mud pump stroke sensor quotation

The Magneto® Pump Stroke Sensor is the latest new product from ASD Holdings (Advanced Sensor Design). ASD has successfully introduced unique products for the Oil & Gas Industry for over a decade. In this newest creation we find that the Magneto® Pump Stroke Sensor has been patented by Advanced Sensor Design. It is the world’s first pump stroke sensor that is mounted to the outside housing of the rig pump. It is mounted and stays in place by the use of a heavy duty magnet. The Magneto PSS is completely capable of detecting and counting Oil Rig “mud pump piston strokes” without having to make or be in contact with the pistons.

It is no longer a requirement to open the covers of the Oil Rig mud pumps to install a C-clamp style micro switch with a metal whisker. (Note picture below labeled C-clamp style micro switch) No longer is it necessary to bore a hole through the pump housing in order to get a proximity switch close enough to a piston to count actual strokes. (Note picture below labeled Cable going through pump housing) The Magneto® Pump Stroke Sensor is simple to install and easy to monitor!

The magnetic base of the Magneto® PSS makes it totally different than anything available in the marketplace today relative to its form and fit. However, that is not its only outstanding feature. Advanced Sensor Design is using “State of the Art” electronic circuitry that has the ability to give the end user (Oil Rig Mud Pump Operator) an On/Off switch type electrical output. Just like what the conventional mud pump sensors emit today. The obvious benefit to the oil rig is that No Special accommodations to their Data Acquisition Systems are required.

Our pump stroke counter systems (CPS101 Series) measure the stroke rate and number of strokes on mud pumps. The oilfield pump stroke system is user-friendly and reliable and is configurable to measure up to three mud pumps at once. Our digital pump stroke counter systems are manufactured here in the U.S. by Crown Oilfield Instrumentation, and Crown’s Pump Stroke Counter provides easy monitoring of strokes per minute on multiple mud pumps. Each mud pumps’s stroke rate can be selected individually and the display is updated regularly for accurate monitoring. LCD displays indicate both pumps strokes per minute and the total number of strokes. Located at the bottom of the panel, push buttons provide easy operation and reseting of each pump. When you need to accurately monitor and maintain the amount of mud being pumped, you can trust Crown’s oilfield stroke counters.

Crown"s One Pump Stroke Counter System monitors and displays strokes per minute and total stokes and has everything you need to monitor one mud pump. Encased in a stainless steel box, the LCD screens are easy to view at a distance, and with buttons mounted on the face place, this system is easy to reset as needed. With a low power, low voltage lithium battery, this system is self-contained and intrinsically safe, with a operational life of 5 years. The Crown One Pump Stroke Counter system is designed to work in the harshest industry conditions and is waterproof and resistant to excessive rig vibrations. With everything ready-to-use right out of the box, this system will get you counting mud pump flow rate quickly and efficiently. Here"s what you"ll get in the one pump stroke counter system:

Made in the US, the Crown One Pump Stroke Counter system is powered by a 3.6 Type D lithium battery, with no external power supply needed. Because it is a self-contained system, the CPS101-2 is intrinsically safe. When the system is not in use it will go into a null state, saving battery power and the life of the LCD screens. Each Screen displays either strokes per minute (0-240 SPM) or total strokes (0-9999).

Crown"s limit switch assembly can be mounted near the mud pump piston with the easy-to-use c-clamp. The stainless steel rod can be bent to reach the piston easily,  making the CPS101-2 one pump stroke counter system mountable in optimal proximity to the pump piston. The cable connecting the limit switch assembly to the stroke counter is made of the most durable materials to give you the best possible stroke counter on the market.

Need more information about our stroke counter systems? Check out our Stroke Counter Page or our Blog. And, if you only need one of the components in this system, give us a call. We"re more than happy to get you exactly what you need.

1.The pumping sensor can be fixed to the mud pump head by the bracket, or the appropriate part of the turntable, and the closest distance between the position of the sensing surface of the measured object and the end surface of the sensor is within 30 mm. (According to the influence of the use environment, the rated working distance is generally taken. 80%), plus the working voltage, when the end of the inductive sports sensor is close, the indicator light is on; when away from the sensor, the indicator is off.

2.The turntable speed sensor can be fixed to the appropriate part of the drive shaft of the turntable with the bracket. It should be convenient to install and repair. The model of the drill is selected. A piece of iron with a length and width of 30mm is welded on the shaft of the drive shaft or the airbag clutch. The position of the end face should be close to the end face of the sensor. Adjust the fixing nut of the sensor so that the distance between the iron sensor is within the effective range of the working distance.

The Two-pump Digital Stroke Rate Meter monitors and displays the Rate and Total Strokes of up to two individual pumps simultaneously. The unit continually displays, on large easy to read, low power LCD displays, RPM, TOTAL ACCUMULATED STROKES (0-9999 total strokes) and STROKE RATE (8-350 strokes per minute) for each pump. The unit is internally powered by a battery source having an operational life of 3 years.

At Matherne Instrumentation, we"re proud to provide both our two-pump and three-pump stroke counters to companies and oilfield operators across the states of Texas, Louisiana, North Dakota, and Pennsylvania. While our offices are based in Odessa, TX; Lafayette, LA; and Houma, LA, we"re proud to serve those across the cities of Midland, TX; Houston, TX; Williston, ND; and Pittsburgh, PA. To learn more or for a quote, please feel free to give us a call today!

The HDI 2100 Pump Stroke Counter is an intrinsically safe, certified, solid-state electronic stroke counter primarily used for monitoring mud pumps. Found most commonly within the HDI 9000 Choke Console System, the HDI 2100 monitors and displays the total accumulated mud pump strokes and the stroke rate of up to 4 individual mud pumps simultaneously. The stroke rate for each mud pump can be individually selected for display and is updated every second. Once installed, there is virtually no maintenance or calibration required. The quartz crystal oscillator provides high precision counts with no drift. The stainless steel case is completely sealed and features stainless steel piezo switches for long life. The entire package is constructed to operate in harsh environments and high vibration conditions encountered in land and offshore drilling. All HDI Gauges provide safety, accuracy, reliability, and low maintenance for the user.

