There is more to plant management than the capacity to produce the volumes to satisfy demand. It is also about the ability to physically move materials around efficiently and safely and plan for the future. Trevor Gauntlettwalks us through some of the business functions for a lubes blender or grease manufacturer and explains some logistical, expenditure and risk pitfalls.
Adistinguishing feature of lubricant oil blending plants or grease manufacturing plants is their wide variety of hardware, from impellers and paddles to bubble or jet mixers in tanks, to sun and planet stirrers in grease kettles; in-line or simultaneous metered blending for very large batches; autoclaves, open kettles or contactors for greases manufacture.
It is rare to find one company with two identically configured facilities, often due to corporate mergers or capital spending decisions taken locally.
For many seeking to introduce a new formulation, component or blend location, this leads to the key question: Can you handle it? However, possibly the biggest surprise to a newcomer to the industry – and even to some experienced players – is the number of ways that question can be interpreted. Do you have the workforce, equipment and storage capacity in place to grow?
To an operator on the blending plant floor, being able to handle it is about manipulating metal drums, pails, intermediate bulk containers, or IBCs, and powders. But it also goes beyond being able to tip a drum and decant its contents. There are many technologies, old and new, and best practices that can be employed to move materials around a plant while minimizing risk.
There are several ways to organize a plant to maximize handling capabilities. The industry has plants that are models of automation with almost complete elimination of manual handling. This has been managed even for sites with complex product portfolios, including many small-volume stock keeping units and dozens of raw materials stored in drums and IBCs rather than bulk tanks.
At one highly automated plant, additive cocktails were moved from storage by robots along roads on the floor to drum decanting units with metered pumps. Neat components in IBCs or drums were delivered from the drum heating ovens by forklifts to metered pumps on the ground floor. The extent of manual handling was to roll drums onto the scales.
Good practices in other plants included drum elevators to raise drums to the gantry at the top of the tanks, but drums were sometimes rolled and tipped in order to decant them. On a less grand scale at another small-volume blending plant with a simple portfolio, manual handling of drums was minimized by using a counterbalanced drum swing, which was tilted with little physical effort to pour the contents into a pail on a floor scale. The pail was then lifted onto the gantry by hand for decanting into the blending vessel, something for which the plant management had yet to find the money to eliminate.
Less good practices included plants that had staff lift and tip full drums into tanks, sometimes straight out of a 90-degree Celsius drum heating oven. This combined several risky practices in one task.
While drum decanting units reduce back and foot injuries incurred by manipulating drums, they can heighten health, safety and environmental risk if the pumps are not dedicated and a hose exchange is required. Such snake pits of hoses can be a source of twisted knees and sprained ankles if someone steps on one.
If a business is growing, conventional wisdom says increased volumes lead to reduced overheads per blend, as fixed costs are more thinly spread. But sometimes, conversely, the overheads can increase. When schedulers ask can you handle it? they are talking about warehouse capacity.
Due to insufficient storage space, the schedulers would occasionally order partial loads of packed additives to ensure we kept key components in stock. This increased the cost per ton of an additive, once the additional part-load cost was included, Ian Atha, former quality manager at Shell and technical manager at Ironsides, told LubesnGreases.
Many plants resort to outdoor drum storage, giving rise to stacks of additive drums positioned around truck turning circles. This incurs increased drum and IBC handling risks, higher possibility of water ingress, potential frost damage and higher working capital costs.
Plant throughput can be limited by the availability of drum heating ovens. Our procurement teams wanted to buy the most concentrated additives, said Atha. They used to say, We dont want to pay additive prices for diluent base oils. This meant that almost all drummed additives were highly viscous and so had to be heated.
On a good day, a batch blending plant may get two blends per shift per blending vessel, but many additives must sit in the heating ovens for two shifts before they are pumpable.
Then there is the issue of how many ovens a plant might have. For a plant with only two, there is a dilemma: 50 C is too cool for some additives while 70 C is too hot for many sulfur-containing additives. Meanwhile, polymer-based thickeners must usually be heated to 90 C, where most additives would start to degrade rapidly.
It is unlikely that the capital cost of a third or larger drum oven is factored into the business case for the introduction of many additives into a plant. This leads to sub-optimal fixes, such as only scheduling blends with the high viscosity additives after they have been in a 50 C oven for the weekend.
