a phosphoric acid solution, which may be provided to the reaction volume through a single reagent inlet. In some cases, at least one of the acid, sulfanilamide, and N-(1-naphthyl)ethylenediamine may be provided separately to the reaction volume, e.g., via a separate reagent inlet. In some cases, the sample may be suitably acidified before being introduced into the device and mixed with the photoactive reagent.

[0016] The reaction volume may include a volume defined by one or more flow paths between respective inlets for introducing fluids into the device and one or more outlets for expelling fluids from the device. The reaction volume may include a reaction vessel and one or more flow paths in fluid communication with the reaction vessel. The flow control system for holding the sample mixture in the reaction volume in part (b) may include a valve operable to provide a closed flow path within the reaction volume and may include a pump, such as a first pump described herein, operable to circulate the sample mixture within the reaction volume.

[0017] It will be appreciated that the flow path within the device may be provided in any suitable manner, for example the flow path within the device may be provided by one or more conduits for containing the sample mixture.

[0018] A sample mixture as referred to herein is understood to refer to any combination of fluids present in a reaction volume, such as one of the sample, diluent fluid, or photoactive reagent, or a combination of one or more of the aforementioned fluids.

[0019] The reaction volume may include a reaction vessel and a photometer flow path for supplying the sample mixture from the reaction vessel to a photometer. The photometer may be positioned to monitor the sample mixture in a separate photometer flow path in fluid communication with the reaction vessel, or the photometer may be positioned to monitor the sample mixture in the reaction vessel, for example, when the reaction vessel includes a photometer flow path. The photometer flow path may comprise, for example, a flow path fluidly connected to the reaction vessel at both ends of the flow path such that the photometer is positioned to monitor the sample mixture at positions along the flow path that begin and end at the reaction vessel.

[0020] The photometer can include an inlet and an outlet that define a flow path for the sample mixture through the photometer where the sample mixture is monitored. In some examples, the conduit or reaction vessel that defines the photometer flow path can include a window through which the photometer can monitor the sample mixture.

[0021] It is understood that the photometer may include any suitable photometer for monitoring absorption at a wavelength absorbed due to the reaction of the photoactive reagent with nitrite ions in the sample, and such photometers are known to those of skill in the art.

[0022] The flow controller may include one or more pumps and one or more valves operable to control the flow rate within the device.

[0023] The flow control system may include a first pump for feeding the sample mixture from the reaction vessel to the photometer flow path and for draining the sample mixture from the reaction vessel. When the first pump feeds the sample mixture to the photometer flow path, this includes circulating the sample mixture within the reaction volume. The flow control system may include a first valve for selecting whether the first pump feeds the sample mixture to the photometer flow path or drains the sample mixture from the reaction volume. For example, the first valve may be disposed downstream of the first pump and operable to connect the flow path from the first pump to the photometer flow path or to an outlet of the device.

[0024] The flow control system may include a second valve for selecting whether to discharge the sample mixture from the reaction vessel and / or the photometer flow path. For example, the second valve may be disposed upstream of the first pump and operable to selectively connect the reaction vessel to the photometer flow path and / or to the inlet of the first pump. When the reaction vessel is connected to the inlet of the first pump, for example, by operation of the second valve, the first valve may be operable to direct the sample mixture from the reaction vessel to the outlet of the device or to the photometer flow path as described above. For example, the first pump may be disposed to circulate the sample mixture through the reaction vessel and the photometer flow path.

[0025] The flow control system may include a sample pump for introducing a sample into the reaction volume, a dilution pump for introducing a dilution fluid into the reaction volume, and / or a reagent pump for introducing a photoactive reagent into the reaction volume. The sample inlet, dilution inlet, and reagent inlet may each optionally include one or more valves to control flow from the respective inlet to the reaction volume and / or to the respective pump.

[0026] If the reagent inlet includes two or more reagent inlets for separately providing components of the photoactive reagent, the fluid control system may include a reagent pump for each inlet, or a multi-channel pump connected to the two or more reagent inlets.

