Maintenance crackers Dow Terneuzen
Problem Statement: To ensure safe and reliable production, Dow needs assurance about the condition of several dozen crackers. These must be taken out of service periodically for inspection and maintenance. In doing so, safety is paramount. The stoves must also be brought back into
as quickly as possible.
Bilfinger continuously ensures flawless maintenance of the crackers. Thanks to years of experience, teamwork and thorough knowledge of the installations, Bilfinger can do this in the shortest possible time.
- Work preparation and planning.
- Prefab manufacturing incl. conservation.
- Physical blinding (securing) of the pipes (cutting off).
- Opening and dismantling of the installation parts for inspection.
- Disassemble parts to be replaced.
- Installing and welding new coils and other parts.
- Closing and assembling installation parts.
- Pressure testing of systems.
- Reporting installation ready for commissioning.
By outsourcing the expert maintenance of their crackers partly to Bilfinger, Dow can be confident that the company is operating with a reliable installation. Moreover, Dow can safely put the cracker back into operation for production within the shortest possible time.
In Terneuzen, Zeeland, the American company Dow produces a wide variety of plastics with more than 3,500 employees and 16 plants. The company has its own quay, where ships deliver raw materials. From there it goes to three large cracking plants, where the raw materials are heated to more than 800 degrees Celsius. Then the molecules disintegrate into various usable intermediates, such as ethylene and propylene, which are further processed into plastics at various plants.
The extreme heat required to crack the raw products is produced in dozens of cracking stoves. And when you know that such a stove needs servicing about every four to six years, you understand that there is at least one stove up for maintenance every month. That's where Bilfinger comes in.
For a long time Bilfinger has been one of Dow's partners in maintenance of cracking stoves. 'The work for maintenance varies each time, and is prescribed by Dow in so-called work packages,' explains operations manager Miechel Corstanje. 'These state exactly what needs to be done, supplemented with drawings and photos. It can vary from minor maintenance, where we open up all the equipment, have it inspected, cleaned and reconnected, to a complete maintenance job where all the coils are replaced, which are parts made of pipe that make up the heart of the cracker. We are sent the work packages in advance and then determine what we need to do all the jobs safely, properly and with high quality.'
A lot of welding
'The age and useful life of the crackers determines exactly what maintenance is needed,' says deputy site manager Michiel Hendriks. 'Dow sees the periodic maintenance of the crackers as an opportunity to have additional work done. Hence, in most cases it does not stop at just inspection and cleaning. In most cases, for us it involves replacing the coils anyway. These are large areas of pipe components, which we now have prefabricated. Once we have opened up the stove, we can remove the old coils and fit the new ones in one go. Then we make sure with welding connections that the new coils are perfectly connected again. In addition to the coils, we usually have work, for example, on the various valves that need to be built in and out. And for some time now we have also been working on parts from the convection section of the crackers. That too involves a lot of welding.'
After safety, timely and high-quality delivery of the cracker is the most important thing for the customer. Because then they can continue production reliably. Decisive in this is the performance of Bilfinger. 'We now do the maintenance work per cracker in about eight to twelve weeks,' says Michiel. 'And if it's just a recoil (replacing the coils) we do it in five weeks. Needless to say, Dow wants to get going again as soon as possible, and thanks to our years of experience, teamwork and thorough knowledge of the installations, we can do it in the shortest possible time.'
Bilfinger has been working at this Dow site for decades. In that time, ever newer and advanced working methods have been introduced. By Dow itself, but also by Bilfinger. The most recent innovation is the introduction of a special type of welding tent . 'Because we do a lot of welding, we have to set up welding tents in different places,' Michiel explains. 'The welding tents ensure that you are not affected by weather conditions or fire hazards caused by welding spatters. They consist of a number of pieces of tarpaulin, which you use to seal off the workplace. However, sealing off a welding tent does not provide enough air refreshment, so it is a confined space. After a special study, we were finally able to set up a pilot where we place welding tents with special openings in them. You have to imagine that depending on the wind and the work, we always keep two hatches in the tent open. A simple solution that creates sufficient air circulation and thus eliminates confined spaces.
Other innovations we're looking into include the angle grinder with a longer neck. Michiel: "Sometimes there is very little space to perform work. By using an angle grinder with a modified, longer neck, the welder can get between the coils more easily. At Dow, the grinder is only used to prepare and finish welding work.' Other examples include a welding helmet with wider vision, spot extraction when working and a new breathing air system with more comfort for the welder.
Because of the amount of crackers, there is a lot of work to do. 'Moreover, Dow announced an ambitious roadmap last summer, to move to circular hydrogen and electric crackers,' says Miechel. 'In this way, Dow is moving toward climate-neutral production by 2050. We look forward to it!