Non-metallic expansion joint codenames, what exactly are they saying?
Don't rush to memorize the standards yet. Get a non-metallic expansion joint code name, and you're actually faced with a string of highly condensed engineering language. Looking apart, there are nothing more than these pieces: product type, nominal size, pressure level, compensation amount, medium temperature code, plus connection method and material. Each piece corresponds to a specific technical parameter. With one less, the manufacturer can't quote, and you can't accept it.
Take an example. It is also a rectangular non-metallic expansion joint, which is used behind the baffle door of desulfurization flue gas and on the chimney at the tail of the kiln in the cement industry. The temperature, corrosive medium and pressure are completely different. If the medium temperature code is not clearly marked in the code, the manufacturer can only report it according to the conventional configuration, and there will be problems nine times out of ten when it arrives at the site.
Why is there no "ripple number" in non-metal code names?
Many engineers are used to the labeling methods of metal corrugated expansion joints-wave number, number of layers and single wave compensation amount. These parameters are the lifeblood of metal expansion joint selection. However, the compensation mechanism of non-metallic expansion joint (fabric fiber expansion joint) is fundamentally different: it depends on the deformation of flexible fabric band and internal thermal insulation cotton, and there is no concept of "wave".Without the number of ripples, the displacement amount (compensation amount) is naturally used to calibrate the capacity.
Then why is there special emphasis on the medium temperature code in the non-metal code? Because the temperature resistance limit of the non-metallic band is the first constraint of material selection. Fluorine rubber, silicone gel, polytetrafluoroethylene, ceramic fiber cloth, each material has different temperature resistance, and it will burn through directly if it exceeds the upper limit. Metal expansion joints do not have this trouble, where the melting point of steel is placed, so the metal code pays more attention to pressure and corrugation fatigue life. This creates a completely different logic of the two product code systems.
National Standard JB/T 12235-2015, just look at these common labeling methods
JB/T 12235-2015 is the current national standard for non-metallic expansion joints. Don't memorize the full text. That thing is hundreds of pages, and it's not for people to read. You just need to master the common annotation logic:
- Type code:F indicates non-metal, rectangles are generally marked as FJ or similar forms, and circles are marked as FY. See the manufacturer's sample for details.
- Size Information:Rectangles are marked with width × height (mm), circles are marked with nominal diameter DN.
- Pressure Class:Expressed in PN, such as PN0.1, PN0.25, in MPa.
- Compensation amount:Axial/lateral/angular displacement capacity in mm or degrees is denoted by X/Y/Z.
- Medium temperature code:This is the non-metallic focus. Some use T + numbers (such as T200 for 200℃), and some use A/B/C grading to represent the temperature range. There are differences in the definitions of various manufacturers, but the logic is consistent.
Rectangular non-metallic expansion joint FJ 2000×1500 PN0.25, translated as: rectangular, cross section 2000×1500 mm, withstand pressure 0.25MPa.
Actual combat: How to judge whether the code name in your hand is suitable for your flue gas pipeline?
Two days ago, I met a customer who asked with the code name of a non-metallic expansion joint, saying that it was used in the flue of a power plant. When I looked at it, the temperature code was fine and the pressure was correct, but the compensation amount was only marked with axial ±40mm, not lateral displacement. There is a tee in the direction of his pipe, and the thermal displacement is mainly from the transverse direction. What about that? You can only calculate the thermal expansion by yourself and lay out the diagram core against the pipe.
So after getting the code name, take a piece of paper and list these items and check them one by one: Is the size right? Can the pressure hold the maximum operating pressure of the system? Is the temperature below the upper limit of sustained temperature resistance of the ring belt material? Does the amount of displacement cover thermal expansion in all directions? Special attentionInterface size and mounting length— — These two things are often not written in the main code, but they must be clearly marked on the drawings, otherwise the flanges will not match up at the site, and the welding will not be welded.
Deflector Configuration: The Deadly Detail That Is Easiest To Be Overlooked
The function of the guide tube, to put it bluntly, is that the protective ring belt is not washed and worn by the high-speed dusty airflow. Under the condition of high dust concentration and fast flow rate in flue gas pipeline, the life of non-metallic expansion joint without guide tube may be cut by more than half.
The deflector is not written in the main code name. In the labeling rules of many manufacturers, the deflector is an optional accessory, which can't be reflected in the code, and only listed separately in the ordering technical agreement. When you check the options, be sure to ask: "Does this model come with a guide tube? Is the inner tube material 316L or Q235?" If the answer given by the manufacturer is vague, not mentioning the material or thickness, don't rush to sign this order.
Being stunned by the manufacturer's code name? Check with this set of checklists
Non-standard custom pits are mostly not deliberately pitted by manufacturers, but deviations in the interpretation of code names by both sides. The national standard only stipulates large frames, and the details are left to the manufacturer. Therefore, the codename representation of similar products from different manufacturers will be very different. To deal with this kind of thing, let's turn our thinking around-instead of memorizing the code rules of each manufacturer, make a checklist:
- ① Belt material structure: fluororubber + polytetrafluoroethylene? Or silicone + ceramic fiber? This determines the upper temperature and corrosion resistance limits.
- ② Frame material: carbon steel painted or stainless steel? For flue gas desulfurization environment, it is recommended to go directly to stainless steel, otherwise it will rot in two years.
- ③ Thickness and density of thermal insulation cotton: the thickness is not enough, the outer skin temperature exceeds the standard, and this is how the scald accident comes from.
- ④ Whether the guide tube is present or not, and what is the material?
- ⑤ Installation length: Be sure to confirm whether the site space meets the minimum installation size, especially the rectangular expansion joint occupies a large space.
- ⑥ Connection method: flange connection or butt welding connection? In the case of flanges, whether the bolt hole distribution matches the pipe flange.
After all these items have been negotiated in black and white, when you look back at the non-metallic expansion joint code name, you will find that it is only an index of the entire technical agreement. The code name itself won't tell you the whole story, but it can at least help you lock in the general direction. The rest of the details have to be confirmed by you and the manufacturer's engineers one by one, which is the real key to not catching blindness in the selection.