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Hudson Welding Consultancy Ltd., Riverstown, Cork (2026)

18/03/2026

WELD KNOWLEDGE WEDNESDAYS

Orbital Welding Coupons – Practice Makes Perfect?

In high purity piping systems built to ASME BPE, weld quality is controlled, not assumed. Closed head orbital GTAW systems deliver repeatability, but only when welding parameters and variables are proven before production begins.

This is where welding coupons come in.

A coupon is a short section of tube welded ahead of production to confirm that parameters and variables are aligned. The objective is simple: verify the weld meets acceptance criteria before any product-contact welds are made.

ASME BPE places strong emphasis on internal weld condition, particularly oxidation (heat tint), governed by heat input and purge quality. In practice, this leads to the “coupon in / coupon out” approach.

Typical triggers for a new coupon include:
• Start of shift
• Change in diameter or wall thickness
• Change of weld head or setup
• Change of purge gas source
• Parameter adjustments

Coupons are visually examined, often with borescope inspection, to confirm internal condition before welding proceeds.

They serve two roles:
• Verify parameters before welding starts
• Confirm consistency throughout production

Modern orbital systems provide weld logs, allowing comparison against the WPS and improving compliance monitoring.

But a key question remains.

A typical ~300 mm coupon is welded under controlled conditions.
Does it represent purge conditions in metres of installed pipework?

Factors like purge volume, oxygen decay, system restrictions, and field fit-up are not fully replicated.

ASME BPE does not define coupon length. It requires acceptable weld condition and verified performance. The coupon is a verification tool, not a full simulation.

Machines confirm parameters.
Coupons confirm the result.

11/03/2026

Weld Knowledge Wednesdays

304L vs 316L Stainless Steel – Understanding the Difference and Verifying the Correct Grade

316L stainless steel is often selected over 304L where corrosion risk is higher, particularly in chloride-containing environments. The addition of molybdenum improves resistance to pitting and crevice corrosion, which is why 316L is commonly specified for pharmaceutical, chemical, marine, and other aggressive service conditions.

However, one of the most common problems occurs before welding even begins.

304L and 316L can appear identical when they arrive at the workshop. As pipe, fittings, plate, or fabricated components, they are visually indistinguishable. If material segregation, traceability, and marking control are not properly maintained during incoming inspection, material mix-ups can occur long before fabrication starts.

A common workshop myth is that a magnet can be used to identify the grade. This is not a valid test. Austenitic stainless steels such as 304 and 316 are generally non-magnetic in the annealed condition, but cold working, forming, or machining can introduce magnetic response.

Welding can complicate the picture further. Austenitic stainless weld metal commonly contains a small amount of delta ferrite, which can create local magnetic response around the weld area. For this reason, a magnet is not a reliable method of grade identification.

Where the material grade matters, the correct control is Positive Material Identification (PMI). PMI verifies the alloy chemistry directly and confirms that the material supplied matches the specified grade.

08/03/2026

International Women’s Day

Today, Hudson Welding Consultancy Limited recognises and celebrates the women working across the construction and engineering industries.

Women currently make up around 10 percent of the construction workforce in Ireland. This shows progress, but it also highlights that women remain underrepresented in many skilled trades, particularly welding.

Our very own Chanel Ní Néill Hudson helped shape the message for today. Her perspective is that while the industry is moving in the right direction, continued progress requires effort from everyone on site. Leadership, supervisors, engineers, and craft all have a role in creating environments where people are respected, supported, and given the opportunity to develop their skills.

HWC also challenge men in the industry to actively ask their female colleagues how they can be more supportive, and to seek their input on what truly matters in creating a fair and respectful workplace. Real equality is built through listening as much as leadership.

As part of this post, HWC reached out to a fantasticly talented pipefitter and welder Leah Murphy who represented Ireland at the WorldSkills International welding competition while working with Murphy International, to ask what she is most proud of in her career so far.

Leah shared:

“One of the achievements for myself was becoming a qualified TIG welder in Murphy International, welding work for Gas Networks Ireland. Being a pipefitting apprentice has also been the best experience so far. All the men I work with are really respectful and patient no matter what the task is and are always willing to help out.”

Stories like Leah’s highlight what the industry looks like when people are supported, respected, and given the opportunity to succeed.

Hudson Welding Consultancy Limited remains committed to supporting the development of skilled professionals across the industry and encouraging more women to pursue careers in welding, engineering, and construction.

18/02/2026

Weld Knowledge Wednesdays

Oxide layers on stainless steel, Part 3: how to reduce colour 🔧

Weld colour forms because oxide layers grow while stainless steel is hot. Reduce oxide growth and colour reduces with it.

