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Title:
DETECTING NITROGEN BLOW EVENT DURING POLYMERIZATION PROCESS
Document Type and Number:
WIPO Patent Application WO/2014/179047
Kind Code:
A1
Abstract:
Processes and systems for detection of a nitrogen blow event during a polymer production process, such as a nylon 6,6 polymer production process, are disclosed and described. Processes and systems for arresting a nitrogen blow event during a polymer production process, such as nylon 6,6 polymer production processes, are also disclosed and described.

Inventors:
MONSTER LEEN (NL)
VONK CORNELIS M (NL)
Application Number:
PCT/US2014/034152
Publication Date:
November 06, 2014
Filing Date:
April 15, 2014
Export Citation:
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Assignee:
INVISTA NORTH AMERICA S R L (US)
INVISTA TECHNOLOGIES SRL (CH)
International Classes:
B29C48/92; F17C13/02; C08F2/01
Domestic Patent References:
WO2006114766A22006-11-02
Foreign References:
US20120047994A12012-03-01
Other References:
None
Attorney, Agent or Firm:
OAKESON, Gary (3 Little Falls Centre2801 Centerville Roa, Wilmington DE, US)
Download PDF:
Claims:
CLAIMS

What Is Claimed Is: 1 . A method of detecting a nitrogen blow event during a polymer fabrication process, comprising:

receiving with a microphone, sound information resulting from nitrogen gas passing through a dieplate that extrudes molten polymer;

converting the sound information into an electronic signal; and

evaluating the electronic signal for a nitrogen blow event using a logic controller at a frequency of at least once every 0.1 seconds.

2. The method of claim 1 , wherein receiving the sound information with a microphone includes measuring sound properties as a function of changing capacity values in a capacitor.

3. The method of claim 2, wherein the capacity values range from about 2 to about 60 pico farads. 4. The method of claim 1 , wherein converting the sound information includes changing it from a high impedance value to a low impedance value using a preamplifier.

5. The method of claim 4, wherein the high impedance value is about 1 ΘΩ and the low impedance value is about 50Ω or less.

6. The method of claim 1 , wherein converting the sound information includes filtering out any signal frequencies falling outside a range indicative of nitrogen gas passing through the dieplate using a sound level monitor.

7. The method of claim 6, wherein the range indicative of nitrogen gas passing through the dieplate is from about 15 kHz to about 40kHz.

8. The method of claim 1 , wherein converting the sound information includes linearizing the signal using a logarithmic mean square detector.

9. The method of claim 8, further comprising standardizing the linearized signal into a standard 4-20 mA signal.

10. The method of claim 1 , wherein the frequency at which the logic controller evaluates the signal is between every 0.1 seconds and every 0.001 seconds.

1 1 . The method of claim 10, wherein the frequency at which the logic controller evaluates the signal is between every 0.08 seconds every 0.02 seconds. 12. The method of claim 1 1 , wherein the frequency at which the logic controller evaluates the signal is about every 0.04 seconds.

13. The method of claim 1 , wherein the nitrogen blow event is caused by an interruption in flow of polymer due to a void in molten polymer.

14. The method of claim 1 , wherein the nitrogen blow identifies an end of a polymer casting event.

15. The method of claim 1 , wherein the polymer is nylon 6,6 polymer.

16. A method of arresting a nitrogen blow event during a polymer fabrication process, comprising:

detecting the nitrogen blow event as recited in claim 1 ; and

automatically closing an autoclave extrusion valve through which nitrogen gas is passing in response to detection of the nitrogen blow.

17. The method of claim 16, wherein closure of the autoclave extrusion valve occurs in less than 1 second from commencement of the nitrogen blow event.

18. The method of claim 16, wherein closure of the autoclave extrusion valve occurs between 0.1 and 0.6 seconds from commencement of the nitrogen blow event. 19. The method of claim 16, wherein closure of the autoclave extrusion valve occurs in 0.54 seconds or less.

20. The method of claim 16, wherein the autoclave extrusion valve is partially closed prior to the automatically closing step.

