What the hell are fixed rods on non-metallic compensators for? Don't wait until the equipment breaks
Although it is called "non-metal", in fact, the skeleton and fixtures are still inseparable from metal. Many people thought that the bright fixed rod was used for lifting or convenient transportation-two days ago, a customer asked me if this thing could be removed, and I thought it was in the way. Disassembled? You try to disassemble it. As soon as the pipe heats up, the compensator will directly blow you into a balloon. The role of the fixed rod is far more important than you think.
The core task of the fixed rod is one word: limit
Limit excessive tension or compression of the non-metallic compensator in the axial direction (i.e. along the pipe direction). The non-metal loop strap itself is soft and elastic, but it can't stand hard tugging. When the pipe is displaced by thermal expansion and contraction, the compensator should absorb this displacement, but if the displacement exceeds the design value, the ring belt will be torn or folded. The retaining bar acts like a seat belt, telling you: At most you can run this far, and it will be dangerous further forward. In fact, both ends of the fixed rod are connected with connecting pipes or flanges, and a preset installation length is locked by a nut to ensure that the compensator works within a predetermined stroke range.
What's the difference between it and the tie rod on the expansion joint? That's a good question. Tie rods are usually used for metal corrugated expansion joints (such as the general corrugated expansion joints and compound hinge transverse expansion joints in our station). Its main function is to bear the blind plate force generated by internal pressure and prevent the bellows from being crushed to death by axial thrust. The fixed rod of the non-metal compensator is more to bear external loads and limit excessive displacement. In terms of material, the fixed rod of non-metallic compensator is generally made of carbon steel or stainless steel, and the surface is anti-corrosion treated. After all, the supporting flue gas and dust environment is often very harsh-such as the "flue gas baffle door" and "rectangular non-metallic expansion joint" in our product list, which are often used in desulfurization and dust removal pipelines. When corrosive gas rushes, if the pole rusts, the strength will drop, and something will happen.
How to judge if the fixed rod is adjusted properly?
Our product information mentioned the question and answer of "How to adjust the tie rod nut of the expansion joint". Although it is a tie rod, the adjustment logic of the fixed rod is similar. The core parameter is the mounting length-this length must correspond to the free length of the compensator in the cold state. For example, the working temperature of the pipeline is 300℃. When it is installed in a cold state, the fixed rod should be artificially compressed or stretched to a certain amount, leaving a margin for thermal displacement. You fit too tightly, there's no room to stretch when it's hot; Loaded too loosely, the loop straps sag when cold. Many on-site failures, nine times out of ten, are that the nut of this pole is not screwed correctly.
Another real case. A non-metallic compensator is connected in parallel next to our "metal corrugated expansion joint in cement industry" used in a cement factory to absorb the vertical displacement. On-site workers suspected that the fixed pole was in the way, so they dismantled it privately. Results After half a year of operation, the non-metallic ring belt was partially torn and the air leakage was serious. Change the ring belt and shut down for two days, resulting in hundreds of thousands of losses. Later, when the engineer checked, it was the lack of fixed rods that caused the deflection displacement to exceed the standard. Think about it, a pole costs hundreds of dollars, and a circle belt costs tens of thousands of dollars. This account is not unknown.
Finally, let's be honest
When selecting, don't just stare at the material and temperature resistance grade of the ring belt. The design and material of the fixed rod should also be checked. Especially for large-size rectangular non-metallic expansion joints, pole cross-section, thread specifications, and the strength of connecting ear plates at both ends have to be calculated. If you are not sure, read directly the article "National Standard for Non-metallic Expansion Joints JB/T 12235-2015" in our station, which clearly states the requirements for structural parts. With this pole, the compensator really locks the safety bottom line.