In natural gas production, managing your gas pressure drops is critical. If mishandled, these drops can jam up your system and cause downtime.
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In this blog, we're going to answer the following 6 questions:
A pressure drop across a valve means that the media is flowing the normal direction&#;from up to downstream. If you didn't have a difference in pressure between upstream and downstream&#;in other words, if those pressures were equal&#;there would be no flow across the valve.
Production fluid, be it oil or natural gas, naturally flows from high to low pressure. That&#;s how the flow is determined in any kind of separation equipment or system.
The pressure drop across a valve may also be called the "differential pressure."
Pressure drop across a valve is determined by the control points both upstream and downstream of the valve. If the valve is in a dump application, the pressure drop will be determined by two things:
Pressure drop does affect flow rate, but does not always reduce it.
Again, every valve flowing media will have a pressure drop, which is what creates the flow. Whether the pressure drop reduces or increases flow rate depends on if the drop moves higher or lower.
Here's the general rule:
If the pressure drop gets higher (meaning there is an increase in differential pressure), there will be more flow across a valve (to a point).
If the pressure drop gets lower (meaning there is a decrease in differential pressure), there will be less flow across a valve.
For example: A 1&#; trim in a 2&#; stem guided valve would be able to flow more with a 100 PSI drop than if it had a 50 PSI pressure drop. This is because there&#;s more pressure in the flow media pushing on it to force it through the 1&#; trim.
Note, however, that this increased flow from increased pressure cannot go on indefinitely. At a certain point, you will reach what&#;s called choked flow, which we'll cover next.
There comes a point where if you&#;re increasing the pressure drop by lowering the downstream pressure, you&#;re not going to increase the flow rate. The fluid will reach its maximum velocity at the vena contracta, and after that point, it will enter a state called "choked flow."
The higher the pressure drop is, the more flow you can get across a given orifice size. If you want to increase volume using the same valve and equipment you have, but you are in choked flow, you won&#;t be able to.
This creates problems in your system because you can't pass the amount of volume that you need. And depending on the application you might be starving another piece of equipment that needs volume to operate correctly.
If you partially close a valve, would it increase the pressure? That depends on your volume.
There are many variables that determine what your pressure drop is, including the application and the flow conditions the valve is exposed to.
That said, our Cage-Guided High Pressure Control Valve can handle higher pressure drops than many valves because of its balanced trim.
This is because with the working pressure of the valve, there is the potential of a high pressure drop, and the valve's operation allows it to work in those high pressure drop applications.
How it works:
To learn more see our video How to Operate the High Pressure Control Valve.
To get your valve out of choked flow, you must decrease the pressure differential. If you are worried about not passing enough volume through the valve in choked flow, you need to increase your valve trim size or you can increase your upstream pressure.
One important distinction to make: Once you&#;re in choked flow, decreasing downstream pressure to increase the pressure differential doesn&#;t do anything to increase flow rate.
If you increase upstream pressure, you&#;re adding more energy to push it across the valve so that can increase the flow rate because it increases the pressure drop.
In other words, when you&#;re in choked flow, you can push more production fluid or gas through but you can&#;t pull more through.
If you add pressure from behind (upstream), you can push more through, but if you take away pressure downstream to create a higher differential, it&#;s not going to allow more flow through the valve.
Cavitation is the formation and collapse of air or gas bubbles in a liquid.
The bubbles are formed when liquid undergoes a rapid change of pressure and falls below the vapor pressure. These bubbles collapse when the pressure recovers.
This can all happen in a very short span just after the vena contracta&#;the point in the valve where the diameter of the flow is at its smallest, and fluid velocity is at its maximum.
Because it happens inside a valve or pipeline, cavitation is not easy to spot. Here are two symptoms that may be caused by cavitation:
How Can I Prevent Cavitation?
There are three things you can do to prevent cavitation in your valves:
Cavitation happens a lot with high pressure drops and high velocities. If you&#;re experiencing a high pressure drop, another problem to watch for is flashing.
While cavitation is more common in liquid, flashing is more common in gas production.
Flashing happens when you reduce the pressure on a liquid hydrocarbons to the point that they "flash" into vapor.
