Oxy-fuel Apparatus – Part III

Posted by Florida Gas Welding

                                                                                 Cutting attaMoose-cortechment

The cutting attachment functions as a convenient and economical approach to cutting operations where the frequency and/or application does not require a torch designed strictly for cutting. When connected to a torch handle, the cutting attachment functions as a cutting torch. It provides the operator with a wide range of cutting capabilities.

The cutting attachment consists of seven basic elements as shown in Figure 5. This figure shows:

the cone end, coupling nut, preheat oxygen control valve, mixing chamber, cutting oxygen lever and tube, cutting attachment head, and tip nut.

 

  

 

Cone End and Coupling Nut

The cone end and coupling nut are designed to permit easy attachment to the torch handle. The tapered cone end is machined to mate with the internal taper of the torch handle head. O-rings on the cone end allow continued separation of oxygen and fuel gases. The O-rings also provide a handtight seal for the connection.

                                                                             WARNING

There must always be two O-rings on the cone end. The absence or damage of either of these O-rings will allow premixing and leaks of oxygen and fuel gases. This can lead to a sustained backfire within the torch handle or cutting attachment.

The center orifice of the cone end, like the center port of the torch handle head, allows the passage of the oxygen supply. The orifices around the oxygen port allow the fuel gas to travel to the mixing chamber in the lower tube of the cutting attachment.

Preheat Oxygen Control Valve

When the cutting attachment is connected to the torch handle, the preheat oxygen control valve on the cutting attachment controls the preheat oxygen supply from the regulator. To function in this manner, the oxygen valve on the torch handle must be opened completely. The preheat oxygen supply is then increased or decreased by opening or closing the cutting attachment control valve. The fuel supply is controlled by the fuel valve on the torch handle.

Mixing Chamber Tube

Fuel and oxygen are mixed to produce the desired preheating flame. To accomplish the necessary mixing of gases, oxygen and fuel are fed into a mixing chamber located in the forward portion of the cutting attachment mixing chamber tube. Oxygen is directed to the mixer through the inner oxygen tube. The fuel gas is drawn from the exterior cavity of the attachment’s lower tube around the mixer.

Mixed gases then flow through the preheat orifices of the cutting attachment head and into the preheat orifices of the cutting tip.

Cutting Oxygen lever and Tube

The cutting oxygen lever is located above the body of the cutting attachment. When the oxygen control valve on the torch handle is open, depressing the lever allows cutting oxygen to flow through the upper tube of the cutting attachment and the center port of the cutting attachment head. The upper oxygen tube is designed to allow the maximum supply of oxygen to the cutting operation and

to provide structural strength by the utilization of high strength tubing.

Cutting attachment head

The cutting attachment head is designed to allow the cutting oxygen and the mixed preheat gas to stay separated during the cutting operation. The exterior of the torch head is threaded and the interior of the head is tapered. The internal taper of the head is stepped allowing the preheat gases to feed the cutting tip through the exterior orifices and the cutting oxygen can travel uninterrupted through the center port of the tip to the heated base metal (see Figure 6, page 23). The exterior threads on the head allow a tip nut to compress a cutting tip into the tapered head. This creates a firm gas-tight metal-to-metal seat.

 

 

Cutting Tip

Cutting tips are available in a wide variety of configurations and sizes. Cutting tips keep the preheat gas mixture and cutting oxygen stream separated and provide flame characteristics needed for a particular cutting application. Tips are sized according to the thickness of metal they can cut. For instance, a number 000 tip is designed to cut metal 1/16” to 1/8” in thickness, and a number 00 tip will cut metal 1/8” to 1/4” in thickness.  The tapered surfaces form a metal-to metal seal (see Figure 6). Inspect both the head and tip tapers frequently for signs of damage or wear.

Cutting Tip

WARNING

A damaged seating surface on either the tip or the head can create a hazardous condition, resulting in a backfire or sustained backfire. This may damage the cutting attachment.

If the seating surface of a tip becomes damaged, DO NOT use it. Discard the damaged tip. If the head requires repair, take the torch to a qualified repair technician.

Preheat Orifices and Oxygen Orifices

Cutting tips are subjected to much abuse in cutting operations. Slag can splatter and stick to the cutting tip, clogging or obstructing the passages through which the gas must flow. Remove splatter from the tip orifices with appropriate tip cleaners.

NOTE

Repeated cleaning can affect the flame configuration and render the tip unsuitable for precision work.

Welding Nozzle

The welding nozzle is usually an assembly consisting of a welding elbow, a gas mixer, and a coupling nut. A wide range of tip and nozzle configurations are available for attachment to the torch handle.

Welding Nozzle

Never starve or choke a multi-flame heating nozzle. This causes overheating of the head and a backfire or sustained backfire may result. Should a backfire occur (flame pops and disappears and/or a hissing sound is heard, the flame is burning inside the nozzle), immediately turn off the oxygen valve on the torch handle. Then, turn off the fuel valve.

Allow the nozzle to cool before using it. If a backfire recurs, have the apparatus checked by a qualified technician before using again.

NOTE

It is better to use a smaller size welding, brazing or heating tip at its full capacity than a larger tip at its minimum flow capacity.

Gas Mixer

The welding / heating nozzle cone end is similar to that of the cutting attachment cone end. The difference is that the welding / heating nozzle cone end is designed to mix the oxygen and fuel gases, whereas the cone end in the cutting attachment is not. When the oxygen meets with the fuel gas, a homogenizing mixing effect occurs. This complete mixing of the gases results in a well-balanced flame composition. Like the cutting attachment cone end, the welding / heating nozzle has two orings.

They maintain the separation of gases prior to the point at which mixing occurs. They allow a hand-tight connection of the welding nozzle and the torch handle.

WARNING

There must always be two O-rings on the cone end. The absence or damage of either of these O-rings allows premixing and leaks of oxygen and fuel gases. This can lead to a backfire or sustained backfire within the torch handle.

 

Coupling Nut

The welding / heating nozzle coupling nut is similar in design to the coupling nut on the cutting attachment. A locking ring in the coupling nut mates with a groove in the forward portion of the welding nozzle mixer, thus allowing the nut to protect the cone end and O-rings (see Figure 7). Examine the O-rings by twisting and pushing the coupling nut away from the cone end.

CAUTION

Use only genuine VICTOR®, Cutskill®, or Firepower® torch handles, welding nozzles and multi-flame nozzles to ensure leak-free connections and balanced equipment.

 

 

 

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