valve end connection types

METHODS OF CONNECTING THE VALVE

Threaded connection

Accumulation of sand, dirt or any foreign material in the pipeline can hinder valve efficiency and severely damage critical valve components. The inside of the pipe must be thoroughly cleaned with air or steam and, when tapping the pipe, it is necessary to measure the size and length of the pipe thread to avoid filling the pipe with the valve seat and the valve disc .

It is also important to wash the threaded ends thoroughly to remove any harmful steel or iron deposits.If, on the other hand, you want a stronger weld, you can use Teflon tape or adhesive for pipes, but only sparingly on the pipe threads, never on the valve threads and not even in the valve body to avoid damage to the disc and seat.

Before installation, close the flow through the valve to allow proper operation and close the valve completely before installation. Place a wrench over the head of the hexagonal bolt near the pipe to avoid possible deformation, finally after installing the valve a support must be placed for the pipe as the yielding pipes can deform the valve and cause it to fail.

Flanged connection

To ensure correct connection and installation of the valve flange, precise and organized steps are necessary:

1. Thoroughly clean the joints.
2. Loosely install two or three bolts on the base.
3. Carefully insert the spacer into the joint (the lower bolts help locate the gasket and hold it in place).
4. Tighten inserted bolts crosswise and NOT round to help eliminate excessively concentrated pressure.
5. After a period of normal use, check if all bolts are tight and retighten if necessary.

Low temperature welding and silver brazing

Before installing the correct valve it is necessary and appropriate to read the installation instructions.

1. First cut the pipe in the vertical direction and remove the burrs by measuring the diameter of the pipe.
2. Use gauze or wire brush to remove debris and cut parts so that the metal surface shines.
3. Apply flux to the outside of the pipe and inside the welding hood, which must completely cover the welding surface.
4. Make sure the valve is open, heat the pipes first and then transfer as much heat as possible from the pipe to the valve without extending the heating time of the valve itself.

Silver Brazing Method

Assemble the parts to be brazed remembering that if the fluxed part is left standing, the

moisture in the flow will evaporate and the dry flux will peel off easily, leaving exposed metal surfaces susceptible to oxidation. When making a connection assembly you must insert the tube into the socket until it encounters a block: the assembly serves to ensure a firm support so that it remains in a straight position during the brazing operation.

REMEMBER: For valves with a nominal diameter of 1 inch or larger it is difficult to heat the

connecting parts to the desired temperature at one time! Two torches are usually required

to maintain a normal temperature over a large area, which is why we recommend adequate preheating of the entire surface of the coating and using an acetylene flame to heat the connected parts.

Do this: start by heating the tube 1 inch from the valve, then alternately cook the tube up

and down a short distance around the tube, turning the tube at the correct angle to avoid

burning the tube (the flame must move continuously, do not leave it in a fixed point).

Heat evenly until the flow over the valve no longer makes any sound, but be careful not to

overheat the valve!

When the flow becomes liquid and appears translucent on the pipes and valves, start cooking the flame back and forth along the axis of the connecting parts to keep the connecting parts warm, especially the valve sleeve seat.

5. Use the right amount of solder

If too much solder is used, some of the solder may flow past the pipe barrier and clog the sealing area (note that the solder and braze continues to flow as the connecting parts are installed)

Silver Brazing Method

Point the welding wire or welding rod at the pipe socket in the valve and move the flame

away from the welding rod or wire as it enters the joint. Now proceed by moving the

flame back and forth as the alloy flows into the joint and once the proper temperature

is reached you will notice that the alloy flows quickly and easily into the gap between the

tube housing and the valve sleeve. Once the joint is filled, the edge of the welded alloy

is visible.

6.Use a brush to remove the excess solder

When the solder is tacky, use a brush to remove the excess solder while after the solder has

cooled, wrap a thread around the valve port.

 Silver Brazing Method

If different brazing materials are used, the strength of the brazed connection may not be

optimal, but its strength depends on how the cleaning and maintenance work has been

carried out between the tube shell and the valve housing. The mechanical tolerances and

surface smoothness of the inner diameter of the bushings of the silver brazed valves are very

precise, in order to ensure adequate adhesion.

REMEMBER: During the cleaning and removal process, detergent residues must be carefully

observed! If the soldering takes place on dirty or unclean surfaces then the silver brazing alloy

does not flow or adhere to the oxides, while the oily and exposed surfaces will oxidize easily:

what will happen is that the debris will reject the flow.

• Thread for cylindrical pipes with general sealing
• Thread for conical tubes with general sealing

RF is called a Raised face. The raised area of the flange faces which contains the gasket sealing surface between mating flanges. This RF flange is the most common type that is used in plants application and it is very easy to identify.

The purpose of RF end connections is to concentrate more pressure on smaller areas. It  helps in increasing pressure joint capability.

NPT end connections are also known as national pipe thread tapered connections. This is United States standards for tapered threads that are used on threaded fittings and pipes. These are found on a taper, on a bolt thread will pull it tight and hence make a tight seal.

NPT end connections rely on thread deformation from a metal to metal sealing design where the connector’s threads connect together.

Valves are manufactured and made with many end connection types that include socket welded, screw end, flanged and butt welds. Special connection can be done and it can be specified such as grooved, union, and with other connectors.

Screw end valves need very less labor connections; it also costs very less for other types. These valve end connections are used on valves that are made of steel and have a socket with an inner diameter that is larger than the pipe’s outer diameter.