Non-metallic rectangular compensator (also calledRectangular non-metallic expansion joint) It is more and more used in flue gas pipes and dust removal systems. However, when asking about the standard when selecting the model, many purchasing and technicians are confused-there is only one national standard, JB/T 12235-2015, but that standard mainly talks about the details of circular and general non-metallic expansion joints, rectangular boundary conditions, flange seals and corner stresses, which are not completely written in the standard. Then what exactly should I take to card in the actual implementation?
JB/T 12235-2015 Non-Metallic Expansion JointsIt is the foundation of the entire industry. It specifies the material (silicone cloth, fluororubber, polytetrafluoroethylene, etc.), fatigue life, airtightness test pressure, but note that it is conservative in the recommended value of deflection angle compensation and lateral displacement of rectangle. For example, the angle compensation amount given in the standard is equivalent to the circular section, and the actual use of rectangular large section often depends on empirical coefficient correction-this is not a standard problem, but caused by the rectangular geometry itself, so you should refer to the test methods in the standard to make up your own check when designing. Two days ago, I encountered a power plant project. The customer directly applied the data in JB/T 12235. As a result, it was found that the corner displacement didn't match at all during the trial installation. Later, we re-tested three cycles according to the fatigue test method in the standard before settling the parameters.
In addition to the national standard, the rectangular compensator has to keep an eye on two subdivision standards: First,HG/T 20592~20635 seriesThe flange connection size in, because most of the two ends of the rectangular compensator are paired with steel flanges. If the customer's site is a pipeline in the chemical industry or electric power industry, the flange standard must be unified (for example, HG/T 20592-2009 PN series); Second,Technical specifications for the design of flue-wind and pulverized coal pipelines in thermal power plants (DL/T 5121)In this regulation, the expansion compensation mode of the rectangular flue duct and the arrangement spacing of the non-metal compensator are clearly written. OurRectangular non-metallic expansion jointExports are often directly connected to this specification. To put it bluntly, if you just look at JB/T 12235, the flange hole distance may not match with the site, and the site welding modification will be time-consuming and laborious.
One more thing that is easily overlooked-the structural strength of the rectangular section itself. The fabric layer and skeleton of the non-metallic compensator are two independent systems, and the rectangular corners are prone to tear in advance due to stress concentration. It is common practice in the industry to refer toSteel Pressure Vessel (GB/T 150)The rectangular section calculation principle in is used to verify the frame stiffness, but this is not a mandatory standard. Some manufacturers' own internal standards will require the corner of the frame to add arc transition and do overall vulcanization, which is actually stricter than the national standards, but it must be clearly written in the bidding documents which system is referred to. Like ourRectangular non-metallic expansion jointIn the product manual, the transition radius of the corner of the frame is uniformly executed according to 3 times the wall thickness, and the corner stress and strain test is done before each batch leaves the factory, which has become the internal SOP.
Finally, it falls to acceptance and testing. JB/T 12235-2015 stipulates that the sealing test of 1.5 times the design pressure should be done before leaving the factory. Due to the large sealing surface area of rectangular compensator, the leakage rate standard is stricter than that of circular compensator (usually within 0.5% leakage). In addition, it is necessary to do thermal displacement review after installation, but many items in this step are ignored. Our product manuals will come with a compensation amount-pressure comparison table, which is derived from the fatigue test data in the standard, and customers can directly correspond to the specification. For example, last year a customer in the cement industry ordered a batch ofRectangular non-metallic expansion jointThe deviation between the measured value of the on-site thermal displacement and the comparison table is less than 3%, which indicates that the formula derived by the standard is reliable.
There is no separate national standard for non-metallic rectangular compensator. For actual implementation, the national standard (JB/T 12235-2015) should be laid down, then the pipeline design specification (DL/T 5121) and flange standard (HG/T series) should be superimposed, and finally the internal process standard and factory test data should be used to complete it. These standard numbers in the selection times basically don't miss items. Verbose sentence: Don't be too troubled. Spending ten minutes more to check the flange standard and corner reinforcement scheme can save three days of on-site rework, which is worth it.