For some industries, it is vital that welding is carried out in a controlled environment, this can ensure high-purity and cleanliness are maintained at all times. High-purity welding is often used in a variety of applications within the semiconductor, aerospace and medical sectors when contaminants need to be kept away from the weld area. These contaminants can have a detrimental effect on the liquids and gases that travel through welded products, therefore it is vital to maintaining the environment created in ISO certified cleanrooms. Without high-purity welding, sub-micron particles of contaminants infiltrating the weld can result in large replacement costs for devices, especially in the semiconductor sector. This article will investigate the factors for successfully producing high-purity welding within cleanroom environments, the different requirements and classifications of ISO certified cleanrooms and give examples of when high-purity welding is required in a range of industries.
The quality and integrity of a weld can be determined from three factors; the penetration, the oxidation and the bead of the weld. It is important during the welding process that the bead fully penetrates the inner tube walling, failing to do this can result in weaker results. High levels of oxidation can result in ‘dirty’ welds which are prone to contamination; the level of oxidation is prevented in high-purity welding through the use of an inert gas which is purged on both the inside and outside of the welded metal. Obtaining optimum beading on a welded joint is achieved through a combination of both weld speed and welding current, beading should show consistency in both spacing and width throughout the entire weld joint. Achieving high-purity welding is almost impossible unless carried out in a controlled environment, it is always recommended that high-purity welding is performed in an ISO certified cleanroom.
Modern cleanrooms have been used since the 1960s after initially being designed by the American physicist Willis Whitfield. Although designs have been improved since then, the principles still remain the same. A cleanroom essentially is a space that controls the level of tainting within the environment, measured through quantity of particles per cubic meter at a predetermined molecule measure. Cleanrooms can have either laminar or unidirectional airflow systems which direct airflow towards filters within the walls or perforated floor panels; this is then recirculated throughout the room. Standards for cleanrooms are outlined in ISO14644-1 which was developed by the International Organization for Standardization; these standards outline nine classes of cleanrooms which are specified by the maximum amount of particles allowed per metre cubed. An outline of the different ISO classifications can be seen below (Table 1):
|Class||Maximum particles/m3 (cumulative)|
Table 1: A table showing the particle regulations for each ISO certified classifications.
As previously mentioned, high-purity welding has universal application across a number of industries and sectors. One example includes the aerospace industry, with welded components experiencing high levels of stress, it is important that high purity and integrity is achieved, often through orbital welding techniques. In the nuclear industry, titanium is often used in nuclear piping due to its improved resistance to corrosion from seawater; titanium is welded in cleanroom environments with argon to avoid oxidation, this helps to preserve the natural strength of the titanium. Finally, high-quality welds are vital in the food production industry to prevent contamination through bacteria. Smooth welds prevent the creation of occlusions which create environments that harmful bacteria can establish and colonise within; this can be achieved through treating the backside and frontside of the weld with equal amounts of oxygen.
Orbital Fabrications’ current facilities boast both ISO certified in-house class 5 and class 6 cleanroom facilities, allowing the delivery of high-quality welds for a range of industries. Their team of welding experts have experience delivering one-off weld assemblies to complete gas and fluid handling systems within their controlled environments. All welds are bagged and sealed upon completion to ensure that products reach customers in the same environment that they leave the cleanroom. If you would like more information about Orbital Fabrications’ cleanroom services, visit our website here for more information.
In addition to cleanroom services, Orbital Fabrications is well established as one of the UK’s top welding companies. With experience working on a range of high-tech fabrication projects, the team has gained valuable experience in orbital welding, manual welding and other specialist welding services. In addition to these welding services, Orbital Fabrications also offers machining services, process pipework production and helium leak testing from their recently refurbished premises in St. Ives, Cambridgeshire.
If you would like more information on Orbital Fabrications’ cleanroom or specialised welding services, call the team on +44(0)1480 464066 or contact us here.