Sales and services for weight indicators, electronic weight indicators, cement recorders, six inch gauges, cylinders, torque assemblies, line pull assemblies, 1502 assemblies, wireline gauges and cylinders, depthometers, electronic depth systems, counters, diaphragms, auto drilling systems, rotary torque systems, and pump stroke counters.

The CNPS-ML-B11 drilling fluid density sensor is a single crystal silicon resonant density sensor for measuring the density of drilling fluid. The sensor adopts EJA118W, a diaphragm-sealed differential pressure transmitter imported from Japan, which has the advantages of high measurement accuracy, stable performance, and good repeatability. The outer mounting bracket is made of stainless steel, and it is corrosion-resistant and has a long service life. The base is detachably attached with a long rod, which can be adjusted according to the depth of the mud. It is an important sensor for oil and gas exploration work, which can be applied to various harsh environments such as oilfields.

Battery and charger used for the transmission box of wireless sensors Battery and charger is used for the transmission box of  all the wireless sensors .

wireless pump stroke sensor/ Wireless Rotary Speed (RPM) for mud logging unit The pump stroke sensor is used to measure the number of piston movements per minute of the mud pump, calculate the inlet flow according to the input single pump volume, pump efficiency and other parameters, calculate the late arrival time and other derived parameters.

Wireless draw work sensor for mud logging unit Wireless draw work sensor used to measure the depth of the well, the time of drilling, the position of the drill bit, the height of the hook, the speed and the direction of motion.

Wireless electric torque sensor  for mud logging unit The sensor is designed to measure the torque of rotary table. As a result, the operating state of drilling rig and bit can be also reflected. Based on the principle of Hall Effect, while the torque is changed, the supply electric current is also changed, which is used to drive rotary table.

Wireless hydrogen sulfide (H2S) sensor for mud logging unit Wireless hydrogen sulfide sensor is used to measure H2S gas concentration in the environment .

Researchers have shown that mud pulse telemetry technologies have gained exploration and drilling application advantages by providing cost-effective real-time data transmission in closed-loop drilling operations. Given the inherited mud pulse operation difficulties, there have been numerous communication channel efforts to improve data rate speed and transmission distance in LWD operations. As discussed in “MPT systems signal impairments”, mud pulse signal pulse transmissions are subjected to mud pump noise signals, signal attenuation and dispersion, downhole random (electrical) noises, signal echoes and reflections, drillstring rock formation and gas effects, that demand complex surface signal detection and extraction processes. A number of enhanced signal processing techniques and methods to signal coding and decoding, data compression, noise cancellation and channel equalization have led to improved MPT performance in tests and field applications. This section discusses signal-processing techniques to minimize or eliminate signal impairments on mud pulse telemetry system.

At early stages of mud pulse telemetry applications, matched filter demonstrated the ability to detect mud pulse signals in the presence of simulated or real noise. Matched filter method eliminated the mud noise effects by calculating the self-correlation coefficients of received signal mixed with noise (Marsh et al. 1988). Sharp cutoff low-pass filter was proposed to remove mud pump high frequencies and improve surface signal detection. However, matched filter method was appropriate only for limited single frequency signal modulated by frequency-shift keying (FSK) with low transmission efficiency and could not work for frequency band signals modulated by phase shift keying (PSK) (Shen et al. 2013a).

In processing noise-contaminated mud pulse signals, longer vanishing moments are used, but takes longer time for wavelet transform. The main wavelet transform method challenges include effective selection of wavelet base, scale parameters and vanishing moment; the key determinants of signal correlation coefficients used to evaluate similarities between original and processed signals. Chen et al. (2010) researched on wavelet transform and de-noising technique to obtain mud pulse signals waveform shaping and signal extraction based on the pulse-code information processing to restore pulse signal and improve SNR. Simulated discrete wavelet transform showed effective de-noise technique, downhole signal was recovered and decoded with low error rate. Namuq et al. (2013) studied mud pulse signal detection and characterization technique of non-stationary continuous pressure pulses generated by the mud siren based on the continuous Morlet wavelet transformation. In this method, generated non-stationary sinusoidal pressure pulses with varying amplitudes and frequencies used ASK and FSK modulation schemes. Simulated wavelet technique showed appropriate results for dynamic signal characteristics analysis.

As discussed in “MPT mud pump noises”, the often overlap of the mud pulses frequency spectra with the mud pump noise frequency components adds complexity to mud pulse signal detection and extraction. Real-time monitoring requirement and the non-stationary frequency characteristics made the utilization of traditional noise filtering techniques very difficult (Brandon et al. 1999). The MPT operations practical problem contains spurious frequency peaks or outliers that the standard filter design cannot effectively eliminate without the possibility of destroying some data. Therefore, to separate noise components from signal components, new filtering algorithms are compulsory.

Early development Brandon et al. (1999) proposed adaptive compensation method that use non-linear digital gain and signal averaging in the reference channel to eliminate the noise components in the primary channel. In this method, synthesized mud pulse signal and mud pump noise were generated and tested to examine the real-time digital adaptive compensation applicability. However, the method was not successfully applied due to complex noise signals where the power and the phases of the pump noises are not the same.

Jianhui et al. (2007) researched the use of two-step filtering algorithms to eliminate mud pulse signal direct current (DC) noise components and attenuate the high frequency noises. In the study, the low-pass finite impulse response (FIR) filter design was used as the DC estimator to get a zero mean signal from the received pressure waveforms while the band-pass filter was used to eliminate out-of-band mud pump frequency components. This method used center-of-gravity technique to obtain mud pulse positions of downhole signal modulated by pulse positioning modulation (PPM) scheme. Later Zhao et al. (2009) used the average filtering algorithm to decay DC noise components and a windowed limited impulse response (FIR) algorithm deployed to filter high frequency noise. Yuan and Gong (2011) studied the use of directional difference filter and band-pass filter methods to remove noise on the continuous mud pulse differential binary phase shift keying (DBPSK) modulated downhole signal. In this technique, the directional difference filter was used to eliminate mud pump and reflection noise signals in time domain while band-pass filter isolated out-of-band noise frequencies in frequency domain.

