The Key Role of Welding

When It Comes to Valves, Welding Is a Natural Part of the Equation

weldingIn all manufacturing prior to the late 1920s, all valves were comprised of threaded or flanged components. It wasn’t until the arc-welding process became the widely accepted ideal way to attach components that the format of valves became more customizable, as we know them today. Traditional welding uses what is called the oxyacetylene process—acetylene gas fueling an open flame and supported by 100% oxygen. Arc welding is much more efficient, using electricity to achieve the process. High amps used at low voltage are passed through an electrode on one side of a circuit to the piece to be welded. As the electrode is moved closer to the piece, an arc of electricity jumps from the electrode to the piece.

There are several considerations when we look at how arc welding is employed in today’s valve world:

  • Type of arc welding used: Arc welding exploration has resulted in a variety of methods, the most efficient and widely used of which is called Shielded Metal Arc Welding (SMAW), also known as “stick welding.” Other methods include Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), Submerged Arc Welding (SAW) and Plasma Arc Welding (PAW).
  • Heat-affected zones: Abbreviated to HAZ, this term refers to areas that can become heat compromised during the welding process and may need to be restored using post-weld heat treatment (PWHT).
  • Connection type: The two connection types when welding valves into piping systems are the butt weld and the socket weld. The butt weld is the most challenging to achieve, as both connection pieces must be perfectly aligned throughout the process and one simply butts up against the other with no point of entry on either side. Socket welds on the other hand entail one piece that fits into another before welding begins.

Proper training is also crucial when it comes to welding. Butt welds in particular require much practice to perfect. In the interest of repeatable quality and measurable industry standards, the welding process necessarily consists of:

  1. WPS: Standing for welding procedure specification, this procedural document is created to outline the methodology used to perform a specific type of arc welding.
  2. PQR: Otherwise known as the procedure qualification record, this is the process that verifies and lends credence to the created WPS. In essence, it illustrates that the WPS works as it says it will to create the desired welding result.
  3. Individual qualification: From there, individual welders must practice and be tested to prove that they can personally achieve a repeatable level of quality in the specific welding procedure. The welder and the weld are examined for performance and quality.

Though it was not always so, for nearly 100 years now, welding and valves have been integrally tied and they will continue to be so for the foreseeable future. Great welds support great valve functionality and we will continue to work together to train and support new generations of welders and valve manufacturers.

To see welding in action here at Shan-Rod, check out this short video illustrating our valve-manufacturing process: