Remote Visual Inspection

Remote Visual Inspection (RVI)

Remote visual inspection answers the question every asset owner starts with: is it cheaper to look inside, or to open it up? Opening a vessel means isolation, permits, cleaning, scaffold, a confined space entry and a shutdown that costs far more than the inspection. Looking inside means getting an optical instrument through a port the size of a fist.

We carry out RVI on site across the UK, using borescopes, videoscopes and remote cameras, on vessels, pipework, tanks, ducts, castings and engines — anywhere the surface that matters cannot be reached by eye.

The part that decides whether the inspection is worth anything is who is looking at the image. Ours is carried out by CSWIP welding inspectors and PCN Level 2 and Level 3 visual inspection personnel, employed directly. That is a different proposition from a camera operator with good footage, and it is the single biggest variable in RVI.

What we can resolve

RVI is a surface method: it sees what is on the internal surface and nothing beneath it. Within that, it is genuinely capable.

• Corrosion — general wastage, pitting, and under-deposit attack that only becomes visible once the surface can be seen.
• Erosion — particularly at bends, tees and downstream of orifices, where flow does the damage.
• Internal weld condition — root profile, excess penetration, burn-through and root misalignment, from the side you cannot otherwise reach.
• Cracking, where it is open enough to see and the surface is clean enough to show it.
• Mechanical damage — impact marks, gouges, distortion, and displaced or missing internals.
• Blockage and fouling — scale, debris, product build-up and collapsed internals.

The equipment, and why it decides the job

Rigid borescopes give the best image quality, because the light path is glass rather than fibre. They need a straight line of sight — ideal for cylinder bores, straight tube runs and castings.

Flexible fibrescopes go round corners, trading resolution for access. Broken fibres show as permanent black dots, so instrument condition matters.

Videoscopes put a sensor at the tip, with articulating steering that can look sideways and backwards. Better resolution than fibre, and the image is digital from the start — so it can be measured, recorded and reviewed by someone who was never on site. This is what most industrial RVI now means.

Pan-tilt-zoom cameras and crawlers for larger volumes — tanks, vessels and ducts, where the instrument is placed inside rather than threaded in.

Selection is driven by access geometry, not preference. A 6 mm port with a 90° bend eliminates most of that list before image quality is even discussed, which is why we ask about access before we quote.

Measurement, and its honest limits

Modern videoscopes offer 3D phase and stereo measurement, building depth from a projected pattern or from parallax. Used properly they measure pit depth, remaining wall at a gouge, and indication length to a genuinely useful accuracy.

Used carelessly they produce a confident number that is wrong. Accuracy depends on tip standoff, the angle to the surface, whether the surface is matte or reflective, and the operator picking the right cursor points. A measurement taken at a shallow angle down a long dark bore is an estimate with a decimal place on it.

So we treat RVI measurements as screening — they tell you what to worry about and roughly how much — and anything close to a rejection limit is confirmed by ultrasonic thickness measurement from the outside. Our reports state the measurement mode and the standoff, because without those a number is not reproducible.

Where RVI is not the answer

Being straight about this is what makes the method worth specifying.

It cannot see into the wall. Sub-surface defects, lack of fusion, inclusions and internal cracking are invisible to it. Volumetric information needs ultrasonics or radiography.

It cannot see through deposit. A vessel with 3 mm of scale on the wall gives you an excellent inspection of the scale. Cleaning is part of the scope or the scope is not achievable — and this is the single most common reason an RVI job produces nothing useful.

Large volumes swallow light. A tip light adequate for a 50 mm bore reveals very little of a 3 m tank, which is a lighting and equipment decision rather than a limitation of the method.

Tight cracks may be invisible even on a clean surface. Where surface-breaking cracking is the concern and the surface can be reached, magnetic particle or penetrant inspection is far more sensitive.

What it costs against opening up

Opening a vessel is not one cost. It is isolation and de-isolation, permits, blinding, cleaning and gas-freeing, scaffold in and out, a confined space entry with attendants and rescue provision, the inspection itself, then reinstatement and re-test. On anything of size the inspection is the smallest line on that list.

RVI removes almost all of it. What it adds is the access requirement and the cleaning needed for the instrument to see anything.

The honest caveat: if RVI finds significant damage you may end up opening the vessel anyway, having paid for both. That is an argument for being clear about which decision the inspection is feeding — if the realistic outcomes are “carry on” or “open it”, RVI buys you the chance of avoiding the opening entirely, and that is usually worth having.

Who is looking at the image

Remote visual inspection is visual inspection. The instrument changes how you get an eye onto the surface; it does not change what is required to interpret what the eye sees.

That distinction gets lost, because RVI is sold on equipment. A high-specification videoscope in the hands of somebody who cannot tell excess root penetration from a lack of it will produce a beautiful recording and a worthless report — and the failure is invisible, because the footage looks the same either way.

Our RVI is delivered by directly employed inspectors holding:

• CSWIP welding inspection qualifications, so internal weld condition is assessed by somebody who knows how the weld was made and therefore what its defects will look like from the root side.
• PCN Level 2 in visual testing, authorised to set up the technique, interpret and evaluate against the applicable acceptance criteria, and report.
• PCN Level 3 capability in house, for procedure and technique development, for examinations where no codified acceptance criteria exist, and for arbitration where a call is disputed.

Two practical consequences. First, an indication gets characterised on site rather than logged as “something at 2.3 m” and argued about later. Second, where the finding needs a judgement the code does not cover, there is somebody qualified to make it and put their name to it — which is what a Level 3 certification actually authorises.

It also means RVI can be specified as part of a welding inspection scope rather than as a separate service with a separate supplier, which matters on fabrication work where the root side is the only thing nobody has looked at.

Specifying a job that produces something usable

Say what you are looking for. “Inspect the vessel” produces a tour; “confirm the condition of the shell-to-nozzle welds and quantify pitting in the bottom third” produces a result. Technique, equipment and time all follow from the question.

Confirm the access. Port diameter, distance to the area of interest, and every bend in between.

Agree the acceptance criteria first. RVI generates a lot of indications, and without an agreed threshold every one becomes a discussion with the crew standing by.

Settle the cleaning — who, to what standard, and whether it happens before we arrive.

Specify the record — stills at defined locations, continuous video, or both.

The recording is the deliverable

A visual inspection carried out by eye produces an opinion. A remote visual inspection produces a file.

That difference outlasts the job. Footage can be reviewed by a specialist who was never on site, shown to a client, a regulator or an insurer, and compared directly against the same location at the next shutdown — which turns a snapshot into a trend. A pit that has grown 0.4 mm in two years is a completely different conversation from a pit of unknown history.

For that to work the record has to be locatable. Footage with no positional reference is a video of some metal. Our RVI results go into the same reporting system as every other method, so images are bound to the specific examination with the technician, the equipment, its calibration and the acceptance criteria attached — and results are available while the crew is still on site rather than days later.

Where we work

On site across the UK from our bases in Cumbria, Durham and Southampton, on process and pressure systems, storage tanks, marine and offshore structures, and nuclear plant — where RVI frequently replaces an entry that would carry a dose penalty as well as a cost.

RVI is often specified alongside other methods on the same visit, and planning them together saves a mobilisation. If you have a system you would rather not open, tell us the access and what you need to know, and we will tell you honestly whether RVI can answer it — including when it cannot.