lining material: in the production and manufacture of electromagnetic flowmeter, in order to meet the measuring tube for measuring the roughness requirement in the future, often need to according to the fluid types to choose excellent lining material.
More need to adopt to different lining material excellent processing method.
Now commonly used lining materials are: chloroprene rubber, EPDM rubber, polyurethane, PTFE fluoride plastic and PFA.
For different pipe lining, different processing technology, here a brief introduction of the process points of different lining, draw reference flow meter
According to the specification requirements of the measurement and is used to measure the medium of the lining to roughly the following: a, neoprene: neoprene is suitable for more than 12 large caliber sensors, used for measuring water, sewage, weak acid, weak alkali medium fluid.
General with adhesive film directly attached on the inner wall of the stainless steel tube, through vulcanization.
This process, the rubber lining of the surface roughness is generally high, operation should pay special attention to the flat seams, but lower relative roughness.
For small diameter neoprene and EPDM rubber lining, good use of mould pressing, attached on the inner wall of the tube and then curing, reduce the lining surface roughness and surface roughness depends on the mould core rod pressure and vulcanization process.
Polyvinyl chloride resin: at present, the domestic polyurethane lining use is more soft material and adopt measures for the process of water lining roughness depends not only on the mold surface roughness of rods, also will be affected by water, exhaust gas, heating, cooling and material composition, the influence of the proportion.
Domestic rigid polyurethane with ethyl carbamate polyester rubber, its forming is the important technological points, remove injection involved in the process of bubbles, make chemical reaction (
Using centrifugal casting process method: guarantee the raw material in storage in a dry state, smooth and uniform on raw materials mixing, stirring, for removing the involved in the bubble of raw material, pipe set appropriate rotational speed, well control the temperature of the raw material processing, hardening, crosslinking.
Request lower roughness of lining material fluorine plastic should be used.
Piping, tanks and other containers used for the PTFE fluoride plastic lining, usually in metal pipe lining into a thin walled teflon tube, or using the teflon tube inserted, and then for bonding process.
This kind of lining is the main drawback of resistance to negative pressure is not high, affected by temperature, bonding is often unreliable.
Three, fluorine plastic: for electromagnetic flowmeter, the fine fluorine plastic lining is PFA.
PFA mainly adopts the way is injected into molten resin, and then injection (
Injection molding method)
By injection molding method, belong to no one.
The quality of the PFA lining has good chemical resistance, heat resistance, high adhesion,
Especially in the area of chemical resistance, heat resistance, using the unique manufacturing technology, can reduce internal stress and the intrinsic bubbles, in order to avoid cracks, such making that flow meter used in harsh environments, still has the very high reliability.
Therefore, in the process of PFA lining manufacture, management is important for injection molding temperature (
Resin viscosity, metal mold temperature)
, metal mold cooling control (
Cooling time, temperature)
Pressure control, resin.
Injection temperature setting should be as low as possible, to reduce the thermal degradation of PFA resin.
Injection molding, metal mold temperature to keep melting point is greater than the resin evenly.
Due to the need for high precision control of cooling, reason should be set up multiple cooling loop in the metal mold, and carry on independent cooling control operation.
In cooling control at the same time, also deal with resin pressure control.
Electromagnetic flowmeter electrode process: electrode processing including polishing and passivation process.
There are three kinds of polishing method, mechanical polishing is stainless steel polishing polishing (three
The mechanical polishing, chemical polishing and electrochemical polishing)
* process first.
Next, the combination, such as mechanical polishing & ndash;
Chemical polishing and mechanical polishing & ndash;
Mechanical polishing for primary polishing, surface roughness of concave and convex processing electrodes to the certain roughness, and then carry out chemical polishing or electrochemical polishing.
Chemical polishing and electrochemistry polishing can remove micro electrode surface roughness, thereby improving the mirror bright, also can complete polishing and passivation process, the purpose of increasing the surface chromium content, forming good passivation layer.
For rough surface due to the existence of macro roughness, to use mechanical polishing method to achieve Ra&le first;
M's roughness, reoccupy chemical polishing or electrochemical polishing method to Ra = 0.
M above the roughness, can obtain after the brightness, bright luster and good passivation layer.
After polishing and passivation of the electrode can form stable passivation layer.
But when in storage, transport, assembly, be sure to keep the surface passivation layer is not damaged.
With the traditional electromagnetic flowmeter sensor, simply by soaking in the water (
Sometimes this method needs a few days and nights of time)
Mode of production, natural form passivation, compared after polishing and passivation process of electrode, can obtain stable corrosion resistance of the electrode, quite high to improve the production efficiency, is a production process.
In this paper by embellish instrument technology co. , LTD. Arrange release.
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