ALTERNATIVE APPARATUSES AND METHODS TO DETERMINE CHEMICAL INJECTION DOSE USING A POSITIVE DISPLACEMENT PUMP

Abstract

An alternative method and apparatus for determining a chemical injection dose to a fluid system is provided. The method and apparatus uses a monitor and control system processor connected to a pressure sensor and a positive displacement pump. The monitor and control system processor determines a stroke of a positive displacement pump by measuring a low-pressure on the suction side of the pump and equates each low pressure point with a pump stroke (or the discharge of a piston volume for dual stroke pumps). The monitor and control system processor calculates the dose by multiplying the number of low-pressure points with the volume of the discharge.

Description

BACKGROUND

The technology of the present application relates to measuring a dose rate and, more particularly, to alternative apparatuses and methods to determine a dose rate using positive displacement pump strokes.

Conventionally, many chemical injection systems require knowing a dose rate for any particular chemical being injected into a fluid system. Hydrocarbon wells, for example, add different chemicals to the wells to facilitate drilling and extraction, such as anti-foaming agents and the like. The chemical injection systems are typically provided with a source tank for any chemical that is injected to the system. The amount or chemicals injected, or the dose rate, is often determined by measuring a change in the fluid volume of the source tank that can be correlated to the dose rate of the chemical.

For a variety of reasons, measuring the dose rate for a chemical injection system using liquid level in the source tank is difficult. The injection systems often have unconventionally shaped source tanks, which makes conversion from liquid level to volume error prone. Also, the dose rates are often low values making changes in level or the like difficult to detect without one or more precise level sensors, which can be expensive. Additionally, temperature changes have an adverse impact on the accuracy and precision of liquid level measurement.

Other means to control dose rates include using flow sensors to identify the volume of chemicals over a particular timeframe, counting pump strokes for a pump with a known flow volume, or the like. These other means to measure dose rate are problematic also. Again, the generally low flow rates and volumes of chemical injection require sophisticated, and expensive, equipment. Also, many injection systems are not capable of measuring pump strokes without providing additional sensors, such as proximity sensors, and the like. In other words, conventionally, it is difficult to measure the stroke of a positive displacement pump that is not already configured to identify a pump stroke for most chemical injection systems.

Thus, against this background, it would be desirable to provide alternative apparatuses and methods to determine chemical injection dose rate using a positive displacement pump without the need for additional equipment or sensors beyond the sensors provided by conventional chemical injection systems.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary, and the foregoing Background, is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter.

In some aspects of the technology, an alternative method and apparatus for determining a chemical injection dose to a fluid system is proposed. The alternative method and apparatus comprises a monitor and control system that is in electrical communication with a pressure sensor and a positive displacement pump. The monitor and control system determines a stroke of a positive displacement pump by measuring a low-pressure signal on the suction side of the positive displacement pump and equates each low pressure point with a pump stroke (or the discharge of a piston volume for dual stroke pumps. The monitor and control system determines dose by multiplying the number of low-pressure points with the volume of the discharge of the positive displacement pump for each full stroke of the pump.

These and other aspects of the present system and method will be apparent after consideration of the Detailed Description and Figures herein.

BRIEF DESCRIPTION OF DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

FIG. 1 is an illustration of a chemical injection system consistent with the technology of the present application.

FIG. 2 is an exemplary pressure wave and piston movement graph over time illustrating concepts consistent with the technology of the present application.

FIG. 3 an exemplary pressure wave and piston movement graph over time illustrating concepts consistent with the technology of the present application.

FIG. 4 is a schematic flowchart illustrating operations of the chemical injection system consistent with the technology of the present application.

FIG. 5 is a schematic flowchart illustrating operations of the chemical injection system consistent with the technology of the present application.

FIG. 6 is a functional block diagram of a monitor and control system consistent with the technology of the present application.

DETAILED DESCRIPTION

The technology of the present application will now be described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the technology of the present application. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.

