Procurement Guide for Large Caliber Nonmetallic Compensator: From Parameter Confirmation to Type Selection and Acceptance, Explain Thoroughly at Once

Find out if you want a non-metallic compensator

Two days ago, I met a customer who was anxious to buy a "large-diameter non-metallic compensator" on the phone. As a result, after chatting for ten minutes, I found out that he was using a rubber compensator on the spot, and the temperature had soared to 350℃-the rubber had been carbonized early. I've seen this happen a lot.

Non-metallic compensators (also called fabric fiber expansion joints) are completely different from metal bellows and rubber compensators. The metal bellows absorbs displacement by deformation of stainless steel corrugated body, and has high pressure resistance but limited compensation; Rubber compensator relies on rubber elasticity, corrosion resistance but fear of high temperature and high pressure. WhileNon-metallic compensatorThe main body is flexible loop belt (multi-layer fabric + fluororubber/silicone coating), and the frame is metal, which is specially designed to deal with high temperature, large displacement and low pressure working conditions. If you buy the wrong one, it will leak at least and the pipe will be broken at worst.

Then how to judge? Look at three indicators: the temperature is higher than 150℃, the pressure is lower than 0.1MPa, and the pipe diameter exceeds DN500-it is the home field of non-metals. If you don't believe me, check JB/T 12235-2015. It is clearly written in the standard.

The first step of model selection: medium, temperature and pressure, you dare to fill in these three numbers, and you will wait for problems later

The most common mistake made by purchasers is to say "probably" and "almost" when reporting parameters to suppliers. Tsk, if one of these three numbers is not accurate, the compensator will not be able to use it.

• Medium: Acidic condensate in the flue gas? The outer surface of the band must be filled with a PTFE anti-corrosion layer. Contains hard particles? The inner layer must be made of wear-resistant ceramic cloth. We have them in our stationNon-metallic expansion joint (fabric fiber expansion joint)Is specialized in dealing with this kind of working condition.
• Temperature: Don't just report "working temperature", but report "maximum instantaneous temperature". The instantaneous temperature of desulfurization flue in many power plants can rush to 400℃, and the ordinary silicone ring belt burns through directly. Here, you must confirm the number of layers of the belt material and the temperature gradient of the supplier-such as a three-layer structure: outer layer of fluororubber (250℃), middle layer of fiberglass cloth (550℃), inner layer of steel wire mesh (support).
• pressure: The design pressure of non-metallic compensator generally does not exceed 0.1MPa. If you report 0.2MPa, you have to use a metal frame with reinforcing ribs, or simply change the metal expansion joint.

You ponder, these three numbers are filled in, do you have to spend money on rework later?

When the caliber is large, the structure has to change accordingly: What is the difference between rectangular and circular design?

Many people think that circles and rectangles are just different in shape, and the choice is universal-a big mistake. After the caliber exceeds 1 meter, the design logic of the two structures is completely different.

Circular non-metallic compensator: Mainly used in round pipe flue, the ring belt is annular integral, and the flange is usually angle steel or flat steel coiled. Because the force is symmetrical, the band thickness can be relatively thin. However, it should be noted that the large diameter circular guide tube must be designed to be tapered, otherwise the fluid will scour the inner wall of the ring belt.

Rectangular non-metallic expansion joint: Square pipe flue is commonly used, such as sintering machine head in steel plant. The biggest problem with rectangular structures isCorner stress concentration。 The loop belt is easy to tear at the corner, so it should be molded with a special die when manufacturing, or a reinforcing layer should be added at the corner. In addition, the four sides of the rectangular frame should be designed separately with pressing strips, which can't be simply rounded.

If you are purchasing large diameter rectangular compensator, be sure to ask the supplier: How to seam the corner band? Is it a lap or a docking? Has the lap length exceeded 50mm? These details determine whether it will last five years or eight months.

What are the hard indicators hidden in the national standard JB/T 12235-2015 that purchasers must know?

Many purchases regard national standards as decorations. JB/T 12235-2015 "Non-Metallic Expansion Joints" I pick a few must-see hard requirements:

• Belt withstand voltage test: Before leaving the factory, an air pressure test of 1.5 times the design pressure must be done, and the pressure must be kept for 5 minutes without leakage.
• Displacement compensation amount mark: The allowable compensation amounts in axial, transverse and angular directions must be clearly marked on the expansion joint. Don't look at the unmarked.
• Flange flange length: The connection between the non-metallic ring belt and the flange must be flanged, the length of the flange shall not be less than 20mm, and fixed by pressing strips. The flanges are too short, and the ring band will slip out of the flange groove during the run.

By the way,Expansion joints and compensators are the same thing, it is also mixed in the standard, so you don't have to worry about the title problem.

Don't just look at the price: the supplier's manufacturing process, the number of layers of belt material, and the length of flange are the real skills

And guess what? Many small factories report bargains, the circle belt has only two layers of cloth and one layer of glue, and the flange flange is folded by 10mm. Loaded it up and ran for three months, leaked. You spend another amount of downtime changing it, which is three times more expensive than buying good goods.

How to judge the manufacturer's real ability? Ask three questions:

1. Number of belt material layers: At least three layers, the inner layer is high-temperature resistant fabric, the middle layer is heat insulation, and the outer layer is sealing anti-corrosion layer. What is the thickness of each layer? What grade of silicone/fluorine is used?
2. Flange flange length: The measured flange side length is not less than 25mm before it is considered qualified. Have you installed stainless steel strips at the flange? Is the spacing of the beading screws not greater than 150mm?
3. Frame welding process: Do corner welds of large-diameter frames do flaw detection? Did you do overall hot dip zinc anti-corrosion? These determine whether the frame will rust out within two years.

By the way, this kind of product in our site is calledRectangular non-metallic expansion joint, andNon-metallic expansion joint (fabric fiber expansion joint)All have been verified by multiple working conditions.

Acceptance of arrival and installation precautions: direction of guide tube, whether the tie rod nut should be removed or not, and how to pre-stretch

• Direction of guide tube: The guide tube must be directed downstream of the medium flow direction. When installed backwards, the fluid directly impacts the loop belt, and the hole is pierced in one week. There are generally arrows on the expansion joint to mark the direction, and if there is no mark, let the manufacturer make up.
• Do you remove the tie rod nut or not?Transport tie rods are used to prevent deformation during transportation and must be loosened or removed before installation. But note: Some designs have limit rods, and that one can't be removed. How to distinguish? Read the instructions. Really confused, just ask the manufacturer: "Does the screw of the expansion joint need to be disassembled?" Generally, the manufacturer will tell you clearly.
• Pre-stretching: The compensator needs to be pre-stretched to the specified length if there is a cold tightening requirement when the pipe is installed. The pre-stretching amount is carried out according to the design value, and after stretching, it is fixed with temporary supports, and then released after the pipe is connected. Don't pull blindly, pull the headband strap and scrap it directly.

Also, check whether the flange surface is flat and the sealing gasket is centered when installing. When tightening the bolts, tighten them diagonally and sequentially, and the torque should not be too large to prevent crushing the flange.

Purchasing is three things in the final analysis

First, confirm the medium/temperature/pressure, don't pat your head; Second, selecting the right structure according to the caliber and shape; Third, inspect the goods and check the process details. Do these three things,How To Buy Large Caliber Non-Metallic Compensator?This question is a sure thing.

If you are unsure of anything, you can directly compare the product information of this site, such asNon-metallic expansion joint (fabric fiber expansion joint)AndRectangular non-metallic expansion jointThe pages all have detailed parameters. Don't be afraid to ask, asking clearly saves money than buying the wrong one.