21 . The method of claim 16, wherein the logic controller is

electronically coupled to the autoclave extrusion valve and sends a signal to close the valve upon determining the existence of a nitrogen blow event. 22. The method of claim 21 , wherein the logic controller is

electronically coupled to the autoclave extrusion valve though a process control system that controls operation of the polymer fabrication process.

23. The method of claim 16, wherein the polymer is nylon polymer.

24. The method of claim 23, wherein the nylon polymer is nylon 6,6 polymer.

25. A nitrogen blow detection system for detecting a nitrogen blow event associated with a polymer production process, comprising:

a microphone configured to detect sound information resulting from nitrogen gas passing through a dieplate that extrudes molten polymer;

a converter module electronically coupled to the microphone and configured to receive sound information from the microphone and convert said sound information into an electronic signal; and

a logic controller electronically coupled to the converter module and configured to evaluate the electronic signal for a nitrogen blow event at a frequency of at least once every 0.1 seconds.

26. The system of claim 25, wherein the converter module further comprises:

a preamplifier electronically coupled to the microphone and configured to receive sound information from the microphone and change the information from a high impedance value to a low impedance value; and

a sound level monitor electronically coupled to the preamplifier and configured to receive a signal from the preamplifier and filter out any signal frequencies falling outside a range indicative of nitrogen gas passing through the dieplate.

27. The system of claim 26, wherein the sound level monitor is further configured to linearize the signal using a logarithmic mean square detector.

28. The system of claim 27, wherein the sound level monitor is further configured to standardize the linearized signal into a standard 4-20 mA signal.

29. The system of claim 25, wherein the microphone is directionally sensitive. 30. The system of claim 29, further comprising a housing coupled to the microphone, said housing configured with an opening to enhance directional receipt of sounds by the microphone.

31 . The system of claim 30, wherein the housing has a substantially tubular shape and the microphone resides inside the tube.

32. The system of claim 30, wherein the housing is insulated to further dampen sounds received other than through an opening in the housing configured allow entry of sounds into the housing.

33. The system of claim 30, wherein the opening of the housing is oriented toward the dieplate.

34. The system of claim 29, wherein the microphone measures sound information received as a function of changing capacity values in a capacitor.

35. The system of claim 29, wherein the microphone is grounded only on one side of the line between the microphone and the controller in order to reduce occurrence of false positive signals.

36. The system of claim 25, wherein the polymer is nylon 6,6 polymer.

37. A nitrogen blow arresting system for arresting a nitrogen blow occurring during a polymer productions process comprising:

a collection of components assembled and configured as recited in claim 25, wherein said logic controller is electronically coupled to an autoclave extrusion valve though which nitrogen gas passes, and configured to signal automatic closure of the autoclave extrusion valve upon detection of the electronic signal indicating occurrence of the nitrogen blow.

38. The system of claim 37, further comprising an electro-mechanical device adapted to receive the signal from the logical controller and shut down the autoclave extrusion valve upon receiving the signal from the logic controller to do so.

39. The system of claim 37, wherein the polymer is nylon polymer.

40. The system of claim 39, wherein the nylon polymer is nylon 6,6 polymer.

41 . A method of identifying an end of a nylon polymer casting event, comprising:

anticipating an end of the casting event based on parameters of the event; and

detecting a nitrogen blow event as recited in claim 1 , wherein the detection of the nitrogen blow confirms the end of the casting event.

42. A method of ending a nylon polymer casting event, comprising: anticipating an end of the casting event based on parameters of the event;

detecting a nitrogen blow event as recited in claim 1 ; and

closing an autoclave extrusion valve coupled to the dieplate in response to detection of the nitrogen blow event.

Description:
DETECTING NITROGEN BLOW EVENT DURING POLYMERIZATION PROCESS

TECHNICAL FIELD The present disclosure relates to systems and methods for detecting and typically arresting nitrogen blow events during polymer casting processes using sound information.

