Our Business

HOME > Our Business

Our Business

Just like a light of the civilization huge plant complex and storage tanks in the petroleum and petrochemical industries are standing in a row throughout the world, from which various products to be distributed will be assets in a variety of scenes of society and life.
Maintenance works for those plants and complex, however, are continuously carried out for the daily production and environmental protection. SKK is fully aware of the Importance of Maintenance and proud of providing the distinguished technologies and services with our clients.

SKK-COWS Oil Sludge Treatment

If and when crude oil is kept in the oil storage tank for a long time, viscosity-like sludge is accumulated at the bottom of the oil storage tank. Viscosity-like sludge consists of the wax content in the crude oil, asphaltene content, mud content, water or the like. Properties and production of the sludge may vary depending on the type of oil and the storage period, and it may be accumulated to 5m high in some cases and may also cause such problems as the reduction of the storage capacity of the tank, the inclination of the floating roof tank or the like.

By the Japanese Fire Service Act, storage tanks for hazardous materials are regularly required for open inspection, and both the oil inside the tank and the sludge that is accumulated on the bottom plate, need to be completely removed.

The problem of crude oil sludge treatment is old and big concern for oil producers and refiners but still continued until now because of their nature, as abovementioned, that there are a huge variety of sludge types, components, qualities as well as storage conditions.

Under the above circumstances, SKK has been executing as an expert of sludge treatment service with forty (40) years’ experience for large scale tanks of crude oil and heavy fuel oil. SKK still pays continuous efforts to develop technologies for cleaning methods, washing machines and recovery units to recover valuable products, which results in the first-class reputation for the technology and system both within and outside of the country.

SKK-COWS (Crude Oil Washing System) has been established as a pioneer for the large scale crude oil tanks in Japan and applied to a lot of clients through the world.
SKK-COWS is the technology which makes able to wash out of thousand tons of the sludge accumulated in the oil storage tank in short term schedule, with small man powers and without accommodating human workforce inside the tank.
This desludging technology recovers oil fraction out of oil sludge in order to reuse valuable oil resources, by which only small amount of sludge residue is disposed at most cases.

The benefits of SKK-COWS are as follows;

 - On site treatment
 - Safe Operation
 - Complete Recovery of Valuable Oil Product
 - Low Cost and Short Term Work
 - Proven Technology with 300 Projects in the last 10 years

This outstanding technology can bring certain economic benefit and environmental protection to clients. We are making our best endeavors to improve the cleaning and recovery technologies for better services.

SKK-DTS Drain Treatment System

SKK-DTS can be used for the treatment of several kinds of waste water disposed from tank & plant washing, pressure test of storage tank, and other processes including high concentration of nitrogen compounds and hydrogen sulfide. We place the treatment equipment on site for oil separation, neutralization of acid/alkaline, separation and dehydration of suspended substances and COD adjustment.
This SKK-DTS is developed to treat oil contaminated water with low cost for large amount of waste water. Since this SKK-DTS can treat the waste water, on site, drained from the process of hot water washing in SKK COW, no further treatment is necessary by clients.

Piping Works

SKK is engaged in installation and maintenance works for process pipeline, transportation line, firefighting pipeline, and other pipelines for power plant, chemical plant, nuclear power plant, and other plants.

Maintenance Service of Tank

SKK provides the following services for various kinds of tanks.
- Inspection with planning, cleaning, NDI
- Cleaning of material surface by blasting, high-pressure water jet, etc.
- Maintenance works such as repair and modification
- Anti-corrosion works
- Civil and dismantlement works
- Application works to the authority and report publishing

Waterproofing and Still Water Works

SKK is engaged in works for waterproofing and still water, crack repair and reinforcement of tunnel, underground joint groove, power underground line sinus road and a manhole, etc.

SKK provide the following works.

 - Reinforcement work of concrete brick structure
 - Survey work of concrete brick structure, etc.
 - Anti-corrosion lining work
 - Corrosion-protection work of steel structure

Environmental Development Project

SKK-SRS Sludge Reduction System

The sludge usually consists of non-organic compounds, oil fraction or water that has been discharged in the tank cleaning and pipe cleaning. By application of the "sludge reduction device", the sludge is reduced to 1%, and the oil content to less than 5%. The reduction sludge is re-used as a soil material and the squeezed oil is to be recycled to the crude oil. This Sludge Reduction System is the technology friendly to the environment and resources.

The combination of SKK-COWS and SKK-SRS is considered the ultimate solution of oil sludge treatment for the following sites.
 - Oil refinery
 - Crude oil production
 - Oil stock storage
 - Disposal site so-called Oil lake or Oil pond

SKK-VRS Vapor Recovery System

Large amount of hydrocarbon vapor is discharged to the atmosphere when crude oil tank gets opened or washed. SKK-VRS is to treat the evaporated gas and recover most of it for recycle usage. SKK-VRS can be applied to most of hydrocarbon vapor discharged from oil and coal plants. The unit consists of washing and adsorption processes.

