Pressure Gauge Selection Elements and Installation Precautions

 The selection of pressure gauges should be based on the requirements for pressure measurement in the process and production process, combined with other aspects, and comprehensively considered and specific analysis. Generally, the following issues should be considered: the selection of the instrument type, the determination of the measuring range of the instrument, and the instrument Selection of accuracy level and consideration of use environment and media performance.

1.Selection of range

The selection of the range determines the range of the instrument according to the size of the measured pressure. For elastic pressure gauges, when measuring stable pressure, the maximum pressure value should not exceed 3/4 of the full range, when measuring fluctuating pressure, the maximum pressure value should not exceed 2/3 of the full range, and the lowest measured pressure value should not be lower 1/3 of the full scale.

2.Precision selection

Accuracy selection, according to the maximum measurement error allowed by production, determine the accuracy level of the instrument on the principle of economy and practicality. 1.5 or 2.5 grades for general industrial pressure gauges are sufficient.

3.Considering the use environment and media performance,

The environmental conditions are harsh, such as high temperature, corrosion, humidity, vibration, etc. The properties of the measured medium such as temperature, corrosiveness, crystallization, flammability, and explosion. To determine the type and model of the pressure gauge.

4.Selection of the shape of the pressure gauge

The choice of the shape of the pressure gauge: The pressure gauge indicated on the spot generally has a surface diameter of 100mm. In the case of higher standards or poor lighting conditions, the diameter of the surface is 200~250mm, and the diameter of the disc-mounted gauge is 150mm.

The selection of the pressure measuring point should reflect the true size of the measured pressure.

① Choose the part of the pipe where the measured medium flows in a straight line. Don't choose the pipe bends, bifurcations, dead ends or other places where vortexes are easily formed.

② When measuring the pressure of the flowing medium, the pressure taking point should be perpendicular to the flow direction, and the inner end of the pressure taking pipe should be kept flush with the inner wall of the connection point of the production equipment, and there should be no protrusions or burrs.

③ When measuring the pressure of liquid (gas), the pressure point should be at the lower (upper) part of the pipe so that no gas (liquid) accumulates in the pressure guiding tube.

Pressure guiding pipe laying

① The thickness of the pressure guiding tube should be appropriate, generally the inner diameter is 6-10mm, the length should be as short as possible, and the longest should not exceed 50m to reduce the slowness of the pressure indication. If it exceeds 50m, a pressure gauge capable of long-distance transmission should be used.

② When the pressure guiding tube is installed horizontally, the inclination of 1:10～1:20 should be ensured to facilitate the discharge of the liquid (or gas) accumulated in it.

③ When the measured medium is easy to condense or freeze, an insulation heat tracing pipeline must be installed.

④ A shut-off valve should be installed between the pressure port and the pressure gauge to prepare the pressure gauge for maintenance. The shut-off valve should be installed near the pressure tap.

Installation of pressure gauge

① The pressure gauge should be installed in a place where it is easy to observe and repair.

②The installation site should avoid the influence of vibration and high temperature.

③When measuring the steam pressure, a condensate pipe should be installed to prevent the high temperature steam from directly contacting the pressure measuring element.

The above information is provided by pressure gauges supplier.

How Do Mass Flow Meters Work?

 How Do Mass Flow Meters Work?

Flow meters are very reliable in providing accurate and precise measurements regarding fluid flow in a system.

In this article, the basic principles of how the different types of flow meter work will be briefly discussed.

Indirect Mass Flow Measurement

Indirect mass flow meters usually measure the mass flow by computing the resulting flow through the pressure and temperature measurement. These are considered indirect measurements because they use different types of sensors and a computing device in order to arrive at a mass flow measurement. These measurements are used in circumstances where a direct reading is not possible because of the inapplicability of the parameters. Volumetric flow meters are a perfect example for this type of meter. These are magnetic, differential pressure, positive displacement, Ultrasonic, non-compensated vortex, and turbine meters.

Direct Mass Flow Measurement

Direct-types of flow meters directly measure the mass of a fluid passing through the device. Measuring the mass flow directly is an effective way of ensuring an accurate reading. This will eliminate the inaccuracies resulting from the varying physical properties of fluids. These types of flow meters are not affected by pressure and temperature changes. To be able to get a measurement in this type of meter, the fluid is allowed to flow straight through a tube and onto the meter. These make direct measurement perfect for higher flow rates and lesser pressure drops.