The technology of the present application is described with specific reference to chemical injection systems for a single stroke positive displacement pump for a hydrocarbon wellbore. However, the technology described herein may be used with applications other than those specifically described herein. For example, the technology of the present application may be applicable to dual stroke pumps, wastewater treatment, HVAC systems, fracking, other fluid system, or the like. Moreover, the technology of the present application will be described with relation to exemplary embodiments. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Additionally, unless specifically identified otherwise, all embodiments described herein should be considered exemplary.

With reference now to FIG. 1, a chemical injection assembly 100 consistent with the technology of the present application is provided. The chemical injection assembly 100 includes, in no particular order, a source tank 102, containing the chemical to be injected, a pressure sensor 104, such as a pressure transducer as shown, a suction manifold 106, which includes at least a suction check valve 108, a discharge manifold 110, which includes at least a discharge check valve 112, a positive displacement pump 114, and monitor and control system 309 that is electrically coupled to the pressure sensor 104 and, optionally, to the positive displacement pump 114.

The pressure sensor 104 measures the head on the source tank 102, which is typically vented to atmospheric pressure. As such, the pressure sensor 104 is located as close to a bottom 116 of the source tank 102 as possible. As shown, the pressure sensor 104 is in fluid communication with the discharge tubing 118, but the pressure sensor 104 could be in fluid communication with the source tank 102 via a port or conduit (not shown) on a sidewall 120 or bottom wall 122 of the source tank 102. The pressure sensor 104 converts the pressure signal to an electrical signal that is sent to a monitor and control system 309, which is described below.

As can be appreciated, the positive displacement pump 114 includes a piston that strokes in a chamber, not specifically shown in FIG. 1. For a single stroke positive displacement pump 114, the piston movement may, in a first instance, cause a low pressure in the chamber to draw a batch of fluid from the chemical source tank 102 through the suction manifold 106, which causes the suction check valve 108 to open and the discharge check valve 112 to close. The piston subsequently changes direction and pushes the batch of fluid, which is a known volume, out the discharge manifold 110, which causes the suction check valve 108 to close (sometimes referred to as slam) and the discharge check valve 112 to open as the fluid is pushed through the discharge manifold 110 to the downstream fluid system. Although a single stroke positive displacement pump is discussed herein for simplicity, the technology of the present application is applicable to dual stroke positive displacement pumps. The technology of the present application also is applicable to piston pumps, as described above, as well as other types of positive displacement pumps, such as, for example, ones that use screws, diaphragms, gears, roller, vanes, a combination thereof, or the like.

The operation of the stroke of the pump, and the associated following slam of the suction manifold 106 suction check valve 108 (sometimes referred to as “stroke and slam”), causes a pressure wave that is in fluid communication with the pressure sensor 104. The pressure wave causes, among other things, a disruption to the pressure signal that may impact the level determination used by the monitor and control system of the chemical injection assembly 100, which is but one reason why measuring the level in the source tank 102 is sometimes difficult during operation of the chemical injection system. The monitor and control system of the chemical injection assembly 100 may be incorporated with the monitor and control system 309 of the present technology in certain embodiments.

The pressure wave 202 is shown by FIG. 2. The pressure wave 202 is shown as pressure measurements over time. Over the same time period as the pressure wave, a proximity sensor (not shown in the figures) was used to track the piston movement 204 over time for the positive displacement pump 114. The proximity sensor was positioned to detect when the piston was at the discharge end of the chamber, such as is shown by piston position 212, indicating the end of a discharge cycle wherein the chamber is being emptied, and the start of a suction cycle, wherein the chamber is being filled. As can be seen from FIG. 2, the pressure wave 202 has a distinct low pressure point 206 that coincides with the piston position 208 indicative of the piston changing direction and traveling from the discharge side of the chamber toward the suction side of the chamber, and corresponding to a transition from a discharge cycle to a suction cycle. In certain instances, the low pressure point 206 of the pressure wave 202 will be know from pump operations. In other words, the low pressure point 206 may be calibrated by a user after operation of the pump 114 where the low pressure point 20 becomes a knowable value after operation of the pump 11 through one or more pump cycles. At piston position 208, the piston is fully on the discharge side of the chamber, and the chamber is empty. The piston position is tracked moving toward the suction end of the chamber at piston position 210, during which the chamber is filled with fluid. The pressure point 207 coincides with piston position 210 indicative of the piston changing direction and traveling from the suction end of the chamber back toward the discharge end of the chamber, and corresponding to a transition from a suction cycle to a discharge cycle, thus completing one stroke. At piston position 210, the piston is fully on the suction side of the chamber, and the chamber is filled with fluid from the source tank 102. A full stroke of the piston is movement from piston position 208, to piston position 207, and back to piston position 208. Similarly, a full stroke of the piston may be considered movement from piston position 207, to piston position 208, and back to piston position 207. The movement of the piston, and therefore, the stroke of the positive displacement pump 114 coincides with the low pressure point 206 as established by the pressure wave 202. Thus, a full stroke of the positive displacement pump 114 may be measured by the pressure transducer where 1 full stroke is measured for each low pressure point 206. In certain embodiments, the stroke may be identified using high pressure points but, as shown by the exemplary pressure wave 202, the high pressure points are not as distinct as the low pressure points in some instances.

