Clean, protect, connect, detach

Transcription

1 Page 1 OKS: Special lubricants for maintenance and service work Clean, protect, connect, detach Practical experience from the inspection of the OMV Schwechat refinery Refineries break down the black gold that is mineral oil and process its components for further use. The refinery s technology then also itself has to be processed at regular intervals. In shutdown maintenance such as this, cleaners, greases, bonded coatings and assembly pastes play a role on practically every handle, as illustrated by the current example of the die service work at the OMV Schwechat refinery. Hans-Jürgen Bittermann On the left a compressed air bolter hisses, while on the right fitters shout loud positioning instructions to the crane driver a large heat exchanger is lowered slowly into the plant. Another special crane approaches from the front. How does the driver manage to manoeuvre in these narrow aisles? These days it s all happening at the otherwise peaceful site of the OMV Schwechat refinery, people and machines are moving around everywhere and there is of course a reason for all this: It s time for the routine planned shutdown, in other words servicing of the technical plant in August and September In concrete terms this means: Stop activities as specified in the Pressurised Equipment Monitoring Ordinance. This involves subjecting the plant technology to a comprehensive safety inspection, and also inspection and preventative maintenance work. It s no wonder that so many people are actively involved in a shutdown service, as the maximum amount of work must be done in a very short time. And that s only possible with external help: In addition to the regular workforce of the OMV Schwechat refinery, some 1700 people - from serviceproviders and service personnel of the component manufacturers - are moving around the site. This thorough check-up costs the company around 32 million Euros. At the same time, OMV is investing another 200 million Euros in increasing the capacity of the ethylene plant and in so doing is boosting monomer production from 650,000 to 900,000 tonnes annually. An additional

2 Page external specialists are actively involved in this a total therefore of some 2500 people who must make the complex plant technology ready for production within the space of a few weeks. At first glance it s astounding that in view of such an investment volume, thought is also given to the use of lubricants and assembly pastes. Normally, these consumables are regarded as being of low importance. This is not the case at OMV, which intentionally looks at these products as being most definitely important time management components. Everyone at every level is aware that: Time is money, and every delay means high turnover losses for the refinery and the associated plastics production at the subsidiary company Borealis. This means that all procedures must be planned down to the most minute detail, every handle must be secure, and only the best tools and equipment are used. Shutdown: Perfect planning and organisation required The entire plant infrastructure must be inspected, serviced and if necessary repaired. Engineer Robert Pappenberger, head of Planning & Control and the shutdown supervisor, knows the specific figures by heart: 2 furnaces, 56 columns, 406 heat exchangers, 388 containers, 2800 valves, 1300 safety valves and 2400 measuring and control devices must be serviced. In addition there are the necessary repairs to the pipelines, and investments that can only be made when the plant is shut down. For the shutdown, the refinery s external service-providers assume responsibility for over 95 per cent of all the work. Pappenberger explains that as its core tasks, maintenance includes technical responsibility, longterm planning and also organisational and monitoring functions. Of course, besides setting the duration of the shutdown, from a safety and economy point of view ( that s the central, crucial point of every service! ) this also includes incorporating knowledge gained from previous shutdowns with regard to safety, the length of the shutdown, the work sequence and costs, as well as the pre-planning of additional activities for future shutdowns. You need a lot of experience to be able to say on site at the plant that this needs doing now, but can wait until the next service, explains engineer Franz Cetl, head of Equipment and Mechanical Engineering. At the Schwechat refinery, that approach obviously succeeds well because mechanical availability is at an impressive 98 %.