Other researchers implemented adaptive FIR digital filter using least mean square (LMS) evaluation criterion to realize the filter performances to eliminate random noise frequencies and reconstruct mud pulse signals. This technique was adopted to reduce mud pump noise and improve surface received telemetry signal detection and reliability. However, the quality of reconstructed signal depends on the signal distortion factor, which relates to the filter step-size factor. Reasonably, chosen filter step-size factor reduces the signal distortion quality. Li and Reckmann (2009) research used the reference signal fundamental frequencies and simulated mud pump harmonic frequencies passed through the LMS filter design to adaptively track pump noises. This method reduced the pump noise signals by subtracting the pump noise approximation from the received telemetry signal. Shen et al. (2013a) studied the impacts of filter step-size on signal-to-noise ratio (SNR) distortions. The study used the LMS control algorithm to adjust the adaptive filter weight coefficients on mud pulse signal modulated by differential phase shift keying (DPSK). In this technique, the same filter step-size factor numerical calculations showed that the distortion factor of reconstructed mud pressure QPSK signal is smaller than that of the mud pressure DPSK signal.

Study on electromagnetic LWD receiver’s ability to extract weak signals from large amounts of well site noise using the adaptive LMS iterative algorithm was done by (Liu 2016). Though the method is complex and not straightforward to implement, successive LMS adaptive iterations produced the LMS filter output that converges to an acceptable harmonic pump noise approximation. Researchers’ experimental and simulated results show that the modified LMS algorithm has faster convergence speed, smaller steady state and lower excess mean square error. Studies have shown that adaptive FIR LMS noise cancellation algorithm is a feasible effective technique to recover useful surface-decoded signal with reasonable information quantity and low error rate.

Different techniques which utilize two pressure sensors have been proposed to reduce or eliminate mud pump noises and recover downhole telemetry signals. During mud pressure signal generation, activated pulsar provides an uplink signal at the downhole location and the at least two sensor measurements are used to estimate the mud channel transfer function (Reckmann 2008). The telemetry signal and the first signal (pressure signal or flow rate signal) are used to activate the pulsar and provide an uplink signal at the downhole location; second signal received at the surface detectors is processed to estimate the telemetry signal; a third signal responsive to the uplink signal at a location near the downhole location is measured (Brackel 2016; Brooks 2015; Reckmann 2008, 2014). The filtering process uses the time delay between first and third signals to estimate the two signal cross-correlation (Reckmann 2014). In this method, the derived filter estimates the transfer function of the communication channel between the pressure sensor locations proximate to the mud pump noise source signals. The digital pump stroke is used to generate pump noise signal source at a sampling rate that is less than the selected receiver signal (Brackel 2016). This technique is complex as it is difficult to estimate accurately the phase difference required to give quantifiable time delay between the pump sensor and pressure sensor signals.

As mud pulse frequencies coincide with pump noise frequency in the MPT 1–20 Hz frequency operations, applications of narrow-band filter cannot effectively eliminate pump noises. Shao et al. (2017) proposed continuous mud pulse signal extraction method using dual sensor differential signal algorithm; the signal was modulated by the binary frequency-shift keying (BFSK). Based on opposite propagation direction between the downhole mud pulses and pump noises, analysis of signal convolution and Fourier transform theory signal processing methods can cancel pump noise signals using Eqs. 3 and 4. The extracted mud pulse telemetry signal in frequency domain is given by Eqs. 3 and 4 and its inverse Fourier transformation by Eq. 4. The method is feasible to solve the problem of signal extraction from pump noise,

\(H(\omega )={f^{ - 1}}h(t)=G(\omega ){e^{ - j\omega \tau }}\) is the Fourier transformed impulse response, \(h(t)\), data transmission between sensor A and sensor B.

These researches provide a novel mud pulse signal detection and extraction techniques submerged into mud pump noise, attenuation, reflections, and other noise signals as it moves through the drilling mud.

In the area of active heave compensation systems, CPI’s unique subsea position sensor is seeing deployment into these applications due to its unique versatility and durability. Specifically, manufacturers and system integrators specifying hydraulic cylinders and accumulators for active heave compensation, are finding that our ATEX and IEC-EX certified sensors are perfect for both subsea, and surface use, both inside and external to the hydraulics.

Oilfield Applications which use the CPI advanced draw wire sensor include many different types of heave compensation systems. For most of these, the CPI SL-2000 Safety Rated Linear Position Sensor, is both a versatile, and a durable solution.

Riser Disconnect Sensing and Control– Related to the above use is the CPI Sensor’s ability to provide critical feedback during a disconnect scenario. A riser disconnect scenario detected by the CPI linear position sensor will cause the valve to limit the oil-flow and the riser will not gain momentum. During disconnect the control system controls the position of the valves and the riser is brought up in a controlled way again using input from our sensors.

Offshore Crane and Winch Systems – Many of these systems benefit from active heave compensation. They rely on the input of motion sensors like the CPI SL-2000. Responding to the signal from these sensors, the winches or cylinders pay in or pay out wire rope to keep the load at a constant elevation. Or sensors are perfect for this application because of their excellent response time, as well as their ability to hand very long stroke cylinders (up to 10 meters)

Subsea Mud Pump – A recent application for our sensor has it deployed 6000 meters below the sea, operating in a hydraulic accumulator, fully submerged in seawater. Our core sensor has no internal pressure vessels and advanced materials engineering prevents the normal corrosive and binding effects of seawater. Even fully submerged in seawater, our sensor is rated for over 1 million cycles.

Our solution to harsh duty hydraulic cylinder position detection is unique in the world, and is often the only practical solution to harsh environments, and long stroke cylinder applications. Here are a few of the characteristics of our robust sensor design.

Non-Contacting Transducer Technology– Our sensor technology employs a unique linear-to-rotary-to-linear measurement system which allows a short rod magnetostrictive sensor to generate absolute position signals accurate to 1mm over a 3 meter stroke length.

Our sensors can be deployed on the oil or the gas side of an accumulator with no need for a dynamic seal on the piston or core drilling the piston rod.

Our standard sensors can be submerged in water, gray water, sea water, process fluids and other corrosive fluids. Deep submersion units like our SL2000 are also available for subsea applications.

The present invention is directed generally to air- or fluid-powered diaphragm pumps including air operated diaphragm (AOD) pumps. More specifically, the present invention is directed toward apparatus and methods for controlling the speed or frequency of such diaphragm pumps. Still more specifically, the present invention relates generally to apparatus and methods for reducing wear on AOD pumps and the waste of energy and air or power fluid when the pump runs dry.

