Thinking strategically about tank cleaning

Oct 22 2020

Tanker Operators would benefit from thinking more strategically about tank cleaning, saving money over the longer term in water disposal costs from a slightly bigger upfront investment in cleaning equipment, says Dasic Marine.

Ian Rippon, sales manager of tank cleaning equipment company Dasic Marine, cites a customer in the milk industry (not in shipping), which was cleaning its tanks using a basic “spray ball” equipment, capital cost £200, and paying £40k annual water disposal costs. 


It purchased a £2,000 cleaning machine tailored to the tank which did the cleaning job in much less time with much less water, reducing the water disposal costs to £800 a year. 


Water from milk equipment cleaning contains fats so cannot be disposed of in normal sewage systems.


Tanker operators can be sceptical about the idea that they can learn something from the food processing industry. But the food industry’s cleaning needs are very similar to tankers. Cleaning often has to be even more rigorous, to comply with strict hygiene regulations, while also under pressure to reduce costs and increase productivity, Mr Rippon says.


And where a tanker company will typically only buy traditional marine tank cleaning equipment once and then forget about it, a company processing food will upgrade equipment regularly, and expect improvements with each new purchase in terms of cleaning effectiveness, speed and water usage.


Tanker companies, with their excessive work load, do not typically think very strategically about tank cleaning – they will often only ask for new machines when their existing machine breaks due to bad maintenance, or they suddenly realise they need one for a new cargo or voyage to a part of the world with higher tank cleanliness demands, Mr Rippon says.


There are many ways tanker companies could benefit from thinking more carefully about their choice of tank cleaning equipment, he says.


A typical tanker may have 10 cargo tanks but up to 50 tanks in total, with the other 40 being tanks such as sewage, sludge, fuel and fresh water with a wide variety of sizes. But tanker companies will typically use the same large cleaning machine for all of its tanks, where it could use a smaller machine on these tanks and use much less water.  Or they will clean tanks by hand, which means “man entry procedures” have to be followed, which is time consuming and potentially very dangerous.


For fuel tanks (smaller than cargo tanks), tanker operators could take advantage of machines developed for cleaning tanks in retail petrol stations that can be used remotely through a 3” opening and  are explosion proof. These can clean a fuel tank with much less water than the large machines used for cargo tanks in as little as 10 minutes, he says. 


The same machine can be used for sulphur tanks, as they are stainless steel and have chemical resistant seals developed for the chemical process Industry.


One tanker operator would carry fuel oil and jet fuel in the same vessel alternately. You need to do a hard clean after carrying fuel oil. But it would do the same level clean after carrying jet fuel, when it only really needed to do a tank rinse, which could be done with much lighter equipment.


Bunker vessel operators, who may need to give their cargo tanks a thorough clean before dry dock, can reduce costs by using gas oil or kerosene for tank cleaning with 6mm nozzles on the tank cleaning machine to soak the bulk heads and soften the dirt, then change to 10mm nozzles to clean with hot water.


After washing, the kerosene (now mixed with vessel fuel) can be put back into its original container. It can be later sold or blended to fuel the actual bunker vessel. This will halve the amount of water you need for the final tank cleaning and mean much less wastewater contaminated with bunker fuel at the end, which is very expensive to dispose of.  


Companies can also reduce tank cleaning costs from having smaller nozzles on board for tank cleaning equipment and using the appropriately sized nozzle. The standard 10mm nozzle might make sense for larger cargo tanks, but a 6mm nozzle would be adequate for smaller tanks, and this would save 10 cubic metres of water an hour, he says. 


A smaller nozzle would also be adequate if you are just rinsing a cargo tank rather than cleaning it, as you need to do before putting food into an otherwise clean tank.


Sometimes crew seem to have a psychological attraction to using large nozzles. “You can hear the impact on the side of the tank, that’s what they like. If they change to 6mm nozzles, you wouldn’t hear it as much but it will still clean as effectively again saving 10 cubic metres of water an hour,” he says.


Aside from the water disposal costs, using less water for cleaning also makes a tanker company more environmentally friendly, which is increasingly important for tanker operators.


Working with suppliers

While tanker operators may not have the time to work out themselves which nozzle is right for each task, they can ask their tank cleaning equipment supplier to take on this task, Mr Rippon says.


The tank cleaning equipment supplier can help create procedures showing exactly what equipment and set-up is most appropriate for each tank – typically a 10mm nozzle or cargo Tanks 2,3,4 & 5 and 6mm for 1s). Nozzles can be changed in just a few minutes by the crew. This can be specified in the operating procedures - exactly as the food industry does, he says.


The nozzles can easily be labelled showing which nozzle is most appropriate for which wash type, he says. 


As an example of how an equipment supplier can make a task easier to manage, Mr Rippon cites an example of a supplier of lifting equipment to a ship where he was a superintendent. This supplier provided the strops, chain blocks and shackles colour coded for the year in a metal box. The next year when they needed recertification, they were swapped out recertified and then given to another vessel. In this way, the company helped make a time consuming and complex management task much easier for the superintendent, he says.


A similar service could work for ships, where a cleaning equipment company supplies a kit with different sized tank cleaning machines and nozzles tailored for the vessel or fleet labelled for which tanks they should be used for, or which grade of products. This kit can easily be returned for overhaul and returned to the vessel in a short time frame or circulated around the fleet guaranteeing availability of a tank cleaning machine, reducing the chance of expensive delays while waiting for machines to be repaired or delivered. 


Mr Rippon’s background after serving at sea with BP and Shell was as a superintendent in tanker operations, first with Clipper Tankers then technical manager with Carisbrooke Shipping and a technical superintendent with Whittaker tankers.


As a sales manager with Dasic, the biggest challenge is often getting a chance to talk to extremely busy superintendents to show how the company can help, he says. 


Having introduced marine tank cleaning to the food and beverage Industries and working with them to tailor it to their specific needs, he would welcome more opportunities to explain how the marine Industry can benefit from the same savings. 


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