3 Page 3 Securing connections and detaching them safely again How problem-free the planned work sequences then actually run during the short shutdowns depends on, among other things, the time taken for the assembly / disassembly of supply lines, apparatus and machines and the measuring and control devices. Whatever connection method is selected: Perfect preparation (cleaning) of the surfaces and use of suitable bonded coating or the correct assembly paste ensures the reliability of the connection and makes its disassembly easier later on. At the Schwechat refinery, products from the OKS company of Munich are used for a number of applications (see interview). OKS, a subsidiary of Freudenberg Chemical Specialities KG, develops, produces and markets worldwide special lubricants as well as cleaning and corrosionprotection products for all types of service and maintenance work. The invisible helper of the maintenance man A brief glance into the world of tribology clearly shows the importance of such products in everyday work. The functions of a lubricant can be varied and, depending on the particular application, can be necessary alone or in combination. Besides the primary demand placed on the lubricant namely maximum power transfer combined with a minimum of friction and minimum wear it is often necessary to fulfil various secondary properties such as water resistance, chemical resistance compatibility with plastics or corrosion protection. Mineral oils, synthetic hydrocarbons, silicone oils, polyglycols, ester or similar synthetic liquids are used as the basis for high-performance lubricants. They differ in terms of, for example, their temperature behaviour, miscibility, lubrication capability, oxidation resistance, material compatibility and manufacturing costs. The choice of the viscosity of a lubricating oil depends on the area in which the lubricant is used. The following basically applies: Low viscosity for low pressure stress and high sliding speeds, high viscosity for high pressure stress, low sliding speeds and high temperatures.

4 Page 4 If, for structural reasons, no oil lubrication is possible or if a cooling function is not required, a lubricating grease is used in most cases. A lubricating grease is an oil that has been bound by a thickener. The thickener acts in a similar way to a sponge that gives off liquid under pressure stress. However, the lubricating film of a grease is always thicker than that of the base oil. Pastes play a dual role in lubricants. With a high component of solid lubricants bound in oil, they perform heavy-duty work in lubrication in the mixed friction range (they are not suitable for hydrodynamic lubrication). Thanks to thermally extremely stabile solid lubricants, they reliably separate the sliding surfaces, e.g. of screw connections that are subjected to pressure and temperature stress. The structure of high-performance pastes is similar to that of the greases. The main difference is in the high solids component that is typical of both assembly pastes (lubrication effect only) as well as for screw pastes (lubrication and separation effect). Solid lubricants are substances that, due to their structure (fine powder) and their chemical / physical properties, form closed sliding and separating films on metal surfaces, either alone or combined with other substances. These films are so thin that fits and tolerances do not have to be changed in mechanical engineering. In lubrication systems, solid lubricants form primary sliding films in high concentrations and secondary sliding films in low concentrations. They prevent extreme wear in the critical phases of solid friction and mixed friction. The terms dry lubricants or bonded coatings refer to solid lubricants that are incorporate into die a varnish-like matrix or organic or inorganic binders. The surfaces must be pre-treated in order to achieve good bonding. The coating is applied by immersion, spraying or painting. The dry and activated sliding film resists high pressure stresses and extreme temperatures, takes up no dirt and guarantees long-term lubrication. Conclusion: Normally, as consumables, little importance is attached to cleaners, greases, bonded coatings and assembly pastes. However, in the case of time-critical shutdown servicing, these products gain a much higher status, although every delay in the process means a high loss of turnover. The practical example of the OMV Schwechat refinery shows that in the servicing of heat exchangers, reactors, valves and the entire technical

5 Page 5 machinery (pumps, compressors, turbines, agitators), special lubricants such as screw and assembly pastes and also cleaners are the service technician s invisible (and essential) helpers. They simplify the work processes of assembly and disassembly, and also make a contribution towards the sustained process safety of the plant technology. Interview Refineries: Safety and quality orientated Anyone who has ever been tormented by a stuck-fast screw connection knows the value of preventative planning in matters concerning connection systems. Engineer Robert Pappenberger, engineer Franz Cetl and senior expert Michael Martin Grill talk about the subject (all: OMV Schwechat refinery). Editorial team: According to what criteria do you select external serviceproviders and suppliers? Pappenberger: We are extremely safety and quality orientated that s the nature of things at a refinery. And we have a narrow time window, because everything must be just right. This means that we accept only the best of the best, and at prices in line with the market. And because quality serviceproviders are especially coveted everywhere, you have to book them well in advance. As far as suppliers are concerned, we look for criteria such as deadline reliability, consultation quality and of course adherence to the technical specifications. Editorial team: And how do you deal with newcomers how can they qualify? Cetl: That happens only very slowly via smaller projects, followed by something larger. And OMV itself runs several refineries, where there is an intensive internal exchange of experience. Editorial team: You recently changed suppliers for individual special lubricants such as assembly pastes and cleaners, and are now working with OKS. What were the reasons for this?

