What parts are the flange metal expansion joint weight put together?
Flange metal expansion joint weight is never a single number, it is the sum of the weights of a bunch of components. Corrugated pipe, flange, guide tube, tie rod, each piece accounts for weight. Take the general-purpose corrugated expansion joint as an example. The flange thickness and the number of bolt holes directly determine the weight of the base-the same flange thickness difference of DN500, PN6 and PN16 is 8~10mm, and the weight difference is more than 30%. The bellows is finer on the other side: the more waves and the thicker the stainless steel plate, the weight is superimposed. If you have a guide tube or liner, you have to add another section. Some customers took the net weight on the nameplate to check the hoisting scheme. As a result, the scene was weighed by more than ten kilograms. The problem was that the nameplate only wrote the bare weight of the bellows + flange, not counting the guide tube and the tie rod.
Core Parameters That Really Affect Weight
Nominal diameter, design pressure, medium temperature, material grade, these four parameters must not be lacking. The same expansion joint of DN500 is used in power station steam pipelines and hot air pipelines in cement industry. The wall thickness and wave number can be several times different-power station steam may have 4 waves, single layer 304, cement hot air pipeline may have 6 waves, double layer 321, and wear-resistant lining is added, so the weight is completely different from the same order of magnitude.
Flange standards are also critical. The outer diameter of GB/T 9119 and HG/T 20592 is different from the outer diameter of the connector, and the outer diameter of the flange and the circular diameter of the bolt hole are also different. Two days ago, a customer asked about the expansion joint of DN400, saying that he should match the flange according to HG/T 20592. As a result, his original drawing was GB/T 9119, and the difference in outer diameter of the two tubes was 7mm, and the difference in flange weight was nearly 5kg. This kind of detailed account is simply not accurate without checking the standards.
Is there a rough estimate?
Yes, and it's simple. First calculate the bellows deployment area, multiply by the stainless steel density of 7.93g/cm³, plus the flange weight, and finally multiply by a coefficient of 1.1~1.2 to leave a margin. This coefficient is not blind multiplication, it just includes the weight of miscellaneous accessories such as deflector tube, tie rod and nut.
The axial expansion joints of DN300 and PN16 have a wave number of 4 waves, a deployment area of about 0.8m², a bellows weight of about 6.3kg and a pair of flanges of about 32kg, adding up to 38.3kg, multiplying by 1.15, and calculating to about 44kg. The actual weighing is generally between 40 and 50kg. This method is suitable for early selection and budget quotation, and can't replace accurate calculation-if you really want to make a drawing for purchase, you still have to let the technical department calculate it piece by piece.
Does that mean the heavier the better?
Not. Expansion joints are flexible elements, not gate valves. In order to appear to use enough materials, some manufacturers deliberately thicken the flange or weld a few more waves. As a result, the stiffness becomes larger, the compensation amount becomes smaller, and the fatigue life is also affected. Think about it, the bellows is designed in that shape to absorb displacement. If you thicken it, can it still deform flexibly?
When selecting the model, you should look at the design displacement, number of cycles and stiffness value. Weight is only a reference index, and cannot be used as a quality criterion. For the expansion joint of the same specification, manufacturer A makes 45kg and manufacturer B makes 38kg, which may not necessarily mean that A is better-maybe A has a large wave number, but a large wave number does not mean that the compensation ability is strong, but it also depends on the single wave displacement. B may be a higher strength material with thin walls but the same pressure resistance.
The most reliable way is to ask the manufacturer for drawings and weight details
Regular manufacturers will attach the overall dimensions and net weight in the technical agreement. For example, the double hinge transverse expansion joint or the curved tube pressure balance expansion joint have completely different structural forms and great weight differences. The double hinge has two sets of bellows and hinge plates, and the pressure balance of the curved tube has a pressure balance ring. It is normal that the weight difference between these two sets is 20%.
When installing, you should also check the hoisting scheme with actual weighing, and don't rely on the numbers on the nameplate alone. Once, a large-diameter expansion joint was hoisted on the project, and the nameplate said 320kg. Halfway through the on-site crane, it was found that it was difficult to lift. One weighed 385kg, and there was almost an accident. Later, the reason was found that the manufacturer changed the flange standard from HG/T 20592 to GB/T 9119. The outer diameter of the flange was two sizes larger, and the weight naturally went up.
Therefore, the weight of flange metal expansion joint seems to be a simple number, and behind it are a lot of variables such as flange standard, material thickness and wave number structure. The early selection is roughly calculated by the estimation formula, the formal procurement requires detailed drawings, and the entrance installation requires actual weighing-after three steps, there will basically be no big mistakes.