Coriolis Mass Flow Meters

Coriolis type of flowmeter measures mass through inertia or through the effect of a moving mass on a body. The Fluid is vibrated by a small actuator and flows through a tube wherein the acceleration results in a measurable twisting force.This force is proportional to the mass flow rate of the fluid flowing through it. Other high-end variations of these meters are integrated with dual tubes for enhanced sensitivity and lessened pressure drops. These flow meters are beneficial in applications where the fluid is a variable or an undefined mixture.

Thermal Mass Flow Meter

Thermal type of mass flow meters arrive in a direct measurement that is derived from the heat transfer along the heated source. These meters have two temperature sensors and a heat source.The sensors will measure the heat transfer as the fluid passes over a pipe and  the meter will measure the rate on how quickly the fluid disperses the heat. This value will be proportional to the mass flow.

Pressure Differential Flowmeter

These types of flow meters measure fluid flow through the principle of differential pressure. The concept behind this is using an obstruction on the flow within the pipe to induce a difference of static pressure between the upstream and downstream end of the device. Based on Bernoulli’s equation, the square of the flow rate is proportional to the pressure drop across the obstruction, therefore, a high-pressure drop means a high flow rate.

Key Takeaways

Mass flow meters measure the volume or mass flow in a system and the values from these meters are often used to indicate the system efficiency and overall operationality. Different types of these meters have unique operational principles specified for different applications.

Your can find the orginal article as https://www.iqsdirectory.com/articles/flow-meter/mass-flow-meter.html  

The Purpose of Gate Valve, Globe Valve, Butterfly Valve

 1. What occasions are gate valves, globe valves and butterfly valves suitable for?

These three kinds of valves are arranged according to the difficulty of switching: globe valve, gate valve, butterfly valve;

Arranged by resistance: globe valve, butterfly valve, gate valve;

Strictly arranged by closing: globe valve, butterfly valve, gate valve;

Sort by price: globe valve, butterfly valve, gate valve; (except special butterfly valve)

These three kinds of valves are all driven valves. According to the above characteristics, it is not difficult to see that the globe valve is mainly used for opening and closing and flow adjustment of small diameter pipes (branch pipes) or the end of the pipeline; butterfly valves are used for opening and closing and flow adjustment of branch and main pipes. ; The gate valve is used for the opening and closing of the main pipe and is generally not used for flow adjustment.

Butterfly valve

The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When the rotation reaches 90°, the valve is fully opened.

The butterfly valve is simple in structure, small in size and light in weight, and consists of only a few parts. Moreover, it can be opened and closed quickly by rotating 90°, and the operation is simple. At the same time, the valve has good fluid control characteristics.

When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop produced by the valve is small, so it has better flow control characteristics. The butterfly valve has two sealing types: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be inlaid on the valve body or attached to the periphery of the butterfly plate.

If you would like to know more, please contact us.

 

Matters Needing Attention to Ensure the Normal Operation of Metal Rotameter

 In order to ensure the normal operation of the metal tube rotameter and achieve the required measurement accuracy, the following points should generally be noted:

•The metal rotor flowmeter must be installed vertically, the fluid flows through the flowmeter from bottom to top, and the verticality is better than 2°, and the horizontal angle is better than 2° when installed horizontally;

•The metal tube float flowmeter installed on the process pipeline should be bypassed, so as to deal with the failure or not affect the production when purging;

•The entrance of the metal rotor flowmeter should have a straight pipe section of more than 5 times the pipe diameter, and the outlet should have a straight pipe section of 250mm to ensure the measurement accuracy of the instrument;

•If the medium contains ferromagnetic substances, a magnetic filter should be installed;

•If the medium contains solid impurities, consider installing a filter between the valve and the straight pipe section;

•When used for gas measurement, ensure that the pipeline pressure is not less than 5 times the pressure loss of the flowmeter to make the float work stably;

•If the temperature of the measured medium is higher than 220°C or the fluid temperature is too low, crystallization is likely to occur, and when heat insulation protection measures are required, the jacket type should be selected for cooling or heat preservation;

•The pipe flanges, fasteners, gaskets and the flow meter flange standards are the same to make the meter install and run normally;

• Generally, the product does not need maintenance after the normal operation of the device. Faults usually occur when the device is just started, and the float is stuck by the solid particles due to the uncleanness of the pipeline. At this time, the pointer of the indicator stops at a position. At this time should first close the valve on both sides of the flowmeter, and then remove the upper flange, take out the float for cleaning, and then reinstall. Pay attention to tighten the flange nut evenly and fill the washer well;

• In order to avoid flowmeter deformation caused by the pipeline, the flange of the process pipeline must be coaxial and parallel to the flange of the flowmeter, and the pipeline should be supported appropriately to avoid pipeline vibration and reduce the axial load of the flowmeter. In the measurement system The control valve should be installed downstream of the flow meter;