Air-operated diaphragm pumps are widely used for pumping liquids, solutions, viscous materials, slurries and suspensions containing solids. Typically, diaphragm pumps are operated under extreme operating conditions that vary widely. Specifically, the viscosity of the liquid being pumped can vary, particularly when the liquid is a suspension containing solids, and the system head can drop dramatically when the liquid source tank runs dry (the pump loses prime).

Diaphragm pumps are a type of positive (or semi-positive) displacement pump that use an energy source to move a diaphragm back and forth. By having one-directional check valves on the inlet and outlet, this reciprocating motion alternately pulls liquid into and pushes liquid out of the pump. One type of diaphragm pump is the air operated diaphragm (AOD) pump, which typically uses compressed air to power the diaphragm movement.

AOD pumps have several important advantages over other types of pumps—including being intrinsically safe by design, able to handle solids in the liquid being pumped, able to handle deadhead conditions without hurting the pump, being self-priming, and able to go in and out of prime (including dry- running) without hurting the pump.

Dry-running occurs when the supply tank becomes empty or is close to empty, and the pump only draws air or a mixture of air and liquid (skimming). Without the resistance provided by the liquid or slurry normally being pumped, the pump enters into a runaway condition in which its speed and energy use increase dramatically. The end result is that the most energy is used when the pump is not actually moving much or any of the working material. In addition, although dry-run operation does not cause immediate damage, it does cause increased wear and tear as there is no liquid to dampen and slow the internal movement. Despite the energy loss and accelerated wear, AOD pumps are nonetheless often used in situations where dry-run is likely because they can survive in these conditions, whereas other pump types would experience catastrophic damage or require re-priming systems.

In addition to speed changes cause by dry-running and re-priming, AOD pump frequency will often change dramatically due to changes in head pressure. In many situations, changes in speed may be undesirable. For instance, filling or measuring applications.

While pump speed or frequency governors for fluid powered diaphragm pumps are known from, e.g., U.S. Pat. Nos. 3,741,689 and 6,129,525, the teachings of which are incorporated herein by reference, such devices are complicated, difficult to install and not feasible for use as a retrofit or add-on feature to existing pumps.

The most common solution to the problem of pumps running dry is the use of a level sensor to measure the level of liquid at the pump source (e.g. a tank, sump, etc.). The most common (and cheap) level-sensing solution uses a mechanical float switch: when the float gets below a certain threshold, air to the pump is interrupted to keep it from running dry. Once the tank fills back up, the float rises and air flow is restored to the pump. There are many variations on this same setup, and there are many different types of level sensors other than a mechanical float, including optical, ultrasonic, radar, etc. All of such approaches, however, share the same general concept: detecting the level of the liquid being pumped and opening or closing a valve to/from the pump accordingly.

Yet, the level sensing approach has several problems/complications. First, it requires some type of sensor/switch to be submerged in or mounted around the liquid being pumped. This can cause problems such as the physical corrosion or contamination of parts exposed to the liquid flow. The level sensing approach also typically requires on a very stable physical mounting arrangement that is unfortunately not compatible with heavy industrial environments.

Level sensing solutions also typically require the reservoir from which liquid is being pumped to be relatively stable and uniform. Many industrial applications, however, must handle a variety of liquids (and even solids suspended in liquids) whose characteristics (density, viscosity, reflectivity, etc.) can vary significantly and thus will cause measurement problems. Of the sensors that make contact with the target liquid, they oftentimes get stuck or are damaged. And although there are some sensors contact-less sensors that can handle these situations, they are very expensive and can require complex calibration.

The problem of dry-run over-speed has also been addressed to some extent by Overspeed Controller Model 1015 marketed by Air Pump Valve Corporation, which is designed to be used with both diaphragm and piston air operated pumps. But the Model 1015 relies on an indirect measurement of flow from pressure drop, which is an unreliable indicator of dry-run because the flow may only increase a small amount—10 to 15% in many applications. Model 1015 and similar solutions (e.g. the Yamada DRD-100 Dry Run Detector) are also hindered by changes in system air pressure due to other plant equipment on the same air supply. Unless the pump is running with a dedicated compressor, the air flow sensing approach of these solutions is unable to reliably differentiate between a loss of prime condition and a drop in air supply caused by a pump turning on nearby.

Therefore, although there are known solutions to the energy waste and accelerated wear caused by dry-run conditions for AOD pumps, those solutions are not robust or very expensive. There is a need for solutions that don"t require sensing the level of the source liquid and that provide more control sensitivity and accuracy than can be obtained from monitoring drive air flow and pressure.

There is a need for an improved air- or fluid-powered diaphragm pump with speed control that can respond appropriately to dry-run conditions and changing system pressure. Due to the large number of air- and fluid-powered diaphragm pumps in current use, it would also be desirable to provide such a system that could be readily added on or retrofitted to existing pump systems. SUMMARY OF THE INVENTION

The present invention satisfies the needs and shortcomings discussed above by providing a liquid pump control apparatus and method with improved performance before and after dry run events.

In one preferred embodiment, the method provided by the present invention includes providing a pump assembly that comprises an air operated pump, an air inlet, an air exhaust, a liquid inlet, and a liquid outlet. The method further provides a pump stroke sensor in communication with the pump assembly that senses pump operating speed and provides for reducing pump operating speed in response to the pump operating speed exceeding a first threshold value.

As a result, if a dry run condition is encountered, the pump assembly reduces pump cycle speed to avoid wear on the air operated pump and reduce waste of drive air and energy.

In another preferred embodiment, a method for controlling a liquid pump assembly is provided that includes providing a liquid pump assembly that comprises an AOD pump, an air inlet, an air exhaust, a liquid inlet, and a liquid outlet. The method senses pump operating speed and reduces pump operating speed in response to pump operating speed exceeding a first threshold value.

In a preferred embodiment, the method for controlling a liquid pump assembly also includes sensing a subsequent drop in pump cycle speed that indicates that the pump has been re-primed. The method includes increasing pump cycle speed upon re-prime so that full pump liquid volume flow rate can be restored. Time delays can also be included, such as to avoid premature re-start of the pump upon re-prime or to provide time for a liquid source tank to be refilled.