For example: If you dump your oil emulsion quickly from a high pressure to low&#;say, 500 PSI down to 60 PSI&#;it can flash, meaning the rich, light, high-gravity oil condensate in your production vaporizes, and you lose that resource forever.
The pressure on your operation&#;s production vessels is what keeps this oil condensate in liquid form.
This is why producers drop gas pressure in &#;stages.&#;
Staging is the process of reducing pressure in stages rather than all at once. Reducing pressure all at once can not only cause freezing, but cavitation and flashing. More oil and condensate can be recovered in liquid form and not be lost to vaporization when staging pressure drops.
This is usually a concern in gas-producing wells. These operations are usually labeled as &#;natural gas production&#;&#;meaning gas is the largest resource the producer is recovering by volume.
However, these wells still produce oil, sometimes called &#;white oil&#; because of its light color, and it can create significant revenue for these producers.
Many producers use a gas production unit (GPU) on their natural gas wells to heat the well stream before reducing the pressure, helping to mitigate freezing. In this set up, the oil and condensates can be recovered in the separator portion of the GPU.
The dry gas, meanwhile, flows out of the top of the vessel. The gas is sent downstream into a sales line. Some of the dry gas is used to power the instrumentation on the GPU.
Note staging is the reverse of the process of compression. The purpose of a natural gas compressor is to re-pressurize natural gas to push it downstream.
When the gas reaches a compressor, producers want the condensate to be &#;knocked out&#; so it doesn't damage the compressor.
To speak with an expert about how to maximize your oil and condensate recovery, contact your local Kimray store or authorized distributor.
If you are a purchase manager or a mechanical engineer, an instrument named flow meter you will always meet, but not expert on it. The flow meter is used in mining, oil and gas, chemical, and power plants. The main purpose of the flow meter is used to measure the quantity of material flowing in the pipelines, it means to calculate the flow rate of a substance through a specified flow section.
Here&#;s everything you will learn in this guide:
The rate of flow across a specified flow segment is the primary metric for flow metering. In order to maximize the effectiveness of automated manufacturing, flow metering must be incorporated into every technical process flow chart.
Each kind has a unique method for determining the flow rate of a fluid. Today&#;s market offers five primary types of flowmeters, including differential pressure flowmeters, velocity flowmeters, positive displacement flowmeters, mass flowmeters, and open-channel flowmeters.
Existing flowmeters are classified as follows:
Flow meters are based on hydrodynamic methods: variable differential pressure, variable level, streamline flow, vortex method, as well as others.
Flowmeter with continuous motion objects: speed, power, etc.;
Flowmeters are based on various physical phenomena: thermal, electromagnetic, acoustic, optical, etc.
For Beginners, we just simply first categorize two types of flow meters based on the medium state: gas and fluid or liquid. Fluid flow meters have 5 subcategories: differential pressure flowmeter, velocity flowmeter, positive displacement flowmeter, mass flow flowmeter, and open-channel flowmeter.
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Variables like temperature, viscosity, pressure, and conductivity may all impact the accuracy of specific types of flow meters. The quality of the water may also be a factor in determining the flow meter&#;s design. Knowing the properties of the flow being monitored is the next stage in selecting a flow meter.
In the previous paragraph, we learned that there are 5 main types of flow meters, and now we introduce them one by one.
Most water and gas flow meters use differential pressure technology. Experience speaks for itself in the form of numerous appearances. Whether it&#;s gas, liquid, or steam, the differential pressure flow meter can detect the number of gases, steam, or liquids that are moving through a system. They find particular utility in applications where extremes of pressure, temperature, or diameter are present. You can find them in the petrochemical, natural gas, power plant, and chemical industries.
Orifice Plate Flow Meter Systems monitor the change in the flow&#;s pressure from upstream to downstream when the flow is partially obstructed in the pipe.
orifice plates 1orifice plate flow meterA Flow Nozzle is an inexpensive and basic design of a venturi meter. The nozzle is fixed between the ends of the material-carrying pipe. A differential pressure sensor monitors pressure decreases in order to calculate the flow rate.
nozzle flow meterVenturi Flow Meters monitor liquid flow rate and measure the change in pressure caused by a flow path&#;s cross-sectional flow area.