•Because the meter transmits signals through magnetic coupling, in order to ensure the performance of the meter, at least 250px around the installation, no ferromagnetic substances are allowed;

•The meter for measuring gas is calibrated under a specific pressure. If the gas is directly discharged to the atmosphere at the outlet of the meter, it will cause a pressure drop at the float and cause data distortion. If this is the working condition, a valve should be installed at the outlet of the instrument;

•Be careful when installing PTFE-lined meters. As the PTFE will deform under the action of uneven pressure, the flange nuts are tightened evenly and symmetrically;

•For instruments with liquid crystal display, avoid direct sunlight on the display when installing, so as not to reduce the service life of the liquid crystal;

•For meters with lithium battery power supply, try to avoid direct sunlight and high temperature environment (≥65℃) when installing to avoid reducing the capacity and life of the lithium battery.

The above information is provided by flow instrument manufacturer.

Mass Flow Meter Installation Process

The mass flow meter is the most accurate meter with the lowest installation requirements in the existing industrial production. Because it can directly detect the quality, density, and temperature of the medium flowing through the measuring tube inside the meter, there is no strict layer on the flow state of the medium. Flow requirements, so there is no requirement for straight pipe sections for the pipelines before and after the flowmeter during the installation process. Just like the regulating valve, it can be installed arbitrarily, which greatly facilitates on-site construction and installation.

Various shapes of mass flow meters

Mass flow meters have various shapes, but their internal structures are almost the same. They basically consist of two U-shaped measuring tubes. Three coils are installed at the bottom and left and right sides between the two measuring tubes. The bottom coil is an excitation coil. The two coils on the left and right measure the mass and the density. In addition, a thermal resistance is buried inside the measuring tube to detect the temperature of the medium.

Details of the installation process

Since the mass flowmeter can detect the density of the medium in real time, without artificially setting a constant density of the medium, the detection value of the mass flowmeter is accurate and reliable, and the construction and installation are simple and convenient.

1. Although the mass flowmeter has no requirements for the pipes before and after the flowmeter during construction and installation, some details should be paid attention to during the installation process;

2. It is necessary to ensure that the front and back process flanges of the flowmeter are welded concentrically, so as to eliminate the additional torque caused by the flanges not being concentric during the installation process, and reduce the use error of the mass flowmeter;

3. Also pay attention to some supporting construction process, especially the influence of eccentric torsion and additional stress on the operation of the flowmeter during the laying of heating wire;

4. Although the mass flowmeter measures the tube inside the shell, the external stress can still generate additional errors that cannot be measured, such as the fixed wire with hot wire in the figure, and deformation caused by the influence of temperature during recovery operation, resulting in a random change of stress superposition;

5. The laying of the heating wire should also be separated from the mass flow meter to prevent the asymmetric stress caused by the thermal expansion of the heating wire and the excessive conductive heat from affecting the medium temperature detection of the mass flow meter.

The above information is provided by flow instrument factory.

Common Failures and Maintenance of Mass Flow Meters

 In liquid chemical production such as petroleum refining, the incoming and outgoing materials of the device are mainly steam, gas energy, and liquid raw materials and products. These materials require high-precision metering instruments. Therefore, the production workshop has very strict requirements on the metering instruments for the incoming and outgoing materials of the device. .

Common failures and analysis of mass flow meters

Failures in the use of mass flowmeters are generally divided into measurement failures caused by process reasons and failures caused by damage to the flowmeter itself.

Measurement faults caused by process reasons:

The most common is the phenomenon of two-phase flow in the measured fluid. Specific to the measurement of liquid, the main reason is that the measured liquid is not filled with the flow meter measuring tube or the upper part of the measuring tube accumulated gas, or solid impurities enter the measuring tube to be stuck in the main body, which causes the mass flowmeter to alarm.

Treatment method: Ensure that the fluid measured by the mass flow meter is one-way flow by changing the installation method of the exhaust gas, and take measures to remove the solid impurities in the measuring tube.

Damage to the mass flowmeter itself causes flowmeter failure:

The most common faults in use are water in the flow meter junction box or loose wiring that causes short circuits and signal loss.

Treatment method: In addition to strictly standardizing on-site installation, daily detailed inspection and maintenance are also required to prevent more serious failures such as the sensor coil burned out due to untimely handling.

The transmitter circuit board is damaged. The most common fault is the damage of the transmitter's power supply board and signal processing output board.

Solution: In addition to strictly standardizing the cable signal wiring, it is also necessary to take measures to prevent lightning and grounding. Use an independent stabilized power supply to ensure the reliability of the power supply and prevent large fluctuations in the power supply voltage from burning the device.