In another embodiment, a liquid pumping system comprises an air operated pump having an air inlet, an air exhaust, a liquid inlet and a liquid outlet. The system also includes a pump speed sensor that is operatively connected to the air operated pump and that has an operating means to determine the pump cycle speed of the air operated pump. The system further includes a controller operatively connected to the pump speed sensor and the air operated pump. The liquid pumping system controls pump cycle speed in response to signals from the pump speed sensor.

In a preferred embodiment, the liquid pumping system also includes a controller in communication with the pump speed sensor and a valve controlled by the controller and in fluid communication with the air inlet. To reduce pump cycle speed under a dry run condition, the controller closes the valve. When re-prime condition is detected, the controller opens the valve.

According to one preferred embodiment, the pump speed sensor comprises a pressure sensor measuring air inlet pressure variations over time to infer pump cycle speed from the frequency content of the measurement. Alternatively, the pump speed sensor make comprise and end-of-stroke detector, a check valve movement detector, vibration or acoustic detectors, or any other means for determining pump cycle speed.

Another object of the present invention is that it provides an improved method and apparatus for controlling a liquid pump assembly before and after dry stop conditions are encountered.

Still another advantage of the present invention is that it provides a method and apparatus for controlling a liquid pump that reduces wear on the pump and reduces wasted energy and drive air supply in the operating environment of the pump.

Yet another advantage of the invention is that it provides an apparatus and method for improved control of AOD pumps before and after dry stop conditions are encountered.

The present invention is able to more robustly detect dry-run conditions than existing flow and pressure based devices since the present invention measure pump speed rather than flow, and pump speed changes much more dramatically than flow during dry-run conditions. The measurement of pump speed also enables it to better differentiate between dry-run and other environmental changes, such as changes in system pressure.

A significant advantage of the method and apparatus of the present invention is that it offers improved detection of dry run conditions in pumping environments, enabling the pump to be shut down or for pump speed to be reduced in response to such conditions, thereby saving energy and reducing pump wear. Although the invention is described in terms of apparatus and methods in connection with an air operated double diaphragm (AOD or AODD) pump, the invention may be utilized with any type pump chosen with sound judgment by a person of ordinary skill in the art.

Hereinafter, the term “compressed air” and “compressed fluid” may be used interchangeably, as may the terms “air” and “fluid;” such terms refer to the air or fluid driving the pump, as distinguished from the process “liquid” that is being moved by the pump. The process “liquid” can include without limitation slurries, mixtures of solids, liquids, and/or gases, or anything else that can flow through a pump. “Air” also means atmospheric air or any other gas. “Vibration” means any mechanical movement as could be measured by accelerometer.

“Acoustic” refers to sound waves propagating through a solid, liquid or gas. “Measuring pressure” includes average or root-mean-square pressure as well as measuring pressure over a period of time that is sufficiently long enough to derive frequency information (such as pump cycle speed) from the measurements. “Reducing” pump operating speed means reducing pump speed or turning the pump off completely. “Controller” means any kind of electronic or other controller for accepting sensor inputs and controlling valves and other control devices. “Pump cycle speed” and “pump speed” mean pump cycle frequency or pump oscillation rate, such as for example the oscillating frequency or rate of the pumping chambers within an AOD pump. A “dry run” condition means any condition in which the pump has lost full prime and is not pumping from a completely full liquid inlet, and doesn"t necessarily mean that the liquid source tank or the liquid inlet are completely dry. Overview

With reference now to FIG. 1, a typical AOD pump 50 such as is well known in the art will generally be described. The pump 50 may comprise a housing 11, a first diaphragm chamber 12, a second diaphragm chamber 13, a center section 14, and a power supply 15. The first diaphragm chamber 12 may include a first diaphragm assembly 16 comprising a first diaphragm 17 and a first diaphragm plate 24. The first diaphragm 17 may be coupled to the first diaphragm plate 24 and may extend across the first diaphragm chamber 12 thereby forming a movable wall defining a first pumping chamber 18 and a first diaphragm chamber 21. The second diaphragm chamber 13 may be substantially the same as the first diaphragm chamber 12 and may include a second diaphragm assembly 20 comprising a second diaphragm 23 and a second diaphragm plate 25. The second diaphragm 23 may be coupled to the second diaphragm plate 25 and may extend across the second diaphragm chamber 13 to define a second pumping chamber 26 and a second diaphragm chamber 22. A connecting rod 30 may be operatively connected to and extend between the first and second diaphragm plates 24, 25. Check valves 32 allow the discharge and suction of process liquids being pumped.

As compressed drive air or fluid flows through air inlet 40 into either the first or second diaphragm chambers 21 or 22 and out air exhaust 42, first and second flexible diaphragms 17 and 23 may flex toward or away from center section 14 with first and second diaphragm plates 24 and 25. This motion forces process liquid into or out of first or second pumping chambers 18 or 26, and check valves 32 will seat or release according to the positive or negative relative pressure induced. First and second diaphragm chambers 12 and 13 oscillate or cycle back and forth as pressurized air is distributed alternately between them. As a result, process liquid is thereby forced from a process liquid source (such as a source tank) through liquid inlet 44 into AOD pump 50, through check valves 32, out liquid outlet 46 and toward a process liquid destination (such as a destination tank).

With reference now to FIG. 2, a block diagram according to one embodiment of the present invention will be described. According to this advantageous embodiment, liquid pump assembly 1 comprises an AOD pump 50 that operates according to discussion above in connection with FIG. 1. Pressurized drive air enters through air inlet 40 and exits through air exhaust 42, compelling pump 50 to pump process liquid from source tank 55 into liquid inlet 44, through pump 40, and out liquid outlet 46.

Under normal operating conditions, the speed of pump 50 can be increased simply by increasing the pressure or flow rate of the drive air delivered to air inlet 40, and the volume of process liquid pumped will increase accordingly. If, however, the source tank 55 runs dry, pump speed will increase dramatically even though little or no process liquid is being pumped. Increased pump speed under such dry run circumstances has several undesired results, including wasted energy, wasted pressurized air, and increased wear on pump 50.

