What is a straight cylinder non-metallic compensator? What is the difference between rectangular and round metal compensators?
Have you ever seen one of those things with a "cloth bag" over a pipe? That is the straight non-metallic compensator-to be exact, it is written in our catalogNon-metallic expansion joint (fabric fiber expansion joint)A kind of. It looks like a cylinder, with a skin of fibrous fabric plus rubber or fluoroplastic, and flanges at both ends, specifically used to absorb the displacement caused by thermal expansion and contraction of the pipe.
Compared with metal compensator, its biggest advantages are large compensation, no thrust and corrosion resistance. Rectangular metal compensator is generally used on flue gas pipeline, which absorbs displacement by corrugation; Circular metal compensators (such as oursUniversal corrugated expansion joint) High pressure resistance but fear of corrosion. What about straight non-metallic stuff? The temperature can be above 1000℃ (with insulation layer), but the pressure is generally 0.5MPa-don't expect it to carry high pressure.
Then how to tell which one to use? Simple and rude: If it is a low-pressure, large-diameter pipeline containing corrosive gases, such as desulfurization flue and cement kiln tail waste gas, straight non-metallic compensator is the first choice. High Pressure? Use the metal bellows obediently.
What do the numbers and letters in the model mean? — — Take the non-metallic expansion joint of this station as an example to disassemble the naming rules
What do you mean by "FVB-600×4-F"? I said don't worry, this string of characters is the manual of this compensator when disassembled.
With usNon-metallic expansion joint (fabric fiber expansion joint)Common numbers for example:FVBRepresents Fabric Vertical Bellows (or something like that), subsequent numbers600Is the diameter (inner diameter 600mm),4Represents the wave number (that is, the number of skin fold layers, the more the wave number, the larger the compensation amount), and the finalFRepresents flanged connections. If you seeFVB-800×6-JThat is, 800mm diameter, 6 waves, with connection (J connection).
Isn't it simple? But be warned-different manufacturers have different model rules. Some are compiled according to the national standard JB/T 12235-2015, and some are named blindly by themselves. If you search for "straight non-metallic compensator model" on the Internet, what comes out may be "DN800-6F". Can't read it? Ask the manufacturer directly to select the parameter table, don't guess.
Don't just look at the diameter when selecting the type: temperature, pressure, displacement amount, which one leaks will be deflated
A desulfurization project bought DN1200 straight cylinder compensator according to the drawings, but the skin was torn after three months of operation. Why? Only the diameter was correct, but the medium temperature was not checked-the actual flue gas temperature was 300℃, while the upper temperature resistance limit of the skin they bought was only 200℃.
- Design temperature: For flue gas pipeline, take at least the highest continuous temperature +50℃ balance. weCorrugated expansion joint for power station industryThere are specific calculation methods in that article, so I won't go into details.
- Working pressure: The withstand voltage of non-metallic compensator is generally ≤0.3MPa, and if it exceeds it, metal or reinforced structure must be used. If the pipeline has negative pressure (such as the inlet of the desulfurization tower), the ability to resist negative pressure must also be considered.
- displacement amount: Including axial, transverse and angular displacements. Many customers only give the diameter, not talking about the direction of the pipe and the position of the fixed bracket. And guess what? When the compensator is installed, it is hot, and the pull rod is dead! How to tune it? Later, I found out that it didn't count the amount of cold tightness.
Also don't forget the media ingredients. Sulfur flue gas Choose an acid-resistant skin (such as a fluororubber or PTFE composite layer). OurRubber PTFE compensatorIt is specifically designed to deal with this kind of scenario-although it is made of rubber, the principle is the same.
The most common mistakes in on-site installation: orientation of guide tube, adjustment of tie rod, and how to fix the skin
Installation errors are more pitiful than selection errors. The wrong choice is a big deal to change, and the wrong installation is directly scrapped. Three iron rules:
Guide tube orientation: The role of the guide tube is to protect the skin from being washed by high-speed media, and the arrow must point to the direction of the media flow! A construction site was installed backwards, and the deflector was in front of the airflow, which forcibly blown up the compensator. Alas, the foundation is wrong.
tie rod adjustment: When the straight-cylinder non-metallic compensator leaves the factory, the tie rod nut is locked, which is in the preloaded state. Once installed in place, loosen the tie rod nut to the installed length (the engineer will mark it clearly on the drawing). Can't figure out how to adjust it? Refer to our previous question and answer "How to adjust the expansion joint tie rod nut"-it is very simple: loosen first, adjust later, and lock again, and pay attention to the synchronization on both sides.
skin fixation: Both ends of the skin are pressed with pressure plates, and the torque of the bolts should be uniform. Almost? Air leak. And there must be an expansion margin-the skin must not be stretched too tightly. WeNon-metallic expansion jointThere is a torque value in the product information, so screw it according to it.
Power station desulfurization and cement kiln tail- -model matching practical combat in two typical scenarios
It is better to look at two real things than to say a thousand words.
Scenario 1: Desulfurization flue of power station。 A 2×300MW unit, the temperature of the inlet and outlet pipeline of the absorption tower is 90-120℃, the pressure is ±3kPa, and the pipe diameter is DN1800. At first, they wanted to use metal rectangular expansion joints, but the corrosion was too severe, so they replaced them every six months. Later, it was replaced with a straight-cylinder non-metallic compensator, and the model was selectedFVB-1800×4-F(4 waves, fluororubber + PTFE layer for skin). It turned out that it didn't break after three years of use. Why? With low temperature, low pressure and large displacement (30mm in axial direction), non-metal is just right.
Scenario 2: Exhaust gas pipeline at the tail of cement kiln。 The temperature fluctuates greatly (from normal temperature to 350℃), contains dust, the pipe diameter is DN2000, and the displacement is mainly 20mm in the axial direction +5mm in the transverse direction. They choseFVB-2000×6-J(6-wave tape takeover, skin plus stainless steel wire mesh to enhance thermal insulation). Note: Pressure is close to normal here, so no problem. But what if there is a pressure fluctuation at the outlet of the fan at the kiln tail? Then you have to add a deflector and a wear-resistant liner.
See? It is also a straight cylindrical type, so the wave number, skin material and connection mode have to change with the working conditions. Don't conquer the world with one model.
Can't figure out the parameters? Send the working condition table to the manufacturer and let a professional engineer help you calculate it. Take the time to figure out the temperature and pressure displacement measurements, and save you enough money to treat the whole department to a big meal. Don't ask me how I know.