How to minimise colour at the source:

• Control heat input
Lower amperage, consistent travel speed, and avoiding dwell at starts, stops, and tie-ins all reduce the time the surface stays in the oxidation range.

• Shielding gas quality and timing
Shielding is about coverage and stability, not high flow rates. Correct torch angle, suitable cup size, and use of a gas lens keep hot metal protected. Long pre-flow and post-flow shield the weld and HAZ as they cool through oxidation-critical temperatures.

• Root purge control
The weld root follows the same rules as the cap. Use stable, low-turbulence purge flow. Purge dams or barriers reduce purge volume and prevent air ingress. Maintain purge until the root cools sufficiently.

• Purge gas selection
Argon is standard. Hydrogen-containing purge gases can reduce oxide formation in approved applications, but only where procedures, materials, and specifications allow.

• Fit-up and tolerances
Good fit-up reduces air ingress, reduces required heat input, and shortens time at temperature. Poor fit-up drives colour.

• Use welding machine features
Pulse settings, slope-in and slope-out, and correct gas timing help control heat input and prevent localised oxidation at arc start and stop.

• Automatic welding
Orbital and automatic welding systems excel at low-colour welding because every parameter is controlled precisely and repeatably. Travel speed, heat input, gas timing, and purge conditions remain constant, eliminating much of the variability that causes colour in manual welding.

Light straw colour generally indicates minimal oxide growth. Dark blues and greys indicate longer exposure to heat and oxygen.

Low-colour welding is not cosmetic. It reflects controlled heat, effective shielding, and proper purge practice.

To better understand oxide layers, and how to prevent them in stainless steel welding, contact Hudson Welding Consultancy Limited, industry leaders in low oxide welding.

28/01/2026

Weld Knowledge Wednesdays:
Chlorides: Chloride Prevention

Did you know that something as simple as an incorrect marker ✍️ can cause corrosion in your piping system? Even minor chloride exposure can initiate pitting, which over time degrades welds and compromises your system’s integrity.

As an example, I once saw a stainless vessel in service for decades. Near a weld, a chloride marker had been used. By touch, you could feel pitting exactly where it was applied. In thick materials, this might seem minor, but in thin, high-purity systems, just millimeters thick, such slight degradation can have massive consequences. ⚠️

It’s not just markers. Chlorides can come from adhesives in masking tapes, cleaning agents, lubricants, and sealants. Chlorides can come from the places you least expect, so having traceability over all materials is incredibly important.

With HWC’s extensive experience, we understand how something seemingly small can lead to serious issues. We are here to protect you and your clients from that risk and ensure long-lasting quality.

17/12/2025

Weld Knowledge Wednesdays 🔧

Welder Repair Rates. The most scrutinised job in the industry?

Welders work under extreme scrutiny 👀
Their work is examined constantly, measured in millimetres, and permanently recorded.

100% of welds must pass visual inspection ✅
If a weld fails visual, it goes no further ⛔

What many outside the trade don’t realise is how tight the acceptance limits actually are.

🔹 A typical 6” pipe butt weld has about 1.4 mm of allowable cap height
The weld must be above flush, but stay below that limit

Too flat ❌
Too proud ❌

That tolerance applies to every single weld, before any NDT begins 🔍

Because cap height is relative to wall thickness, the scrutiny increases on thin wall pipe.

🔹 A 2” Sch 10 butt weld has an allowable cap height of about 0.55 mm 📏
Less than half a millimetre of tolerance.

In higher specification work, the scrutiny increases again.

🔦 ASME BPE systems often require 100% internal visual inspection by borescope, meaning welds are examined externally and internally before acceptance.

🧪 Most projects then apply mandatory NDT, typically 5 to 20%, adding another independent layer of examination.

☢️ In pipelining, 100% visual and 100% radiographic testing is common. Under these conditions, even a small number of repairs across an entire project can result in a welder being stood down from a task, having their position reviewed, or being reassigned, despite producing hundreds or thousands of sound welds.

Many welders complete full projects with zero repairs, but the margin for variation is extremely small ⚠️

This level of scrutiny is relentless, traceable, and permanent, yet rarely reflected in industry respect or pay 💭

At Hudson Welding Consultancy Limited, repair rates are used as a process indicator, not a judgement of the person holding the electrode 🤝
Used properly, they highlight issues with procedures, fit up, access, sequencing, and supervision, not just the welder.

10/12/2025

Weld Knowledge Wednesdays
Arc Eye is a Site Safety Issue.

Arc eye is not caused by heat or brightness. It is a UV exposure injury that can affect anyone working near hot works, not only welders.

Welding arcs produce intense UV-C and UV-B radiation. These wavelengths damage the cornea and cause the delayed pain, tearing and gritty feeling that appears later that night. Repeated exposure over time also increases the risk of cataracts.