BACKGROUND

In a process for producing nylon polymer, an autoclave pressure profile is used to move molten nylon polymer out of the autoclave and extrude it through a dieplate. Following extrusion, the molten nylon polymer is quenched in cooling water and cut into flakes or pellets. The pressure profile for extrusion can be maintained using compressed nitrogen gas within the autoclave. Typical autoclave pressures can be from 3 and 9 barA.

A "nitrogen blow" event will occur if the nitrogen gas is allowed to escape through the dieplate at the end of the cast (i.e. production process), or due to a significant unexpected gap in the flow of molten nylon polymer. This event, if allowed to go unchecked for a period of time, can be undesirable and unsafe. Thus, the autoclave extrusion valve should be quickly closed in order to quickly stop or prevent the nitrogen blow.

Traditionally, an operator has been stationed at the casting line and assigned to monitor the nylon polymer production process. Upon perceiving the commencement of a nitrogen blow, the operator quickly activates the switch to shut the autoclave extrusion valve. In order to act quickly upon perceiving the beginning of a nitrogen blow, the operator should not be distracted by engaging in other activities while monitoring the process. Thus, the cost in time and manpower for the single purpose of monitoring the process and operating the autoclave extrusion valve is high.

Moreover, even when paying strict attention to the process, an operator may be only marginally successful in closing the autoclave extrusion valve in time to optimally avoid or minimize a nitrogen blow. This is due to the swiftness of the event compared to the reaction time of the operator.

SUMMARY The disclosures herein relate to methods involving production of polymer and problematic issues associated therewith. In one aspect, the disclosures include methods of detecting a nitrogen blow event during a polymer fabrication process, such as a nylon or nylon 6,6 polymer fabrication process. In certain embodiments, such methods may generally include: 1 ) receiving with a microphone, sound information resulting from nitrogen gas passing through a dieplate that extrudes molten polymer; 2) converting the sound information into an electronic signal; and 3) evaluating the electronic signal with a logic controller at a frequency of at least once every 0.1 seconds.

In addition, methods of arresting a nitrogen blow event during a polymer fabrication process are also disclosed herein. In some aspects, such methods may include detecting a nitrogen blow event as recited herein, and automatically closing an autoclave extrusion valve through which nitrogen gas is passing in response to detection of the nitrogen blow.

Embodiments of nitrogen blow detection systems are likewise disclosed. One exemplary embodiment of such a system may include: 1 ) a microphone configured to detect sound information resulting from nitrogen gas passing through a dieplate that extrudes molten polymer; 2) a converter module electronically coupled to the microphone and configured to receive sound information from the microphone and convert the information into an electronic signal; and 3) a logic controller electronically coupled to the converter module and configured to evaluate a signal from the converter module at a frequency of at least once every 0.1 seconds. Also disclosed herein are embodiments of a system for arresting a nitrogen blow occurring during a polymer production process. In one aspect, such a system may include a collection of components assembled and configured as recited herein to detect a nitrogen blow event, and further an arrangement where the logic controller of such a system is electronically coupled to an autoclave extrusion valve though which nitrogen gas passes. In such an arrangement, the logic controller can be configured to signal the automatic closure the autoclave extrusion valve upon detection of a signal indicating occurrence of a nitrogen blow.

The present disclosures additionally set forth embodiments of methods of identifying an end of a nylon polymer casting event. Such an event may include anticipating an end of the casting event based on parameters of the event, and detecting a nitrogen blow event occurring during the casting. In such cases, detection of the nitrogen blow confirms the end of the casting event.

In yet other embodiments, methods of ending a nylon polymer casting event are set forth. In one embodiment such a method may include: 1 ) anticipating an end of the casting event based on parameters of the event; 2) detecting a nitrogen blow event as recited herein; and 3) closing an autoclave extrusion valve coupled to the dieplate in response to detection of the nitrogen blow event.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of apparatus and logic components making up a system for detecting a nitrogen blow event during a polymer production process in accordance with an embodiment of the present invention;

FIG. 2 is a partial perspective view of an embodiment of a directional sound assembly for use in enhancing the directional sensitivity of a microphone used to obtain sound information from a polymer production process according to an embodiment of the present invention;

FIG. 3 is a side view of the assembly of FIG. 2 with an outer insulated housing in a retracted position; FIG. 4 is a side view of the assembly of FIG. 3 with the outer insulated housing in a forward position;

FIG. 5 is a graphical representation of sound information obtained during a typical nitrogen blow event associated with one autoclave;

FIG. 6 is a graphical representation of sound information obtained from the system located at the autoclave of FIG. 5, which sound information was produced from a nitrogen blow occurring at an adjacent autoclave; and

FIG. 7 is a graphical representation depicting nitrogen blow events, valve opening and closing events, and microphone level values in accordance with examples of the present disclosure.