Maintenance of mass flowmeter

As long as you pay attention to some details during the installation process, the mass flowmeter is almost maintenance-free after it is put into operation, and the probability of failure is very small. As long as it is ensured that the medium is not in a two-phase flow state during the flow process, stable operation can be achieved.

Perform some simple settings during the first commissioning of the mass flowmeter, such as the form of the output signal, the various coefficients of the flowmeter itself, the density of the medium in use, the upper and lower temperature limits, etc., basically before commissioning No need to change after setting.

The above information is provided by flow instrument manufacturer.

Principle and Installation of Mass Flow Meter

 The working principle of mass flow meter

The Coriolis mass flowmeter uses the principle of modulation of the fluid mass flow rate on the vibration of the vibrating tube. The sensor consists of a vibrating tube (measuring tube), a signal detector, a vibration driver, a supporting structure and a shell. The transmitter is based on a microprocessor, which provides driving force to the sensor and converts the signal measured by the sensor into a mass flow signal. It also has the function of compensating and correcting the mass flow and density measurement according to temperature parameters. The output current signal or frequency signal can communicate with DCS according to a certain protocol.

Mass flow meter installation

1) The mass flowmeter works based on the principle of vibration, and in the process of its work, electromagnetic technology is used for vibration excitation, torsion angle detection and detection signal processing, so the mass flowmeter installation position cannot be large. The vibration source of this type cannot be installed near transformers, motors and other equipment that generate strong magnetic fields to prevent external interference from affecting its normal operation.

2) There is no requirement for straight pipe section in the installation of mass flowmeter, but stress should be avoided when connecting the sensor and pipe. If the concentricity between the sensor and the pipeline centerline is deviated during the installation of the mass flow meter, it will cause stress in the vibrating tube, which will cause pressure, tension, or shear force to affect the alignment of the pipeline and cause the asymmetry of the detection probe , Resulting in zero point changes and affecting measurement accuracy. If the concentricity deviation between the pipeline and the sensor is too large, the zero point may not be adjusted. Therefore, reinforcement measures should be taken to stabilize the pipeline near the instrument. When installing the flow sensor, a soft connection method should be adopted as much as possible, and the flange connection screws should be evenly and symmetrically tightened. In order to reduce the influence of residual stress, the flow sensor must be zero-point calibrated after installation. In order to facilitate the installation and zero adjustment of the mass flowmeter, stop valves should be installed at the front and back of the mass flowmeter.

3) The connection cable between the sensor and the transmitter should use the manufacturer's special cable; the transmitter receives low-level signals, so the cable should not be too long. When installing the transmitter, make sure that the partition used to separate the intrinsically safe sensor cable from the power supply and output cable is installed in place; ensure that the sensor junction box and the transmitter housing are sealed to avoid short-circuits that may cause measurement errors or flowmeter failures.

4) Choose different sensor installation orientations according to the different properties of the fluid, and always keep the fluid in the sensor flow tube full. The U-shaped tube of the mass flow meter for gas feed measurement faces upwards to avoid accumulation of condensate in the measuring tube; the U-shaped tube of the mass flow meter for liquid feed measurement faces downwards to avoid gas accumulation in the measuring tube.

The above information is provided by mass flowmeter manufacturer.

 

Electromagnetic Flowmeter Installation Recommendations(Part 2)

6. Installation plus bypass pipe

The pipeline where the flowmeter is installed should have a valve that can cut off the medium in the pipeline to facilitate daily maintenance and maintenance. When the process does not allow flow interruption. A bypass pipe can be added to the pipe where the flowmeter is installed.

7. Install according to the calibration direction

When the flowmeter sensor has a clear flow mark, it should be installed in the calibration direction.

8. Cable entry, cable and conduit

The inlet of the flowmeter, the cable and the threading pipe should be bent downwards and open at the lowest point to prevent water from entering and causing a short circuit.

9. Welding flange

When installing the flowmeter, the flange should be welded first, and then the flowmeter should be installed. It is not possible to weld the flange directly with the flowmeter sensor to avoid the welding slag burning the lining.

10. Distance between converter and sensor

The signal wire between the converter and the sensor cannot be longer than 50m, and the signal wire must be sheathed with galvanized pipe.

11. Grounding measures of the sensor

The flow signal generated by the sensor is very small, only a few millivolts at full scale, so the sensor should be well grounded. The grounding requirements of electromagnetic flowmeters have two aspects:

From the analysis of the working principle of the electromagnetic flowmeter and the loop of the flow induction signal current, the ground terminal of the sensor and the converter must be at the same potential as the measured medium.