[0027] It will be appreciated that where the fluid input to the inlet of the device is provided at a pressure higher than the pressure in the reaction volume, a valve, optionally in combination with a pump, can be used to control the supply of fluid into the reaction volume. Alternatively, where the fluid input to the inlet of the device is not pressurized, a pump, optionally in combination with a valve, can be used to control the supply of fluid to the reaction volume.

[0028] Two or more pumps for introducing fluids into the reaction volume may be provided by a single multichannel pump, e.g., a dual channel pump, having separate flow paths through the pump. The channels of the multichannel pump may be configured to provide a predefined volumetric rate flow rate, e.g., an equivalent volumetric rate flow rate through each channel.

[0029] A multi-channel pump may provide additional pumping functionality to the sample pump, diluent pump, and reagent pump. For example, the sample pump may include a multi-channel pump, e.g., a multi-channel pump for simultaneously introducing sample and diluent fluids into the reaction volume, e.g., a dual channel pump in fluid communication with the sample inlet and the diluent inlet.

[0030] The reaction volume can include a first outlet flow path for discharging the sample mixture from the reaction volume and a second outlet flow path for only partially discharging the sample mixture from the reaction volume to leave a predetermined volume of the sample mixture in the reaction volume. For example, the reaction vessel can include a first outlet and a second outlet, the second outlet being arranged to only partially discharging the sample mixture from the reaction vessel. Thus, the volume of fluid introduced into the reaction volume can be controlled, for example, by introducing a volume of fluid into the reaction volume and reducing the volume to a certain level by discharging the sample mixture.

[0031] The flow control system may include a third valve for selecting whether to discharge the sample mixture through the first or second outlet flow path of the reaction volume, for example, the first and second outlet flow paths may be connected to the third valve.

[0032] The first pump may be arranged to eject the sample mixture through the first and second ejection channels. For example, the first and second ejection channels may be fluidly connected to the inlet of the first pump. For example, the third valve may be fluidly connected to the inlet of the first pump and may be connected to the inlet of the first pump via the second valve.

[0033] The device may include a calibration outlet through which a sample introduced into the device can be extracted to perform offline measurements to calibrate the device. The flow control system may include a valve for selecting whether to direct the sample to the calibration outlet or to the reaction volume.

[0034] The apparatus may further comprise a controller configured to cause the apparatus to: (i) providing a first volume of a sample of the metalworking fluid to be tested through a sample inlet into a reaction volume; (ii) delivering a second volume of diluent fluid from the diluent inlet into the reaction volume to form a diluted sample mixture; (iii) providing a third volume of a photoactive reagent from the reagent inlet into the reaction volume to form an activated sample mixture; (iv) obtaining a photometric measurement of the activated sample mixture using a photometer, where the photometric measurement provides an indication of the nitrite content of the sample.

[0035] The controller may be configured to synchronize operation of one or more valves and one or more pumps of the fluid control system to control fluid flow within the device. For example, the controller may be configured to synchronize operation of the first pump with operation of the first, second, and / or third valves to control flow within the device.

[0036] The first, second, and third volumes of sample, dilution fluid, and photoactive reagent may each be introduced into the reaction volume, for example, by timed operation of a pump, e.g., a sample pump, a dilution pump, or a reagent pump, coupled to the respective inlets to introduce each volume of fluid. The timed operation of the pump may include operating the pump for a set amount of time. The timed operation of the pump may be based, for example, on a known or set volumetric flow rate provided by the pump. A controlled volume of fluid may also be introduced into the reaction volume by timed opening of a valve at each inlet to allow a set volume of fluid to flow through the valve. A fixed volume of fluid may be provided by capturing the fluid in a volume between two or more valves. In some examples, a fixed volume of fluid may be provided by introducing a fixed volume of fluid into the reaction volume and then partially draining the reaction volume to leave a set volume of fluid.

[0037] The valves present in the device may include any suitable valves known in the art, for example, solenoid valves or ball valves. The valves may suitably comprise multi-way valves, for example, three-way valves, or on / off valves, as appropriate. The valves may suitably comprise normally closed or normally open valves, and three-way valves may comprise both normally open and normally closed flow paths through the valve. The valves may be automatically operable, for example, if the valves comprise solenoid valves or if the valves comprise electronically operable valve actuators. For example, the valves may be actuable by a controller, which may control the timing and duration of the opening of the valves.