According to one advantageous embodiment, liquid pump assembly 1 limits pump speed during dry run conditions. Pump stroke sensor 60 is adapted to measure or detect the oscillating frequency (i.e. the pump stroke frequency) of first and second diaphragm chambers 12 and 13 and thus the “speed” of pump 50 generally. Generally speaking, pump stroke sensor 60 provides pump speed information to controller 70, and controller 70 reduces pump speed, or turns pump 50 completely off, through a pump control mechanism such as valve 80 in communication with drive air inlet 40. For example, if valve 80 is located in series with drive air inlet 40, controller 70 can stop pump 50 simply by closing valve 80 to remove the compressed air driving pump 50. So as source tank 55 runs dry, pump stroke sensor 60 detects an increase in the oscillation or speed of pump 50, and provides that information to controller 70. Controller 70 then limits or stops pump 50 by limiting pressurized drive air by operating valve 80.

According to other advantageous embodiments of the invention, some or all of the components of pump assembly 1 can be located remotely from component pump 50. For example, without limitation, an existing pump installation can be modified or retrofitted with remotely-located components for ease of modification. In a further example, in pumping environments where immersion in explosive gases poses a problem, the electrical components and/or power supply components of pump system 1 may be remotely located from pump 50.

According to other advantageous embodiments of the invention, some or all of the components of pump assembly 1 can be fully integrated rather being implemented as separate components. For example, without limitation, pump stroke sensor 60 can be integrated with controller 70 or controller 70 can be integrated with pump 50. Those skilled in the art will appreciate that the location of and level of integration of the components of pump assembly 1 may be varied considerably without departing from the scope of the present invention. Pump Stroke Sensor

Pump stroke sensor 60 may be implemented according to the present invention in many ways. In a particularly advantageous set of embodiments, the pump stroke sensor measures or detects pump oscillations, or pump cycle speed. This set of embodiments in which pump cycle speed is detected contrasts with prior art pump speed limitation approaches that are based on air/fluid consumption or flow; source tank liquid level; or liquid density, reflectivity, or other characteristics. Because pump cycle speed is a better indicator whether a pump is operating in a primed vs. unprimed (i.e. dry) condition, this set of embodiments is particularly advantageous for avoiding pump wear and air/energy waste under unprimed/dry conditions. In particular, as pump 50 runs dry, the oscillation or cycle speed of pump 50 increases significantly (sometimes by a factor of two or more) and thus provides an excellent indication that a dry-run condition has been encountered.

In one particularly advantageous embodiment, pump stroke sensor 60 is implemented by mounting a pressure sensor in fluid communication with air exhaust 42 and measuring or detecting the air exhaust pressure as a function of time. The cycle speed of the pump 50 can then be readily ascertained as the frequency of the detected pressure signal as it oscillates over time.

Pump stroke sensor 60 can also be implemented by mounting a pressure sensor in fluid communication with air inlet 40, liquid inlet 44, or liquid outlet 46. Alternatively, a flow meter rather than a pressure sensor can be mounted at or near air exhaust 42, air inlet 40, liquid inlet 44, or liquid outlet 46 if the flow meter is sufficiently responsive to detect flow changes at a frequency corresponding to the maximum speed of pump 50. Still alternatively, the pump stroke sensor may be implemented with an acoustic sensor that is in acoustic communication with pump 50, air inlet 40, air outlet 42, liquid inlet 44, or liquid outlet 46. In another alternate embodiment of the invention, the pump stroke sensor may be implemented with a vibration sensor that is mounted on or near the housing 11 of pump 50 or on or near any other component of pump assembly 1. The cycle speed of the pump 50 can then be readily ascertained as the frequency of the detected pressure signal, vibration signal, or acoustic signal as such signal oscillates over time.

Pump stroke sensor 60 can also be implemented by mounting a linear displacement sensor, contact closure switch, or other mechanical sensor in communication with a moving component of the pump 50. For example, end-of-stroke limit switches could be used in communication with the first or second diaphragm plates 24 or 25, in communication with the check valves 32, in communication with the valve spool or other component of the drive air valve that routes pressurized air alternatingly to first and second diaphragm chambers 21 and 22, or in communication with any other component of pump 50 that moves in conjunction with pump oscillation. The cycle speed of the pump 50 can then be readily ascertained as the frequency of the detected displacement signal as it oscillates over time.

Pump stroke sensor 60 can also be implemented by mounting an accelerometer in communication with pump housing 11, in communication with any other component of pump 50 or of pump assembly 1, or in communication with any of air inlet 40, air exhaust 42, liquid inlet 44, or liquid outlet 46. The cycle speed of the pump 50 can then be readily ascertained as the frequency of the detected accelerometer signal as it oscillates over time. Indeed, any measurement of any physical properties of the components of, inputs to, or outputs from pump assembly 1 that correlate in time with the cycle speed of pump 50 can be employed without departing from the scope of the present invention. Reducing Pump Speed

Pump assembly 1 can reduce pump speed or stop pump 50 completely through several advantageous mechanisms. In one particularly advantageous embodiment of the invention, after controller 70 determines that the speed of pump 50 is too high, controller 70 can partially or fully close a valve 80 that is in fluid communication with air inlet 40, interrupting the supply of pressurized drive air or drive fluid to thereby reduce the speed of or turn off pump 50. Without departing from the present invention, valve 80 can be any type of valve or other device known in the art for limiting the flow of pressurized air or fluid. For example, without limitation valve 80 can be a solenoid-driven butterfly valve, a poppet valve, or a fixed or controllable pressure regulator in electrical communication with controller 70. Alternately, some combination of valves and fixed and controllable pressure regulators could be employed without departing from the invention. Still alternatively, valve 80 could be located in fluid communication with air inlet 40 to switch between the primary high pressure air supply and a lower pressure supply.

To reduce rather than stop air flow to pump 50, valve 80 can also have a small bypass tube or other bypass path that permits a small flow of air even when valve 80 is fully closed. Alternatively, valve 80 could be designed so that it never fully closes, permitting a small flow of air even in response to a command from controller 70 to “close” the valve.

Valve 80 can alternatively be located so as to be in fluid communication with liquid outlet 46 so that when valve 80 is closed pump 50 is “deadheaded” and thus effectively stopped. In still other alternate embodiments, valve 80 can be located so as to be in fluid communication with liquid inlet 44 or air exhaust 42. Alternatively, multiple valves 80 can be located at some combination of air inlet 40, air exhaust 42, liquid inlet 44, and/or liquid outlet 46.

