Have you really figured out the role of acid and alkali resistant non-metallic compensators?

As the old saying goes, if you choose the wrong compensator, the pipe will be repaired every day. Especially when encountering acid-base media, a bunch of people come up and ask: Do you use metal or non-metal? Today, let's talk about acid-alkali-resistant non-metallic compensator, and explain its functions, doorways and pits. Don't be too long-winded, you will have a spectrum in your heart after reading it.

Let's start with the name: What is it?

To put it bluntly, compensators and expansion joints are the same thing-they are both devices used to absorb the thermal expansion and contraction, vibrational displacement of pipes. The "acid-alkali-resistant non-metallic compensator" is the kind that specializes in carrying corrosive media, and the material completely draws a clear line with metal hoses and corrugated expansion joints.

This kind of product is usually called in our businessrubber compensator、PTFE compensatorOrNon-metallic expansion joint (fabric fiber expansion joint)。 There are also compound types, such asRubber PTFE compensator, lined with PTFE outer bread rubber. There are many names, but the actual core is one: the main body is not metal, and it relies on polymer materials or fiber fabrics to achieve elastic compensation and corrosion resistance.

Isn't it better for metal compensators to withstand temperature and pressure? Just look down and you will see.

Acid and alkali resistance, why can't metals work, and how can non-metals do it?

No matter how awesome the metal is, it has to kneel when it encounters strong corrosive media such as concentrated sulfuric acid, hydrofluoric acid and wet chlorine. 316L stainless steel won't last a few days in front of hydrochloric acid, let alone ordinary carbon steel. Corrosion not only causes leakage, but also causes hydrogen embrittlement, stress corrosion cracking, especially headache.

Non-metallic materials take a different approach-Polytetrafluoroethylene (PTFE)Known as the king of plastics, except for molten alkali metals and high-temperature fluorine, he is almost not afraid of any acid and alkali;Rubber(Mainly EPDM, butyl and chloroprene) can carry dilute acid and alkali, and the price is cheap and elastic;Fabric fiber(Glass fiber, silicone rubber coated cloth) High temperature resistance, but mainly used to compensate for displacement.

For example, the flue gas in the desulfurization system is not high in temperature but contains a large amount of sulfurous acid and chloride ions.rubber compensatorOrNon-metallic expansion jointIt's much more reliable than metal bellows. And guess what? Some customers saved money on stainless steel, but as a result, it was perforated in half a year, and the renovation cost was twice as expensive as buying non-metal.

What kind of work does it do for you in actual working conditions?

Acid and alkali-resistant non-metallic compensator not only solves corrosion, its daily work includes at least the following three things:

• Displacement compensation:The axial, transverse and angular displacements caused by thermal expansion and contraction of pipelines and deviation of equipment installation are absorbed by corrugations or fabric wrinkles in non-metallic layers. Especially on rectangular pipes (such as flue of power plants and dust removal pipes of steel plants),Rectangular non-metallic expansion jointAlmost standard.
• Vibration isolation and noise reduction:The rubber material itself has damping properties, which can absorb the vibration transmitted by pumps and fans. On the contrary, metal bellows are easy to conduct high-frequency vibration.
• Sealing and pressure bearing:Many conditions require zero leakage. flangedRubber PTFE compensatorOrPTFE compensatorWith the special lining layer, it can withstand the pressure of 0.6~2.5MPa while preventing a drop of acid from seeping out.

Two days ago, I met a buddy who did chlor-alkali engineering. They directly usedPTFE-lined hoseDo pipe connections, but places with many elbows still rely onrubber compensatorSaid it had been used for five years without changing it-tsk tsk, worry-free.

Don't scratch at the selection: rubber, PTFE, fabric fiber, how to pick?

Many purchases ask "Which is best" as soon as they come up? There is no best, only the most suitable. I list a generic selection logic:

• The medium temperature is lower than 100℃, dilute acid and alkali, and the vibration is large:userubber compensator(EPDM or neoprene), which is cheap and has good vibration damping effect. But don't touch strong oxidizing acids (concentrated nitric acid, concentrated sulfuric acid) and organic solvents, the rubber will swell.
• Medium temperature-30~200℃, strong acid and strong alkali, requiring extremely high chemical resistance:UpperPTFE compensatorOrPTFE-lined hose。 PTFE is invincible in corrosion resistance, but has poor elasticity, limited displacement, and cannot be used in vacuum (easily deflated).
• Wide temperature range (-40℃ ~1000℃), large diameter rectangular pipe, containing dust and flue gas:chooseNon-metallic expansion joint (fabric fiber expansion joint)。 The structure is multi-layer fabric + insulation cotton, which can compensate for displacement and insulate heat. For example, high-temperature air ducts in power plant flues and cement industries are used more.
• It should be acid and alkali resistant and have good comprehensive elasticity:ConsiderationRubber PTFE compensator, lined with PTFE contact media, and the outer rubber plays a sealing and compensating role. The price is somewhere between pure rubber and full PTFE.

Isn't it a little messy? Simple note: the pieces with "PTFE" are corrosion resistant, the pieces with "rubber" are elastic and cheap, and the pieces with "fabric" are high-temperature and large-diameter. When selecting, be sure to give the composition, temperature, pressure and displacement of the medium. Don't just throw "acid and alkali resistance" and be done.

Installation and routine maintenance, say a few words if you have stepped on the pit

Say a thousand words and ten thousand, pretending to be wrong is equivalent to buying it for nothing. I've seen too many cases of compensators being scrapped early because of sloppy installation. Here are a few pits you have to bypass:

• The pre-stretch/compression is backwards:Non-metallic compensators usually leave the factory with installation length markings. Pre-stretching is required if the ambient temperature is lower than the design temperature during installation; Otherwise, pre-compression. Many people don't care about the hard installation of 3721, but as a result, it will either crack or explode once it runs.
• Ignore deflector and limit rod:Having a guide tube (e.g.expansion joint guide tube) Must ensure that the media flow direction is consistent with the arrow. Tie rod (expansion joint tie rod) is for transportation protection, and it should be loosened after installation, otherwise the compensator will not move. Otherwise, the stress concentration will tear off the takeover.
• Flange bolts are not screwed by torque:The rigidity of the sealing surface of rubber and PTFE is poor. If the bolts are tightened too tightly, the compensator body will be crushed, and if they are tightened too loosely, they will leak. It is recommended to use a torque wrench and tighten it symmetrically in 3 times according to the value given by the manufacturer.
• Daily inspection does not check displacement indication:Some compensators are marked with displacement scales. Glance at them every quarter. If you find abnormal deformation (such as exceeding the maximum stroke), quickly check whether the pipeline support and hanger have been displaced.

Finally, let's say it-the acid-and alkali-resistant non-metallic compensator, reliable suppliers and installation teams are much more important than the price difference saved. You save 500 yuan in purchase fees and may lose 5,000 yuan in discontinued production losses. Taste yourself.

aboutFunction of acid and alkali resistant non-metallic compensator?The core is four words: erosion and inflation. Choose the right materials, install the right method, and use it for another ten years without panic.