How to choose Chai Flue Expansion Joint? How to install? Teach you how to do it step by step

1. Don't be in a hurry to buy, first understand what the diesel flue expansion joint is for

The exhaust pipe of diesel generator set has high temperature and great vibration. If the pipe interface is hard connected, it will leak and crack before running for long. The diesel flue expansion joint (to put it bluntly, it is a compensator) is used to absorb these thermal expansion and contraction displacements, and at the same time isolate the vibration, so that the whole smoke exhaust system is stable. Two days ago, I met a customer, and I bought an ordinary pipe for cheap and welded it directly. As a result, the weld cracked after less than a month's operation, and all the oil and gas leaked into the computer room. The smell... Alas, forget it.

So don't underestimate this little thing. It is installed between the engine exhaust port and the smoke pipe, or at the corner and wall of the smoke pipe, which can greatly reduce the stress of the pipe, and can also be used as a vibration isolation pad. We have one on our stationUniversal corrugated expansion joint、Metal rectangular expansion joint,Non-metallic expansion joint (fabric fiber expansion joint)All of them do this job, but the specific kind to use depends on your working conditions.

Second, the first step of type selection: take a ruler to measure these three data, otherwise it can't be installed

Many old iron bought expansion joints and asked "how much is one?" As a result, when they bought them back, either the caliber was wrong or the length was different. Remember, measure three numbers first, just take a tape measure:

• Pipe inner diameter (or outer diameter): Diesel flue usually uses a circular pipe, and the diameter of the center circle of the flange screw hole can also be measured. If the measurement is wrong and the flange does not match, it is equivalent to buying it for nothing.
• Installation length: Refers to the distance between the flanges at both ends of the expansion joint. Don't estimate, it needs to be real, especially in places where the space is tight. If it is 1cm long, it may not get stuck.
• displacement amount: Pipe thermal expansion = linear expansion coefficient × temperature difference × pipe length. The exhaust temperature of diesel is generally 400~600℃, and the temperature difference is large. You can roughly calculate how many millimeters to compensate in the axial direction and the horizontal direction respectively. Really don't count, ask the manufacturer for technical parameters, or refer to ourHigh temperature axial expansion jointThe selection table of.

Tips: Measure a few more points when measuring, take the maximum value, safety first.

Third, metal expansion joint vs non-metal expansion joint, which is more suitable for your diesel engine

Which one to choose? Don't dwell, look at three points: temperature, corrosion, and budget.

Metal expansion joint(For example, ourMetal rectangular expansion joint、Universal corrugated expansion joint) It can withstand high temperature and strong pressure resistance, and is suitable for the straight section of the main smoke exhaust pipe, especially when the temperature exceeds 500 ℃. The disadvantage is that it is relatively stiff, can't absorb too much lateral displacement, and the price is relatively higher.

Non-metallic expansion joint(e.g.Rectangular non-metallic expansion joint、Non-metallic expansion joint (fabric fiber expansion joint)) Soft, large compensation displacement, and can also isolate noise and vibration, especially suitable for scenes where the space in the computer room is compact and multi-directional displacement is required. However, the temperature resistance is usually below 300℃. If the exhaust temperature is very high, you have to add heat insulation layer or use an inner lining structure. By the way, non-metal has good sealing performance and low leakage rate. Many projects use this.

And guess what? Nowadays, diesel engine projects will most likely use non-metallic expansion joints in the computer room and metal in the outer flue. Combined with both sides, it saves money and is reliable.

4. Installation practice: Follow these 5 steps, don't be afraid of installing wrong

Installation is actually not difficult, but many people are planted in the details. You follow my steps, and I guarantee you to get it done in one go:

1. Check dimensions and appearance: After unpacking, check whether the model, caliber and length are correct, and then see if there is any transportation bump. EspeciallyNon-metallic expansion jointThe cloth surface is scratched and it will be wasted.
2. Clean the flange surface: Clean the oil stains, welding slag and burrs on the pipe flange and expansion joint flange. Otherwise, the sealing gasket is not compressed firmly, and the air leaks properly.
3. Confirm Installation Direction: Metal expansion joints usually have arrows pointing in the direction of media flow. Stop acting backwards! Non-metallic ones do not have arrows, but be careful that the guide tube (if any) is in the direction of the airflow.
4. Bolt tightening sequence: First pre-tighten diagonally, and then gradually tighten to the specified torque. Don't screw one side to death, or the other flange is crooked. We have one on our stationHow to adjust the tie rod nut of expansion jointQuestions and answers, which contain specific moment values.
5. Removing transport screw: Many people forget this step! The new expansion joint will have several screws to fix the corrugation when it leaves the factory to prevent deformation during transportation. After installation, it must be removed, otherwise the expansion joint can't move, which is equivalent to white installation. You can see "Does the screw of the expansion joint need to be removed" in the FAQ.

attention: Do not scratch the corrugated surface with welding rods or wire balls during installation, especiallyPTFE-lined hoseThis kind of coated thing is easy to rust when scratched.

5. It's not the end of installation. Just check these three places daily

After the Chaifa flue expansion joint is installed, it is not once and for all. Every quarter or after every overhaul, it is enough for you to spend five minutes looking at it:

• Whether the appearance is distorted or bulging: Is there any dent or crack in the corrugation of the metal? Are the non-metallic fabrics fluffed and layered? Hurry up and record if you find it.
• Leak inspection: When running, use soap water nozzle sub-connection, bubbling is leakage. Or observe for black ash around the pipe. A leak indicates that the gasket is aging or not pressed properly during installation.
• displacement indication: There is the expansion joint of the tie rod. Look at the scale or mark on the tie rod. Does it exceed the design displacement range? If the deviation is serious, it means that there is something wrong with the pipe support.

Speaking of which, ourService life of expansion jointAs mentioned in the question and answer, under normal working conditions, metals can be used for 5~10 years, and non-metals can be used for 3~5 years. But if you inspect in place and find problems in advance, you can save a lot of maintenance costs.

6. Last question: When should I change? Don't wait for the air to leak before regretting

Then when do you have to change? A few signs for you:

• Metal corrugations show visible cracks or corrosive perforations.
• Non-metallic fabric surfaces are broken, carbonized, or stitches are broken.
• The expansion joint is permanently deformed and cannot go back, such as being flattened or elongated by more than 10%.
• The amount of leakage has increased significantly, and it is useless to mend it.

Tsk, don't wait until the smoke is out before you change it. Be more careful at ordinary times, and change when you should. We have one on our stationrubber compensator、PTFE compensatorWait for alternatives of different materials, but remember one thing: choose the same specifications and materials as the original factory, and don't replace them randomly. If you are really unsure, ask the manufacturer directly for model selection suggestions.

Okay, the diesel flue expansion joint from selection to installation to use to change, all for you to understand. Follow it and your diesel smoke exhaust system will run steadily for at least a few years.