It should be noted that the figures are merely exemplary of several embodiments of the present invention and no limitations on the scope of the present invention are intended thereby. DETAILED DESCRIPTION

Although the following detailed description contains many specifics for the purpose of illustration, a person of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the herein disclosed embodiments.

Accordingly, the following embodiments are set forth without any loss of generality to, and without imposing limitations upon any claimed invention. Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, as this may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

As used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a microphone" includes a plurality of microphones, and reference to an autoclave includes a plurality of autoclaves.

In this disclosure, "comprises," "comprising," "containing" and "having" and the like can have the meaning ascribed to them in U.S. Patent law and can mean "includes," "including," and the like, and are generally interpreted to be open ended terms. The term "consisting of" is a closed term, and includes only the devices, methods, compositions, components, structures, steps, or the like specifically listed, and that which is in accordance with U.S. Patent law.

"Consisting essentially of or "consists essentially" or the like, when applied to devices, methods, compositions, components, structures, steps, or the like encompassed by the present disclosure, refers to elements like those disclosed herein, but which may contain additional structural groups, composition components, method steps, etc. Such additional devices, methods, compositions, components, structures, steps, or the like, etc., however, do not materially affect the basic and novel characteristic(s) of the devices, compositions, methods, etc., compared to those of the corresponding devices, compositions, methods, etc., disclosed herein. In further detail, "consisting essentially of or "consists essentially" or the like, when applied to devices, methods, compositions, components, structures, steps, or the like encompassed by the present disclosure have the meaning ascribed in U.S. Patent law and the term is open- ended, allowing for the presence of more than that which is recited so long as basic or novel characteristics of that which is recited is not changed by the presence of more than that which is recited, but excludes prior art embodiments. When using an open ended term, like "comprising" or "including," it is understood that direct support should be afforded also to "consisting essentially of language as well as "consisting of language as if stated explicitly.

As used herein, "nitrogen blow" and "nitrogen blow event" refer to an occurrence where nitrogen gas blows or vents out of a dieplate through which molten polymer, such as nylon 6,6 polymer, is extruded. Often, but not always, a nitrogen blow may indicate or signal the end of a casting event in which the polymer is being produced. Also, it is noted that the term "nitrogen blow" also includes blow events that may occur as a result of nitrogen and/or even other gases that may be present. Thus, the nitrogen blow in some cases may caused by a void in the molten polymer, which is typically nitrogen, but can also include or be steam or degradation gas. Thus, it is not important that the gas be nitrogen for the systems and methods of the present case to be effective, and the term "nitrogen blow" generically includes nitrogen and/or other gaseous blow events that can occur.

As used herein, "sound information" and the like refer to the acoustic properties of sound, such as pitch, frequency, and volume (i.e. pressure or level). Such properties, including their measurement are well known.

The term "apparatus" and "system" can be used interchangeably herein. It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range includes "about 'x' to about 'y'". To illustrate, a concentration range of "about 0.1 % to about 5%" should be interpreted to include not only the explicitly recited concentration of about 0.1 wt% to about 5 wt%, but also include individual concentrations (e.g., 1 %, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1 %, 2.2%, 3.3%, and 4.4%) within the indicated range. In an

embodiment, the term "about" can include traditional rounding according to significant figures of the numerical value. In addition, the phrase "about 'x' to 'y " includes "about 'x' to about 'y'".

The term "about" as used herein, when referring to a numerical value or range, allows for a degree of variability in the value or range, for example, within 10%, or, in one aspect within 5%, of a stated value or of a stated limit of a range.