[0038] The pump present in the device may include any suitable pump, including one or more multi-channel pumps. The pump may comprise a rotary gear or vane pump, a positive displacement pump such as a peristaltic pump or a diaphragm pump. The pump is preferably operable automatically, for example by a controller that can control the timing and duration of the opening of the valve.

[0039] A valve or pump described as a valve or pump to perform a certain function may preferably be considered to be operable or arranged to perform said function, or vice versa. Operating a valve to perform a particular function as described herein may, in some examples, include taking the following actions: for example, no action is taken to change the flow through the valve, e.g., when the valve is already in the desired configuration, such as having a normally open valve in the desired configuration.

[0040] Although the valves and / or pumps described herein may be referred to as first, second, third, etc., these may be viewed merely as labels and do not imply any ordering of components or dependency on others. An apparatus may suitably include any combination of one or more of the valves or pumps described independent of the others.

[0041] The controller may be suitably configured to operate the multi-channel pump to simultaneously introduce at least a portion of the first, second and / or third volumes of the respective fluids into the reaction volume. For example, the controller may be configured to operate a dual-channel pump to simultaneously introduce a first volume of sample into the reaction volume with a portion of the second volume of diluent fluid, and to operate a separate diluent pump to introduce only diluent fluid to provide the remaining portion of the second volume of diluent fluid.

[0042] The controller may be configured to operate the apparatus to introduce a volume of sample that is greater than the first volume into the reaction volume, and to expel the sample mixture from the reaction volume to leave the first volume of sample, to provide the first volume.

[0043] The controller may be configured to operate the device to circulate the diluted sample mixture and / or the activated sample mixture through the reaction volume, for example, circulating the sample mixture through the reaction volume helps mix the components of the sample mixture and ensure even distribution throughout the reaction volume.

[0044] In some embodiments, providing the second volume of dilution fluid and / or providing the third volume of photoactive reagent occurs at least partially simultaneously with the circulation of the diluted sample mixture and / or the activated sample mixture, respectively, within the reaction volume.

[0045] Obtaining photometric measurements of the activated sample mixture may include obtaining photometric measurements of a substantially stationary sample mixture in the reaction volume. For example, the controller may control pumps and / or valves such that the sample mixture does not actively flow through the photometer by switching off one or more pumps of the device.

[0046] The controller may be configured to obtain a photometric measurement of the diluted sample mixture prior to introducing the photoactive reagent. For example, a first volume of sample and a second volume of diluent fluid may be introduced into the reaction volume and a photometric measurement of the diluted sample mixture may be obtained as a background measurement. The controller may then operate the device to introduce a third volume of the photoactive reagent into the reaction volume prior to obtaining a photometric measurement of the activated sample. The sample may then be compared to the background measurement to provide an indication of the nitrite content of the sample.

[0047] The controller may be configured to periodically obtain measurements that provide an indication of the nitrite content of different samples of the metalworking fluid. For example, the controller may be configured to operate the apparatus to automatically obtain measurements of the nitrite content of the samples at predetermined time intervals, such that measurements of the nitrite content of the metalworking fluid source can be monitored over time. The controller may be configured to operate the apparatus to empty the reaction volume of the sample mixture and / or rinse the apparatus with dilution fluid and / or sample between measurements.

[0048] The controller may be configured to operate the device to perform the following sequence: Optionally, emptying the reaction volume or vessel; flowing the sample of the metalworking fluid through the dilution fluid and / or the sample of the metalworking fluid and draining the fluid from the reaction volume to empty the reaction volume; introducing a sample into a reaction volume and optionally reducing the volume of the sample to provide a first volume; introducing a dilution fluid into the reaction volume to dilute the sample; circulating the sample mixture within a reaction volume; obtaining a background photometric measurement of the sample mixture; introducing a photoactive reagent into the reaction volume and circulating the sample mixture within the reaction volume; obtaining a photometric measurement of the sample mixture; and Optionally, comparing the photometric measurements to a background measurement to determine the nitrite content of the sample.