FIG. 3 shows a pressure wave 302 for a dual stroke pump as opposed to a single stroke pump 114 shown in FIG. 2. The pressure wave 302 has two (2) distinct low pressure points 304, 306 as the piston travels from the first end of the chamber, to the second end of the chamber, and back to the first end. The first low pressure point is consistent with a single stroke pump. A two stroke pump (or dual head pump) provides first and second low pressure points 304, 306 as the chamber fills as the piston moves in the first and second directions. Thus, the two low pressure points coincide with two (2) discharges of volume for 1 full stroke of the piston. Similar to the low pressure point 206 above, the low pressure points 304, 306 may be known in advance of operation or discernable by operation of the pump as installed in a system.

With reference to FIG. 4, a methodology 400 is shown for calculating and adjusting the dose rate for chemical injection assembly 100 using a positive displacement pump 114, without a proximity sensor, flow sensor, or secondary vessel. The methodology 400 is performed on a monitor and control system 309 (further described below). The monitor and control system 309 includes at least one input device, such as a graphical user interface employing a touch screen, a data import programming interface, a keyboard, or the like to receive a chamber volume for the positive displacement pump 114, step 402. The chamber volume provides input regarding a volume, or dose, injected into the media system for every pump stroke. Note, the volume may be influenced by the pressure and temperature of the fluid system into which the dose is being injected. In certain embodiments, the volume is input directly from the pump data, and may be imported via an application programming interface. In certain aspects, the volume is input via a user interface. In other aspects, the volume of the source tank 102 can be determined before and after a single (or multiple) pump strokes where the volume of the chamber is the change in volume of the source tank divided by the number of known strokes. The dose at step 410 may be a total volume of the dose, a dose per unit of time, or the like. The low pressure points may, in certain embodiments, be input via the user interface as well, especially if the low pressure points (which may alternatively be known as low pressure thresholds) are determined by operation of one or more pump cycles, where a pump cycle includes piston movement from a full discharge position, to a full suction position, back to a full discharge position (or from a full suction position, to a full discharge position, back to a full suction position).

Next, the monitor and control system receives one or more signals from the pressure sensor 104 indicative of the pressure in the source tank as well as the pressure on the suction side of the positive displacement pump 114, step 404. Generally, the input is a continuous analog input although the pressure sensor may digitize the signal or take samples rather than a continuous reading. If the pressure sensor 104 did not digitize the signal, the monitor and control system 309 digitizes the pressure signal such that each pulse in the resulting digital signal corresponds to a dip in the analog signal that coincides with a stroke of the pump 114, step 405. The monitor and control system 309 determines/counts the number of low-pressure points (206, 304, 306) that have been transformed to digital pulses, step 406. The number of low-pressure points, such as may be determined by a summer or accumulator, is the same as the number of strokes of the pump 114 for a single stroke pump resulting in injection of the fluid from the source tank 102 into the fluid system, such as a hydrocarbon wellbore. As can be appreciated, for a dual stroke pump each low-pressure point is one of the two strokes, but injects a full volume of chemical from the source tank 102, etc. Using the volume per stroke, as determined in step 402, and the number of suction piston strokes, as determined in step 406, the monitor and control system calculates the total dose volume of the fluid from the source tank 102 into the fluid system, step 407. Optionally, the monitor and control system also determines a time frame for the counted number of strokes, step 408. If the time period is monitored, as determined by optional step 408, the dose per period of time may be calculated by the monitor and control system 309 as the monitor and control system 309 causes the positive displacement pump 114 to stroke until the dose is achieved, step 410.