In addition, where features or aspects of the disclosure are described in terms of a list or a Markush group, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group. For example, if X is described as selected from the group consisting of bromine, chlorine, and iodine, claims for X being bromine and claims for X being bromine and chlorine are fully described as if listed individually. For example, where features or aspects of the disclosure are described in terms of such lists, those skilled in the art will recognize that the disclosure is also thereby described in terms of any combination of individual members or subgroups of members of list or Markush group. Thus, if X is described as selected from the group consisting of bromine, chlorine, and iodine, and Y is described as selected from the group consisting of methyl, ethyl, and propyl, claims for X being bromine and Y being methyl are fully described and supported.

As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features that may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order that is logically possible.

Embodiments of the present disclosure integrate with a polymer, e.g., nylon 6,6, production process in order to provide a greater degree of automation and significantly reduce, or eliminate, the requirement of operator assistance in order to run the process. Consequently, a number of advantages are provided including cost savings and efficiency, as well as improved safety, by elimination or at least reduction of, time required by an operator to be present in the vicinity of the production equipment.

Referring now to FIG. 1 , a schematic view of an embodiment of a system 10 for detecting and/or arresting a nitrogen blow event during a nylon polymer production process is shown. By example, nylon polymerization processes will be discussed herein, and more specifically, nylon 6,6. That being stated, it is understood that when nylon polymerization is discussed, the principles described herein can relate to not only nylon 6,6, but other nylon polymers, polyamide polymers, or even other polymers that are not related to nylon as though fully described herein with respect to any particular polymer of interest where extrusion and a gaseous blow event may occur. Thus, in the process, an autoclave 20 processes materials into molten nylon polymer. In the example, shown, the autoclave includes an agitator or auger 25, though autoclaves without agitators or augers can likewise be used. At a specified point in the process, the autoclave is pressurized with nitrogen gas and an autoclave extrusion valve 30 is opened to allow the molten nylon to exit the autoclave under pressure from the nitrogen gas. After moving through the autoclave extrusion valve, the molten nylon continues to be pushed through the system until it reaches an extrusion dieplate 40, where it is extruded through the dieplate (e.g., cast) into strands and pieces which are then quenched in cooling water and cut into flakes or pellets.

As the autoclave empties and the molten polymer supplied to the dieplate becomes exhausted, there comes a point where the pressure of the nitrogen gas in the system may overcome the remaining molten nylon polymer and cause the nitrogen gas to blow out of the dieplate. This event can be violent releasing with significant force and can cause droplets of molten nylon polymer to splatter or spray uncontrolled into the environment surrounding the dieplate. As previously mentioned, this event is undesirable and can even be dangerous to any operators in the immediate area. It also causes a significant mess that can require cleaning of equipment, including surrounding equipment.

Because of the sounds that are made when nitrogen gas begins exiting the dieplate, it is possible to know when a nitrogen blow event is beginning. Referring again to FIG. 1 , a microphone 50 is shown for receiving sound information resulting from nitrogen gas passing through the dieplate 40. The microphone can be any microphone that is capable of sufficiently receiving the desired sound information.

In one embodiment, the microphone 50 may be a capacitor microphone. Such microphones are known, for example the Bruel and Kjaer type 4189 microphones, which has a sensitivity of 50 mV/Pa. Other microphones can also be selected for use. Typical capacitor microphones include a metal housing and a metal membrane as a measuring device. Underneath the membrane is a back- plate. Sound information, such as sound waves will be received by the microphone and cause the metal membrane to vibrate. These vibrations cause a variation in distance between the membrane and back-plate. The combination of membrane and back-plate forms the capacitor. Vibration of the membrane results in a varying dielectric value between membrane and back-plate. This variation in dielectric value is expressed as variation of the capacitor capacity. Thus, the incoming sound information and the properties thereof are measured as a function of changing capacity values in the capacitor. While capacity depends on the diameter of the membrane, in some embodiments, the diameter can be in the range of 2 to 60 pF (i.e. pico farad).

