Instrument joints-instrument joints include all instrument meter joints, instrument pipe joints, instrument valve joints, instrument source component joints, instrument electrical joints, metal hose joints, etc. It has a wide variety of different specifications, and each instrument connector has its own function.
1. The structure of the pipe joint:
The standard pipe joint consists of a nut, a snap ring (some have only one snap ring), a joint, and a pipe.
The principle of the sealing of the pipe joint: the clamping ring compresses the pipe to deform by tightening the nut to form a seal.
2. Quick connector installation and removal steps
(1) Wrap an appropriate amount of thickness with raw material tape at the threaded quick joint;
(2) Tighten the quick connector with appropriate force;
(3) Cut the top of the pipe to be inserted vertically with a cutter;
(4) Insert the top of the cut pipe into the quick connector, and insert it firmly;
(5) Verify that the pipe is firmly connected, and pull out the pipe with appropriate strength, and the pipe cannot be pulled out.
(1) First check whether the medium passing through the joint pipeline is cut off;
(2) While holding the chuck to the quick connector with one hand with the index finger and thumb, pull out the tube with the other hand.
3. Installation of new pipe joints
Step 1: Insert the tube into the joint and confirm that it is as low as the bottom end of the nut
Step 2: Tighten the nut by hand, and mark a position (see 6 o'clock)
Step 3: Use a wrench to turn the nut clockwise 1 and 1/4 turns, see the mark at 9 o'clock
4. Precautions for the installation of new pipe joints:
For pipe diameters of 1 inch (25mm) and below, tighten it by hand and then use a wrench to rotate 1 ¼ turn. For 1/16, 1/8, and 3/16 inch (2, 3, 4mm) pipe diameters, just use a wrench to rotate 3/4 turn. For 1 ¼, 1 ½, 2 inches and 28, 30, 32, 38mm pipe diameter joint installation, you need professional tools, because it is rarely used in the field.
5. Reinstallation of pipe joints
For pipe joints that have been tightened, please mark the position between the nut and the joint before removing it. When reinstalling, first tighten the nut by hand, and then use a wrench to lift the nut to the original position. Location is fine. For pipe joints that have been repeatedly disassembled and assembled many times, the nut can be rotated to the original position by 10°～20° (not more than 1/3 of the side of the hexagonal nut, that is, not more than B).
The manufacturer provides special tools that can be used to check whether the pipe joints are tightened. Different pipe diameters have different standards.
Precautions when choosing a pipe: Pay attention to the wall thickness of the pipe within the specified range (see the table below), because the pipe wall is too thick, the snap ring does not work, and the pipe wall is too thin, which will cause the pipe to deform and crack
6. Sealing of pipe joints
There are two ways to seal the pipe joint
Sealing of raw material belt:
Pay attention to the following points:
Clean the joint threads before loading the raw material belt
The direction of the upper raw material belt is clockwise
The raw material tape cannot extend beyond the threaded end of the connector
After the raw material tape is cut, it must be close to the thread
Sealing of sealant
Pay attention to the following points:
Clean the joint threads before applying the sealant
Coat the second and third turns of the thread with sealant. (360°)
7. The material of the pipe joint
Stainless steel: SS
Carbon steel: S
Because the hardness of metal pipes is softer than the material of pipe joints, copper joints cannot be used for stainless steel pipes;
If the pipe and the pipe joint are of the same material, the metal pipe needs to be annealed (generally metal materials such as stainless steel, copper, titanium, carbon steel, alloys, etc. have been annealed)
Very soft pipes (such as Tygon polyethylene) or non-plastic PVC pipes should be lined and sealed during installation.
8. Types of pipe joints
Examples of labeling of names:
1/4 tube: indicates a tube of 1/4 inch OD
Tube 1/4: indicates the joint to connect 1/4 inch OD tube
8mm tube: indicates a tube of 8mm OD
Tube 8mm: indicates the joint for connecting 8mm OD tube
The British system mainly includes: 1/4, 3/8, 1/2 several sizes
The metric system mainly includes several sizes of 6, 8, 10, 12mm
Male: means male connector (male connector)
Female: means female connector (female connector)
Male cone or female cone refers to RT threaded joints, namely ISO 7/1 standard, male or female flat mainly refers to RS, RP or RG threaded joints, namely ISO 228/1 standard
NPT joints are not specially marked, and ST joints are rarely used in Daya Bay Nuclear Power Station, and no special markings are made.