FIG. 5 shows an exemplary dose methodology 500 for the technology as described in the present application. The monitor and control system receives one or more signals to inject a dose of chemicals to a fluid system, such as, for example, a wastewater treatment or hydrocarbon wellbore, step 502. The monitor and control system obtains a volume of the dose, step 504. Obtaining the volume of the dose at step 504 may be input by an operator or the monitor and control system may retrieve the volume of the dose from memory. If input by an operator, the operator may input the data with a graphical user interface, a data port, or the like. Optionally, the monitor and control system may obtain a dose over time. Next, the monitor and control system determines the number of strokes required to deliver the chemical dose (be the data total volume or volume in a determined time) from step 504, step 506. The monitor and control system calculates the number of low-pressure points (206, 304, 306) that are required to provide the required number of strokes for the volume, step 508. Again, the low-pressure points (a.k.a low-pressure threshold) may be input to the monitor and control system based on the low pressure observed during a pump cycle. The monitor and control system next controls the pump to stroke by turning the pump on/off, step 510. The monitor and control system counts the number of low-pressure points (206, 304, 306), step 512, which could be when pressure reaches or decreases below a threshold. The monitor and control system determines if the counted or measured number of low-pressure points is equal to or exceeds the number of low-pressure points calculated in step 510, step 514. If the monitor and control system is equal to or exceeds the low calculated number of low-pressure points, the monitor and control system stops the pump until the next injection signal, step 516. Otherwise, the monitor and control system allows the pump to continue to stroke, step 510. In certain embodiments, the technology of the present application may use a high pressure point rather than a low-pressure point. Thus a boundary pressure point may be a high pressure point or a low pressure point in the pressure wave measured by pressure sensor 104.

When a sufficient volume of chemical has been delivered from the source tank, it may be possible to calibrate the volume of the discharge from the pump for each low-pressure count by calibrating the total volume of chemical discharged from the source tank to the total number of low-pressure points counted over a time frame.

Still with reference to FIG. 5, the monitor and control system receives input from the pressure sensor 104. The pressure sensor 104 may preprocess the signal or the monitor and control system may process the signal to digitize the input for processing. In one example, the pressure wave (202 or 302) may be converted to a square wave where a logic 1 indicates a transition from the pump suction to discharge cycle and a logic 0 indicates other states, or vice versa.

FIG. 6 shows an exemplary embodiment of the monitor and control system 309. The monitor and control system 309 described herein can determine the number of pump strokes and calculate a dose volume (or volume over time) of fluid moved by a positive displacement pump using the input from the pressure sensor 104. The methods and systems disclosed herein provide technical advantages over conventional chemical injection systems because, among other things, it does not require complex and expensive flow sensors, source tank volume measurement, or additional sensors not provided on conventional chemical injection skids, such as proximity sensors. FIG. 6 is a block diagram illustrating an overview of a device (or devices) on which some implementations of the disclosed technology can operate. The monitor and control system 309 can include one or more input devices 320 that provide input to a central processor unit (CPU) 310, which may be a single CPU or a plurality of CPUs, of the monitor and control system 309. CPU 310 is generic and may include, among other things, CPU(s), GPU(s), HPU(s), combinations thereof, and the like). The monitor and control system 309 may include the CPU 310 as well as a monitor and control processor 311 to control operation of the pump based on the control modules and schemes described herein. The input devices 320, such as are common with basic input/output systems (BIOS), maybe data ports that receive data from, among other things, the pressure sensor 104. Other input devices may include, for example, a mouse, keyboard, touchscreen, or the like. The CPUs 310 and input devices 320 may be coupled by hardware devices such as, for example, a PCI bus, a SCSI bus, a combination thereof, and the like. The monitor and control system 309 may further have one or more displays 330 and other input/output devices 340, such as, for example, audio (for alarms and warnings), printers, text messages, short message services, intra or internet connections, cellular or satellite communication, etc.