A converter module 65 is electronically coupled to the microphone 50 and is configured to receive sound information from the microphone and convert it into an electronic signal. The converter module can include a preamplifier 60 and a sound level monitor 70. In the example shown in FIG. 1 , the preamplifier is integrated into the microphone and the sound level monitor is shown as a separate module. That being stated, this is just one exemplary example of a possible arrangement. Others can be used as would be appreciated by one skilled in the art after considering the present disclosure. Thus, in some embodiments, the preamplifier may be an integral unit with the microphone. The preamplifier generally functions to convert or change sound information or signal received from the microphone from a high impedance value to a low impedance value. For example, the impedance value of the capacitor microphone may be about 1 G Ω and the preamplifier may lower the value to about 50 Ω or less. One example of such a preamplifier is the Bruel and Kjaer type 2671 model. The B&K microphone preamplifier type 2671 has a sensitivity of 1 mV/mV. The actual output signal is a constant 12V DC with the microphone signal superposed on this 12V DC.

As mentioned, the sound level monitor 70 can be part of the converter module 65 and can be electronically coupled to the preamplifier 60. In some specific embodiments, these two devices may be coupled with a coaxial cable. The sound level monitor can perform at least three basic operations on the signal received from the preamplifier. First, the sound level monitor filters the signal received. It has been found that a nitrogen blow produces sounds primarily having a frequency in the range of 15 to 40 kHz. Therefore, in one aspect, the sound level monitor may be configured to filter out substantially all sound information with frequencies falling outside those indicative of nitrogen gas passing through the dieplate 40. In one embodiment the sound level monitor may filter out all, or substantially all, frequencies falling outside the range of from about 15 kHz to about 40 kHz.

In addition to filtering, the sound level monitor 70 can be configured to perform the function of linearizing the signal. This function may be accomplished using, for example, a logarithmic mean square (LMS) detector component (not shown) within the sound level monitor. Other mechanisms or components capable of linearizing the signal may be used as well. The sound level monitor additionally can be configured to standardize the signal prior to its output. In some aspects, the signal may be standardized into a standard 4-20 mA signal.

Referring still to FIG. 1 , a logic controller 90 electronically coupled to the converter module 65 is shown, which may be in some embodiments coupled to sound level monitor 70 directly. The logic controller is configured to evaluate a signal from the converter module. In some embodiments, the logic controller may also be electronically coupled to, or in communication with (either directly or indirectly) the autoclave extrusion valve 30. Upon perceiving a signal from the converter unit that indicates possible commencement of a nitrogen blow event, the logic controller can signal the autoclave extrusion valve to close. The closing of the autoclave extrusion valve blocks the pathway of the nitrogen gas to the dieplate 40 and therefore stops or otherwise arrests the nitrogen blow event, or at least the full nitrogen blow event.

Due to the speed at which a nitrogen blow event occurs (often within 1 second or less), it is beneficial to have the logic controller 90 evaluate, sample, receive, or otherwise perceive, the signal from the converter module 65 with a high frequency so that an autoclave extrusion valve closure signal or command may be sent and received by the autoclave extrusion valve 30 and close it in time to reduce, prevent, or otherwise minimize the nitrogen blow event. In some aspects, the logic controller may evaluate the signal from the converter module at a frequency (i.e. interval) of at least once every 0.1 seconds (i.e. one tenth of a second). In another aspect, the frequency or interval may be between every 0.1 seconds and every 0.001 seconds. In a further aspect, the frequency or interval may be between every 0.08 seconds and 0.02 seconds. In a further aspect, the frequency or interval may be about every 0.04 seconds.

The nylon polymer casting or fabrication process is controlled by a process control system or unit (i.e. process controller) 80. This unit or system controls the basic operations of the autoclave 20 and other process components. One example of such a unit or system is the TDC3000 DCS made by Honeyville. In some cases the process control system may fully or partially include or integrate the nitrogen blow detection system of the present disclosure. In other

configurations, the nitrogen blow detection system may be separate from the process control system.

