Navigating Temporary Repairs: Risks and Compliance Essentials

Navigating Temporary Repairs: Risks and Compliance Essentials

Post Construction Codes (PCCs) API 510/570/653 define these as temporary repairs but a feature of ASME PCC-2 is that it provides technical details and leaves the user to decide themselves.

What is temporary?

There’s no agreed definition of temporary. The nearest is from API codes as ‘to the next maintenance/replacement opportunity’. Temporary means; not designed to be permanent. It often means:

Non-compliant with the construction code

There are many types of code non-compliance; major, such as materials or fabrication features, or administrative, such as personnel qualifications, documentation or certification, with varying influence on repair integrity.

Types of PCC-2 temporary repair.

Repairs in PCC-2 you may consider temporary are:

• Fillet-welded lap patches and cover-sleeves
• Welded leak-boxes
• Mechanical clamps
• Composite wraps

Risk features
Look at the figure below. The features of a temporary repair cause problems, not its designation as temporary. Each of the features shown increases the risk of failure. Taking additional risk is not prohibited; FFS studies, by definition, allow a damaged component to operate under more risk than the construction code likes.

Developments in composite materials

Manufacturers’ documentation on composite/epoxy materials and wraps contains information about:

• Long-term temperature resistance
• Ageing and environmental degradation
• NDE and monitoring
• QA/QC of preparation and application

Most are not in mandatory sections of construction codes. The latest 2022 Edition of PCC-2 has increased its consideration of these areas, but views are still developing.

Reminder

For sure, integrity engineering is about taking risks. You’ll still find yourself providing gentle, sympathetic reminders that temporary means temporary.

How long exactly before you do this repair?

LET’S THINK ABOUT …REPAIR ACTION WINDOWS

What are they?

Repair action windows are time periods within which an integrity-compromising defect must be repaired. They are specified by statutory regulations or Integrity Engineer ‘Competent Persons’.

Where are they used?

Typically, in two applications:

1. Hazardous gas/liquid pipelines regulations (e.g. US 49 CFR 192-195) where consequences of failure are well known. The UK PSSRs use them also (in a fashion)
2. General pressure equipment containing stored energy or hazardous fluid risk

Why?

To encourage owner-users into action, rather than ignoring the problem or repeatedly deferring repairs. A typical repair window hierarchy is:

• Immediate repair, normally associated with ‘imminent danger’
• 30,60,90 or 180 days

Do they work?

Sometimes, but not always. ‘Imminent danger’ notifications requiring immediate repair have the highest success rate because the message is clear. The fig below shows what can happen if you specify longer (30 days+) repair windows. Six actions are possible (typically in order 1 to 6 shown), to dilute the original assessment. The activities are called ‘re-assessment’ or similar. The passing of time encourages their acceptance, reducing repair urgency. Some logic floats behind this:

• If a defect is not getting worse and hasn’t caused failure yet, why repair it?
• We have other, worse defects that haven’t caused failure yet.

What about more time before repair = more risk?

Think of it the other way around, i.e., a 60-day repair window is less risky than allowing 90 days. It sounds convincing until you think about the numbers game behind it.

If a damaged component has an estimated fixed probability of failure (POF) …let’s say 1 in 100, or 1%, in the next 30 days (you can guess the number, but won’t know if you’re correct)

Then;

It is equally as likely to fail tomorrow  as after 30 days or 60 days

Arguably, the POF number is unimportant; the item could fail tomorrow. It’s different if the defect gets worse day by day, but if the damage is expected to progress that quickly (with all the possible prediction errors), it’s difficult to argue for 30 days. Why not 15 days, or 10 days?

There’s the problem: if you specify repair within 10 days, and it doesn’t fail, your assessment looks wrong, taking us back to the ‘intervention’ actions of the figure. It’s a simple principle:

Once you specify a repair window longer than repair immediately your recommendations are at risk of being questioned, diluted or overturned as time progresses.

What happens when it goes wrong?

Read this report on a pressure vessel failure due to poor repair practices. If you want to gain the best insight into managing and designing repairs for pressure equipment, you won’t go far wrong in following the well-recognised ASME PCC-2 standard.

Our hugely popular ASME PCC-2 Pressure Equipment Repair course covers all the important points on the selection, design, examination and testing of both permanent and temporary repairs.