In some implementations, the monitor and control system 309 also includes a communication device capable of communicating wirelessly or wire-based with a network node. The communication device can communicate with other devices or a server through a network using, for example, TCP/IP protocols.

The CPU 310 includes a memory 350 in the monitor and control system 309 or separate from but operatively connected to monitor and control system 309. The memory 350 includes one or more hardware devices for volatile and non-volatile storage, and can include both read-only and writable memory. In some instances, the memory may be random access memory (RAM), caches, registers, read-only memory (ROM), flash memory, optical and magnetic memory, external drives, and the like. The memory 350 is not a propagating signal divorced from underlying hardware and is non-transitory. Memory 350 includes program memory 360 that stores programs and software, such as an operating system 362, calculation system 364 to calculate or determine, among other things, the number of pump stroke pulses (low pressure points), target strokes per minute, actual strokes per minute, controlled dose rate, and the like (see above), and other application programs or systems 366. The memory 350 includes data memory 370, such as the aforementioned height and weight/mass data, that may be necessary or useful for the calculation system 364 to perform the operations described herein.

The processor may be, for example, a conventional microprocessor such as an Intel microprocessor, Motorola microprocessor, or the like. One of skill in the relevant art will recognize that the terms “machine-readable (storage) medium” or “computer-readable (storage) medium” include any type of device that is accessible by the processor.

The memory is coupled to the processor by, for example, a bus. The memory can include, by way of example but not limitation, random access memory (RAM), such as dynamic RAM (DRAM) and static RAM (SRAM). The memory can be local, remote, or distributed.

The bus also couples the processor to the non-volatile memory and drive unit. The non-volatile memory is often a magnetic floppy or hard disk, a magnetic-optical disk, an optical disk, a read-only memory (ROM), such as a CD-ROM, EPROM, or EEPROM, a magnetic or optical card, or another form of storage for large amounts of data. Some of this data is often written, by a direct memory access process, into memory during execution of software in the computer 500. The non-volatile storage can be local, remote, or distributed. The non-volatile memory is optional because systems can be created with all applicable data available in memory. A typical computer system will usually include at least a processor, memory, and a device (e.g., a bus) coupling the memory to the processor.

Software is typically stored in the non-volatile memory and/or the drive unit. Indeed, for large programs, it may not even be possible to store the entire program in the memory. Nevertheless, it should be understood that for software to run, if necessary, it is moved to a computer readable location appropriate for processing, and for illustrative purposes, that location is referred to as the memory in this paper. Even when software is moved to the memory for execution, the processor will typically make use of hardware registers to store values associated with the software, and local cache that, ideally, serves to speed up execution. As used herein, a software program is assumed to be stored at any known or convenient location (from non-volatile storage to hardware registers) when the software program is referred to as “implemented in a computer-readable medium”. A processor is considered to be “configured to execute a program” when at least one value associated with the program is stored in a register readable by the processor.

The bus also couples the processor to the network interface device. The interface can include one or more of a modem or network interface. It will be appreciated that a modem or network interface can be considered to be part of the computer system. The interface can include an analog modem, isdn modem, cable modem, token ring interface, satellite transmission interface (e.g. “direct PC”), or other interfaces for coupling a computer system to other computer systems. The interface can include one or more input and/or output devices. The I/O devices can include, by way of example but not limitation, a keyboard, a mouse or other pointing device, disk drives, printers, a scanner, and other input and/or output devices, including a display device. The display device can include, by way of example but not limitation, a cathode ray tube (CRT), liquid crystal display (LCD), or some other applicable known or convenient display device. For simplicity, it is assumed that controllers of any devices not depicted reside in the interface.