In another embodiment of the invention, controller 70 infers that a dry run condition is encountered if pump cycle speed increases dramatically and then levels off or stabilizes at a higher speed. Re-Priming/Re-Starting

After pump assembly 1 determines that a dry stop condition has been reached and slows down or stops the pump 50, the pump can be re-primed or re-started using several alternative advantageous mechanism according to the invention. In one simple embodiment, the pump can be restarted manually and the pump stroke sensor 60 and controller 70 can use the aforementioned techniques to determine promptly whether or not the dry stop condition still exists (such as when the source tank 55 is still empty). If a dry stop condition is again detected, the pump speed will be reduced or stopped as described earlier. In one advantageous embodiment, a delay time is introduced between the time at which the pump speed is reduced or stopped and the time at which a re-start is initiated and the prime check recurs periodically until prime is detected and the pump can return to full speed to resume full liquid pumping volume rate of flow. The delay time between dry run detection and restart can be set in advance, can be user-selected, or can be configurable according to operating environment conditions. For example, the delay time could be increased successively after each unsuccessful check for prime until prime is detected, after which the delay time could revert to its initial value or another value. Alternatively, a fully-manual approach could be employed whereby the pump can only be re-started by a user input or a signal from another system in the operating environment. Still alternatively, some hybrid of any or all of the aforementioned re-start approaches could be employed without departing from the invention.

Alternatively, if the pump speed is merely slowed down (rather than fully stopped) in response to a dry run condition, the pump speed will necessarily slow down even further once the system has re-primed (such as when source tank 55 is no longer empty).

According to one embodiment of the invention, controller 70 can infer from this additional reduction in pump speed that the system has been re-primed (i.e. source tank 55 is no longer empty) and can then open valve 80 to move the pump assembly to normal operating speed. Still alternatively, the assembly could use a hybrid or combination of the aforementioned manual re-start after a long delay time combined with a reduced-speed mode within the longer re-start delay time intervals.

An alternative advantageous embodiment of the invention improves re-prime detection using a bypass valve with a pressure regulator. In this embodiment, the pressure regulator would be set to a low enough pressure level so that any re-priming would completely stop the pump. This contrasts with an air bypass that only restricts air flow, since a flow restriction would still allow the full system pressure to operate on the fluid. Using a pressure regulated bypass according to this embodiment may make re-prime detection easier in situations where there is not much change in pump speed between dry run and primed conditions while the pump is in a bypassed, low-speed mode. Rather than detecting a slow down, the system would only have to detect a complete stop.

In addition, a number of user-initiated manual control mechanisms can be employed without departing from the invention. For example, a user-activated switch or push button can be provided that will manually override the controller functions in order to initiate pumping operations immediately, overriding any re-start delay time established by controller 70. Or the assembly could respond to an input from another source such as an external system"s control signal, an output from another sensor within the operating environment, etc. and override any delay time or reduced-speed mode. For example, a float sensor in source tank 55 could indicate a dangerously high level of liquid in the tank to override any delay time or reduced speed mode in order to restart pumping operations immediately. Calibration and Correction

Pump assembly 1 can be advantageously calibrated to perform in a variety of operating environments. The system can be manually calibrated by having a user place pump assembly in a dry run condition (such as with an empty source tank 55). As the pump 50 operates in calibration mode at a high cycle speed in the dry run condition in that particular operating environment, the dry run threshold speed above which the pump speed is to be reduced in operation can be determined. The dry run threshold speed will typically be set with a speed margin somewhat below the speed at which the pump runs in dry run calibration mode; that margin can be set automatically via controller coding or by the user. Alternatively, the dry run threshold speed could be automatically set as the maximum speed at which the pump operates at any interval over the lifetime in which the pump assembly is installed in a particular operating environment.

In yet another alternative advantageous embodiment, the dry run threshold speed level could be set at the factory or before installation according to pump model number and projected installation environment (i.e. drive air pressure). Alternatively, an adjustment knob or other user adjustment mechanism could be provided to enable the dry run threshold speed to be adjusted in the field.

In many industrial environments, there may be considerable variation in the pressure or flow rate of the drive air or drive fluid supplied to pump assembly 1. If, for example, the drive air pressure supplied to the pump assembly increases from 20 psi to 80 psi due to changes in the industrial environment, the speed of a typical AOD pump 50 might, for example, double. In light such possible environmental variations, one aspect of the present invention provides a correction mechanism to prevent pump assembly 1 from concluding that the doubled pump speed indicates a dry run condition and to prevent controller 70 from closing valve 80 in response to the (false) dry run indication. In one advantageous embodiment, pump assembly 1 includes a pressure sensor in fluid communication with air inlet 40 that measures or detects the average or root-mean-squared pressure of drive air delivered to pump 50. If the average or root-mean-squared pressure of the drive air changes considerably, controller 70 can adjust the dry run threshold cycle speed and/or the re-prime threshold speed. In one particularly advantageous embodiment, pump stroke sensor 60 is a pressure sensor located in fluid communication with air inlet 40 and that both detects the average pressure of drive air and also determines pump cycle speed.

Similarly, and without departing from the present invention, the pump assembly 1 can make adjustments to the dry run threshold speed and/or the re-prime threshold speed by monitoring the flow rate or pressure at air exhaust 42, at liquid inlet 44, or at liquid outlet 46.

According to yet another advantageous embodiment, the pump assembly 1 can incorporate detecting the average pressure at air inlet 40 into the dry run and re-prime detection mechanisms. In many operating environments, the average drive air pressure delivered to the pump 50 changes predictably depending on the availability of process liquid at liquid inlet 44. As the pump 50 runs dry, it typically speeds up and uses more air, which can cause the supply air pressure at air inlet 40 to drop if the main air supply cannot supply sufficient air or is inadequately regulated. Similarly, when the pump re-primes, the extra resistance and pump slow-down can lead to an increase in average pressure of the drive air at air inlet 40. Measures of the air pressure drop across valve bypass along with the absolute air pressure can be used to derive the air flow rate. According to this aspect of the invention, these air pressure measures can be used independently or in combination with pump cycle speed to adjust the delay time and cycle speed thresholds associated with determining dry run conditions and re-prime conditions.