6 Page 6 Grill: Mainly because of the technical people who really are very well trained by OKS which is also located in our immediate proximity. This proximity is a great advantage for us! Cetl: The people really are very competent, and know not only the technical properties of OKS products but also about the practical requirements in a refinery. This is a decisive point, given the deadline stress involved in a service! Grill: I d go as far as to say that manufacturers of lubricants and their products are interchangeable. But choosing the right product from the mostly broad range is more important. To do this however, the technical consultants must have the right background, the right experience. That s clearly the case with our OKS consultants. That s why we changed to this manufacturer! Editorial team: So is the requirements profile for a lubricant so different? Grill: Of course! Just take a look at the needs of the machine technology: The load-bearing capability of, for example, the assembly paste at high temperatures must be reliable, as must compatibility with the process medium or the materials being connected. In addition: The product must not be too complicated to work with and handle. Time-consuming mixing of several components is inconceivable for us. The demands placed on the surface should also not be excessive. Meeting all these requirements is not a trivial matter! Pappenberger: At our refinery, the number of screw and bolt connections is roughly estimated at 300,000. Of course, not all of them are undone. But every screw or bolt connection that causes problems when being undone or reconnected holds up work and costs both time and money. That s where the correct lubricant is a great aid to work. In addition, service intervals have been extended from three to six years. And of course we want to ensure that a screw or bolt connection is easy to undo even after that length of time has passed. That s why we pay very precise attention to the specification of the lubricant. hjb

7 Page 7 Brief introduction: OMV AG With 6,475 employees (in 2004) and a Group turnover of 9.88 billion Euros, OMV Aktiengesellschaft is Austria s largest industrial company listed on the stock market. As Central Europe s leading oil and natural gas Group, OMV has a refining capacity of 26.4 million tonnes per year and 2,385 filling stations in its core Danube region, extending from the Black Forest to the Black Sea. This puts it in an ideal strategic position in Europe s largest growth market for mineral oil products, and it supplies energy to 100 million people in 12 countries. This market has an annual consumption of approximately 80 million tonnes of mineral oil products. The OMV refinery in Schwechat is one of the largest and most modern inland refineries in Europe. Here, with a workforce of about 800, OMV distils and refines crude oil and semi-finished products to produce high-quality mineral oil products and basic petrochemical materials. Around 60 % of all mineral oil-based products used in Austria originate from the high-tech plant at Schwechat, which processes some 9 million tonnes of crude oil annually. In January 2005, the Schwechat refinery became one of the first plants in Europe to receive the ISO certificate EN ISO 14001, thereby confirming the leading role played by OMV in matters concerning environmental protection. Key word: Friction Friction is the mechanical resistance to the relative movement of two surfaces. Friction is undesirable in lubrication systems, because it is associated with energy loss, friction heat and wear. For an optimum problem solution, all influencing variables in a tribological system must be known, and allowance must be made for complex interactions. Ambient influences (dust, temperature or moisture) and structural factors (material, surface or geometry of the friction bodies) play just as great a role as stress factors (speed, pressure stress or vibrations) as far as selecting the correct intermediate material (lubricant) is concerned. Brief introduction OKS As a company of the Freudenberg Group, one of Germany s largest family companies, OKS Spezialschmierstoffe GmbH of Munich develops, produces and markets internationally high-performance lubricants and chemical engineering products via technical trading and mineral oil trading specially for maintenance and assembly.

8 Page 8 Fold-out picture: The OMV Schwechat refinery, with its annual processing capacity of around 9 million tonnes of crude oil, is one of Europe s largest refineries. Figure 1: Screw and bolt connections are the connection method of choice in a refinery: easy to undo, quick to reconnect provided that the choice of assembly paste was a good one. Figure 2: The load-bearing capability of, for example, the assembly paste at high temperatures must be reliable, as must compatibility with the process medium or the materials being connected.

9 Page 9 Figure 3: The service intervals at the Schwechat refinery have been extended from three to six years. It must still be easy to undo a screw or bolt connection even after this time this figure shows servicing of compressors. Figure 4: The lubricant must not be too complicated to work with and handle. Time-consuming mixing of several components is inconceivable in a refinery, given the deadline pressure of a shutdown.