Compensator debugging steps, follow no error

Compensator debugging steps, follow no error

A customer called the day before yesterday and said they had installed a new one in their factoryUniversal corrugated expansion jointAs a result, it leaked as soon as it was turned on. As soon as I heard it, I knew that it was probably that the limit screw was still screwed and unremoved. You say it was wrong or not? The compensator looked simple, but there were many ways to adjust it. Today we'll break it apart and crumble itCompensator debugging stepsMake it clear thoroughly. If you follow these six steps, you will be sure to make no mistake.

Step 1: Don't worry when you get the compensator, check the model and appearance, and remove the screw that should be removed

Equipment arrived? Don't rush into the pipe yet. The first step is the most important —Check model number。 Do you see if the model number on the nameplate is consistent with the design drawings? For example, what you buy isHigh temperature axial expansion jointAs a result, arubber compensatorThat certainly won't work. The appearance also has to be swept: did the bellows bump? Is there a scratch on the flange surface? Is the deflector distorted?

Screw removal。 Almost allMetal corrugated expansion jointWhen leaving the factory, the bellows will be locked with the limit screw to prevent damage during transportation. If you install it without disassembling it, the bellows can't be expanded or contracted at all, and it will burst directly when it heats up. How far? It's simple-loosen all the nuts on the screw, and then pull the screw out or put it in the longest position to allow the bellows to move freely. Pay attention to keep these screws well, and they may be used in future maintenance.

Tips:Some manufacturers will mark the screw, and you see it to remind you to "dismantle it quickly".

Step 2: Do pre-compression or pre-stretching according to the direction of the pipe, don't do it in the opposite direction

Many people stumbled over this step. The compensator should be pre-deformed in advance to adapt to the thermal expansion and contraction of the pipeline. Specifically, whether it is pre-compressed or pre-stretched depends on the temperature and environment when the pipe is installed.

For example, steam pipe, when the temperature is high during operation, the pipe will extend, then you installMetal hoseOrDirect buried (fully buried) type expansion jointDo it when youPre-stretching-Stretch the compensator a little longer to reserve space for the pipe to shrink. Conversely, if it is a cryogenic pipeline (such as a liquid nitrogen pipeline) and the pipeline shrinks during operation, you have to doPre-compression。

Then how to judge the direction? The easiest way:See the installation instructions given by the manufacturerThe amount and direction of the pre-deformation will be written on it. If not, you pre-adjust it at 50% of the design displacement value of the pipe. Use special tools when adjusting, don't pry the bellows, it is easy to damage.

Note:Pre-stretched or pre-compressed dimensions must be measured with a caliper, don't rely on feel. If you skew a few millimeters, you will be in great trouble later.

Step 3: The gasket should be centered when the flange is connected, and the bellows should be avoided when welding. Pay attention to the guide tube arrow

Then there is the installation link. If it is a flanged connection,Gasket must be centered。 The gasket is biased, and it will be squeezed and deformed as soon as the bolt is tightened, and it will leak 100% later. The gasket material should also be selected correctly-metal winding pads for high temperature steam, corrosive mediaPTFE compensatorMatching PTFE gasket.

If it is welding, pay attention to:The welding current must never pass through the bellows。 The ground wire of the welder should be connected to the pipe, not to the flange of the compensator. The arc will break through the thin bellows wall, and the compensator will be wasted directly. When welding, the bellows should be wrapped with a damp cloth or asbestos cloth to prevent welding slag from splashing and burning.

And the deflector tube. Mostlyexpansion joint guide tubeThere will be an arrow on it, and that arrow indicatesDirection of medium flow。 Installed backwards, the guide tube will not only fail to divert the flow, but also hold up impurities and accelerate wear. Especially lined products such asPTFE-lined hose, the direction of the arrow is installed backwards, and the PTFE layer can easily be washed off. If you take a closer look, the arrow usually says the word "flow direction". Don't pretend to be reversed.

