3. Pipe fitting
Threads on pipe fittings are tapered and rely on the stress generated by
forcing the tapered threads of the male half of the
fitting into the female half or component port.
Tightening the assembly's nut draws the fitting into the flared end of the tubing, resulting in a positive seal between the flared tube face and the fitting body.
The flare fittings are designed for use with thin-wall to medium-thickness tubing in systems with operating pressures to 3,000 psi

4. It handles average fluid working pressures to 3,000 psi and is more tolerant of vibration than other types of all-metal fittings.
Tightening the fitting's nut onto the body draws a ferrule(ring) into the body. This compresses the ferrule around the tube,
causing the ferrule to contact, then penetrate the outer circumference of the tube, creating a positive seal.

5. When a sleeve fits well, the arm is free to move, twist
Three basic types now are available: SAE straight-thread O-ring boss fittings, face seal or flat-face O-ring (FFOR) fittings,
and O-ring flange fittings. The choice between O-ring boss and FFOR fittings usually depends on such factors as fitting location,
wrench clearance, or individual preference.
When a sleeve fits well, the arm is free to move, twist

6. A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression.
Threaded  connectors:
These connectors are used in some  low-pressure  fluid  power  systems  and  are usually made of steel, copper, or brass, and are available  in  a  variety  of  designs.
Threaded connectors are made with standard pipe threads cut on the inside surface.  The end of the pipe is threaded with outside threads. Standard pipe threads are tapered slightly to ensure tight connections.
Flange connectors:
Bolted   flange   connectors are suitable for most pressures now in use.  The flanges  are  attached  to  the  piping  by  welding, brazing, tapered threads (for some low-pressure systems),  or  rolling  and  bending  into  recesses.

7. Welded connectors:
The   subassemblies   of   some   fluid   power systems are connected by welded joints, especially in high-pressure systems which use pipe for fluid lines.
Brazed connectors:
Silver-brazed  connectors  are  commonly  used for  joining  nonferrous  (copper,  brass,  and  soon) piping  in  the  pressure  and  temperature  range where  their  use  is  practical.  Use  of  this  type  of connector is limited to installations in which the piping temperature will not exceed 425°F and the pressure  in  cold  lines  will  not-exceed  3,000  psi.
Flared connectors:
Flared connectors are commonly used in fluid power systems containing lines made of tubing. These  connectors  provide  safe,  strong,  dependable connections  without  the  need  for  threading, welding,  or  soldering  the  tubing.  The connector consists of a fitting, a sleeve, and a nut.
The fittings are made of steel, aluminum alloy, or bronze.
This type of connector eliminates all tube flaring, yet provides a safe, strong, and depend- able   tube   connection.   This   connector   consists of a fitting, a sleeve or ferrule, and a nut

9. Seal is relatively soft, non – metallic ring, captured in a groove or fixed in a combination of rings, forming a seal assembly, to block or separate fluid.
Fluid power seals are usually typed according to their shape or design.  These types include T-seals, V-rings, O-rings, U-cups and so on.
The  T-seal is  always  paired  with  two special  extrusion-resisting  backup  rings,  one  on each side of the T.
The backup rings T-seals   are   used   in   applications   where   large clearances could occur as a result of the expansion of the
thin-walled hydraulic cylinder.

10. V-rings  can  provide  excellent  service life; otherwise, problems associated with friction, rod  and  seal  wear,  noise,  and  leakage  can  be expected.
The V-ring is the part of the packing set that does the sealing.  It  has  a  cross  section  resembling the  letter  V, from  which  its  name  is derived.