Every petrochemical facility has miles of tubes and pipes made from various exotic alloys and a large number of expensive equipment like heat exchangers, pressure vessels, and distillation columns. All petrochemical equipment with their pipelines must operate safely and efficiently, making welding maintenance and repair crucial for safe and productive petrochemical operations.
Maintenance and Repair Of Petrochemical Facilities
Shutdowns and turnaround maintenance and repairs of petrochemical facilities are often highly complex tasks that focus on safety, efficiency, and repair quality. Repairs and maintenance must be done as quickly as possible without safety risks or inadequate weld quality. Prolonging the plant shutdown can cause millions of dollars in lost production revenue. So, repair efficiency is paramount. At the same time, petrochemical equipment must be repaired according to strict codes and standards, and welders and other contractors must follow all safety protocols.
Petrochemical facilities can produce many different end products, and each has unique challenges when maintaining its production equipment. So, welding maintenance contractors must be ready to weld equipment made from various highly exotic alloys, thicknesses, and joint geometries. Thankfully, welding is an exceptionally versatile method of joining metals, so there is a welding process suitable for almost any problem and industry application.
Maintenance and repair of petrochemical plants involves working on equipment like process vessels, cooling towers, pipe supports, pressure vessels, heat exchangers, fluid catalytic cracking units, hydroprocessing reactors, storage tanks, HF alkylation units, and of course, various types of pipes and tubes.
Welding Challenges in the Petrochemical Industry
Since the equipment in petrochemical facilities is so diverse, welders have to overcome many challenges when maintaining or repairing it. Below are just some of the common problems welders may face when welding pipes and equipment in petrochemical plants.
Hydrogen and Associated Cracking
Hydrogen is a common culprit behind weld cracking, especially in the petrochemical industry. Hydrogen can negatively influence weld strength and cause cracking in several ways.
- Hydrogen embrittlement – Occurs when hydrogen is introduced into the metal where it diffuses. Metals become brittle from hydrogen diffusion, but the degree of embrittlement depends on the material’s microstructure and the amount of absorbed hydrogen.
- Cold and delayed hydrogen cracking – Typically refers to cracking occurring during or after the weld cooling on steels.
- Hydrogen stress cracking – Acids like wet hydrogen sulfide and hydrofluoric acid can cause atomic hydrogen to penetrate hardened or high-strength steels and cause hydrogen stress cracking.
- High temperature hydrogen attack (HTHA) – Can occur in petrochemical process equipment exposed to hydrogen at high temperatures. High pressures and temperature drive hydrogen into steel, where it reacts with unstable carbides and forms a methane gas. Next, methane accumulates in the grain boundaries, which leads to cracking. Hot areas like the inlet nozzle on a heat exchanger are susceptible to HTHA. Weld cladding and choosing a suitable alloy are some of the ways to prevent HTHA.
Metals absorb hydrogen at high temperatures, especially in a molten state. So, welding is one of the critical risk factors for hydrogen diffusion and cracking. It’s vital to minimize moisture and to apply proper preheating to prevent excessive hydrogen diffusion. Preheating using induction heating equipment, like the Miller ProHeat 35, provides uniform elevated temperature which removes residue moisture from steels and slows down the post-weld cooling process, which is essential for letting the hydrogen diffuse out of the weld and heat affected zone (HAZ).
Corrosion
The petrochemical industry relies on many different corrosive chemicals that can cause pipes and equipment to corrode, and welds can often be more susceptible to corrosion. This issue can be challenging to detect, especially when dealing with corrosion under insulation (CUI) and internal corrosion.
Welding pipes and operating equipment, like pressure vessels, made from stainless steel poses a risk of developing intergranular corrosion. Overheating stainless steel during welding can lead to chromium (Cr) carbide precipitation (sensitization), which leads to intergranular corrosion. It’s essential to use advanced welding techniques like pulsed MIG, Miller’s regulated metal deposition (RMD), Lincoln Electric’s STT, or pulsed TIG to prevent excessive heat input and maintain the corrosion resistance of stainless steels.
Working With Exotic Alloys
Few industries rely on as many exotic alloys as the petrochemical industry. Besides carbon steel, welding in petrochemical plants often includes stainless steels (austenitic, duplex, and super duplex), titanium, Inconel, Chrome-moly steels, high-strength steels, aluminum, and other exotic alloys. Many of these advanced alloys are challenging to weld and require highly skilled operators, which makes weld automation and modern welding power sources crucial for high productivity and weld inspection pass rates.
Welding Processes For the Petrochemical Industry
Welding for petrochemical maintenance and repair can take place in your shop or on-site, depending on the project’s characteristics and scope. Regardless of the job area, it’s vital to choose your welding process and equipment correctly to achieve high productivity and make welds that pass the codes and meet the client’s expectations.
MIG and Flux-Cored Welding
Wire welding processes, like MIG and flux-cored, can improve your productivity compared to stick or TIG welding processes, thanks to a higher deposition rate and welding speed. But, applying advanced MIG welding processes like pulsed MIG and RMD can drastically improve your efficiency and time-to-completion.