Step 4: Cold tightening and tie rod nut adjustment, different compensator adjustment methods are different

This step is technical work. Let's start with what "cold tightness" means. Cold tightening is to artificially tighten or push open the pipe at room temperature, so that the compensator is stressed in advance. The purpose is to reduce the maximum stress of the pipeline during operation. The cold tightness is usually calculated according to 50% ~100% of the design displacement, which will be written on the specific numerical design drawing.

Let's talk about the tie rod nut. Different types of compensators have completely different adjustment methods:

• Universal corrugated expansion joint: The tie rod mainly plays an auxiliary support role, and the nut only needs to be loosened to not restrict the axial movement of the bellows, so it does not need to be screwed to death;
• Large tie rod expansion joint: There are two nuts on the tie rod, one locking and one adjusting. When adjusting, loosen the locking nut, then rotate the adjustment nut to compress or stretch the bellows to the specified displacement, and then tighten the locking nut. Pay attention to the synchronous adjustment of the tie rods on both sides, otherwise the compensator will be crooked;
• Compound hinge transverse expansion joint: Its pull rod is a hinge structure, and the nut only plays a role in fixing the position of the hinge. When adjusting, it is necessary to ensure that the hinge rotates flexibly;
• Rotary compensator: There is no pull rod, and it is adjusted by rotating sleeve. Make sure the sealing surface is clean and lubricated.

There was a previous article devoted toHow to adjust the tie rod nut of expansion jointYou can flip through it. In short, check after adjustment: Are each nut evenly stressed? Is the bellows twisted?

Step 5: Take your time to boost the system pressure, and stare at the pressure gauge to see if there is any leakage when holding pressure

After installation and debugging, start pressure testing. Don't take this step in a hurry.System boost should be slowIt is recommended to be staged: first rise to 30% of the design pressure, stop and check it again; No problem go up to 60% again and check again; Finally rise to the design pressure (or test pressure). Each boost is spaced at least 5 minutes apart to allow the pressure to stabilize sufficiently.

During the pressure holding period, you mainly focus on two things: One ispressure gaugeAnd see if the pointer keeps going down. If the pressure drops quickly, it means there is a leak. The other isCompensator itselfSee if the bellows has any abnormal bulging and deformation. Especiallyrubber compensatorAndRubber PTFE compensatorRubber parts are prone to bulge and break under overpressure, so be careful. If a leak is found, immediately relieve the pressure and treat it. Never screw the bolts with pressure.

Note:If the pressure test medium is water, the water should be drained clean after the test, especially in winter, to prevent the corrugated pipe from freezing and cracking. Some customers try to save trouble and not drain water, but the next day they find that the compensator is cracked. Is it a loss?

Step 6: Inspect more in the first week after operation, listen to the sound and watch the displacement, and find and deal with problems early

The first week after the equipment is officially in operation is the most prone to problems. At this time, you should go to the scene more often and do three things:

• Listen to the sound: Get close to the compensator to listen for a "fizz" of air leakage, or a "rattle" of metal rubbing. The latter may be that the tie rod nut is loose and the bellows hits the wall;
• Look at displacement: Make a mark on the compensator shell, and measure the distance during each inspection to see if the actual displacement is within the design range. If the actual displacement exceeds the design value, there is a problem with the pipe support or guide;
• Touch temperature: Feel the surface temperature of the compensator with the back of your hand. If it is locally overheated or overcold, it may be that the insulation layer falls off or the medium flows unevenly.

Some power plant installedCorrugated expansion joint for power plant industryOn the third day of operation, I heard an abnormal noise, and it was checked that the solder joint of the guide tube fell off and was stuck in the bellows. Fortunately, it was found early and didn't cause an accident. You see, more inspections, how much can you save on maintenance costs?

Compensator debugging stepsNot rigid dogma, every device has its own temper. If you are unsure, ask the manufacturer's technical support directly, and don't think about it yourself. After all, safety comes first, do you think that's the case?