Welded Cylinders

To maintain the contracted tolerances all cylinders are automatically re-rolled and inspected after welding as a standard practice, this eliminates the need for the customer to return any cylinders that may have distorted after their own welding, with the cost of transport alone making this service a viable option.

Any weld, if required, can be fully or partially tested by the designated non destructive method with the results interpreted to all major codes. In all cases, weld maps are supplied, on completion, to indentify the results to the item under test.

Barnshaws can offer single cylinders or multiple belted shells circumferentially welded up to 20 meters in length with a maximum weight restriction of 20 Tons.

SUBMERGED ARC WELDING

Widely used for the welding of carbon and stainless steel, the submerged arc welding process has the ability to produce high quality, defect free welds at high deposition rates, with deep weld penetration, this together with the ability to fix the submerged arc unit to a motorised column and boom manipulator makes the process a highly suitable system for the seam welding of cylinders.

Submerged arc welding is a method in which the heat required to fuse the metal is generated by an arc formed by an electrical current passing between a continuously fed wire consumable and the work piece.

The distinguishing feature of this process is that the weld area is submerged under a blanket of granular flux, which in addition to shielding the arc from contamination provides a slag which protects the weld metal, as it cools.

Arc current, voltage, travel speed and joint tracking are monitored and adjusted by controllers which in turn affect the shape and appearance of the weld, producing a high quality weld deposit.

As illustrated, during welding, the heat of the arc melts the tip of the wire consumable forming a molten pool along with some of the flux, as both solidify the flux forms a slag on top of the weld metal which once cool can easily be removed with any surplus flux being collected by a vacuum recovery system for re-cycling.

TOLERANCES

Standard tolerance offered for welded cylinders / shells are based on the following specification, however with prior agreement, in some instances these can be reduced.

INSPECTION / TRACEABILITY

All welded contracts undergo a full in-house inspection service throughout production, maintaining pre and post rolled measurements as well as final dimensional / tolerance reports, we also offer full traceability which is maintained in accordance with the appropriate procedure.

CAPACITY

PROCESSES AVAILABLE

Submerged Arc (SAW)

Submerged arc welding (SAW) requires a continuously fed consumable solid or tubular (metal cored) electrode. The molten weld and the arc zone are protected from atmospheric contamination by being "submerged" under a blanket of granular fusible flux consisting of lime, silica, manganese oxide, calcium fluoride, and other compounds. When molten, the flux becomes conductive, and provides a current path between the electrode and the work. This thick layer of flux completely covers the molten metal thus preventing spatter and sparks as well as suppressing the intense ultraviolet radiation and fumes that are a part of the shielded metal arc welding (SMAW) process.

Manuel Metal Arc (MMA)

Manual Metal Arc (MMA) welding involves striking an arc between a covered metal electrode and a work piece.

The heat of the arc melts the parent metal and the electrode which mix together to form, on cooling, a continuous solid mass. The central metal electrode or core wire acts as a consumable, providing the filler metal for the weld. MMA welding can be used to join most steels, stainless steels, cast irons and many non-ferrous materials. For many mild and high-strength carbon steels, it is the preferred joining method.

Tungsten Inert Gas (TIG)

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas (argon or helium), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. A constant-current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas and metal vapours known as a plasma.

GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminium, magnesium, and copper alloys. The process grants the operator greater control over the weld than competing processes such as shielded metal arc welding and gas metal arc welding, allowing for stronger, higher quality welds. However, GTAW is comparatively more complex and difficult to master, and furthermore, it is significantly slower than most other welding techniques. A related process, plasma arc welding, uses a slightly different welding torch to create a more focused welding arc and as a result is often automated.

Metal Inert Gas (MIG)

MIG/MAG welding uses filler metals, in the form of a solid wire electrode or a tubular-cored wire electrode, fed through a welding gun. The filler metals are melted off continuously in an electric arc. The energy generated in the arc is created by an electric welding power source. The arc and the molten weld pool are protected by a shielding gas that flows out of the gas nozzle located on the welding gun.

Shielding gases for welding are either inert (MIG) or active (MAG). Inert in this case means that the gas does not react with the molten weld pool or the melting electrode. Inert gases include argon and helium. Active gases provide a greater opportunity to optimise the process and the properties of the finished welded product. Many materials, such as non-alloyed steel, require the use of an active gas to ensure process stability and reliability. Argon/carbon dioxide and argon/oxygen are examples of active gas mixes.