venturi flow meterRotameters are variable flow meters that measure the force of gravity acting on a fluid by rotating a float that travels vertically through a tapered tube. They are frequently employed for liquid and gas measurements. Rotameters are simple, affordable, monitor low pressure drops, and have linear output and a large variety of conditions.
variabelt area rotameterFlow velocity is measured with velocity flow meters. They generate a reading by monitoring the flow&#;s depth and average air velocity, enabling engineers to maintain the appropriate flow throughout the stream. The range of velocity flow meters is higher than that of differential pressure flow meters. There are pilot tubes, calorimetric, turbines, and electromagnetic velocity flow meters.
pipe velocityUtilized in ventilation and HVAC systems, Pilot Tube Flow Meters measure flow velocity by converting kinetic energy to potential energy.
pitot tubeCalorimetric Flow Meters, also known as thermal flow monitors, determine the distinction between continuous and controlled heating using the principles of heat transfer. The first sensor monitors the temperature of the heating element, while the second measures the temperature of the fluid.
calorimetric flowmeterTurbine Flow Meters are used with clean and viscous liquids with an accuracy of 0.5% to measure the turbine&#;s speed. They have a rotor with many blades placed perpendicular to the flow. The output frequency is a sine wave or square wave. Signal conditioners can be put on them, but only on categories that are explosion-proof.
liquid turbine flowmeterliquid turbine flowmeter2Electromagnetic Flow Meters sometimes referred to as magnetic flow meters, are volumetric devices that employ Faraday&#;s law of electromagnetic induction.
types of electromagnetic flow meter3Vortex Flow Meters assess flow rate by placing a barrier directly in the flow channel, causing liquids or gases to go around the impediment. Flow around the barrier generates two symmetrical vortices on the opposite side, altering the flow&#;s pressure. Between the vortices, a flow sensor records pressure fluctuations.
vortex flow meterUltrasonic Flow Meters compute flow volume by measuring fluid velocity using ultrasound. There are two varieties of ultrasonic flow meters: in-line and clamp-on. In-line ultrasonic meters consist of two sets of ultrasonic devices oriented in opposition and put into the flow pipe. Clamp-on devices utilize the same two components, but neither device is placed into the pipe.
ultrasonic flow meters1Hydraulic Flow Meters are utilized for testing, diagnosing, and maintaining hydraulic systems by measuring the flow rate or volume of a liquid within a hydraulic system. They evaluate the system&#;s efficiency and effectiveness and fix any issues that arise.
hydraulic flowmeterAir Flow Meters monitor air pressure and velocity. They are suitable for obtaining rapid, consistent measurements of ventilation systems and for process monitoring.
Positive displacement flow meters use rotors as sensors to detect viscous liquid flow. By using vanes, gears, pistons, or diaphragms, airflow is displaced. The rotation of the rotors is proportional to the flow volume. They are utilized for measurements when a straight pipe is unavailable or as a substitute for turbine meters and paddlewheel sensors when the flow is too turbulent.
The volumetric flow rate is calculated by dividing the mass flow rate by the fluid&#;s density using a mass flow meter. It employs the Coriolis Effect, an inertial force that operates on moving objects inside a given reference point. The thermal Mass Flow Meter employs two sensors to monitor temperature, an active heat sensor to measure heat loss in the liquid, and a flow meter to calculate the flow rate.
Mass Gas Flow Meters or Coriolis Flow Meters are based on motion mechanics and the Coriolis Effect. When fluid enters a sensor, it is divided, causing the sensor&#;s tubes to vibrate and produce a sine wave. The mass flow rate is determined by the time delay between the oscillations of the two tubes. They are used for checking for leaks and measuring low flow rates.
Digital Flow Meters are any devices with a digital display that measures flow. Power providers utilize a standard digital meter to monitor the flow of energy to your home and to transmit your usage statistics to the electrical company, which uses the information to bill you.
Slurries, water, and other closed-pipe fluids are measured using water flow meters. Liters or cubic meters are used to express the flow rate.
Fuel flow meters count the volume of liquid being moved. The user may see on a mechanical or digital display how much fuel has been transferred during a transaction.
Peak flow meters evaluate lung capacity and are used to treat breathing problems. By breathing into the mouthpiece, which records the volume of air taken in per minute in liters, the portable, low-cost gadget assesses lung capacity.
