Accurate flow measurement is the key to reduce the energy consumption or materials, and reduce cost, use advanced flow measurement technology can improve the control precision, make the parameters meet the requirements, so as to improve the quality and yield of the product.
In new plant a 1. 4 million t diesel hydrogenation unit and building new sulfur device, choose several sets of thermal mass flowmeter, used to measure gas, such as nitrogen, hydrogen and purify the wind, from the point of use, in measuring gas flow rate has achieved satisfactory results.
Thermal gas mass
flow meter is a direct measurement of gas mass flow meter, the use of orifice differential pressure measuring and matching with usual method to measure the combination of pressure and temperature transmitter temperature and pressure changing gas flow, this method requires more parts, so the cost is high, low accuracy, high failure rate, easy installation and maintenance is not, the thermal mass flowmeter can overcome the above shortcomings.
1.
Working principle of thermal mass flowmeter and composition (
As shown in figure 1)
Thermal mass flowmeter is composed of sensor and transmitter, sensor components including 2 with heat pipe protection resistance temperature detector (
Platinum thermal resistance)
。
When the two platinum thermal resistance were placed in a fluid, one of the heated, another for induction process temperature, temperature difference between two platinum thermal resistance related to the process flow and process medium, high flow or denser medium make heated accelerated cooling the platinic resistance and temperature difference between two platinum thermal resistance speed decreases, and temperature difference between two platinum thermal resistance under the conditions of no flow achieve ZUI, with the increase of flow heated platinum thermal resistance cooling speed, temperature difference is reduced.
Fluid velocity changes directly affect the degree of thermal diffusion, in turn affect the two platinum thermal resistance between the size of the difference in temperature.
Through the control circuit of platinum thermal resistance temperature can be transformed to dc voltage signal, these two signals at the output terminals output, and is used to drive two adjustable set points shall be reported to the circuit, the two quote circuit can be operated according to the flow or temperature field set separately.
Fluid velocity and temperature difference is a function of the following: & rho;
υ
=K(
q /△t)
1.
Of the 67 type: & rho;
As the fluid density;
υ
For the fluid flow velocity;
K is the equilibrium constant;
Q as the heat flow;
Delta t for temperature difference.
Due to traffic and the relation between the cooling effect of the platinic resistance related to gas mass flow measurement directly, as shown in figure 1 sensors are put in fluid, mass flow rate can be calculated from the transmitter circuit.
Instrument company's thermal diffusion technology provides a high precision (
±
1%)
, high repeatability,
0.
5%)
Air or gas mass flow meter, equipped with advanced microprocessor line & other
Intelligent & throughout;
On signal output circuit, the user can easily set, also can use the built-in keyboard or handheld communication device for display or alarm signal is field adjustable.
2.
Main characteristics (1) easy installation, plug type or online flange installation;
(2) have no moving parts;
(3) 316 stainless steel and other corrosion metal shell, no wear, corrosion, ensure sensor long-term stable operation;
(4) range is very wide, measuring range to 1000:1, have EX4X explosion-proof waterproof packaging, products can be used in dangerous places.
Also has a modular flow circuit, flow transmitter has the function of strong multifunction processor, high-precision AD converter, fast storage and high-speed communication bus.
Main processor board including independent 16 bits D/A and analog output RS -
232/485 a serial port, the output signal of 4 ~ 20 ma and 0 ~ 10 v, d.
c。
Two kinds.
Flow component interface board with his own microprocessors and 16 AD converter, data flow components between slabs after processing through high-speed bus sent to the main processing board.
Input power can be compatible with the voltage standard the parts.
Flowmeter measurement system block diagram is shown in figure 2.
Gas mass flowmeter sensors based on the technology of thermal diffusion, with no moving parts, it has a good reliability and can work in harsh environment long-term reliable, especially for low flow measurement ZUI for sensitive, overload capacity is strong, full scale a lot higher than that of in the actual flow, won't cause damage to the instrument.
But due to the thermal mass flowmeter is USES the platinum thermal resistance measurement, so the measuring gas cannot liquids such as water, this is because the liquid thermal conductivity than gas would bring to measure larger error;
In addition to mixed gas, as a result of the medium is not the same as the coefficient of thermal conductivity, components is relatively stable.
So flowmeter is needed when a real gas calibration, the same as used by the media.
Company for each flowmeter calibration group has a number of different media storage, correction for practical use, this makes flowmeter wider application range.
3.
Practical application of our factory in 1. 4 million t diesel hydrogenation and new sulfur device adopts several thermal type gas mass flowmeter, the measured gas, such as nitrogen, hydrogen, purify air, including gas of chlorine and hydrogen is a component, and the actual flow rate in the device small, velocity of flow is low;
Clean and purify the wind belongs to the mixed gases, the amount is more, burn for compressor is used to help in the process, the demand is higher, so the flow parameters for the flow directly affect the complete combustion of fuel.
From the use of more than a year, the flow meter in the measurement of the above several kinds of gas, no matter use in low flow or normal flow range is very accurate, can meet the accuracy requirement, and stable operation, little what fault, process flow and control requirements.
In both the accuracy in measuring more than gas, installation, maintenance, cost, etc is better than that of the orifice flowmeter.
Above all, a thermal type gas mass flowmeter is a new type of gas meter, if correctly according to the technological condition selection, can achieve the ideal effect of measurement, to ensure accurate operation of the production and control.
Wow, this sounds like a bit of a cruel question, but it is a vitally important question to ask yourself if you are struggling with your
insertion ultrasonic flow meter and you would like to stop the mass flow meter problem.
Beijing Sincerity Automatic Equipment Co., Ltd also maintains a friendly, fair, and creative work environment, which respects diversity, new ideas, and hard work.
Beijing Sincerity Automatic Equipment Co., Ltd knew if this worked for us, it would work for others, so we took the exclusive product and program and re-developed it to be more accessible to customers.
Our company specializes in manufacturing
mass flow meter mainly rosemount vortex flow meter.
Simultaneously being able to offer not only the product but also the service, gives the customer a quality 'one-stop-shop' service.
