The throttle device using common problems and prevent
Throttling device because of its simple structure, stable and reliable, long life, wide application range, high standardization degree, without solid flow calibration, and low cost and widely used. Throttling device installation requirements higher, a small mistake can cause a great error, so that the failure of a complete set of measurement.
1, the installation problem
(1) the orifice plate installation problems
Standard orifice of the acute Angle should be installed in the incident flow position; Segmental orifice orifice must, at the bottom of the pipe orifice and beneath the pipeline wall collocated arc edge; Double orifice, open hole are large orifice before, after open hole are small orifice. Orifice plate and pipe should be concentric accurately, the error shall not be greater than 0.01 D, orifice plate front end face perpendicular to the pipe axis, vertical degree may not be greater than 1 degree.
(2) the sealing gasket size, installation issues
Sealing gasket inside diameter should be slightly bigger than the inner diameter, otherwise it will produce the beams. Sealing gasket should be aimed at the central part, otherwise install eccentric, cover some of the circulation area, the velocity distribution distortion, cause serious asymmetry of velocity distribution.
2, installation location selection problem
(1) installed on the velocity distribution profile bad places
In order to guarantee good velocity distribution, there must be proper length of colonel swam straight pipe, such as the conditions are not allowed to flow to install the regulator will be improved.
(2) installed in the downstream of valve
Control valves should be installed in the downstream of the instrument, in order to avoid any velocity distribution disturbance generated by the valve, which affect instrument measurement. For ease of maintenance, instrument in the upstream and downstream usually equipped with isolation valve upstream valve should be fully open at this time, still should is enough distance from instrument, avoid instrument import the velocity distribution of distortion. In some constant standby line shall be set up do maintenance section.
(3) take pressure generally located in the flange, ring room or clamping ring. Take pressure in horizontal tube, when measuring gas flow rate, should be located in the top of the vertical pipe section, to prevent liquid or dirty dirt to enter, when measuring the liquid flow, should be located in the lower part, prevent gas entering. Guide pipe should be according to the shortest for laying pipeline, the longest do not exceed 80 m; Diameter not less than 8 mm. Two guide pipe should be close to, or because of two different guide pressure fluid temperature in the tube will cause the fluid density change and produce the transducer zero drift. Installation guide pipe need to consider to have ruled out when the pipe water or gas, the top should be a bleed valve, and concave department should set up the water drain valve, colleagues should avoid level of pressure pipe installation guide, guide the gradient of pressure pipe shall not be less than one over twelve.
(4) install the yb in pulse source attachment
Most instrument all too late to follow record pulsating flow, therefore, cause a lot of measurement error, the unsteady flow is a kind of slow pulse form of cash, also should avoid. Flow meter should be installed away from the pulse source, according to the facts in his inevitable should be in line with inflatable cushion and choke low-pass filter to reduce the ripple, or USES the instrument with good response (e.g., electromagnetic, ultrasonic, etc.).
(5) the instrument installation in harsh environment
Instrument external environmental conditions will affect the life of the instrument, measurement accuracy, and safety. Major environmental factors that affect the instrument are: temperature, humidity, safety and electrical interference, etc. Flow meters are installed at the scene of the production and the production of iron and steel company environmental instrument is poorer, to find a completely will not affect the environment of the instrument is more difficult. Therefore, when the flow instrument selection and installation of flow meters to consider the influence of environmental factors, as far as possible may choose suitable for the flow meter working environment.
Flow meter is not accurate or operation is not normal, often are not necessarily flow instrument faults, but the installation or other factors in the system. So when in the design, installation, and should be considered when using the throttle device.