An operator can see a liquid as it passes through a pipe thanks to flow indicators. They are a component of an industrial process that requires an instantaneous inside view of the flow within a pipe and are sometimes referred to as sight flow indicators. The mass or speed of the flow is not calculated or measured by flow indicators. They are the most basic type of flow meter and have no moving components, they are often referred to as plain sight indicators.
Different type of meter measure has different working principles, so let&#;s learn how each type of flow meter is measured.
The flow is determined in a differential pressure drop device by measuring the pressure drop over blockages inserted in the flow. The differential pressure flow meter is based on the Bernoulli Equation, which states that the pressure drops and subsequently measured signal are functions of the square flow speed.
differential pressure transmitterDP(&#;P) = ρv2 / 2 (1)
where
DP(&#;P) = Differential Pressure (Pa, psi)
ρ = Fluid Density (kg/m3, slugs/ft3)
v = Flow Velocity (m/s, in/s)
Note that it is common to use &#;head&#; instead of &#;pressure&#;
h = DP / γ (2)
where
h = Head (m, in)
γ = Specific Weight (N/m3, lb/ft3)
pressure drop ratioA liquid is continuously pumped into the vessel while simultaneously flowing out of a hole in the bottom or a side wall. Variable-level flowmeters are based on the relationship between flow rate and the height of the level in the vessel. The main transformer is a container with an aperture of area S. The liquid level in the vessel&#;s height is what is being measured, and the flow rate, which is the flow rate coefficient, is determined from the relationship and is independent of the liquid&#;s density.
Slit flowmeters, which are tiny weirs in the wall of a vessel into which a liquid is continuously delivered, are frequently used to measure the flow rate of liquid in open channels (trays). The height of the liquid level over the lower edge of the slit determines the flow rate. A flowmeter of this type has the following characteristics, which are determined by the shape of the slit cross-section: The flow rate for a rectangular slit that is b1 wide and b2 high, profiles b1(b2) have been designed on which they are applied and a linear relationship is established.
The primary transformer in streamlined flow flowmeters absorbs the dynamic pressure of the flow and moves under its action by a value proportional to the flow rate. The most common are constant pressure differential flowmeters, in which a streamlined body glides vertically and the weight of the body produces a counterforce.
Among these are Rotameters flowmeters, as well as floating and piston-type (slide valve) flowmeters. The rotameters are manufactured in the shape of a vertical conical (conicity, 0.001-0.01), upwards diverging glass pipe on which the graduations are created, a float travels inside the pipe with inclined ribs on its upper rim.
The float rises and spins in response to the flow, ensuring that the float is centered in the center of the flow. The height z of the float lift determines the volume flow rate of the liquid. It is proportional to the size of the circular gap Sc(z) between the pipe walls and the float and is dependent on the float parameters (volume Vf, midsection area Sf = (/4)df2 and density of the float material (f).
In specific measurement settings, the relationship Sc(z) is virtually linear for tiny pipe taper angles. Where A is determined by an initial calibration Float flowmeters work in the same way. Under the operation of a dynamic head, the piston in a piston-type flowmeter travels in a bush with specially formed windows through which the liquid flows out at a flow rate .
float flowmeterThe frequency of fluctuations in pressure or velocity that occur in the cross-flow across a body (cylinder, prism, plate) is calculated and depends on the flow rate in vortex flowmeters. The Strouhal number Sr = du-1f relates the frequency f to the mean streamlining velocity u and the body size d. The flow rate for a flow section area S = (π/4)D2 is determined by the relation
vortex flow meterSr = const ensures proportionality between and f, which is attained when the cylinder is streamlined across the range 104 &#; Ro &#; 2 × 105 (Ro = ωd/u is the Rossby number). This guarantees that the observed flow rate has a wide range.
vortex flowmeter schematicHowever, is constrained by the circumstances of sustained vortex formation (for example, water u > 0.2 m/s). Typically, primary transformers with d/D values between 0.15 and 0.2 are utilized (D is the diameter of the pipeline). The pressure pulsations are converted into an electric signal using piezo ceramic pressure pickups. Flow rate measurement error is estimated to be 0.5-1.5%.
flow meter installation 1flow meter installation2flow meter installation3Tachometric flowmeters have a rotary element whose measuring velocity is proportional to the volume flow rate.
