Two days ago, a brother from a cement factory called, saying that their flue expansion joint leaked like rain, and the negative pressure was unstable. The environmental protection department came to the door every three and five to "drink tea". I know from the description-it is the old habit of fatigue cracking of corrugated pipe and aging and leaking of non-metallic layer. The flue expansion joint is tortured by high-temperature smoke and dust every day, and it can be carried for three to five years. Drag it off? The efficiency of the system drops at least, and the whole pipeline suffers at worst. You have to change it if you need to change it, but there are many ways to change it and what kind of it.
Before you do it, find out the family background
Is the original expansion joint metallic or non-metallic? Rectangular or circular? How big is the caliber? What is the operating temperature and pressure? Are there any corrosive ingredients in the media? This data directly determines what alternative products you should buy.
For example, the temperature of the flue gas pipeline of a power station is often five to six hundred degrees Celsius, and the pressure is not small. Under such working conditions,Corrugated expansion joint for power station industryOrHigh temperature axial expansion jointIs the first choice. If the dusty flue gas in the cement industry is mostly rectangular pipes, thenRectangular non-metallic expansion jointOrNon-metallic expansion joint (fabric fiber expansion joint)More reliable-good flexibility, wear resistance, and cheap. Don't forget to take a tape measure and measure the mounting space to see if there is any bracket interference. Sometimes the old expansion joint is tightly installed, and the new one can't fit in if it is a little worse in size. Rework can be too torturous.
Type selection is a technical job
After figuring out the family background, it is necessary to make a trade-off between metal and non-metal. Metal has high pressure resistance and long life, but its ability to absorb displacement is limited, so it is suitable for straight pipe sections; Non-metal has good flexibility and corrosion resistance, especially suitable for rectangular flue, and is easy to install. Take the desulfurization flue as an example. The flue gas contains sulfur and high humidity. Not only is it half cheaper to use non-metallic expansion joints than metal ones, but it is also worry-free-stainless steel can't bear the corrosion of wet sulfur, but fabric fiber expansion joints can be easily handled.
If the pipe displacement is more complicated, such as angular or lateral displacement, then don't expect a single expansion joint. Can considerCompound hinge transverse expansion jointOrCurved tube pressure balance expansion joint— — These two are specially designed to deal with multi-directional displacement, and the structural design can digest the force and moment. In addition, don't forget the guide tube when selecting the model. Many people don't know the function of the guide tube-it is installed on the inner wall of the expansion joint, which blocks the high-speed smoke from directly washing the bellows, and its life can be doubled. In a high-flow flue, this thing can't be saved. If you save it, you dig a hole for yourself.
When it comes to construction, the details determine success or failure
After the old expansion joint is removed, check the pipe port for any deformation. Some old pipeline welds are crooked, and the ports are tilted up. If the new parts are not trimmed, the sealing surface will not fit at all. Hoist new expansion joints after trimming the ports-pay attention to directions! There is generally an arrow pointing at the expansion joint, which is the flow direction of the medium. If it is installed backwards, it will be dry for nothing. The bolts should be pre-tightened symmetrically, do not screw to death once, twice or three times to ensure that the sealing surface is evenly stressed.
If you are using an expansion joint with a tie rod (such asStraight pipe pressure balanced expansion jointOr double hinge transverse type), remember to adjust the tie rod nut. The tie rod is usually pre-tightened under transport to prevent damage to the bellows by shock. After installation, loosen the pre-tensioning tie rod to let the expansion energy-saving freely expand and contract. How exactly to adjust? Refer to our article on the adjustment of the tie rod nut of the expansion joint, which is illustrated and illustrated, and you can understand it at a glance. When welding, control the heat input and don't burn the bellows-especially stainless steel bellows, overheating can cause intergranular corrosion and crack in no time.
Don't leave in a hurry after changing, debugging and acceptance will take a wave
Touch the sealing surface with your hand or spray it with soapy water to see if there is any air leak. Then run in the temperature state and stare at the expansion joint-the displacement is smooth or not? Is there any abnormal distortion? Pay attention to the sound. If it is "rattling", there is a high probability that the installation is offset or the tie rod is stuck. At this time, quickly stop the machine for investigation, and the consequences of holding on will be serious.
Pipe brackets. If the bracket is loose or stuck, the expansion joint can't hold it-the displacement is all stuck on the bellows, the stress is concentrated, and it will be scrapped sooner or later. Finally, record the initial displacement value and installation date for future inspection and comparison. Keep the data, and you will know it in your heart the next time you change it.
Several pits that are prone to rollover to help you avoid
First, don't be cheap and replace the special type with the general-purpose type. For example, a high-temperature flue, you take aUniversal corrugated expansion jointHard on, it will fail in minutes. Why? The design temperature and pressure level of the general type can't bear it at all, and the wall thickness and material of the bellows are wrong. Second, try to use rectangular non-metallic expansion joints for rectangular flues, and don't take circular hard changes-the shape does not match, and the air leaks until you doubt your life. Third, while changing the expansion joint, check the nearby smoke baffle door or insulation door, such asDouble-sealed single-axis circular baffle door、Electric plug-in insulation door。 If the seal is not tight, repair it together to save you the trouble next time. Anyway, think more about it when you make a plan, which is much better than reworking later.
In the final analysis, the replacement of the flue expansion joint is: the working conditions are found out, the road is selected, the construction is meticulous, and the acceptance is in place. Do these four points and don't have to worry about it for at least five years. Finally, the equipment thing, if you fool it, it will fool you. Don't wait until it leaks into a fountain to remember to change it.