The lining material should be selected according to the corrosiveness, wear and temperature of the tested medium:
First, natural rubber (soft rubber)
1, better elasticity, wear resistance and tearing force
2, resistant to general weak acid, weak alkali corrosion
3. Water and sewage
Second, acid-resistant rubber (hard rubber)
It can withstand the corrosion of hydrochloric acid, acetic acid, oxalic acid, ammonia water, phosphoric acid and 50% sulfuric acid, sodium hydroxide and potassium hydroxide at normal temperature, but it is not resistant to corrosion by strong oxidants.
It can measure general acid, alkali and salt solutions.
Third, neoprene (Neoprene)
1, excellent elasticity, high tearing force, good wear resistance
2, resistant to general low concentration of acid and alkali, salt solution corrosion, but not resistant to oxidation of the medium, and temperature requirements <80 ° C;
It can measure water, sewage, mud and pulp.
Fourth, Polyurethane (Polyurethane)
1, excellent wear resistance
2, poor acid and alkali resistance, temperature requirements <40 ° C
Measure medium-strongly worn coal slurry, mud and slurry
Five, polytetrafluoroethylene (PTFE)
1. Boiling hydrochloric acid, sulfuric acid, nitric acid, aqua regia, concentrated alkali and various organic solvents
2, good wear resistance, poor bonding performance, temperature requirements -80 ~ +180 ° C;
Measuring concentration, concentrated alkali strong corrosive solution and sanitary medium
Vortex flowmeter selection
(1) Selection of vortex flow transmitter
In the measurement of saturated steam, VA type piezoelectric vortex flow transmitter is adopted. Because of the wide range of vortex flowmeter, in practical applications, it is generally considered that the flow of measuring saturated steam should not be lower than that of vortex flowmeter. The lower limit, that is to say, the fluid flow rate must not be less than 5 m/s. According to the size of the steam, the vortex flow transmitters with different calibers are selected, and the caliber of the transmitter cannot be selected by the existing process pipe diameter.
(2) Selection of pressure compensation pressure transmitter
Since the saturated steam line is long and the pressure fluctuates greatly, pressure compensation must be adopted. Considering the corresponding relationship of pressure, temperature and density, only pressure compensation can be used in the measurement, because the saturated steam pressure of Mingtong Company is 0.3-0.7MPa. Range, the range of pressure transmitter can be selected 1MPa.
(3) Display instrument selection
Display instrument intelligent flow display instrument with voltage regulation compensation, instantaneous flow display and cumulative flow accumulation function.
Ultrasonic flowmeter measurement principle
When the ultrasonic beam propagates in the liquid, the flow of the liquid will cause a small change in the propagation time, and the change in the propagation time is proportional to the flow velocity of the liquid, and its relationship conforms to the following expression.
θ is the angle between the sound beam and the direction of flow of the liquid
M is the number of linear travels of the sound beam in the liquid
D is the inner diameter of the pipe
Tup is the propagation time of the sound beam in the positive direction
Tdown is the propagation time of the sound beam in the reverse direction
Let the speed of sound in the stationary fluid be c, the velocity of the fluid flow be u, and the propagation distance be L. When the sound wave is in the same direction as the fluid flow direction (ie, the downstream direction), the propagation velocity is c+u; otherwise, the propagation velocity is cu. Two sets of ultrasonic generators and receivers (T1, R1) and (T2, R2) are placed at two places separated by L. When T1 is in the forward direction and T2 transmits ultrasonic waves in the reverse direction, the time required for the ultrasonic waves to reach the receivers R1 and R2 respectively is t1 and t2, then
Since the flow velocity of the fluid in the industrial pipeline is much smaller than the sound velocity, that is, c>>u, the time difference between the two is ▽t=t2-t1=2Lu/cc. Thus, the propagation velocity of the acoustic wave in the fluid is known. When it is known, the flow rate u can be obtained by measuring the time difference ▽t, and the flow rate Q can be obtained. The method of measuring the flow using this principle is called the time difference method. In addition, a phase difference method, a frequency difference method, or the like can be used.