Export metal expansion joint, you think it's just pipe with corrugation?
Don't answer in a hurry yet. After ten years in this business, I have seen too many export projects overturn-either the pipe is cracked, or the supervisor refuses to accept it, and the customs clearance is stuck. To put it bluntly, the export of metal expansion joints is really not about adding a flange to the domestic bellows and sending it out. Standards, selection, materials, certification, which link falls off the chain, losing not only money, but reputation.
Standard system: One EJMA difference is enough for you to drink a pot
The domestic GB/T 12777 and the mainstream EJMA standards in Europe and America are different in the calculation of fatigue life of bellows. EJMA correction of temperature compensation coefficient is very fine, especially for high temperature conditions, thinning amount and cycle life have to be recalculated. Two years ago, there was a Middle East project. The customer took the domestic selection table directly, and chose a general-purpose corrugated expansion joint to dry the high-temperature axial pipe section. As a result, it leaked in half a year. Why? Because EJMA stipulates that high-temperature axial expansion joints, the ones with vacuum barriers, should be used above 300℃. You think it's just pipe with corrugations? Not even close.
Three major pits of model selection and rollover
Displacement compensation type confusion. Export project pipeline trend is complex, light compensates axial displacement? Not enough. For example, air-cooled island, cross wind, thermal expansion and contraction, it is necessary to use air-cooled island vacuum pipeline double hinge expansion joint or double hinge transverse type. Otherwise, the lateral displacement will be deadlifted, and the bellows will tear directly.
Pressure rating is falsely scaled. Overseas customers have high requirements for safety factor, and the steam pipeline is PN16 or even PN25. Can't the universal corrugated expansion joint hold it? Replace with straight pipe pressure balance type expansion joint or external pressure single type axial type, which has high pressure and can absorb blind plate force. Before, a German customer inspected the goods, took a pressure gauge to measure them one by one, and returned the goods directly with a false mark.
Ignore media corrosiveness. Stainless steel 304L is the regular option, but desulfurizing flue gas or chemical media, must be on 316L or even 254SMO. Corrosive environment lined PTFE hose and PTFE compensator are standard. Don't ignore the deflector either-it not only prevents scour, but also improves the flow regime and reduces pressure loss. A German customer specially took a ruler to measure the inner diameter and wall thickness of the guide tube during acceptance, and the difference of one millimeter was not enough. Do you think it's the details that make or break?
Installation and maintenance: common sense but no one takes it seriously
When the expansion joint of the large tie rod leaves the factory, the pre-stretching amount has been set, and the nut can be loosened at will on the spot? Bellows instability is light. The screw of the expansion joint is a transportation protection device, which must be dismantled after installation, otherwise the compensation function will be completely wasted. Overseas supervisors don't care if you "did this before". People take the drawings one by one. Last year, in a Southeast Asia project, the worker did not remove the screw, and the supervisor directly sent NCR (non-conformity report) after discovering it, and the customer almost claimed compensation.
A Real Case: Vietnam Cement Plant
Last year, a cement plant project was exported to Vietnam, and the pipeline medium was high-temperature dusty flue gas with a temperature of 850℃. At first, the customer saw that it was cheap, so he chose the general-purpose corrugated expansion joint. We suggest replacing it with the combination of metal corrugated expansion joint and rectangular non-metal expansion joint in cement industry, and adding double-sealed single-axis circular baffle door at the position of flue gas baffle door. After two years without any failure, the customer added an order for double straight pipe bypass pressure balanced expansion joint. You see, if you choose the right products and standards, the repurchase rate will come naturally.
So stop thinking that export metal expansion joints are just tubes plus corrugations. Standards, materials, certification, installation, which end is not paid attention to, the pit is waiting for you.