In the case where the process control system 80 includes or integrates the nitrogen blow detection system, the logic controller 90 may control or

communicate (i.e. signal) the autoclave extrusion valve 30 through the process control system. However, in other cases, the logic controller may control or communicate with the autoclave extrusion valve directly.

As shown in FIG. 1 , the process control unit 80 may in some

embodiments, also be electronically coupled to the converter module 65 and further to the sound level monitor 70 directly as shown. However, even when this is the case, the process control system or unit generally does not or cannot evaluate, process, perceive, or monitor, the signal from the sound level monitor at an interval sufficient to adequately close the autoclave extrusion valve in time to satisfactorily or optimally arrest a nitrogen blow (usually only about once per second). However, when coupled to the converter module, the process controller can act as a backup or supplement to the logic controller 90. In this way if the logic controller were to fail, the process control unit may still close the autoclave extrusion valve when needed. In embodiments where the process control unit can be made to communicate more rapidly with the converter module, it may be that the logic controller is not used.

When the autoclave extrusion valve 30 is closed, the nitrogen blow is prevented or arrested. Due to the speed and efficiency of the present systems, the autoclave extrusion valve through which nitrogen gas is passing may be automatically closed in less than 1 second from commencement of the nitrogen blow event. In some aspects, closure of the valve may occur between 0.1 and 0.6 seconds from commencement of the nitrogen blow event. In further aspects, the valve may be closed in about 0.54 seconds or less. The closure of the extrusion valve can be by the use of an electro-mechanical device 95, such as a solenoid or other similar device, which can be adapted to receive the signal from the logical controller and shut down the autoclave extrusion valve upon receiving the signal from the logic controller to do so. Referring now to FIGS.2-4, a directional sound assembly 100 is shown in accordance with one aspect of the disclosure. In some embodiments, the microphone may be directionally sensitive in order to better focus on sound coming from the dieplate. In an effort to further boost or enhance the directionality of the microphone and to further dampen or eliminate sounds from the

surrounding environment, such as from other batch autoclaves operating nearby, an assembly as shown in FIG. 2 may be used.

As shown, microphone 50 is resident in a first directional housing 140 which is configured to direct sound to the microphone. The first directional housing shown is tubular in shape. However, a number of other shapes that enhance or facilitate the directionality of sound receipt by the microphone are suitable. A wide range to suitably durable materials may be used for the first directional housing, such as plastic materials, including for example PVC. In one aspect, materials may be selected because they are inexpensive. Additionally, material may be selected for their specific sound dampening properties.

An outer housing 1 10 and a sound insulating layer 120 may be optionally included in the assembly 100. In use, the directional sound assembly is located near the dieplate and pointed with an opening toward it. In order to facilitate positioning of the assembly, support rod 130 may be used. The support rod can be coupled to the first directional housing 140 and extend inside and through the assembly and allow the sound insulating layer and outer housing to rest thereon. Further as shown in FIGS. 3 and 4, the outer housing and/or sound insulating layer can be retracted as needed to address any issues with the assembly, such as facilitating placement or removal of the microphone 50.

Referring now to FIGS. 5 and 6, graphical representations of signals recorded are shown which use the microphones and assemblies of the present disclosure. In FIG. 5, the sound level of a typical nitrogen blow event is provided from a nylon producing system to which a microphone in accordance with the present disclosures has been assigned. In FIG. 6, the sound level obtained upon occurrence of a nitrogen blow event at an adjacent system is shown. As can be seen, the sound levels recorded for the adjacent system are significantly different, and therefore, the systems and methods described herein can be programmed to distinguish between these profiles. As such, multiple systems may be employed with adjacent autoclaves also in operation.

It should be noted that connection and wiring of the components and modules of the present system should be done with care to ensure that the likelihood of any phantom positive signal or other signal interference is minimized or prevented. In one example, the microphone may be grounded on only one side of the line connecting the components from the microphone to the logic controller, and in particular between the microphone and sound level monitor. By such a grounding configuration, the occurrence of false positive signals may be reduced.

