The threat of microbial contamination in grounded aircraft

Description:

Shell’s Global Technical & Quality Manager, Rob Midgley, walks through a presentation explaining the different types of microbes found in aircraft that can lead to corrosion and what options are available to diagnose and treat the issue.

Title: Fuel Management in Grounded Aircraft Transcript

Duration: 4:39 minutes

[Background music plays]

Bright, uplifting music

[Animation]

The Shell™ pecten logo appears, then fades. A three dimensional model of Earth rotates while white silhouettes of planes fly across the globe. On the right side of the screen, a photo of Rob Midgley.

[Text displays]

Flightpath: Navigating the Route to Sustainable Aviation

[Text displays]

This episode

The Hidden Threat of Microbial Contamination in Grounded Aircraft

[Slide: Why are we here?]

As the aviation industry navigates the impact of COVID-19, many aircraft are parked up – we have all seen the images of regimented rows of passenger aircraft dutifully waiting to take to the skies again.

During these unprecedented times, it is important to avoid any unnecessary risk to your airline in the future.

Therefore, in the next 60 minutes, we’ll be discussing some considerations when inhibiting aircraft of storage and investigating how Shell might be able to help manage the potential challenges that might arise.

The presentation will be followed by a short Q&A.

Safety first: please ensure you’re dialing in from a safe environment. Do not take this call while driving, even when using a headset or hands-free.

Put your questions in the comment box and we will address them during the Q&A session.

This sharing is not to be reproduced in any form without the consent of Shell.

Session will be recorded.

[Caption]

Rob Midgley

Global Technical & Quality Manager, Shell

Voiceover: Rob Midgley

At Shell Aviation, we’re committed to helping our customers to progress both in good times and bad.

With up to 80% of the world’s passenger fleet grounded, this is creating the ideal conditions for microbial growth. Here we investigate that challenge and the options available to airlines.

[Slide: Micro-organism type]

[Bulletpoint list]

·       Bacteria

·       Aerobic or anaerobic

·       Pseudomonas spp. Klebsiella spp. Desulphovibrio spp. (SRB)

·       Yeasts Candida spp. Rhodotorula spp.

·       Moulds Cladosporium resinae (now Hormoconis resinae), Aspergillus fumigatus

Voiceover: Rob Midgley

We'll start off by looking at the different types of microbes. And these organisms really require three things to be able to survive. One is a water phase in which to live. So they tend to live not in the fuel itself, but in any water that is present. They tend to consume the fuel. So using the fuel as a food source, and they also need access to oxygen. So if you have those three things in combination, then we can start to see microbial growth.

[Slide: Factors Affecting Microbiological Growth]

1. Water. Accumulation of water in tank stimulates growth.

2. Temperature. The optimum temperature for most growth is 20 to 35 degrees Celsius. Higher temperature may favour other microbes, and most microbes will grow at less than 20 degrees Celsius but slowly.

3. Aircraft Design. Undrainable water / fuel tanks. Warm inboard tanks / trim tanks.

4. Specific Flight Operation. Operating a low altitude flights. In warm climates. Has low utilisation (e.g. corporate operations.) With underutilised fuel tanks. Which are marked or in storage. Uplifting of a suspected fuel. Operating transoceanic flights.

Voiceover: Rob Midgley

Long turnaround times on the ground tend to accelerate growth. If we extend that turnaround time on the ground, then we're in the position where we are now with COVID, where we're on the ground all the time. We see low utilization as being a trigger for increase in microbial growth.

[Slide: Why is Microbiological Contamination a Problem?]

Some history

[Bulletpoint list]

·       A worldwide problem, commercial and military aircraft, especially those based in a tropical climate.

·       Three basic categories: bacteria, moulds, yeast.

·       Most common is the Resinae “Jet Fuel Fungus”.

·       Consume fuel and produce corrosive organic acids.

Can lead to:

[Bulletpoint list]

·       Engine fuel filter blockage

·       Fuel pump failure

·       Wing tank corrosion

·       Destroy codings and sealands

·       Foul fuel probes

Voiceover: Rob Midgley

Why do we see it as a problem? Well, it starts to lead to certain corrosion problems on an aircraft.

Seals become brittle and they tend to shrink.

[Slide: Microbial Corrosion]

Two photos fill the screen. On the left, anaerobic pitting of mild steel. On the right, mild steel rising showing blistering and biocorrosion.

Voiceover: Rob Midgley

This picture here, especially on the left, which is quite dramatic of steel, it's not just pitting. That's a hole right away through a steel plate. That's due to microbial activity.

[Slide: Fuel Quality Management]

How is fuel in storage tank and pipework managed?

[Bulletpoint list]

·       Fuel in storage tanks where tanks are drained daily or weekly when not used for supplying.

·       Fuel in pipework will be regularly drained via low point otherwise to flush every quarter. It is preferably to remove any dead-legs (or stagnant area).

