Automated weld management software demonstrates time and again that optimized manual welding stations will achieve about 20 per cent arc-on time. That is not the average, of course – the average is lower. The question is, what are some of the issues that steal time from actual welding?

Swapping out cylinders and running out of shielding or cutting gas are examples of hidden causes of downtime. Fabricators need to do everything possible to keep their best welders operating at peak efficiency. If you find you are continually swapping out empty cylinders or have experienced safety issues related to cylinder handling, it may be time to consider a central gas system (CGS).

Centralized gas distribution consolidates gas supply in a central location for more security, as well as easier and simplified operation and gas management. CGSs also eliminate the situation in which potentially untrained staff swap out cylinders.

Installing a CGS has upfront costs but delivers a proven long-term payback. Cylinder bundles, liquid cryogenic tanks, and bulk systems lower overall costs and transportation charges, reduce the volume of residual gas being returned to the gas supplier, and free up floor space.

A variety of displays can communicate gas status to personnel, including something as detailed as digital display for volume of gas remaining to an alert that one cylinder is running low and is ready for manual, semi-automatic, or fully automatic switchover at the manifold.

Manifolds that integrate a purge circuit allow the impurities to be completely removed. Closing the process isolation valve and opening and closing the purge valve several times purges the air from the system quickly and with minimal wasted gas while completely isolating the welding line from contamination. While not as critical for some processes, it can be for critical applications such as automated TIG welding of pipe for pharmaceutical, semiconductor, and medical products.

There are four different configuration options for CGSs.

Cylinder Bundles. The first option is portable cylinder bundles, moved by a crane or forklift truck, with a portable manifold. Portable systems tend to be in six, 12, or 18 packs of cylinders, and they are “bundled” together and typically stationed near the point of use. This choice is valuable if you need to move your source gases closer to where they will be used, either in the shop or in the field. For instance, portable bundles are useful in shipyards, construction sites, and fabrication shops where you don’t have a pipeline system. In other words, this is a valuable approach in any situation where individual cylinders can’t supply high enough volumes of gas.

A good example of this is when four to six people (or more) are welding or cutting in a confined area where it is difficult to get and replace gas cylinders, such as in shipbuilding and repair, refinery and power, and demolition. They are all pulling from the same gas source through a manifold with multiple outlet points. You might have six welders tied into that manifold, all using the gas. If they are all using a gas volume of 25-35 cubic feet per hour at the same time, you are looking at close to 120-plus SCFH. Single high-pressure cylinders typically store 280 to 330 SCFH.

A key question to ask is what the application is and how many operators will be drawing from the gas source.

Manifolds like this one that integrate a purge circuit allow impurities to be completely removed. Closing the process isolation valve and opening and closing the purge valve several times purges the air from the system quickly and with minimal wasted gas while completely isolating the welding line from contamination. It can be critical for applications such as automated TIG welding of pipe. ESAB

A misconception welders sometimes have is that they have greater control with a single-cylinder station right next to where they're performing the work. However, the gas control that they require can be achieved by attaching a flowgauge or flowmeter to the gas solenoid valve on their machine. They may also think that it is easier to move a single cylinder around a job site. But the only way to go is to get into some type of manifolding system because they will be performing fewer cylinder changeouts and spending less time adjusting the equipment. It's just there to run continuous operation as long as they need the gas. There is really no downside to the switch for the welder.

Stationary Manifolds. For shops that use a large volume of gas, a second option is to have a bank of cylinders on a wall, called stationary manifolds. The gas is fed through a pipeline system that distributes it to various stations throughout the facility. These high-pressure cylinders tend to be attached to the wall and deliver about 3,000 lbs. of pressure to the pipeline. A permanently mounted pipeline or line regulator regulates the pressure into the downstream piping system to deliver the preset pressure to the station regulators and flowmeters. Although they look very much alike, the flow capacity from the line regulator is far greater than the flow that is going to be required at the station regulator.

These manifold systems are designed to be managed manually or to switch automatically from one cylinder bank to another. A basic manifold system requires you to manually switch the lever to the alternate cylinder bank when the primary bank is depleted. This is not ideal if downtime is a concern. A semi-automatic manifold, on the other hand, will switch over automatically when triggered by pressure differentials. The depleted cylinders then can be replaced without shutting down the system; these now become the reserve bank of cylinders.

Cryogenic Liquid Cylinders. Banks of cylinders can be very effective but still might require too many changeouts, depending on your application. An intermediate choice before going to a bulk storage approach is a manifold system using cryogenic liquid cylinders, often referred to as liquid dewars. These often are used on systems requiring delivery of high-pressure and extremely high flow rates such as laser or automated cutting tables.

The value of these liquid cylinders for cutting and welding is that one of these tanks is the equivalent of 18 or more high-pressure cylinders, so they can provide much more gas without resorting to a bulk tank.

These liquid cylinders are easily damaged, however, so if you are using them, they should be placed in a low-traffic area and possibly caged or cordoned off.

Bulk Systems. If you are considering a bulk system, it is because you need extremely high volumes of gas and find that the economics of investing in the construction involved in putting in a bulk tank makes more sense in the long run.

Shops might think the break point between a liquid cylinder or bulk tank storage relates to the number of welding stations in their facility, but it’s truly about the total volume of gas that is needed and distributed. Your gas distributor will be able to explain the calculation they use for this. They also will help you determine what regulators or flow control devices are required based on the amount of pressure and flow needed for your operation. The distributor will in fact run this calculation and help you determine the best financial option.

To ensure your system is set up properly, specification of the correct pipe material, diameter, and joining method is important. Working with the manifold and regulator supplier during CGS design can help ensure the correct equipment and piping specification.

A check list to determine the right manifold for an application is helpful. It asks nine questions to determine your needs:

This is an example of a semi-automatic switchover manifold, in this case designed for high purity gases. ESAB

Right-sizing your CGS will involve discussing your operations and growth expectations with your gas distributor. Ultimately, such an investment will save both time and money on the shop floor, with more efficient use of your gases and better use of your welding team’s time.

Curt Rocha is global product manager, ESAB Welding & Cutting Products, 2800 Airport Rd., Denton, Texas 76207, 940-381-1360, www.esab.com.

ESAB Welding & Cutting Products

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