[0049] The controller may be configured to record the nitrite content of the sample and / or the photometric measurement in a database and provide an entry into the database indicating, for example, the time of measurement and the nitrite content, or data providing an indication of the nitrite content, e.g., the photometric measurement data. The controller may alternatively or additionally be configured to provide an indication when the nitrite content of the sample is outside of the threshold range. For example, the controller may be configured to provide an indication visually on a display, or to provide an electronic notification to a user in real time, for example, by providing an email or notification to a workstation or mobile device.

[0050] The controller may be configured to provide an indication and / or a control signal for adjusting the nitrite content of the metalworking fluid based on the indication of the nitrite content of the sample metalworking fluid. For example, the controller may be connected in a feedback loop whereby if the measured nitrite content is outside a threshold range, the controller may be configured to provide a control signal for adjusting the nitrite content of the metalworking fluid source from which the sample was obtained. Providing the control signal may be based on two or more separate measurements that the nitrite content of the metalworking fluid is outside a threshold range.

[0051] A further aspect of the present invention provides a method for in-line monitoring of nitrite content in a metalworking fluid using an apparatus as hereinbefore defined, the method comprising: (i) withdrawing a sample of the metalworking fluid to be tested from a metalworking fluid stream and providing a first volume of the sample through a sample inlet into a reaction volume; (ii) providing a second volume of diluent fluid from the diluent inlet into the reaction volume to form a diluted sample; (iii) providing a photoactive reagent into the reaction volume through a reagent inlet to form an activated sample; and (iv) obtaining a photometric measurement of the activated sample, the photometric measurement providing an indication of the nitrite content of the sample.

[0052] The diluent fluid, metalworking fluid, and photoactive reagent may be substantially as defined hereinbefore.

[0053] It should be appreciated that the method may include operating the apparatus to perform the steps for which the controller is configured as described herein.

[0054] A further aspect of the present invention provides a computer program product comprising program instructions configured to program a computer system to perform the methods described herein.

[0055] A further aspect of the present invention provides a control system for an apparatus as hereinbefore described, the control system comprising a processor and a computer memory containing program instructions configured to program the computer system to perform the method described herein.

[0056] A further aspect of the present invention provides a metalworking fluid delivery system for supplying a metalworking fluid to a metalworking process, the metalworking fluid delivery system including the apparatus and / or control system described herein.

[0057] A further aspect of the present invention provides a method of refurbishing a metalworking fluid delivery system by comprising the apparatus and / or control system described herein.

[0058] A further aspect of the invention provides the use of the apparatus described herein to automatically monitor and optionally record the nitrite content of a metalworking fluid periodically, for example at predetermined time intervals.

[0059] The invention will now be described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0060] [Figure 1] 1 shows an example of an apparatus for in-line monitoring of nitrite content in metalworking fluids. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] 1 shows a schematic diagram of an exemplary apparatus in which a sample inlet 2 in use connected to a source of metalworking fluid to be monitored is connected via valve V5 to a sampling volume / flow path 42, and via valve V6 to a vent 4 and outlet 6, which may be arranged as a return line to return fluid to the source of the metalworking fluid from which the sample was obtained. Valves V5 and V6 are operable to retain a volume of sample within sample volume 42.

[0062] An in-line filter separates valve V5 from calibration valve V4, which is operable to direct the sample via flow path 16 for off-line calibration, or to direct the sample via flow path 14. Flow path 14 is connected to the inlet of reaction vessel 18 via dual channel sample pump P2. Thus, dilution fluid may be introduced into reaction vessel 18 simultaneously with the sample by pump P2.

[0063] The diluent inlet 8 is connected to a source of diluent fluid, e.g., water, and the diluent inlet 8 may be opened or closed by operating valve V7. The diluent inlet 8 is connected to an inlet of a reaction vessel 18 via a flow path 12 and a dual channel sample pump P2. The diluent inlet is also connected from a first outlet 20 of the reaction vessel to a flow path 30 via a flow path 10 and a diluent pump P3, so that a diluent fluid may be introduced into the reaction volume independently of the sample.