Cleaning Works of Pipeline

Based on various experience, SKK provides the following services.
 - Pig Cleaning
The most suitable pig can be selected, depending on the inside condition, fluid, and pipeline configuration.
 - Water Jet
 - Fluid Circulation

Divided-type Washing Machine


Features of AMW Washing Machine are as follows;

1)Since the rotation move of nozzle and body is driven by two air motors, the machine can be safely used even in hazardous area.

2)Regardless of the washing oil pressure, the nozzle speed and rotation of the body can be adjusted. (The air motor for nozzle and air motor for body is individually installed.)

3)As the machine is vertically inserted with the nozzle angle to be 90 degree as shown below that only body is rotating and air motor to nozzle is not running, it can be used as the washing in oil phase such as jet mixer.

4)The nozzle makes the strengthened jet with convergence, rectification straightforward and less spreading.

5)Repeat washing (for bottom plate, ceiling and corner), all-round washing and manual spot washing can be selected by a simple operation. In the repeat washing, the range (angle) also can be arbitrarily determined as four directions.

6)Compared to the nozzle speed of repeat movement, the rotation speed of body is as extremely slow as 1/17 that of nozzle, the washing trajectory can be dense and washing effect is very high.

7)Since the gear case and the nozzle part are separated, it is easy to install the washing machine. It is also possible to reduce the production cost if sharing the gear case.

RJM (Rotary Jet Machine)

1) Prevention for Sludge Accumulation in the oil storage tank

A preventing and suppressing method for sludge accumulation, by agitating the sludge using tank mixers and giving the flow of agitated sludge, has conventionally applied as one of preventive methods for sludge accumulation. Because of the increase in the size of the tank and the quality change in the imported crude oil, the effect on preventive measures for sludge accumulation over the entire surface of the tank cannot be expected.

SKK has therefore manufactured RJM (Rotary Jet Machine) for an effective and preventive method for sludge accumulation. The construction method combining RJM and SKK-COWS are much more effective to cope with the persistently continued sludge accumulation in the tanks.

2) Prevention of Sludge Accumulation and Desludging Method

Most of the sludge is basically a component of the oil and it is dissolved in the oil by heating or agitating.

The dissolving method is as follows;

aa) Heating (Generation of a solid solution, Growth suppression of sludge)
bb) Agitating (Fragmentation of the solid solution, Floating state of sludge)
cc) Addition of chemicals. (Suppression of solid solution)

By applying the above-described method individually or in combination, prevention of sludge accumulation and desludging may be attempted. There are many oil storage tanks with steam heater installed in the tank bottom and with propeller-type mixer installed to the side plate. In the case of a crude oil tank, however, a heating type system scatters valuable light fractions of the crude oil and it is very dangerous because of lower flash point. As heating cost is high, heating type tank is not suitable for the crude oil storage tank.

Many mixer systems must be installed to agitate evenly the internal parts of tank and yet leakage oil also is a concern due to abrasion of the mechanical seal of the rotating shaft portion. Blind spot is caused by the flow velocity distribution of the oil. In the case of tank with propeller-type mixer installed to the side plate, the sludge is accumulated from the current situation and so where the sludge in a tank fitted with a conventional propeller-type mixer is accumulated, it does not show sufficient effects.

Since chemical addition is expensive and not to be agitated enough, presently there are few track records and its effect is not clear.

In the recent tank open cleaning works, however, SKK-COWS (COW construction method) has gained a considerable effect. The principal of SKK-COWS operation is to break and dissolve accumulated oil sludge into fresh crude oil through jet washing machines.

3) RJMS (Rotary Jet Mixer System)

aa) Summary on RJMS (Rotary Jet Mixer System)

Rotary jet mixer system is the application of a liquid circulating dissolution method of crude oil washing method (COW method) used in the sludge removal of the tank open cleaning works.

Followings are summary on the system;

①Suck the crude oil in the tank by a pump and transfer the sucked oil to RJMS.

②Aiming at the accumulated sludge, inject from the nozzle and break, agitate the sludge and dissolve, disperse oil sludge into fresh crude oil.

This method was originally developed as an oil tank cleaning method of tankers and recent years the similar method was frequently applied to an open construction on land tanks, which gradually achieved satisfactory results as a safe and inexpensive method.

bb) Conceptual Diagram for RJMS

cc) Drawing of RJM (Rotary Jet Mixer)

Yokkaichi Logistics Center

In order to implement smoothly SKK’s nationwide cleaning works, along with the storing of several varieties of cleaning equipment and construction materials, the logistic center is located at Yokkaichi in Mie Prefecture. This logistic center makes ready for the maintenance of equipment, and the efficiency function for delivery.


Tent Warehouse

Tent Appearance

Equipment Storage Yard