Find out before inspection: What is the difference between non-metallic compensator and metal expansion joint inspection?
In many projects, the standard of metal parts is used to set non-metal parts, and the result is that it is qualified from the factory, and it leaks as soon as it goes to the flue. This happened to me no less than ten times. Non-metallic compensator (that is, we often call fabric fiber expansion joint, the product of this station is calledNon-metallic expansion joint (fabric fiber expansion joint), andRectangular non-metallic expansion joint、rubber compensatorThese) the main body is a flexible loop belt, which is compounded by multiple layers of fibers and rubber. The force deformation is completely different from the metal bellows. You said that taking the rigidity and fatigue life of the bellows hard to move up, isn't that carving a boat for a sword?
According to JB/T 12235-2015. This standard is a special standard for non-metallic expansion joints in our country, and it is different from metal parts from technical indicators to test methods. For example, it is no problem to beat 1.5 times the design pressure in the pressure test of the metal expansion joint, but even if the bulge deformation of the non-metal ring belt exceeds 20%, it is unqualified-if you beat high pressure according to the set of metal parts, the ring belt will collapse directly, and the manufacturer will still be wronged.
Appearance and dimensional inspection: Don't just look at surface smoothness
The key lies in the loop lap and flange flatness. The ring belt of the non-metallic compensator is compounded by fluorine rubber, silicone rubber, glass fiber cloth, etc. The fit between each layer directly affects the sealing. In practice, measure the flatness of the flange sealing surface with a plug gauge, and the error cannot exceed 1.5mm/m. Are there any bubbles or wrinkles at the lap of the loop band? Shine a flashlight on the back, and where the light is transmitted is the weak point-this trick is dirty, but it works.
In addition, material confirmation is the most overlooked pit in inspection. Ask the manufacturer for the factory material report, and choose para-fluorine rubber or silicone rubber according to the design temperature: EPDM (EPDM) is used below 150℃, and silicone-fluorine compound must be applied above 250℃. Two days ago, there was another customer. The flue gas temperature was 280℃ and silicone rubber was used. It was powdered in three months, and the ring belt broke when touched. And guess what? The manufacturer's material report says "silicone rubber", but the upper temperature limit is only 200℃. Isn't this fooling people?
Performance testing: air tightness, pressure resistance and displacement compensation ability, all of which can't be missed
Inflate to 0.02MPa, check the connection between the ring belt and the flange with soapy water, and do not bubble for 5 minutes. Don't think low pressure is fine. The negative pressure in the flue is large, and a small leak can suck in the flue gas and corrode the steel structure.
Hold the pressure at 1.5 times the design pressure for 10 minutes. Note that non-metallic parts cannot be hit with high pressure like metal parts. If the ring belt bulges or deforms more than 20%, it is unqualified. How to define 20%? Take a vernier caliper to measure the height of the bulge, divide it by the original thickness of the ring belt. If it exceeds 0.2, it will be regarded as waste.
Many people directly omit the test of displacement compensation ability-batch sampling, install the compensator on the test bench, pull and compress to the designed displacement, and see if there are cracks or delaminations in the ring after 50 cycles. This test best exposes the problem of tape interlayer adhesion. Once, we made a random inspection of the power plant. After 50 cycles, the side of the ring belt was delaminated. Looking at the cross section, we found that the fluororubber layer and the glass fiber cloth were not stuck firmly at all, and they were opened by hand. The factory later admitted that the cure time was 4 hours less.
On-site inspection after installation: Thrust, guidance and protection of pipelines are more critical than factory inspection
Just because the non-metallic compensator passes the factory inspection does not mean that the site will be fine. Check the parallelism and coaxiality of the flange interface before installation, and adjust the pipe support if the deviation exceeds 2mm. How close is the guide bracket to the compensator? The standard requires that the first guide bracket should be no more than 4 times the pipe diameter away from the end face of the compensator. If it is far away, the lateral force generated by the thermal expansion of the pipe will directly tear the ring belt apart.
In addition, non-metallic bands are afraid of splashes and open flames. It must be covered with fireproof cloth during electric welding. I have seen a project where the weld slag fell on the ring belt and burned a hole, and the whole compensator was scrapped. Last point: tighten the screw after installation, but don't screw the pre-tightening bolt to death-non-metallic parts need to be pre-deformed, otherwise they will tear directly due to thermal expansion. How much exactly? Look at the design displacement direction, leave half of the axial displacement, and adjust the bolt to the free state with the lateral displacement.
In the final analysis, the inspection scheme of non-metallic compensators is not just copying the set of metal parts. JB/T 12235-2015 is clearly written. The key is these four test items: appearance size, material confirmation, performance test and on-site installation. If you keep these four switches in place, the compensator life will not be bad. If any ring is saved, tsk, the later maintenance cost can make you regret it for three years.