Two days ago, a customer told me that the flue expansion joint of their factory suddenly exploded, and the high-temperature smoke sprayed out, and several workers were almost burned. Alas, this matter really can't be careless. If you encounter this situation, don't panic. Follow the following steps to save your life and stop your loss. Remember, the core of flue expansion joint burst treatment method is four words: fast, accurate, stable and preventive. I'll break it up and break it up.
Step 1: Emergency shutdown and safety confirmation-life saving is important, don't rush to start
When you see the expansion joint explode, is your first reaction to rush up and block it? Never! Hundreds of degrees of high-temperature smoke, residual pressure, and corrosive gases that may leak out can kill people. What's the right thing to do? Press the emergency stop button to cut off the fuel source, and then open the relief valve to relieve pressure. Remember, shutting down the furnace is not just closing the valve. You must confirm that the whole system is in a pressure-free and cooling state.
- Cut source:Close the fuel valve, shut off the power supply, and put a "No Closing" sign.
- Release:Open the release valve on the flue to allow the residual smoke to evacuate. Don't try to be fast, leak slowly.
- Gas measurement:Use a portable gas detector to measure the concentration of surrounding gases, especially highly toxic gases such as carbon monoxide and hydrogen sulfide.
- Cooling:Cool naturally or spray with mist water to cool down, but be careful not to let cold water hit the high-temperature expansion joint directly, which will explode.
Tips:Be sure to work for more than two people and take care of each other. Get a set of heat-proof gloves, goggles and gas mask. Don't bother. No one is allowed to approach the leak until the safety is confirmed.
Step 2: Judge the burst type and location-cracked or the whole circle collapsed?
Okay, now that the system is secure, you should go to the scene and see what's going on. Don't rush to fix it, see it clearly first. You can't put a piece of mud on it, can you? We have to prescribe the right medicine.
Look at the crack:Was it a partial tear, or was the entire expansion joint toroidally collapsed? The local crack can be supported for a while by temporary plugging. If the whole circle collapses, it must be stopped and replaced. Don't hesitate.
Looking at the location:Is the burst point on the corrugation of the expansion joint itself, or at the connection of the flanges on both sides? Air leakage at the flange is often caused by loose bolts or gasket failure. Tightening may solve the problem. If the bellows bursts, it will have to be replaced.
Look at the direction of the leak:Is the flue sprayed directly from the crack, or is it leaking from the edge? Direct injection indicates high pressure and deep cracks, which must be treated immediately. If it leaks, it may be carried for a few hours, but it can't be dragged.
Think about it, if you patch it indiscriminately and end up in the wrong place, isn't that a wasteful effort? What about that? Take a flashlight and take a photo with a camera for comparison. Only when the judgment is clear does the next step make sense.
Step 3: Temporary plugging operation-use the right materials and support them to the maintenance window
Assuming that you judge that it is only a local crack, and the production line can't be stopped (for example, the order is pressed), you can make a temporary plugging first and last until the next shutdown for maintenance. But note that temporary is temporary, don't think of it as permanent.
- Select materials:Don't use ordinary cement or tape, it can't handle the high temperature. Use high temperature resistant sealant (1000℃ grade) with ceramic fiber blanket, or directly with metal patch (stainless steel sheet + heat resistant bolt).
- Clear Surface:Use a wire brush or angle grinder to clean the rust and oil around the burst, and expose the metallic luster to stick firmly.
- Caulking:Squeeze the high temperature resistant sealant into the crack, cover it with a ceramic fiber blanket, and tie it with stainless steel wire or clamp on the outside.
- Monitoring:After blocking, send a special person to guard it, and measure the surface temperature every 5 minutes to see if it continues to expand. Once the air leak is found to be aggravated, stop the furnace immediately.
Note:Temporary plugging can only be used in low-pressure and low-temperature areas (such as smoke temperature below 600℃ and pressure below 0.1MPa). If it is a high-pressure boiler flue, don't take the risk, just stop the furnace and change parts.
Step 4: Standard steps for replacing expansion joints-dismantling, cleaning, installing new, and tightening
It's time to really fix the problem. If you want to change the expansion joint, don't think about it yourself. Go through this process, and you will basically not go wrong.
Demolition
Use a plasma cutter or angle grinder to cut the old expansion joint from the flange joint. Take care to protect the flange surface and don't cut deep marks. After cutting, take off the old part entirely, and check the flange surface for deformation or corrosion.
Clear face
The old gasket, rust and welding slag left on the flange surface are all polished clean. File the high points with a flat file and pass them through with sandpaper again. Blow off the dust with compressed air after cleaning. Remember, surface flatness directly affects the sealing effect.
Install new
After unpacking the new expansion joint, check for shipping damage first. Note the installation direction: There are usually arrows on the expansion joint to indicate the flow direction of the medium. Don't install it backwards. Pad a new high temperature resistant gasket between the flanges (graphite clamp metal mesh gasket is best), then lift the expansion joint in place and align it with the bolt hole.
fastening
Many people suffer from this. Don't screw a bolt at once! According to the diagonal order, gradually tighten in three steps: first screw it with your hand until it is strong, then screw it with a wrench to 50% torque, and finally screw it to the end according to the torque value in the instructions. Screw each bolt twice, each time diagonally. Finally, check whether the flange gap is uniform with a gauge, and rework if it is not uniform.
Note:After the change, remember to do an airtightness test, pass low-pressure air or water to see if there is any leakage. Only when it's fine can it be put into operation.
Step 5: Daily checks to prevent recurrence-temperature, displacement, corrosion, and no leakage
You said you'd be all right with a new one? Pattern Tucson broken. Expansion joint burst is often caused by long-term temperature exceeding the standard, excessive displacement or corrosion thinning. If the root cause is not eliminated, it will be in vain if it is changed.
- Temperature:The surface temperature of the expansion joint was measured once a week by infrared thermometer and compared with the design value. If the temperature exceeds the design upper limit for a long time, it is necessary to check whether the flue gas system has dead spots or dust accumulation.
- Displacement:The function of the expansion joint is to absorb the thermal expansion and contraction of the pipe. You have to regularly observe whether its expansion and contraction amount is within the normal range. You can make a mark and measure it with a caliper. If the displacement is stuck or too large, there is a problem with the pipe bracket or guide.
- Corrosion:Focus on the bottom of the bellows and the weld, which are most prone to dust and liquid accumulation. Use an ultrasonic thickness gauge to measure the wall thickness. Once it is found that the thinning exceeds 30%, arrange for replacement quickly.
Is it possible to save a lot of money by finding it early? Yes. The cost of a burst overhaul is enough for you to do dozens of preventive inspections. So don't be lazy, keep the inspection ledger in mind, and implement the responsibility to people.
In fact, the burst treatment method of flue expansion joint is not so mysterious, and the core is calm judgment, safety priority and standardized operation. If you follow these five steps, you will never get blind. Alas, to be honest, many accidents are because the first step is not done well, and people rush up when they panic, and the result is a big problem. I hope this practical post can help you step on the right rhythm.