Back Gouging for Full Penetration Welds
Back Gouging for Full Penetration Welds
When it comes to critical strength application or members where pressure vessels are involved, on many occasions, we will have to complete an entire penetration weld so as to meet the parameters of the job or project. The term Complete Joint Penetration (CJP) is how it is referred in the industry. In most cases, these welds are to be completed only from one side, requiring some kind of root pass on an open root joint unlike other applications where access is possible to the entire backside where an open root pass kind of weld is not required.
When a full penetration weld needs to be completed where both sides are going to be welded, quite often we may have to back gouge out the root of the primary weld before we apply any kind of filler material behind the joint of the weld. The amount to be taken away, the type of metal used and often the location or position of the weld will be the determining factor on how we carry out the process of gouging out the weld. When the metal isn’t too thick, it doesn’t take too long and doesn’t require a lot of gouging – an electric or air grinder is sometimes an ideal tool when it comes to back gouging.
Based on the configuration of the joint, either a thick or a thin coarse or rough disc may be the ideal tool to get the task done. We have to be watchful while making use of the grinder in a furrow. In case the wheel fastens to the joint, there are chances of it a splintering a break even before you can blink an eye. The least protection for the face is a face shield and safety glasses. Moreover, since many of the grinding wheels are not meant to be used on the edge, ensure that it is ok to use your wheels for this particular application. Remember – always, safety first!! In case the metal is larger, thicker or if the gouge is lengthy or in a tight position then the grinder may not be the answer. If that is the case, a thermal process has to be worked out to remove the metal.
The many options that a fabricator would have in mind are air carbon arc gouging, plasma arc gouging or an oxy-fuel gouging tip. Both plasma arc gouging and air carbon arc gouging are methods that require electrical power. In cases where diesel or gas powered generator are accessible, the process becomes more portable. Generally, plasma arc gouging has a special source of power committed for just that process. An experienced and skilled operator can use both these methods to get rid of a great amount of metal in a very short time.
Air carbon arc gouging is done by either stick welding or shielded metal arc welding machine and a little compressed air. The oxy-fuel gouging tip process is only possible on carbon steel since time is required for preheating the base material and the procedure takes a longer time when comparing it to other operations.
This process is portable since only a fuel gas tank, an oxygen tank, hoses, some regulators and a torch is enough to get us started. The consumable for carbon arc gouging are comprised of carbon electrodes coated with copper while the consumables for plasma arc cutting is comprised of both the electrode and copper constricting cup.
Between the two processes, carbon arc gouging is more portable because only the electrode lead from the energy source requires to be threaded to the site of work. Generally, the length of the plasma arc gouging torch doesn’t exceed over 25feet as a result of which the source of power will not be too far away from the site of work.
The introduction of inverter power sources plasma gouging and cutting has become an easier and simpler option where less sized power sources are concerned since their weight and size have increased the portability of plasma gouging. Since all gouging procedures give rise to a plenty of sparks which can cover quite a distance,
we have to keep this in mind when we are repairing to do any kind of gouging which involves any of the mentioned procedures. Make sure that there isn’t any kind of combustibles around and have a fire extinguisher close at hand. It is often seen that these procedures consumes more amperage than what is usually consumed for welding.
Keeping this in mind we must wear a darker shaded lens for our welding hood which matches the amperage that we use. A chart for the right shades is available with ANSI Z49. Again, since these procedures result in a quite a bit of noise hearing protection is also strongly recommended. Proper ventilation and plenty of fresh air are other important considerations to be kept in mind. Regard of the procedure, the aim is to get rid of the un-welded materials up to the stage we get to sound metal. After the material is removed, welding is carried on to top up the emptiness.
We can get rid of the material from the ridge on a pressure bowl or from the butt join’s back or even from a crack in the cast-iron portion.
Take a look at the Longevity website (www.longevity-inc.com) or the YouTube Channel (www.youtube.com/longevitywelding) for any information about the various equipments for the different welding and cutting processes. You can find anything you need at Longevity as we have the exact machines for all your applications, so just go through and choose what best fit and suit for your needs – for both materials and products.