[0064] A reagent pump P4 and an optional second reagent pump P5 are also connected to the flow path 30 for introducing photoactive reagents into the reaction volume. The reagent pumps P4 and P5 may be connected to respective reagent reservoirs for storing the photoactive reagents or components thereof.

[0065] The reaction vessel 18 comprises an outlet 20 connected to the inlet of a first pump P1 via a flow path 30, a third valve V3, a flow path 34 and a second valve V2. The outlet of the first pump P1 is connected by a flow path 38 to a first valve V1, where the first valve V1 is connected to the outlet 6 via a flow path 40. The first pump can thus be actuated to expel the sample mixture from the reaction volume via the outlet 6.

[0066] The first valve V1 is also connected to a photometer flow path 24 that includes a photometer 26 arranged to monitor fluid provided by the photometer flow path to the photometer 26. The photometer flow path 24 includes a flow path 28 that connects to an inlet of the reaction vessel 18. The first pump P1 can thus be operated to circulate the sample mixture from the outlet 20 of the reaction vessel 18, through the photometer 26, and back to the reaction vessel 18 via the flow path 28.

[0067] The second valve V2 is additionally directly connected to the photometer flow path 24 via the flow path 36. Thus, the photometer flow path 24 may be connected to the inlet of the first pump Pl via the second valve V2, and the first pump may be operated to eject the sample mixture in the photometer flow path through the outlet 6 via the first valve Vl.

[0068] The reaction vessel 18 includes a second outlet 22 connected to a third valve V3 via a flow path 32. The second outlet 22 is arranged to only partially remove the sample mixture present in the reaction vessel 18. The third valve V3 is thus operable to select whether the first outlet 20 and the second outlet 22 of the reaction vessel 18 are connected to the outlet 6 via the first pump P1.

[0069] Although not shown in Figure 1, the components of the apparatus shown in Figure 1 may be connected to a controller configured to control the flows within the apparatus and to control the operation of the photometer. An example of the operation of the apparatus in use will be described with reference to the apparatus of Figure 1.

[0070] Valves V5 and V6 may be actuated to connect sample inlet 2 to outlet 6 to allow sample to flow through sampling volume 42. Valves V5 and V6 are then closed to retain the sample to be monitored within sampling volume 42.

[0071] Prior to introducing the sample mixture into the reaction vessel 18, the reaction vessel 18 can first be emptied by operating valves V1, V2 and V3 to connect the first outlet 20 of the reaction vessel 18 to outlet 6 via flow paths 30, 34, 38 and 40, and operating the first pump P1 to pump the sample mixture from the reaction vessel 18 to outlet 6.

[0072] The device can then be flushed with fresh sample mixture by introducing sample from the sampling volume 42 into the reaction vessel through flow path 14 by operating valves V5 and V4 and sample pump P2, and simultaneously introducing diluent fluid from diluent inlet 8 through flow path 12 by operating valve V7 and pump P2. Generally, once the sample has been introduced into the reaction vessel from the sampling volume 42, valve V6 can be actuated to open to vent port 4. The sample mixture can also be circulated back to the reaction vessel 18 from the first outlet 20 through flow paths 30, 34, 38, 24 and 28 by operating valves Vl, V2 and V3, and pump Pl, and the sample mixture can be discharged through flow path 40 to outlet 6. Following this, the reaction vessel 18 can be emptied of sample mixture as previously described.

[0073] The partially diluted sample mixture is introduced from sample volume 42 into reaction vessel 18 by operating valves V5 and V4 and sample pump P2 to introduce sample along flow path 14, while simultaneously introducing diluent fluid from diluent inlet 8 via flow path 12 by operating valve V7 and pump P2.

[0074] The volume of the partially diluted sample mixture in the reaction vessel 18 is then controlled by the operating valves V3, V2 and V1, the second outlet 22 is connected to the outlet 6 via the flow paths 32, 34, 38 and 40, and the first pump Pl is operated to partially discharge the partially diluted sample mixture from the reaction vessel.

[0075] The dilution fluid from the dilution inlet 8 is then introduced through the flow path 10 by opening the valve V7 and operating the dilution pump P3. The dilution fluid is supplied to the reaction vessel 18 through the flow paths 30, 34, 38, 24 and 28, and at the same time, the diluted sample in the reaction vessel 18 may be circulated from the first outlet 20 to the flow path 28 by the same flow path as the dilution fluid introduced from the flow path 10.