In operation, the monitor and control system 309 can be controlled by operating system software that includes a file management system, such as a disk operating system. One example of operating system software with associated file management system software is the family of operating systems known as Windows® from Microsoft Corporation of Redmond, Washington, and their associated file management systems. Another example of operating system software with its associated file management system software is the Linux operating system and its associated file management system. The file management system is typically stored in the non-volatile memory and/or drive unit and causes the processor to execute the various acts required by the operating system to input and output data and to store data in the memory, including storing files on the non-volatile memory and/or drive unit.

Some portions of the detailed description may be presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the methods of some embodiments. The required structure for a variety of these systems will appear from the description below. In addition, the techniques are not described with reference to any particular programming language, and various embodiments may, thus, be implemented using a variety of programming languages.

In alternative embodiments, the machine operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine may operate in the capacity of a server or a client machine in a client-server network environment or as a peer machine in a peer-to-peer (or distributed) network environment.

The machine may be a server computer, a client computer, a personal computer (PC), a tablet PC, a laptop computer, a set-top box (STB), a personal digital assistant (PDA), a cellular telephone, an iPhone, a Blackberry, a processor, a telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine.

While the machine-readable medium or machine-readable storage medium is shown in an exemplary embodiment to be a single medium, the term “machine-readable medium” and “machine-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “machine-readable medium” and “machine-readable storage medium” shall also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the presently disclosed technique and innovation.

In general, the routines executed to implement the embodiments of the disclosure, may be implemented as part of an operating system or a specific application, component, program, object, module or sequence of instructions referred to as “computer programs.” The computer programs typically comprise one or more instructions set at various times in various memory and storage devices in a computer, and that, when read and executed by one or more processing units or processors in a computer, cause the computer to perform operations to execute elements involving the various aspects of the disclosure.

Moreover, while embodiments have been described in the context of fully functioning computers and computer systems, those skilled in the art will appreciate that the various embodiments are capable of being distributed as a program product in a variety of forms, and that the disclosure applies equally regardless of the particular type of machine or computer-readable media used to actually affect the distribution.

Further examples of machine-readable storage media, machine-readable media, or computer-readable (storage) media include but are not limited to recordable type media such as volatile and non-volatile memory devices, floppy and other removable disks, hard disk drives, optical disks (e.g., Compact Disk Read-Only Memory (CD ROMS), Digital Versatile Disks, (DVDs), etc.), among others, and transmission type media such as digital and analog communication links.

Although the technology has been described in language that is specific to certain structures and materials, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and materials described. Rather, the specific aspects are described as forms of implementing the claimed invention. Because many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, etc. used in the specification (other than the claims) are understood as modified in all instances by the term “approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should at least be construed in light of the number of recited significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass and provide support for claims that recite any and all subranges or any and all individual values subsumed therein. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all subranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).

Claims

1. A method for calculating a chemical dose for a chemical injection system having a source tank and a positive displacement pump with a piston chamber having a chamber volume, without a proximity sensor, flow sensor, secondary vessel, or pump stroke sensor, the method comprising: receiving the chamber volume for the positive displacement pump at a monitor and control system processor;receiving, at the monitor and control system processor, one or more signals from a pressure sensor wherein the one or more signals are indicative of the pressure in the source tank;processing one or more signals, by the monitor and control system processor, such that a pressure drop below a low-pressure point generates a pump stroke signal;counting, by the monitor and control system processor, each pump stroke signal to obtain a counted number of pump strokes; andcalculating, by the monitor and control system processor, a calculated total dose volume of fluid from the source tank injected into the fluid system by multiplying the received chamber volume by the counted number of pump strokes.

2. The method of claim 1, comprising receiving at the monitor and control system processor a received total dose volume to be delivered by operation of the positive displacement pump.

3. The method of claim 2, comprising turning the positive displacement pump on when the monitor and control system processor receives the total dose volume to be delivered and turning the positive displacement pump off when the calculated total dose volume equals or exceeds the received total dose volume.

4. The method of claim 2, comprising receiving at the monitor and control system processor a time frame for delivery of the received total dose volume such that the monitor and control system processor controls causes the positive displacement pump to deliver the calculated total dose volume of the time frame.