How about fuel in wing tanks of grounded aircraft?

[Bulletpoint list]

·       Can it be drained regularly?

·       Is there or what is/are the threats?

·       What can one do? Preventatiev and/or corrective measure?

Voiceover: Rob Midgley

How do we prevent microbes from forming?

That really comes down to the challenge of how a wing tank is built.

[Slide: Fuel Storage Tank Vs. Aircraft Fuel Wing Tanks]

Voiceover: Rob Midgley

On the left, we've got a photograph of the inside of a supply tank, a bulk supply tank.

We can design this tank specifically to drain water because it doesn't have to do anything else.

If we look to the right, you see what happens once we get onto the aircraft.

We've got the equivalent to the tank bottom there in the center of the photograph. You can see it's now a flat bottom, so it doesn't have a positive sump on it. To try to deal with that, we try to suck out parts of that low point within the tank using things called scavenge rakes.

That should try and suck out any water that's sitting in the bottom of this tank and deliver it to the engine while the engine is operating.

Of course, that only works if the engine is operating. Whilst your airplane sat on the ground during COVID, they’re is no scavenging any of that water.

[Slide: Sampling]

[Bulletpoint list]

·       IP Guidelines – investigation of the Microbial Conetnt of Fuel Boiling Below 390deg C and associated (currently under revision)

·       Must be representative – interface, bottom, tank drain.

·       Containers – sterilise with 70 percent Isopropanol

·       Test within 48 hours.

ANY TEST RESULT IS ONLY AS GOOD AS THE SAMPLE.

Voiceover: Rob Midgley

Sampling, more than any other fuel property, it's really critical getting good, accurate sampling for microbial testing.

So drain points, flexible hoses, sample containers, make sure they're sterile before you're using it.

[Slide: Analysis]

Visual examination of samples

[Bulletpoint list]

·       Laboratory analysis – IP385/95, IPPM BY/95

·       On-site tests- Dip Slides, MicrobMonitor2, Fuelstat™ resinae

·       ATP Photometry – Hy-lite test

[On right are four pictures of testing tools, labelled respectively: MicrobMonitor2, Easicult, Fuelstat Resine, and Merck HY-LiTE.]

Voiceover: Rob Midgley

If we start to look at the test kits, then there are a number that are approved through IATA guidance.

My personal view of this is if you're going to do microbial testing, it's useful to have more than one technique at your disposal because some of these tests will tell you something and others will be stronger in other aspects of it.

[Slide: Biocide Application]

Approved Biocides:

[Bulletpoint list]

·       Biobor JF manufacturer by Hammonds (flash point of 40oC).

·       Kathon FP1.5 manufactured by Dow Chemical Company (flash point of 138 oC) has been banned for GE and CFM engines.

Method of Introducing Biocides

[Bulletpoint list]

·       Adjustable metered injection

·       Non-adjustable meter injection

·       Overwing fill port

 

Voiceover: Rob Midgley

What happens if you get an indication on the test that you have a microbial contamination? Well, it's common to use in the airline industry one of the two approved biocides. One's Biobor JF, produced by Hammonds. And the other one is Kathon FP1.5

[Slide: Aircraft Fuel Tank Contamination]

Guidance

[Bulletpoint list]

·       IATA & JIG guidance

·       Test results

·       Result: ‘severe’ = ACT

·       Diverse action strategies

Voiceover: Rob Midgley

When we get the results that come from the test kits, we can get different levels of judgment on them. And when we get to that severe or action level, it's really telling you “you need to act”. And that action can be one of two things:

Either biocide injection, which is the most common reaction to it, or if left untreated, it might mean that you're needing to defuel the aircraft and then do some tank entry and cleaning.

[Slide: Summary]

1. There is a need to include water draining and microbiological growth monitoring in your fuel management strategy – especially in light of the unprecedented grounding of aircraft

2. Advisable to have a strategy to manage potential complications in place

3. Biocide treatment is continually evolving. It is important to keep a lookout for fresh developments (e.g. banning of KATHON FP1.5, biocide injection standard-setting, etc.)

4. Please reach out to your account manager when inhibiting aircraft for storage to investigate how Shell might be able to help you to protect your fleets and the potential challenges that might arise.

Voiceover: Rob Midgley

In that microbial testing you need to understand sampling methodology, what it is you’re sampling and also the strengths and weaknesses of what the microbial test kits will tell you. But, you really need to have a strategy.

This programme was specifically designed to highlight the problem of microbe growth and the options available to airlines. 

This initiative is outside of Shell's core services, but is an area where we have expertise through our own supply chain management and, on a case by case basis, we may be able to directly support our airline customers. So, if you identify that you have a microbe problem in a particular location please do engage with Shell and we will work with you to understand the extent of the problem, what resources we have available and any treatment options, in the hope that we may be able to help you.