Clean flue expansion joint of desulfurization system, the easiest pit to step on during model selection
After so many years of desulfurization, if the expansion joint on the clean flue is chosen wrong, it is really digging a hole for yourself. Two days ago, a customer spat with me, saying that the expansion joint that had just been installed for half a year began to leak, and it cost tens of thousands to overhaul it once. In fact, nine times out of ten, this matter was buried in the selection stage. Today, let's talk about the easiest pits to step on in the selection of net flue expansion joints. You can compare them and don't take detours.
How "toxic" is the net flue environment? — — Find out the working conditions first
Many people ask "How much is the expansion joint" as soon as they come up, and don't talk about the working conditions at all. Let me tell you, the flue cleaner is not just any pipe. Although the temperature is not high, generally 60-80℃, the humidity is high, the acidity is strong, and the flue gas still carries sulfur dioxide and sulfur trioxide that have not been removed, and the condensation is dilute sulfuric acid. In addition, the net flue gas from the desulfurization tower is basically saturated, and there are many water droplets, which is quite corrosive.
Think about it, if you use ordinary carbon steel bellows in this kind of environment, it will rust through in less than half a year. So the first pitfall is-choosing blindly without figuring out the media composition and temperature range. Remember that the net flue expansion joint must be resistant to acid corrosion, chloride ions, and can withstand negative pressure.
Non-Metal Expansion Joint vs Metal Expansion Joint, How to Choose?
This question is asked by the most people. Metal expansion joints, such as our commonly usedMetal rectangular expansion joint、Universal corrugated expansion jointThe advantages are high voltage resistance and long life, but it is afraid of acid. Once there is condensed water in the flue, the inner wall of the metal bellows is easy to pit, and the metal expansion joint requires high installation accuracy, and it is easy to become unstable if it is slightly deviated.
In contrast,Non-metallic expansion joint (fabric fiber expansion joint)It's simply tailor-made for the clean flue. Its main body is silicone gel, fluororubber, polytetrafluoroethylene and these materials, with glass fiber cloth, which is corrosion-resistant and temperature-resistant, with large compensation and cheap. The disadvantage is that the pressure bearing capacity is weak, but the net flue is basically low pressure, and negative pressure is not afraid-people have skeleton support.
Clean flue, preferably non-metallic expansion joints. Unless your temperature exceeds 200℃ or the pressure is very high, consider using stainless steel and lining. Don't listen to people fool about the strength of metal. In the clean flue, suitability is more important than strength.
Rubber compensator, rubber PTFE compensator, PTFE compensator, which one is used?
These three brothers have similar names, but they are not used the same.
rubber compensatorIt is made of ordinary rubber, with good elasticity and low price, but its temperature resistance is not good (generally not more than 80℃), and its acid resistance is average. It can be used in the flue for a short time. In the long term, butyl rubber or neoprene rubber can be made do, but when it encounters flue gas containing hydrofluoric acid, it will be directly wasted.
Rubber PTFE compensatorThe rubber inner wall is lined with a layer of tetrafluorine (PTFE). PTFE has top-grade corrosion resistance, almost no acid, and is non-sticky. Therefore, the rubber PTFE compensator in the net flue not only retains the elasticity of rubber, but also has the anti-corrosion of PTFE, which is a compromise with good cost performance. However, it should be noted that the PTFE layer should not be too thin, otherwise it will be easily damaged.
PTFE compensator, that is, pure PTFE corrugated compensator, the whole body is PTFE. This thing is corrosion resistant, and its temperature resistance can reach about 200℃, but it has poor elasticity, small compensation and expensive price. Generally used in particularly harsh strong acid conditions, or absolute cleanliness is required. If the condensed water in the clean flue has a particularly low pH or contains halogens, it must be it.
How to choose? Let me give you a formula: rubber PTFE compensator for ordinary acid resistance, polytetrafluoroethylene compensator for harsh strong acid, rubber compensator for temporary making do or very low temperature. Don't be cheap and use the rubber compensator as the main force. If you leak, you will cry.
Installation and routine maintenance, don't wait for a leak to regret it
If you choose the right product, it will still be useless if you don't install it in place. The net flue expansion joint installation has several points that can be easily overlooked:
- The guide tube should be in the right direction.The direction of the arrow on the expansion joint is the direction of the medium flow. If it is reversed, the smoke directly washes the non-metallic ring belt and wears it out quickly. If you are using a metal rectangular expansion joint, the guide must be directed towards the medium, which is the same asFlue gas baffle doorThe installation logic is the same.
- Pre-stretch or pre-compression do not mess around.During installation, the adjustment of the tie rod screw is particular. How to adjust it can be read our article on the adjustment of the tie rod nut of the expansion joint.
- Look at three points in daily inspection:Look at whether there are bulges and cracks on the outer surface (whether the fabric fiber layer of the non-metallic expansion joint is brittle); Second, listen to whether there is a hissing air leak sound; Three touches to see if there are any signs of condensation seeping out. Rubber compensators pay special attention to ultraviolet aging, and outdoor installation should be shaded.
Also, don't underestimate the drainage problem. There is more condensed water in the clean flue, so it is best to set a condensed water discharge port at the bottom of the expansion joint, or keep the slope. Otherwise, the water is soaked, and no matter how good the PTFE compensator is, it can't bear it.
Anyway, when it comes to type selection, explain the working conditions clearly and find reliable manufacturers (for example, we haverubber compensator、Rubber PTFE compensator、PTFE compensator、Non-metallic expansion jointFull series), and then install it according to the specifications, and the net flue expansion and energy saving will be used for five or six years without problems. I'm afraid that if you want to save trouble, just buy a general-purpose corrugated expansion joint and go up, which is purely blocking yourself.