5. The method of claim 2, comprising receiving a temperature signal from a temperature sensor to sense temperature at the monitor and control system processor such that the monitor and control system processor adjusts the received total dose volume to compensate for changes in a temperature sensed by the temperature sensor.

6. The method of claim 1, comprises determining the low-pressure point that generates the pump stroke signal by monitoring a pressure wave over at least one pump stroke to calibrate the low-pressure point.

7. A method for determining that a positive displacement pump has delivered a volume of fluid from a fluid source into a fluid system, comprising: monitoring, by a pressure sensor, a pressure of the fluid source between the fluid source and the suction manifold of a positive displacement pump where the suction manifold comprises at least one suction side check valve;generating, by the pressure sensor, a signal indicative of the pressure;receiving, at a monitor and control system processor, the signal indicative of the pressure from the pressure sensor;determining, by the monitor and control system processor, whether the signal indicative of the pressure indicates that the pressure is equal to a low pressure point;accumulating a sum of low-pressure points, by the monitor and control system processor, indicative that the positive displacement pump has delivered the volume of fluid to the fluid system.

8. The method of claim 7, wherein each low-pressure point of the accumulated sum of low-pressure points equals a single stroke of a single stroke positive displacement pump.

9. The method of claim 7, wherein each low-pressure point of the accumulated sum equals the delivery of the volume of fluid and equals ½ of a single stroke of a dual stroke positive displacement pump.

10. The method of claim 7, wherein generating the signal indicative of the pressure by the pressure sensor comprises digitizing the signal indicative of the pressure by the pressure sensor.

11. The method of claim 7, comprising transmitting the signal indicative of the pressure from the pressure sensor to the monitor and control processor.

12. The method of claim 7, wherein the monitor and control system processor digitizes the signal indicative of the pressure received from the pressure sensor.

13. The method of claim 7, comprising receiving a temperature signal from a temperature sensor to sense temperature at the monitor and control system processor such that the monitor and control system processor adjusts the volume of fluid delivered to compensate for changes in the sensed temperature.

14. A system for delivering a chemical dose from a chemical source tank to a fluid system, without a flow sensor, proximity sensor, or measuring a level change in the chemical source tank, comprising: a chemical source tank, the chemical source tank having one or more chemicals to be injected to the fluid system;a positive displacement pump having a suction manifold and a discharge manifold, the suction manifold of the positive displacement pump being in fluid communication with the chemical source tank and the discharge manifold being in fluid communication with the fluid system, the positive displacement pump being configured to inject a chemical dose;a pressure sensor to sense a pressure of the chemical source tank, the pressure senor being in fluid communication with the chemical source tank and located between the chemical source tank and the suction manifold; anda monitor and control system processor operationally coupled to the pressure sensor to receive signals from the pressure sensor indicative of a pressure wave between the suction manifold and the chemical source tank when the positive displacement pump is in a suction cycle, wherein the monitor and control system processor counts a stroke of the positive displacement pump by counting a low-pressure point generated by the pressure wave, wherein the monitor and control system processor can determine the chemical dose delivered by multiplying a volume of chemical delivered multiplied by the counted low-pressure points.

15. The system of claim 14, wherein the positive displacement pump is a single stroke positive displacement pump and each low-pressure point counts as a single pump stroke.

16. The system of claim 14, wherein the positive displacement pump is a dual stroke positive displacement pump and two (2) low-pressure points counts as a single full pump stroke.

17. The system of claim 14, wherein the monitor and control system processor is operationally coupled to the positive displacement pump to turn on the positive displacement pump to inject the chemical dose to the fluid system and to turn off the positive displacement pump when the positive displacement pump has injected the chemical dose.

18. The system of claim 14, wherein the monitor and control system processor calibrates the low-pressure threshold to count the low-pressure point based on monitoring the low-pressure points of the pressure wave during one or more cycles of the positive displacement pump.

19. The system of claim 17, comprising a chemical source tank level system wherein the chemical source tank level system is not used to determine the chemical dose.