[0076] The diluted sample mixture can then be homogenized within the reaction volume from the first outlet 20 of the reaction vessel 18, through the photometer 26, and back to the reaction vessel 18 via flow paths 30, 34, 38, 24 and 28 by operating valves Vl, V2 and V3, and pump Pl.

[0077] Pump P1 is turned off to stop circulation of the diluted sample and provide a substantially stationary sample to photometer 26, which is then operated to obtain photometric measurements of the diluted sample.

[0078] Reagent pump P4 is then operated to provide photoactive reagent to flow path 30, and the sample mixture is circulated from first outlet 20 to flow path 28, as previously described, to provide photoactive reagent to reaction vessel 18. If present, reagent pump P5 may be operated in substantially the same manner to introduce a second component of the photoactive reagent, which may be done simultaneously or sequentially with respect to the introduction of the first component of the photoactive reagent using pump P4.

[0079] The sample mixture containing the photoactive reagent can then be circulated from the first outlet 20 of the reaction vessel 18 into the reaction volume through the photometer 26 and back to the reaction vessel 18 via flow paths 30, 34, 38, 24 and 28, thereby homogenizing the sample mixture by operating valves V1, V2 and V3, and pump P1 to form an activated sample mixture.

[0080] Pump P1 is turned off to stop circulation of the activated sample mixture and photometer 26 is turned on to obtain a photometric measurement of the activated sample.

[0081] The photometric measurements and background measurements may be recorded in a database with another identifier, e.g., a batch identifier, for the metalworking fluid sampled and measured, and / or with the time, e.g., date, at which the measurements were taken. The photometric measurements and background measurements may be compared to provide an indication of the nitrite concentration in the sample, which may be recorded instead of or in addition to the photometric measurements. The nitrite concentration may be determined in real time with the collection of the photometric measurements, and a warning signal may be recorded or sent to a user in real time if the nitrite concentration is outside a threshold range. An indication of a nitrite concentration outside a threshold range may alternatively or additionally trigger a control signal to adjust the nitrite content of the metalworking fluid source from which the sample was taken. The threshold range for issuing a warning signal may be different from the threshold range for triggering a control signal, e.g., the threshold range for issuing a warning may be narrower (and / or in terms of upper and lower limits) than the threshold range for issuing a control signal. The warning or control signal may optionally only be issued based on two or more measurements, e.g., at least two measurements taken consecutively, where a first nitrite content measurement outside the threshold range may trigger a second measurement, with the trigger for issuing the warning or control signal being dependent on both measurements. Alternatively or additionally, the two or more measurements may include two or more measurements taken at regular time intervals, e.g., such that the measurements can be analyzed to determine the presence of a pattern of nitrite content outside the threshold range over time.

[0082] It is understood that the volumes of sample, diluent fluid, and photoactive reagent introduced into the reaction volume are set so that the concentration of nitrite in the sample can be calculated from the absorbance measured by the photometer, for example, using a predetermined calibration function. The exact volume ratios and total volumes of the different components can be appropriately varied based on the particular system. In one example, the diluent fluid is water and the photoactive reagent includes sulfanilamide and N-(1-naphthyl)ethylenediamine, and about 1-2 ml of sample, about 40 ml of water, and about 5 ml of photoactive reagent solution can be introduced into the reaction volume for measurement.

[0083] After the measurement, the photometer flow path 24, including the photometer 26 and flow path 28, may be emptied of the sample mixture by operating the second valve V2 to connect the photometer flow path 24 to the inlet of the first pump Pl via flow path 36, and operating the first valve Vl to connect flow path 38 to flow path 40, and to the outlet 6. The sample mixture may also be emptied from the reaction vessel 18 by operating valves V1, V2 and V3 to connect the first one.