The Miller PipeWorx 400 is a high-end, state-of-the-art, multi-process welding power source designed for shop use. It supports pulsed MIG and RMD. Both can significantly improve weld quality and productivity and make the welding process less challenging for the operator. Since RMD produces thicker weld bead profiles on pipe root welds, you can often eliminate the need for a hot pass.
In addition, you can even weld stainless steel pipes without a purging gas in some applications using the RMD, which can dramatically improve productivity. Pulsed MIG provides less heat input than traditional spray transfer, eliminates arc wonder and spatter, and enables out-of-position welding. Pairing RMD and pulsed MIG provides an all-around one-wire, one-gas, pipe welding solution from root to cap that’s easier for the operator than the traditional MIG welding process and its variations.
But what about conducting equipment repairs on-site? That’s more of a territory of the EX360 FieldPro multi-process power source. This workhorse of a welder is rugged, powerful, lightweight, and loaded with advanced welding processes tailored for applications like welding petrochemical piping and other equipment. It features the RMD MIG, pulsed MIG, flux-cored, TIG, and stick welding processes, and outputs up to 425A, with a 60% duty cycle at 350A and 34VDC.
The EX360 FieldPro also supports the ArcReach technology, which minimizes the non-value-added time of your operators. ArcReach allows your operators to operate the EX360 FieldPro remotely without going to the machine itself. Since petrochemical facilities are complex, it’s not always viable or safe to bring the welding power source close to the welding area. Sometimes, welders must get into tight spots to access the weld joint. It’s a huge time waste for the operator to get out of the welding position just so they can modify the output power by a few amps. So, ArcReach can be very beneficial when working on-site, especially on complex sites like petrochemical plants.
TIG Welding
While TIG welding is slower than MIG and requires more skills from the operator, it’s sometimes a preferred choice for tasks where weld accuracy is paramount. Welding valves and repairing details on heat exchangers are good examples where TIG’s precision is highly beneficial. In addition, the TIG welding process offers exceptional weld purity and heat input control, making it an excellent choice for high-risk welds where absolute dimensional accuracy and weld dimension control are needed. This welding process can be used to weld almost all metals and exotic alloys, so its applications are highly diverse.
Our TIG welder rentals include Miller’s Dynasty and Syncrowave advanced TIG power sources. These machines will let you tailor the welding arc precisely to your needs. With the ability to output as low as 3A and up to 400A, you can weld thin and delicate parts and thick pipes and vessels using our Dynasty 400. In addition, its Auto Line technology allows for any input voltage (208-575V), making on-site jobs more convenient, even when running on dirty or unreliable power. You can weld using multiple AC TIG waveforms, with up to 5000 pulses per second, and maximum frequency and balance adjustability. No matter how delicate the job or how challenging the alloy, Red-D-Arc’s TIG welders are up to the task.
Orbital Welding
Manual TIG welding is inherently slow and requires highly skilled operators. Naturally, TIG isn’t always the go-to choice, even if it provides maximum weld quality. But, operator training for automated orbital TIG welding is far easier than manual TIG. In addition, it offers high-quality welds consistently without the element of human error or operator fatigue.
Orbital welding systems are automated mechanical devices that rotate the welding torch around the pipe during welding. The welding torch stays at an optimal position at all times, which results in significantly fewer weld defects and consistent weld production. Orbital welding is an excellent choice for joining process pipes and tubes in petrochemical facilities. You can use our Axxair fusion closed orbital weld heads to weld tubes with minimum clearances where manual welding is almost impossible due to constricted space between the tubes. Or use larger Axxair SATO open orbital weld heads to weld large diameter pipes in a minimal space.
Orbital welding is the best solution for high-productivity petrochemical pipe and tube welding on site, or in your shop. Likewise, orbital pipe beveling and cutting equipment can dramatically reduce the time needed for pipe joint preparation and improve weld inspection pass rates. Petrochemical pipes and tubes often transport hazardous chemicals at high temperatures and pressures, requiring absolute weld integrity and quality. It’s challenging to produce the code-required welds manually, especially with the skilled welder shortage affecting everyone globally. Weld automation solutions like orbital TIG systems are an excellent solution for making high-quality TIG pipe welds that pass inspection and meet code and client criteria.
Rent or Lease Welding Equipment From Red-D-Arc
Red-D-Arc has a massive fleet of advanced process welders, including multi-process machines and dedicated MIG or TIG systems. We also provide modern, state-of-the-art weld automation equipment for welding pipes and pressure vessels in the petrochemical industry. Regardless of the job at hand, Red-D-Arc has a system for it.
Instead of buying expensive welding equipment, rent it and immediately experience the ROI. Buying costly gear, like weld automation equipment and high-end power sources, takes a long time to pay off, and you also need to cover the costs of storage and long-term maintenance. Welding equipment rentals for petrochemical contracting allow you to scale in and out of the job and take on the most challenging jobs, even if you don’t own a fleet of high-end machines. Contact us today, and our experts will help you choose the most suitable welding gear, whether you are repairing or maintaining an entire petrochemical facility or just specific parts of it.
