Are metal compensators pipe fittings? Not. But if you go around the construction site, eight out of ten purchasers will buy it as a pipe fitting. Why? It looks like it-with flanges at both ends and a stainless steel bellows in the middle. When welded to the pipe, it looks like an elbow and a tee. But if you really choose the type according to the idea of pipe fittings, trouble will come.
Pipe fittings do "connect" and compensators do "compensate"
Let's talk about what pipe fittings are first. Elbow, tee, four-way, flange, blind plate, these things do the work of connecting and changing direction. They are rigid parts, and the shape they are when installed is whatever, and the thermal expansion and contraction of pipes have nothing to do with them. What about metal compensators? Its serious name is corrugated expansion joint, which belongs to the flexible element of pipeline. Its core function is to absorb thermal displacement, reduce vibration and noise. You can see from the product classification of this site that general-purpose corrugated expansion joints, external pressure single axial expansion joints and straight pipe pressure balance expansion joints are all under the category of compensator, and they don't go along with pipe fittings at all.
To put it bluntly, the pipe fitting is rigid connection, the compensator is flexible compensation, and the force in the pipeline is completely different. You weld a compensator at the elbow and want it to absorb the displacement that the elbow can't absorb? The direction is reversed.
Why do people keep confusing them?
On the one hand, the metal compensator does have connectors and flanges at both ends, and the installation method is almost the same as the pipe fitting-welded, bolted, and done. On the other hand, some manufacturers themselves scream, mixing "metal compensator" with "metal hose". This station is clearly distinguished: metal hose and PTFE-lined metal hose are specially designed to absorb vibration and lateral displacement; Whether the compensator is a general-purpose type or a high-temperature axial type, it mainly carries axial displacement. The two things look alike, but the functional emphasis is completely different. Confused, the selection straight away.
Two days ago, a customer came to me with the drawing of a metal hose and asked me if it could be used as an expansion joint. I said that if there is axial thermal displacement at your installation position, the hose can't hold it at all, and the corrugated pipe will become unstable as soon as it is compressed. Only then did he realize that he had taken the two things seriously.
Ask Yourself Three Questions Before Choosing a Model
Ordinary pipe fittings have no displacement compensation ability, which is the most essential difference between it and compensator. Metal compensators are divided into particularly fine displacement types: axial type, transverse type, hinge type and pressure balance type, each with its own applicable scenarios. When selecting, ask yourself three questions first: How much thermal displacement does the pipe go? What is the pressure rating? What is the medium?
Take an example. The steam pipeline has high temperature and large expansion amount, so it is necessary to use high-temperature axial expansion joint or external pressure single axial expansion joint; If the space available in the middle of the pipe is limited, it is necessary to consider the double hinge transverse expansion joint or the curved pipe pressure balance expansion joint. If you only report the nominal diameter and pressure and let the manufacturer deliver the goods, it is equivalent to asking the doctor to prescribe the medicine based on his height, which is unreliable. The medium has to be made clear. If the corrosive medium should be lined with PTFE, it has to be lined with PTFE. Take ordinary stainless steel to carry it hard, and it will leak in less than two years.
The installation link can better see that it is not a pipe fitting
Pipe fittings are simple to install, welded or threaded, and the position is right. Compensators are different. Before installation, check the amount of pre-stretching or pre-compression. When hoisting, the bellows can't be stressed, let alone take it to bear the self-weight of the pipeline. For example, sleeve-type pipe expansion joints and rotary compensators, the installation requirements are stricter, and they are slightly sloppy, ranging from leakage to direct scrapping of bellows instability. You said it was a pipe fitting. How could there be so much attention to pipe fittings?
So, exactly how to buy it?
Back to the topic – are metal compensators pipe fittings? The answer is clear: no. The difference between it and pipe fittings is not only that its functions are different, but that the whole design logic is different. Pipe fittings are standard parts and can be chosen at will; The compensator is a non-standard customized part, and the compensation amount must be calculated according to the working conditions.
If you buy the compensator as a pipe fitting in the pipeline design stage, only look at the nominal diameter and pressure, and there is a high probability that something will go wrong. The correct way is to hand over the parameters of pipeline layout, medium temperature and installation position to the manufacturer, and let them help you calculate the compensation amount and choose the appropriate model. Each of the double hinge transverse expansion joints and straight pipe pressure balance expansion joints in this station is designed for specific working conditions. Just take a pipe fitting instead, and don't even think about it.