Ground, take the earth as zero potential to reduce external interference.

Under normal circumstances, process pipelines are all metal pipes, which are grounded. This requirement is easy to meet. However, in the case of large external electromagnetic field interference, the electromagnetic flowmeter should be equipped with a separate grounding device. The grounding wire should be a multi-strand copper wire with a cross-section greater than 5mm2. The grounding wire of the sensor must not be connected to the common ground wire of the motor or other equipment. To avoid the influence of leakage current. The grounding resistance should be less than 10Ω.

The above information is provided by flow instrument factory.

Electromagnetic Flowmeter Installation Recommendations(Part 1)

1. Ensure that the full pipe is installed

The measuring tube of the electromagnetic flowmeter must be full, and there must be no part full. If the pipeline is not full or the outlet is vented, the sensor should be installed on a siphon.

Avoid installation upstream of the downward pipeline

Avoid the highest point of the pipeline, which tends to accumulate bubbles

2. Horizontal and vertical installation

The sensor can be installed horizontally and vertically, but it should be ensured to avoid the influence of deposits and bubbles on the measuring electrode, and the electrode axis should be kept horizontal. When installing on a horizontal pipeline, the two measuring electrodes should not be directly above and directly below the pipeline. When installed vertically, the fluid should flow from bottom to top.

The inlet straight pipe should be larger than 5D, and the outlet straight pipe should be larger than 2D. Those with specific installation requirements should be installed according to the electromagnetic flowmeter manual. The plug-in inlet straight pipe section should be ≥ 20 D, and the outlet straight pipe section ≥ 7D (D is the nominal diameter of the sensor).

3. Installation when the outlet is empty

When the outlet is in the empty state, the sensor should not be installed in the empty place of the pipeline, but should be installed in a lower place. When the sensor is installed below the pipe, it should be ensured that the sensor is filled with liquid and there is no empty pipe state.

4. Series installation and parallel installation

If several sensors need to be connected in series on the same pipe in sequence, the distance between each sensor should be at least the length of 2 sensors.

If two or more sensors are installed parallel to each other, the distance between the sensors must be greater than 1m.

5. Installation between elbows, valves and pumps

To ensure the stability of the measurement, straight pipe sections should be set before and after the sensor, the length of which is given in the figure below. If this is not possible, a current regulator should be used or the cross-sectional area of the measuring point should be reduced.

The above information is provided by flow instrument manufacturer.

Electric High Temperature Steam Globe Control Valve

 

ZWZP Electric High Temperature Steam Globe Control Valve

Electric High Temperature Steam Globe Control Valve

This high temperature control valve is composed of an electric actuator and a high precision low flow resistance regulating valve body. The electric high-temperature steam globe control valve has the advantages of tight closing, compact structure, light weight and convenient maintenance.The BCST electric high temperature control valve is equipped with a 3810 series (or PSL series) electric actuator and a small precision regulating valve body. It accepts a standard signal of 4-20 mA or 1-5 V·DC to convert the current signal into a corresponding linear displacement.The electric high temperature control valve adopts a balanced valve plug structure, which is widely used in the occasions where the flow rate is large, the temperature is high, and the leakage amount is not strict.

Technical Parameters of BCST High Temperature Steam Globe Control Valve:

DN(mm)		20	25	32	40	50	65	80	100	125	150	200	250	300
Seat Dia.(mm)		20	25	32	40	50	65	80	100	125	150	200	250	300
Rated Kv	Single-seated	6.9	11	17.6	27.5	44	69	110	176	275	440	630	875	1250
	Cage Guided	6.3	10	16	25	40	63	100	155	250	370	580	900	1300
Allowed Pressure Difference (MPa)	Single-seated	3.8	3.2	3	2	1.8	1.5	1.4	1	0,7	0.6	0.5	0.3	0.1
	Cage Guided	6.4	6.4	5.2	5.2	4.6	4.6	3.7	3.7	3.5	3.1	3.1	2.6	2.2
PN(MPa)		1.6、2.5、4.0、6.4、10.0
Rated Travel(mm)		16			25		40			60			100
Bonnet Type		high temperature type(+250～+450℃)
Seal Packing		PTFE, flexible graphite
Plug Type		Single seated,cage guided
Flow Characteristic		Equal percentage,linear
Actuator Type		3810 series electric actuator,PSL series electric actuator
Actuator Parameter		Power voltage:220V,input singal:4-20mA or 1-5V·DC,output signal:4-20mA·DC
		Protection level:IP65,Explosion-proof:ExdⅡBT4(ExdⅡBT6 customized),manual function: handle
		Ambient temperature:-25～+70℃,ambient humidity:≤95%

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