Certified clear safety glasses block UV and can protect against incidental UV from nearby tacking when the arc is not viewed directly. They do not replace a welding helmet and they do not prevent full-field exposure from direct or reflected arcs.

If someone develops arc eye despite being issued proper PPE and not engaging directly in welding, it usually indicates the glasses were not worn at that moment or were lifted briefly. This is a planning and behavioural gap rather than a blame issue and highlights the need for consistent control around hot works.

Hudson Welding Consultancy Limited supports contractors with welding quality, production planning and practical HSE guidance to help teams work safely and efficiently.

03/12/2025

Weld Knowledge Wednesdays: Not All Materials Are Considered Equal – Certification Is Key

When it comes to manufacturing compliant metallic products, material selection is one of the key factors in achieving final certification. Getting this wrong at the start of a project can result in entire systems being rejected at verification or handover, leading to costly rework, delays, and reputational risk.

To avoid this, material certification requirements must be clearly defined from the outset. Standards such as EN 10204 and ISO 10474 establish the framework for material certification and determine whether a 3.1 or 3.2 certificate is required. A 3.1 certificate confirms inspection and testing carried out by the manufacturer, while a 3.2 certificate includes independent third-party verification, often required by clients or specifications.

The same principle applies in high-purity ASME BPE piping systems. ASME BPE defines allowable surface finish designations, but compliance is not determined by visual appearance alone. Surface finish acceptability is governed by the specified finish class, finishing method, acceptance criteria, and traceability. Two tubes may look identical on the workshop floor, but if the required ASME BPE surface finish classification and documentation are not met, the system cannot be certified.

This risk is also seen with Clean for Oxygen Service materials. The material itself may be identical, but without CFOS certification and traceability, it is not acceptable for oxygen service.

Hudson Welding Consultancy helps projects get material selection and certification right from the start, avoiding costly rework and protecting handover compliance.

27/11/2025

Sorry for the unscheduled delay in our Weld Knowledge Wednesdays – so here’s WKT Week 47

Radiography & Acceptance: Get the Levels Right, Avoid Rework

A lot of project rework comes from one simple mix up:

ISO 5817 is not a radiography acceptance standard.
It only tells you the allowable size of weld imperfections.
It does not tell an inspector what can be accepted on an X-ray.

Radiography has its own rules:
• ISO 17636-1/-2 how the X-ray must be taken
• ISO 10675-1 what counts as acceptable on the film

ISO 10675-1 has three acceptance levels:
A (strict), B (medium), C (least strict)

These match directly with ISO 5817:
• 10675 Level A ↔ 5817 Level B
• 10675 Level B ↔ 5817 Level C
• 10675 Level C ↔ 5817 Level D

If these levels don’t match from tender stage, two things happen:

• Welds that fully meet the required 5817 level get rejected because the RT was done too strictly.
• Or welds that don’t meet the requirement get passed because RT was too loose.

Both lead to unnecessary repairs, wasted hours, and pressure on the schedule.

Setting the correct pair of acceptance levels at tender stage stops this problem before it starts. It ensures welds are inspected fairly and consistently throughout the project.

Hudson Welding Consultancy Ltd. works with clients to align these requirements early so inspections support progress, not delays.

19/11/2025

Weld Knowledge Wednesdays Week 47: Welder Qualification Testing

A welder qualification test confirms that a welder can follow a WPS and produce welds that meet the acceptance criteria of ASME IX or ISO 9606. The test checks real skill under controlled conditions.

Top tips to prepare

• Read the WPS fully and ask if anything is unclear.
• Check your equipment. Small faults like a leaking gas hose can cause a failed test.
• Check the fit up and make sure the test pieces are clean.
• Stay calm. Nerves can affect even experienced welders.
• Do not compare your progress to others. Take your time and focus on control.
• Aim to finish knowing you did your best.

Weld test FAQs

Why do I need to test again for a new company?
Qualifications belong to the employer. Each company must verify that you can weld with their materials, processes and WPS requirements.

Why do I need different thicknesses and diameters?
Your qualified range comes from the test coupon. Thin and small diameter tests qualify narrow ranges. Larger tests qualify more.

Why must I follow the WPS exactly?
Your qualification is valid only for the essential variables listed. Parameters, consumables and temperatures must match the WPS.

Why do I sometimes need a fillet test?
ASME IX allows butt welds to cover fillets. ISO 9606 treats fillets as separate, so a fillet test is required for ISO projects.

What do the test positions mean?
Positions like 1G or PA, 5G or PF and 6G or HL 045 qualify different production positions. Higher difficulty positions qualify more.

Hudson Welding Consultancy Ltd.

18/03/2026

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17/12/2025

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