Clean thinking

Major developments in tank farm cleaning solutions are being ignored in favour of dated methods across the region's low cost labour environments.
Clean thinking
By Administrator
Wed 20 Aug 2008 04:00 AM

Major developments in tank farm cleaning solutions are being ignored in favour of dated methods across the region's low cost labour environments.

Everyone knows the energy industry is booming in the Middle East, but where are all these hydrocarbons stored? Accordingly, the tank farm industry has seen an increasing demand for its services - design, construction and maintenance.

Cylingas, a subsidiary of Dubai based ENOC, is a leading provider of infrastructure to the oil and gas industry - designing and producing tanks for the last 30 years. Most recently it completed the US$20 million project with Vopak Horizon in Fujairah. Year on year it has seen business growm and this shows no signs of halting. The company predicts a growth rate of around 60 - 70% each year in the industry for the foreseeable future.

Building tanks in Dubai is particularly difficult due to the desert sand.

"Yes, it will increase. It has to," enthuses Parun Sainani, Cylingas marketing executive, of demand. "Take the example of Dubai, there was one airport. Now they're building another in Jebel Ali and expanding the existing international airport. More airports equals more planes, all of which require jet fuel and, therefore, storgae tanks."

Location, location, location

The desired location of the terminals may also throw an added complication into the mix. "Selecting the location is a major undertaking in the first place since there are so many rules and safety regulations that have to be considered," says Sainani. "A major consideration has to be the proximity of residential areas to the site."

Given the density of the products to be stored, having a strong foundation for the tank is of utmost importance. This requires thorough investigation of the composition of the land on which the tank is to be built.

"Building tanks in Dubai is particularly difficult due to the desert sand," explains Sainani. "The soil is very loose providing a poor foundation for any structure. In order to build on the land we would need to compact it and increase its strength by laying rocks and concrete."

Such reasoning explains why Fujairah is the preferred location for many tank farms in the UAE, as the rocky ground is considerably harder in comparison to other locations.

The cost of the tanks is vastly different depending on the size, type and requirements of the customer. For example, storing sulphuric acid is near the top of the price range since a stainless steel tank is required. Similarly, the storage of liquid natural gas (LNG) is particularly expensive given the need for it to be stored at minus 180 degrees.

The size of the tanks themselves varies depending on the project. In the case of the Vopak Fujairah, the tanks are 55 metres in diameter and 25 metres in height. Such product, temperature, and scale variations illustrate some of the challenges that companies in the tank farm business face.

Cleaning costs

One considerable expense arising from the tank farm industry is the costs of cleaning the tanks - stemming from various circumstances. Most common is product changeover in the tanks, particularly when moving from black products like crude oil to white products such as naphtha gas.

Paul Dann, general manager of Hyrdoflow, a UAE based high pressure water jetting company, explains that crude oil is particularly difficult to remove due to the sludge that develops. Removing such sludge often requires workers to enter the vessel, collect the crude and ‘bag it up'. In the case of some of the larger tanks, Hydroflow employs workers to abseil down the inside of the tank, thus eradicating the need for costly scaffolding.

New developments in the cleaning industry have occurred largely in reaction to safety considerations - in particular, avoiding man-entry into the hazardous tanks.

The dangers involved in entering such highly flammable vessels are evident when considering the safety equipment used by workers. Wetsuits and breathing apparatus are both absolute necessities despite the tanks being made ‘gas-free' well before cleaning.

It is now possible to undertake a significant amount of cleaning remotely through the use of automated systems. Many of these tools are, in fact, more powerful than hand-held alternatives so they are capable of doing a more effective job in cleaning and removing deposits.In the case of smaller tanks, automated cleaning systems come in a variety of different forms. Hydroflow use devices such as high pressure nozzle systems that are inserted through the manholes and rotate to break down the chemicals.

With higher volume tanks, such automated devices can be attached to extendable arms, thus still eliminating much of the need for man-entry.

Systems have also been developed that vacuum the sludge out of tanks through its pipes. Chemicals are then inserted into the sludge so as to thin it. The sludge is then injected back into the tank through the use of a high pressured automatic system that continues to decompose the product.

The method works circulatory and continuously until the sludge becomes liquefied enough to eject itself from the tank. Through the use of such measures, hydrocarbon waste is minimised and may be reused by the owner.

"The technology that is available just isn't getting used in a lot of places because of the costs involved," says Dann. Such new technology is still being pioneered by cleaning companies such as Tubetech International - a UK based industrial cleaning company. They have developed cleaning systems that work in smaller tanks - 20 metre diameter tanks and less - using ultrasound set at various frequencies.

As part of the system, probes are inserted into the sludge that vibrate and break substances apart into their constituents. Such processes can even been undertaken whilst tanks are still online. "We're yet to do it," says Mike Watson, managing director of Tubetech, "but it's a process we're looking to get involved with if the market responds."

Planning for the future

There have been major developments in the cleaning industry - many revolving around safety. Still more can be done if customers are willing to be pragmatic and take a risk. "The industry is very static and neandathol," says Watson. "There is an ‘it's been done this way for so long - why change' kind of culture."

Instead of maintenance merely being an afterthought for the investor, it must be considered in the design process itself. That is, many situations that make cleaning a necessity, or more time consuming, could be prevented in the first place.

Due to the heavy, sulphur rich crude oil that is frequently stored in vessels, sediment often forms in the bottom of the tank and in its pipelines. Like limescale in a kettle, such sediment gradually builds up over a period of time and eventually needs to be removed.

Tanks could be designed in a way so as to minimise the problem in advance. Measures could include the insertion of permanent remote arms into the tank. Such arms would rotate periodically and create sonic pulses at the base of the tank. The pulses would not detrimental to the tank, but would be sufficient to knock the molecules off the heating coils and keep heavy sediment moving.

Such constructions would, however, require the customer to make an initial investment. Watson believes that the additional costs incurred would amount to only one or two percent of the total cost of building the tank, and such outlays would be returned since the tanks could either be cleaned whilst online or, if taken offline, they would be cleaned ten times more quickly.

Still, customer demand does dictate the design of the tank, and with labour costs loiw in the Middle East, old-fashioned methodolgies still abound.

Despite a recent proposal to a collection of leading tank fabricators, Tubetech is yet to be given the opportunity to road test their plans.

Cylingas has indicated that it has considered designing hydrocarbon storage  tanks in such a way that allows them to be cleaned whilst online. The company offers automatic cleaning systems such as floating suction devices that can remove many mpurities, but the bottom line with most customers remains cost minimisation when building their tank farms.

At a time when more dowstream facilities and dedicated polymer parks are due to come on-stream, the nature of the tanks and the technology that is deployed, sits firmly in the hands of the developers and end-users. The technology is out there, but it remains to be seen whether cleaner, clearer thinking will change the tank farm buyer's mentality.

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