Flowmeters in the shape of a miniature turbine have found wide applications, with the rotational speed of the turbine being determined by the frequency meter&#;s measurement of the number of electric pulses per unit of time. Turbine flowmeters are built as either an axial small turbine (Turbine flowmeter with rotation in the direction of flow) with variable helix angle propeller blades or a tangent small turbine (Turbine flowmeter with rotation normal to the direction of flow) with flat, radially placed blades. As the moving element of ball-type flowmeters, a ball is moved around the circuit by the swirling flow with the assistance of a propeller guide.
Power flowmeters measure the value of a parameter that describes how a force acts on the flow, with the force&#;s impact being proportional to the mass flow rate. The force increases the flow&#;s speed. The flowmeters are divided into three categories based on the type of acceleration: turbo-power flowmeters, Coriolis flowmeters, and gyroscopic flowmeters.
The torque on the rotating shaft is monitored and inversely proportional to the mass flow rate in the flowmeter depicted in the Turbo-power flowmeter.
typical installation of turbine flowmeterThermal flowmeters are based on the flow rate of the amount of heat received by a liquid flowing from a heater. A heater (typically an electric one) is injected into the flow on the pipeline portion, and its power W is recorded, as well as the difference in flow temperatures ΔT = Tout &#; Tin at the upstream and downstream. The mass flow rate is hence proportional to the heating power W with ΔT held constant. Because the coefficient K is affected by heat losses into the surroundings, the nonuniform distribution of velocity throughout the pipeline cross-section, and other factors, a preliminary calibration was done. When the flowmeter is thoroughly made and calibrated, it can provide an accurate flow rate measurement of ±(0.3-0.5)% and can be used as a reference for inspecting and calibrating other flowmeters. The thermoanemometric technique determines local velocity by measuring the temperature of a hot wire or hot film supplied with a continuous current. Using existing relationships, this local velocity may then be connected to the mean velocity.
When measuring the flow rate of a liquid, electromagnetic flowmeters typically require a conductance of at least 103 Ohm/m. Their operation depends on the interplay of the transverse magnetic field and the moving current-conducting liquid. In this instance, the magnetic induction of the transverse field B, the liquid flow rate V, and the distance D between the electrodes all contribute to the electromagnetic force E that is produced in the liquid (located along the normal both to the velocity vector of the liquid and to the vector of the magnetic field intensity). D is the same as the inner diameter of the pipe.
The source of the current (E) is indicated by
electromagnetic flowmeter schematicThe benefits of the electromagnetic flowmeter include its ability to measure abrasive, extremely viscous, and aggressive liquids as well as its independence from the viscosity and density of the material, lack of pressure loss, scale linearity, and high-speed response. But, It is unable to measure the flow rates of gases, vapors, or dielectrics.
types of electromagnetic flow metertypes of electromagnetic flow meter2types of electromagnetic flow meter3Flow measurement is a continual responsibility for each sector, which is why flow meters have grown so important. A flow meter must be properly placed in order to provide accurate and trustworthy data.
flow meter installation 4The following are some of the most important measures to take while installing a flow meter:
The volume of fluid that travels through a certain cross-sectional area per unit of time is defined as flow rate. Accurate flow rate measurement with a suitable flowmeter is critical to ensure fluid control systems work smoothly, safely, and economically.
The most repeatably accurate flow meters now available are thought to be ultra-high accuracy flow meters like Coriolis flow meters. When great precision is essential for maintaining a continuous level of product quality, safety, and profitability, Coriolis meters are the best choice. in general cost more than any other flow technology. A flow meter with an accuracy of 5% which is much less expensive than another flowmeter with an accuracy of 0.2% could provide sufficient results for your process to function smoothly and give large cost savings. Understanding the precise accuracy requirements for your application and accuracy vs budget concerns might be challenging at times. You can get free assistance from our sales engineers in locating the ideal solution for your application.
The flow meter isn&#;t that complicated. You just need to learn basic terminology, category, and work principles. Go deep and learn if you needed from the real selection or use the application as much as you, you will quickly handle or expert soon.
Looking to learn more about industrial valves? Reading the following articles will help you expand your automation process knowledge.
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