Articles or papers related to tank cleaning operations
Amendments to MARPOL Annex II concerning Cargo Residues and Tank Washings of Persistent Floating Products This Resolution MEPC.315(74) adopted on 17 May 2019 added amendments to MARPOL Annex II concerning ‘Persistent Floaters’ when washing cargo tanks of high viscosity noxious liquid substances in North West European Waters. MEPC.315(74) may be viewed, downloaded or printed below:
Returning a cargo tank back to a water-white standard is, or should be, the default tank cleaning operation following the discharge of any product on a chemical tanker. From that default position and depending on the next product to be loaded, additional cleaning can take place to suit the supplied product specifications. Should the specifications of the next product not have been advised, then cleaning should be carried out to the highest known specification for that particular product. Of course,…
Wall-Wash Test Precautions and some Causes of Failure Always use disposable plastic gloves when wall washing – the human hand contains more salt than normal requirements and is a common cause of chloride contamination. Wear clean clothes and do not allow working gloves in the tank, avoid all contact of clothing with the tank, wear protective disposable shoe covers. Use a clean bucket on a clean line for transferring test equipment into the tank. Wash the funnel and sample bottles…
Organic vs Inorganic……..what’s the difference? There are a multitude of publications which refer to ‘Organic’ or ‘Inorganic’ Chlorides, with ‘Organic’ Chlorides being an undesired contamination. But which is which and what products contain which element? The following is an attempt to explain this. Organic Chlorides are an undesired contamination in crude oils. The presence of even a very small amount (a few ppm) of chlorides can be catastrophic during crude oil fractionation in the refineries which can cause considerable damage…
The Chart below serves as an indication of the typical tests that may be expected on the 1st Foot Samples based on the previous cargo history. These typical tests are an indication only, and may vary according to Terminal Requirements. This Chart may be viewed, downloaded or printed as a pdf document here:
Oxidized residues of previous cargoes can cause a failure of the PTT. To improve the results, wash with a Sodium Hypochlorite Solution (Bleach) in freshwater. Sodium Hypochlorite is normally supplied as a 12% solution. Make a 2% solution of this supplied 12% solution in water (freshwater preferred, otherwise seawater) and recirculation wash at a maximum temperature of 40 deg C. 2% of a supplied 12% solution is 200 liters in 10,000 liters of water. Also used to remove red/yellow dye…
Sodium Hydroxide may react with the calcium and magnesium in seawater during tank cleaning operations to form calcium and magnesium hydrates which shows as white powdery deposits left on the cargo tank surfaces, especially when using hot water washing. A freshwater rinse following a caustic recirculation wash prior to the final seawater wash will assist in the prevention of such deposits. Such deposits may be removed by washing with an acid-based cleaner. Washing with a Potassium Hydroxide Solution instead of…
Dye discolouration caused by the carriage of dyed gasoline (for example) can be removed by recirculation washing with a Sodium Hypochlorite (Bleach) Solution. Sodium Hypochlorite is normally supplied as a 12% solution. Make a 2% solution of this supplied 12% solution in water (freshwater preferred, otherwise seawater) and recirculation wash at a maximum temperature of 40 deg C. 2% of a supplied 12% solution is 200 liters in 10,000 liters of water.
MEPC77/INF.9 17 September 2021 Findings on improved prewash procedures for solidifying or high-viscosity substances (paraffin waxes) Submitted by the Netherlands. This IMO paper relates to a Dutch initiative regarding Paraffin Wax Substances which fall under the new MARPOL Annex II discharge requirements for persistent floaters, which have been found washed upon a number of Dutch beaches in considerable quantities. The outcome of the Dutch initiative was an improved unloading and washing strategy resulting in hardly any paraffin waxes found on…
Causes of PTT Failures: A failure of a PTT occurs only when a contaminant reacts with Potassium Permanganate. Such reactions are caused by all inhibited products and organic matter. Potassium Permanganate does not react with hydrocarbons. Recommended Procedure: By spraying, or recirculation washing, the tank with Potassium Permanganate you will pass the PTT time (just by pre-empting the surveyors medium). First, clean the tank has to a water-white standard before applying the Potassium Permanganate by spraying. The different ways of…