[0084] From outlet 20 of reaction vessel 18 to outlet 6 via channels 30, 34, 38, 40, the first pump Pl is activated to discharge the sample mixture from reaction vessel 18 to outlet 6. Finally, the reaction volume can be washed with dilution fluid by introducing dilution fluid via channel 10 by opening valve V7 and activating dilution pump P3. Dilution fluid is supplied to reaction vessel 18 via channels 30, 34, 38, 24 and 28, while dilution fluid is circulated from first outlet 20 of reaction vessel 18 to channel 28 by the same channel as the dilution fluid introduced from channel 10 to reaction vessel 18. The reaction vessel 18 and photometer channel 24 are then emptied as described above, and the cycle of washing and emptying the reaction volume is repeated, for example three times, with the final emptying step being performed immediately or before further sample measurements are performed.

[0085] In certain examples, the controllers described herein may be configured to perform any of the methods or specific steps of the methods. The controllers described herein may refer to a single controller and / or processor, or control may be distributed among multiple controllers and / or processors, which may physically form part of the device or may be a remote controller communicatively coupled to the device. The activities and devices outlined herein may be implemented using controllers and / or processors, which may be provided by fixed logic, such as an assembly of logic gates, or by software executed by a processor, and / or by programmable logic, such as computer program instructions. Other types of programmable logic include a programmable processor, a programmable digital logic (e.g., a field programmable gate array (FPGA), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM)), an application specific integrated circuit, ASIC, or any other type of digital logic, software, code, electronic instructions, flash memory, an optical disk, a CD-ROM, a DVD ROM, a magnetic or optical card, other type of machine-readable medium suitable for storing electronic instructions, or any suitable combination thereof.

[0086] The above-described embodiments should be understood as illustrative examples. Further embodiments are envisioned. It should be understood that any feature described in connection with any one embodiment may be used alone or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Moreover, equivalents and modifications not described above may also be used without departing from the scope of the invention as defined in the appended claims.

[0087] Other variations and modifications of the device will be apparent to those of ordinary skill in the art in the context of this disclosure.

Claims

1. 1. An apparatus for in-line monitoring of nitrite content in a metalworking fluid, comprising: a sample inlet for receiving a sample of the metalworking fluid; a diluent inlet for receiving a diluent fluid; a reagent inlet for receiving a photoactive reagent; a reaction volume for containing a sample mixture in fluid communication with the sample inlet, the dilution inlet, and the reagent inlet; a photometer for monitoring the sample mixture; a flow control system for controlling fluid flow within the device, comprising: (a) selectively introducing the sample, the diluent fluid, and / or the photoactive reagent into the reaction volume through the respective inlets to form the sample mixture; (b) retaining the sample mixture in the reaction volume; (c) discharging the sample mixture from the reaction volume. a flow control system; The apparatus may further include a controller configured to operate the apparatus, (i) providing a first volume of the sample of a metalworking fluid to be tested through the sample inlet into the reaction volume; (ii) delivering a second volume of the dilution fluid from the dilution inlet into the reaction volume to form a diluted sample mixture; (iii) providing a third volume of the photoactive reagent through the reagent inlet into the reaction volume to form an activated sample mixture; (iv) obtaining a photometric measurement of the activated sample mixture using the photometer, the photometric measurement providing an indication of the nitrite content of the sample. An apparatus comprising a controller.

2. 2. The apparatus of claim 1, wherein the reaction volume comprises a reaction vessel and a photometer flow path for delivering the sample mixture from the reaction vessel to the photometer.

3. 3. The apparatus of claim 2, wherein the flow control system comprises a first pump for delivering the sample mixture from the reaction vessel to the photometer flow path and for expelling the sample mixture from the reaction vessel.

4. 4. The apparatus of claim 3, wherein the flow control system comprises a first valve for selecting whether the first pump supplies the sample mixture to the spectrophotometer flow path or expels the sample mixture from the reaction volume.

5. 5. The apparatus of claim 2, wherein the flow control system comprises a second valve for selecting whether the sample mixture is discharged from the reaction vessel and / or the spectrometer flow path.

6. The apparatus of any one of claims 1 to 5, wherein the flow control system comprises a sample pump for introducing the sample into the reaction volume, a dilution pump for introducing the dilution fluid into the reaction volume, and / or a reagent pump for introducing the photoactive reagent into the reaction volume.

