How to pick the expansion joint manufacturer? A 10-Year Selection Consultant's Guide to Avoiding Pitfalls
Two days ago, I met a customer. As soon as he came up, he threw me a drawing and asked, "How much is this expansion joint?" I said, don't worry. Is your working condition steam pipe or flue gas pipe? What's the temperature? He was stunned for a moment and said, "Oh, it's just ordinary pipes. Can't you use your general-purpose corrugated expansion energy-saving type?"-I can run into this kind of conversation dozens of times a year. If you choose an expansion joint manufacturer, if you only stare at the price, you will probably roll over. Today, I'll talk to you about the pits I've stepped on and the thunder I've seen in these 10 years of selection.
1. Don't just look at price: product line breadth is the first sieve
Many purchases ask, "How much is your expansion joint per meter"-as soon as I hear this, I know that I am either a novice or just want to be cheap. What is the "universal price" of expansion joints? The same caliber,High temperature axial expansion jointAndThe materials and processes of general-purpose corrugated expansion joints are completely different, and the price difference is three or five times too normal.
How to judge whether a manufacturer is reliable? Look at his product catalogue first. If evenMetal rectangular expansion joint、Non-metallic expansion joint (fabric fiber expansion joint)、rubber compensatorThese basic categories are not all together, and most of them are small factories. For truly powerful manufacturers, the product line will cover:Corrugated expansion joint for power station industry、Metal Corrugated Expansion Joints in Cement Industry、Desulfurization flue gas baffle door、Special hose for vacuum、Direct buried (fully buried) type expansion joint…or even likeDouble hinge expansion joint for air-cooled island vacuum pipelineThis kind of niche thing can also be done.
Why is a wide product line important? Because different industries have different requirements for expansion joints. Power plant main steam pipeline needsExternal pressure single axial expansion jointTo cope with high pressure and high temperature, kiln tail flue gas in cement industryRectangular non-metallic expansion jointMore suitable, chemical plant corrosive media have to be usedPTFE-lined hoseOrPTFE compensator。
2. Customization ability is the real skill-how to choose high temperature, corrosion and vacuum conditions?
Half of the expansion joint failures on the market are because you bought the wrong model, not because the thing itself is broken. For example, in high temperature conditions (over 1000℃), you still use ordinaryUniversal corrugated expansion joint？ That's not saving money, it's giving away heads. Must get on at this timeHigh temperature axial expansion jointIncoloy 825 or higher must be used as the bellows material, and thermal fatigue life must also be calculated.
Corrosion conditions are more headache. In strong acid and strong alkali medium, ordinary metals will be wasted in a few minutes. Either withPTFE-lined hoseEither withPTFE compensator。 However, note that the process of lining PTFE is very particular-the thickness of PTFE layer, flanging treatment and negative pressure resistance almost leaked. There was a chemical plant project before, and it was used on siteRubber PTFE compensatorAs a result, it cracked within half a year. Why? Because the manufacturer did not do the bonding process of rubber and PTFE thoroughly.
What about vacuum conditions? Don't think that expansion joints are safe under negative pressure. Under vacuum, bellows will become unstable, and cases of deflation abound. At this time, you must useSpecial hose for vacuumOrExternal pressure single axial expansion jointAnd a reinforcing ring should be installed.
Therefore, to judge the technical strength of the manufacturer, it depends on whether he can open his mouth to complex working conditions: what material to choose for high temperature? What liner to choose for corrosion?
3. Installation and after-sales: Should the tie rod be disassembled? What if the deflector is in the wrong direction?
Buying back the expansion joint is only the first step, and buying it for nothing is equivalent to buying it for nothing. Too many people have asked me:Do you need to remove the screw of the expansion joint？ The answer is simple: Before installation, the tie rod and screw for transportation must be removed, otherwise the expansion joint will not work properly. But some manufacturersLarge tie rod expansion jointOrCompound hinge transverse expansion jointThe tie rod is designed to withstand internal pressure thrust, and this cannot be disassembled.
Specific Function of Expansion Joint Guide TubeIs to protect the bellows from medium scour and reduce the flow resistance. When installing, the direction of the arrow of the deflector must coincide with the direction of the media flow. Once the on-site construction teamStraight pipe pressure balanced expansion jointThe guide tube was installed backwards, which caused violent vibration and the pipeline almost fell apart. The manufacturer sent technicians to dismantle them and reinstall them, which delayed the construction period for three days.
What about after-sales? Don't just listen to verbal promises. Ask clearly: Is it broken to send it back for repair or door-to-door service? How long is the response time? Are there any spare parts in stock? Some small manufacturers, when you call, he directly says, "This model is no longer produced, you can find another place"-this kind of after-sales is equal to nothing.
4. Low-price trap: Beware of "general-purpose" that cuts corners into "general-purpose waste"
The longer I work in this business, the more I understand a truth: cheap goods are not good, especially in the field of expansion joints. Some people bought the so-called "universal corrugated expansion joint" cheaply, and as a result, it was used on steam pipelines. The wall thickness of the corrugated pipe was only 0.3mm, and the Q235 used for the flange was not 16Mn, which cracked and leaked after half a year's operation. Is this called a universal type? It's called generic scrap.
- Reducing the wall thickness of corrugated pipe— — Originally, 1.0mm gave you 0.5mm, and the fatigue life was directly discounted in half.
- Omitting guide tube— — Without the guide tube, the medium directly washes the bellows, and the wear is accelerated.
- Replace stainless steel with ordinary carbon steel— For exampleSleeve type pipe expansion jointThe sleeve material, the national standard requires 304, and he uses 201, which will rust out in a few years.
- Reduce the number of corrugations— — Originally, 12 waves were designed, but he made 8 waves for you. The compensation amount was not enough, and the pipeline stress exploded.
userubber compensatorimpersonateMetal hoseBecause rubber is cheap, but temperature and pressure resistance are completely different things. If you put rubber on a hot pipe, it will melt in less than three months.
How to prevent it? First, manufacturers are required to provideMetal hose pressure standard、Model and size of expansion jointCheck the technical parameters, drawings, etc. item by item.
In the final analysis, choosing an expansion joint manufacturer is not to buy food, but to find a technical partner. Price, delivery date, quality and after-sales are indispensable.