Step 1: Find out your flue operating conditions first-temperature, pressure and medium are indispensable
Before choosing the Round Tube Flue Expansion Joint model, don't rush through the product brochure. Ask yourself three questions first:What's running in the pipeline? How hot is the temperature? How stressful?If these three points are wrong, the rest is all useless.
You are installing the flue of the power station industry. The flue gas temperature is always above 400℃, and the pressure is still a little negative. That normal rubber compensator can't handle it, come onHigh temperature axial expansion jointOrCorrugated expansion joint for power plant industry。 On the other hand, if it is a ventilation duct with normal temperature and low pressure, it is more cost-effective to use non-metallic expansion joints-it is cheap, easy to install, and can absorb multi-directional displacement.
Are there any corrosive gases in the medium? For example, the wet flue gas after desulfurization contains sulfide. At this time, it is necessary to consider lining with PTFE or stainless steel. Don't choose ordinary carbon steel to save money, it takes less than half a year to perforate.
Tips:When the temperature exceeds 350℃, it is best to choose heat-resistant alloy (such as Incoloy 800) for metal bellows, and the temperature resistance grade of fabric layer should be confirmed for non-metallic expansion joints. Not sure? Look directly at this siteNon-metallic expansion joint (fabric fiber expansion joint)AndHigh temperature axial expansion jointThe product parameters are clearly marked above.
Step 2: Measure the quantity of displacement-axial, transverse and angular displacement, don't get confused
Many customers only give a "pipeline will move", and then ask me to recommend the model-this can't be chosen, brother!
You need to know exactly how the pipe moves. For example, the thermal expansion and contraction of horizontal pipes mainly produce axial displacement (elongation or shortening); Lateral and angular displacements should be considered if the pipe is turned or if there is a support and hanger offset.Remember clearly: choose general type or straight pipe pressure balance type for axial displacement; When the lateral displacement is large, the lateral type of the compound hinge is upper; If the angular displacement is large, the curved tube pressure balance type is more suitable.
Last month, a cement factory customer with a flue diameter of 1.2 meters and a temperature of 200℃ told me that "the displacement is about 5 centimeters". I asked whether it was axial or horizontal? He was stunned. Later, after on-site measurement, the axial direction was only 2mm, but the lateral displacement was 30mm. And finally got him matchedCompound hinge transverse expansion jointThe problem is solved completely. If he used the ordinary axial type as he had thought at first, the tie rod would collapse within two months of installing it.
So, don't be lazy and take a ruler and measure it! The axial displacement depends on the distance change of the fixed brackets at both ends of the pipeline, the transverse displacement depends on the offset of the pipeline center line, and the angular displacement measures the inclination angle of the flange surface. Write it down after the measurement, and take your seat directly when selecting the model.
Step 3: Look at the material – metal bellows or non-metallic fabric? Wrong choice equals white clothing
This step is the most tangled? Actually, it's just one sentence:High temperature and high pressure, need long life, choose metal bellows; For low temperature and low pressure, complicated displacement and limited budget, choose non-metallic fabric expansion joint.
Common metal bellows areUniversal corrugated expansion joint、Straight pipe pressure balanced expansion joint、Sleeve type pipe expansion jointWait. Advantages: High voltage resistance, long service life (usually more than 10 years). Disadvantages: Expensive, high installation requirements, cannot absorb too much lateral displacement.
What about non-metallic expansion joints? This site'sNon-metallic expansion joint (fabric fiber expansion joint)Andrubber compensatorThe inside is made of silica gel cloth and fluorine adhesive cloth, which can withstand within 300℃, has good elasticity and can absorb axial, transverse and angular displacements at the same time. Disadvantages: The pressure cannot be too high (generally below 0.1MPa), and the life is shorter (3~5 years).
PTFE compensatorSpecialized in dealing with strong corrosive media, such as pickling workshops. If you encounter an acid-base environment, prioritize it.
By the way, don't ignoreRubber PTFE compensator— — It is both corrosion-resistant and elastic, but the upper limits of temperature and pressure should be checked clearly.
Step 4: Take your seat-pick the most matching model from the product library of this site
All the data in the first three steps are complete? Okay, let's go ahead and pick. According to the working conditions and displacement, let me help you list the corresponding relationship:
- Mainly high temperature and axial displacement→ ViewHigh temperature axial expansion jointOrCorrugated expansion joint for power plant industry
- Large diameter, low pressure, complicated displacement→Non-metallic expansion joint (fabric fiber expansion joint)OrRectangular non-metallic expansion joint(if rectangular flue)
- It is necessary to withstand internal pressure thrust to avoid transmission of thrust to pipe support→Straight pipe pressure balanced expansion jointOrCurved tube pressure balance expansion joint
- Large lateral displacement, such as an L-shaped pipe→Compound hinge transverse expansion joint
- Need to insulate flue gases, such as boiler outlets→ CollocationFlue gas baffle doorOrDouble-sealed single-axis circular baffle doorUse Together
- Buried pipeline or limited space→Direct buried (fully buried) type expansion jointOrExternal pressure single axial expansion joint
If you are unsure, look directly at the "Applicable Working Conditions" table on each product page, where the temperature, pressure and displacement ranges are listed. Don't just look at the picture, click in and read the parameters.
Step 5: Confirm the connection method and installation space – flange or welding? Is it long enough?
The model has been chosen, but whether it can be fitted is another matter. Find the connection method first:Flanged connectionCommon in low-pressure pipelines, easy to disassemble and assemble;welded connectionUsed for high pressure or high temperature, good sealing performance. Is your existing pipe a flange or a weld? If it turns out to be a flange, the expansion joint must also be equipped with a flange. If it turns out to be welding, thenUniversal corrugated expansion jointGenerally, short tubes are brought out of the factory, and butt welding is OK on the spot.
Then measure the installation space-the expansion joint has a minimum installation length and a maximum compensation length. Such asSleeve type pipe expansion jointThe amount of expansion is large, but the length is also long, you have to reserve room for the sleeve to slide. Don't buy it back and find it can't fit, then it will be embarrassing.
guide tubeDo you want to add it? If the medium flow rate is high or there are particles, be sure to add a guide tube to prevent the bellows from being washed and worn. This site has a specialexpansion joint guide tubeAccessories, which can be selected individually. Likewise,tie rodThe function is to prevent the expansion joint from excessively stretching or compressing, and the adjustment nut should not be screwed to death during installation, leaving a heat compensation margin. How to tune it? Refer to the Q&AHow to adjust the tie rod nut of expansion jointThat article.
Additional reminder:Don't ignore these accessories, they can save lives in critical moments. For example, the flue of the cement industry is dusty, and the bellows will be worn out in half a year without a guide tube. When the time comes, it is better to change the expansion joint as well as a better guide tube.
Okay, in five steps, you can basically avoid 90% of the pit. Finally, one more word:Round pipe flue expansion joint modelIt is not the more expensive the better, nor the cheaper the better. The right working conditions for you are king. If you are not sure, send a private message to customer service, or directly turn to the product library of this site. Each model has detailed parameters, so you can't go wrong if you are right.