According to yet another advantageous embodiment, the pump assembly 1 can include automatic calibration of fixed and adjustable thresholds for dry run and re-prime events. Instead of using a fixed pump speed threshold to determine dry run and re-prime events, the assembly can re-calibrate those thresholds over time. For instance, in one embodiment the pump assembly 1 could wait until the pump cycle speed plateaus or until it remains at some speed for some period of time after an increase in speed has occurred. For example, if the pump cycle speed increased steadily during a 2 minute period but didn"t thereafter change or drop, controller 70 could conclude that a dry run condition had been encountered. According to this aspect, pump cycle rate acceleration is used by controller 70 to determine when a maximum pump speed has been attained and held. The approach of this embodiment would be beneficial in situations where system parameters that affect pump cycle rates change substantially over time (e.g. drive air pressure, process liquid type or composition, and drive air and process liquid plumbing configuration). According to yet another aspect, pump cycle rate acceleration could be combined with some absolute pump cycle rate criteria for determining dry run and re-prime events. For example, the pump cycle rate might still need to be both above some pre-determined threshold level and also relatively unchanging over time. Hardware Implementation and Controller Coding

A pump assembly, including controller circuitry, electrical power supply (such as a battery), and controller software code, used to construct a liquid pump assembly 1 according to one advantageous embodiment of the present invention is disclosed in provisional U.S. Patent Application No. 61/365,516 (19 Jul. 2010), which is incorporated herein by reference. Other Advantageous Embodiments—Net Positive Suction Head (NPSH)

In many pump operating environments, users may be required to ensure that pump speed is not so high as to cause the liquid inlet side to drop pressure too much, which can cause the liquid to boil and can induce cavitation and reduced pumping efficiency. This concern is particularly important in pump applications (such as non-AOD pump applications) where damage to the pump assembly may result from cavitation or loss of prime. Pump system designers often employ a design concept known as Net Positive Suction Head (NPSH). NPSH (a) (i.e. NPSH available) is a calculated or experimentally-derived value that embodies the specific application"s ability to make fluid available to the suction system. NPHS(r) (i.e. NPSH required) is a value that indicates the required NPSH for a given pump in order to avoid cavitation. NPSH(r) is typically experimentally determined by the pump manufacturer for each type of pump manufactured. The pumping system designer can then ensure that NPSH (a) for a particular pump operating environment will be greater than the NPSH(r) over the range of projected operating conditions. Given the considerable variation of different pump operating environments, a relatively large safety margin generally has to be employed by the designer to ensure that NPSH(s) never drops below NPSH(r). In practice, this design consideration yields a pumping system configuration in which pump 50 is pumping at a pump speed well below the design speed maximum for that particular pump in that particular pump operating environment.

By employing assemblies and methods similar to the dry run avoidance system described above, the present invention in one advantageous embodiment provides a liquid pump assembly 1 in which pump cycle speed can be increased without exceeding NPSH (a) for a particular pump 50 and pumping environment. According to one aspect, AOD pump cycle speed is monitored according to the aforementioned techniques employing pump stroke sensor 60 and controller 70 is configured so that pump assembly 1 provides a range of pump cycle speeds (rather than just full-power, reduced-power, and pump stop modes). For example and without limiting the generality of the invention, in one aspect pump assembly 1 can employ a valve 80 comprising a continuously variable orifice, pressure regulator, or other continuously variable control mechanism. In yet another example, in another aspect of the invention the pump assembly 1 can employ a valve 80 comprising a discretely variable orifice, pressure regulator with discrete settings, or other control mechanism with discretely variable settings. In yet another embodiment, the pump assembly 1 of the invention could alternatively interject time delay pauses during some or all pump strokes in order to keep the overall average flow of the process liquid at a desired level.

According to one embodiment, the pump assembly 1 can first run at a relatively slow pump cycle speed that is known by the operator to correspond to an NPSH(r) value that is well below NPSH(a) for that pump 50 in that operating environment. Pump assembly 1 could then advantageously gradually increase the available drive air pressure at air inlet 40 (or reduce interjected time delay pauses) so as to gradually increase pump cycle speed, thereby gradually increasing the suction pressure from source tank 55 at liquid inlet 44. If pump cycle speed increases too much, cavitation between source tank 55 and liquid inlet 44 can occur and pump speed will then increase further and may vary dramatically. According to this aspect of the invention, controller 70 and pump stroke sensor 60 can detect this increased pump speed and speed variation, either separately or in combination, and the pump assembly 1 can infer that pump 50 is cycling too quickly because NPSH(r) has exceeded NPSH (a). Accordingly, the pump assembly 1 can then reduce pump speed by reducing drive air pressure via valve 80 or using other techniques for pump speed reduction disclosed herein. Pump speed can be reduced gradually until the system stabilizes without cavitation, as detected using pump stroke sensor and controller 70. Accordingly, in one embodiment of the invention, in response to an indication of pump speed instability from loss of prime is detected, the pump assembly is configured to reduce the cycle speed of pump 50 until desired operating conditions are restored. Likewise, periodically, the pump assembly according to another aspect can increase pump speed in order to determine whether a higher pump cycle speed (and thus improved pumping operations) can be achieved without cavitation or pump speed instability.

In yet another embodiment of the invention, the pump assembly can comprise a pressure sensor in fluid communication with the liquid inlet 44 to directly monitor liquid inlet pressure. When the pressure drops near the NPSH, the pump cycle speed can be stopped or reduced according to the apparatus and methods described herein for reducing pump speed. Other Advantageous Embodiments—Non-AOD Pumps

The present invention is directed to pumping applications involving a wide range of classes of pump 50, including without limitation AOD pumps, pumps driven by compressed air or fluid, other positive displacement pumps, vacuum-driven pumps, AC motor driven pumps, and any type or class of pump that transfers a liquid volume via a mechanical work mechanism. Many classes and types of pump assemblies 1 share the operating characteristics and application considerations discussed herein with respect to AOD pumps and other liquid pumps, including without limitation the characteristic of a correlation between the cycle speed of pump 50 and a dry run or loss-of-prime condition at liquid inlet 44 and source tank 55.

In one advantageous embodiment of the present invention, a liquid pump assembly 1 comprises an AC motor driven pump 50 that operates at approximately the same pump cycle speed under primed and unprimed conditions. According to this aspect, the pump assembly 1 comprises a current meter measuring the electric current drawn by pump 50. When the electric current drawn drops below a threshold current lev