7. 5. The device of claim 3 or 4, wherein the reaction volume comprises a first outlet flow path for discharging the sample mixture from the reaction volume and a second outlet flow path for only partially discharging the sample mixture from the reaction volume to leave a predetermined volume of the sample mixture within the reaction volume.

8. 8. The apparatus of claim 7, wherein the flow control system comprises a third valve for selecting whether the sample mixture is discharged through the first outlet flow path or the second outlet flow path.

9. 9. Apparatus according to claim 7 or 8, wherein the first pump is arranged to eject the sample mixture through the first and second ejection channels.

10. An apparatus as described in any one of claims 7 to 9, wherein the flow control system comprises a sample pump for introducing the sample into the reaction volume, a dilution pump for introducing the dilution fluid into the reaction volume, and / or a reagent pump for introducing the photoactive reagent into the reaction volume, and the sample pump comprises a multi-channel pump for simultaneously introducing the sample and the dilution fluid into the reaction volume, for example a dual channel pump in fluid communication with the sample inlet and the dilution inlet.

11. 2. The apparatus of claim 1, wherein the controller is configured to operate the apparatus to provide the first volume by introducing a volume of the sample into the reaction volume that is greater than the first volume and draining metalworking fluid from the reaction volume to leave the sample in the first volume.

12. 12. The apparatus of claim 1 or 11, wherein the controller is configured to operate the apparatus to circulate the diluted sample mixture and / or the activated sample mixture within the reaction volume.

13. 13. The apparatus of claim 12, wherein the supplying of the second volume of dilution fluid and / or the supplying of the third volume of photoactive reagent are performed at least partially simultaneously with the circulation of the diluted sample mixture and / or the activated sample mixture within the reaction volume, respectively.

14. An apparatus according to any one of claims 11 to 13, wherein the controller is configured to obtain photometric measurements of the diluted sample mixture prior to introducing the photoactive reagent.

15. An apparatus according to any one of claims 11 to 14, wherein the controller is configured to periodically obtain measurements providing an indication of the nitrite content of different samples of metalworking fluid.

16. 16. The device of claim 15, wherein the controller is configured to operate the device to empty the reaction volume of sample mixture and / or to wash the device with the dilution fluid and / or the sample between measurements.

17. 17. An apparatus according to any one of claims 11 to 16, wherein the controller is configured to record photometric measurements and / or nitrite content of the sample in a database and / or to provide an indication when the nitrite content of the sample is outside a threshold range.

18. 18. Apparatus according to any one of claims 11 to 17, wherein the controller is configured to provide an indication and / or a control signal for adjusting the nitrate content of the metalworking fluid based on the indication of the nitrite content of the sample.

19. An apparatus as described in claims 11 to 18, wherein the controller is configured to issue indicators and / or control signals to adjust the nitrite content of the metalworking fluid based on the nitrite content of the sample.

20. A method for in-line monitoring of nitrite content in a metalworking fluid using an apparatus according to any one of claims 1 to 19, comprising the steps of: (i) withdrawing a sample of the metalworking fluid to be tested from a metalworking fluid stream and providing a first volume of said sample through a sample inlet into a reaction volume; (ii) providing a second volume of a diluent fluid from the diluent inlet into the reaction volume to form a diluted sample; (iii) providing a photoactive reagent into the reaction volume through a reagent inlet to form an activated sample; (iv) obtaining a photometric measurement of the activated sample, said photometric measurement providing an indication of the nitrite content of said sample. and 21. The method of claim 20, wherein the diluent fluid is water, the metalworking fluid is an aqueous metalworking fluid, and / or the photoactive reagent comprises sulfanilamide and N-(1-naphthyl)ethylenediamine.

22. A method according to claim 20 or 21, comprising operating an apparatus according to any one of claims 11 to 19.

23. A computer program product comprising program instructions configured to program a computer system to carry out the method of any one of claims 20 to 22.

24. A control system for an apparatus according to any one of claims 1 to 10 comprising a processor and a computer memory containing program instructions according to claim 23.

25. Use of an apparatus according to any one of claims 1 to 19 for automatically monitoring and optionally recording the nitrite content of a metalworking fluid on a regular basis.

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