In some cases, the nitrogen blow event may be unexpected. In other cases, the nitrogen blow event may be anticipated when coming to the end of the nylon polymer batch or casting (i.e. producing) event. In the latter case, it is possible to utilize the nitrogen blow detecting system and methods of the present disclosure to positively identify an end of casting or processing event, and for ending the event itself. In such cases, the parameters of the event are monitored, and in some cases by the process control system 80. As the event reaches its late and final stages, the detection of the beginning of a nitrogen blow can then be used to positively identify the end of the batch and in some cases to terminate the function of the process equipment and thus end the event.

In order to further improve accuracy of detection and minimize error, particularly when utilizing the nitrogen blow detection system to indicate an end of batch or casting event, it may be useful to calibrate the detection system to the environment and equipment that it monitors. Once the microphone is

appropriately placed near the autoclave and other equipment and directed toward the dieplate, initial sound readings can be taken and the information collected. Alarm limits can be set according to these initial readings. Alternatively, alarm limits can be set based on prior knowledge of the casting process in general or in view of a given piece of casting equipment. In one aspect, a general alarm limit may be sound levels of about 90 db or above. EXAMPLE

The following example is put forth so as to provide those of ordinary skill in the art with a description of a process for detecting and/or arresting a nitrogen blow event in accordance with the present disclosures and as described herein. No limitation to specific steps, equipment, materials or values should be inferred thereby as such are merely exemplary.

One embodiment of a sequence of events for operating the nitrogen blow detection and/or arrest systems presently disclosed is as follows:

Prior to start-up of a cast, both the High-High (HH) and High (H) alarm limits for the microphone signal in the process control system are cleared. This prevents activation of the nitrogen blow detection system due to air flowing out of the extrusion valve actuator (air is also used to close the valve, this air is typically released in order to open the valve).

The process control system disables the blow detection enabled signal to the logic controller. As a result, the logic controller has no access to the extrusion valve control.

Sometime after start of the cast, process controller writes both the HH- alarm limit (e.g. 92 dB) and the H-alarm limit (e.g. 90 dB) to the

microphone signal database point.

At the end of the cast, nitrogen will be released through the dieplate and cause sound in a specific frequency range (e.g. 15 kHz to 40 kHz).

The intensity of the sound is measured and constantly reported to the process controller and the logic controller using an electronic signal (e.g., an analog signal). The signal corresponds with a range of 34 dB to 94 dB. The configuration of the microphone signal in the process controller is such that the extrusion valve will be closed or interlocked if the measured sound-level exceeds the HH-value.

During the last few minutes of the cast, the logic controller or the process controller or both will also close the extrusion valve if the microphone signal exceeds the H-value. FIG. 7 depicts an example graph with real time data of time plotted against sound level. In this example, the gas blow detection limit can be set to be above the normal operating sounds of the casting equipment, but below the level that would be experienced or produced prior to or during a nitrogen blow event.

Additionally, as mentioned, the microphone and sound equipment can be configured to filter out frequencies outside of the 15 kHz to 40 kHz range, which is an exemplary frequency range indicative of nitrogen blow events. In the particular example shown, the extrusion valve is partially closed prior to the nitrogen blow event, as labeled in the FIG. This process is typical for autoclave nylon production. For example, the top-layer of molten polymer inside the autoclave may have rather different properties relative to the rest of the polymer, as the top-layer has often had a greater opportunity to exchange water to the gas atmosphere above. As a result the viscosity of the polymer leaving the dieplate may be rather different than in other parts of the polymer, resulting in abnormally high throughputs for the last 1 -2 minutes of the cast. To prevent issues related to this sudden high throughput, the valve can be partially closed to reduce the throughput. This early partial closing also helps in closing the extrusion valve more quickly upon early detecting of the nitrogen blow event. Thus, at lower valve positions, there is less air in the valve actuator that needs to be vented off to close the valve. As shown in FIG. 7, the actual response to the detected nitrogen blow is demonstrated after the small horizontal portion of the graph related to the extrusion valve output profile.

Although the subject matter has been described in language specific to structural features and/or operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features and operations described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the described technology.