Additive suppliers have become increasingly conservative in their recommendations for handling temperatures due to several instances of noxious gas formation. These can occur due to overheating in drum ovens, transfer lines, unstirred blending vessels or bulk storage tanks. Thus, any place where a heated drum is opened should have adequate ventilation. If not, management may have to consider breathing apparatus to protect staff. However, this could lead to increased costs as staff seek compensation for the additional perceived risk. Lower handling temperatures mean higher viscosity additives and longer transfer and blending times or capital expenditure on more efficient impellers or more expensive pumps.
Dust hazards caused by powder handling are common at grease manufacturing plants. Some facilities have fully automated solids handling equipment, but operators at other plants work with full body breathing apparatus, cutting open bags and shaking them into the conveyors. Automated solids handling systems are often designed into new plants, but retro-fitting into old plants can be difficult.
For some purity grades, suppliers have low-dust versions of lithium hydroxide with 1 percent mineral oil added to create more coherent granules. This is great for reducing the amount of protection required for operators until the plant wants to manufacture a specialty product with an API Group IV or Group V base oil that has a specification on mineral oil contamination.
The Thick of It
Viscosity is the biggest operational handling issue for many and can manifest itself as a problem in additives deliveries, bulk storage tanks, transfer lines and the choice of blending technology. Higher viscosity due to low operating temperatures leads to longer transfer times for bulk packages or running pumps at a higher rating to cope with increased viscosity. This is not something plant engineers like.
For remote plants in cold countries, winter deliveries by rail or road can cause major problems. Most additives are thermal insulators, so heating the railcar only heats a very thin film around the frozen block of additive. This film quickly reaches the temperature of the steam or the electrical heating element and degrades because there is no convection to move energy into the bulk.
A batch blend based on a cool additive package takes longer and/or requires more heating to achieve complete mixing, adding to variable costs and perhaps limiting overall production to one blend per shift where two were possible previously. Several engineers claim the viscosity of the performance package can become the rate limiting issue for inline blending, as the combination of package viscosity and high treat rates mean that their lower mass flow rates dictate the time of the blend.
Buying a more dilute version of the additive is not the preferred solution of procurement. More drums or IBCs of (more dilute) material means more deliveries, so more vehicle movements on site and in the warehouse. Rail-served plants could potentially take more railcars per shipment, but this could only happen if their storage tanks and rail sidings are large enough. Therefore, these measures should be costed against the cost of upgrading pumps, adding suction heaters to tanks or heating to tanks or transfer lines.
When implementing a new formulation at a new plant, we had to consider the availability and type of heated bulk storage tanks at the new plant, Atha explained. Next were the subtle differences associated with steam, hot oil or electrical trace heating systems. Each has its unique characteristics, depending on the relationship between the practical additive pumping temperature and the degradation temperature for the release of noxious gases or oxidation.
Most of the chemical compatibility issues in mixed-use blending plants will be familiar to readers. Dyes, emulsifiers, high TBN additives or packages, polyalkylene glycols and gel-forming succinic half-esters will deteriorate many blends that they are not intended for.
Dedicated lines and tanks are the solution, but many plants werent designed for complex portfolios and there often isnt the space, budget or both to install this equipment, said Atha. This leaves plant chemists devising compatibility matrices detailing the levels of contamination that can be tolerated when switching between blend types.
The effort and resources required to reach the appropriate level of cleanliness depend on whether you have piggable lines or rely on flushing with base oil. Ideally, a high TBN oil should never precede an ashless hydraulic fluid. Lines that can be cleaned by small devices known as pigs or spheres can achieve the majority of clean-up, but many plants dont have them. If flushing to remove calcium from a tank before you blend a hydraulic fluid takes 3 metric tons of base oil every time – material that could then be used in, for example, a crankcase blend without reducing its value – you have to store it in clean containers. Otherwise it is downgraded to waste. Over a year that is a lot of money, Atha said.
Plants can only handle silicone antifoam or solid blocks of viscosity modifier if they have a high shear mixer. Many do not, leading to product failures and reputational damage. One plant with simultaneous metered blending, or SMB, was gradually adding neat silicone fluid into the lines and expecting it to be fully dispersed in the blending process. The SMB had insufficient shear to disperse the silicone fluid, which should have been dissolved in a carrier first, since silicone fluid does not dissolve in base oil.
As the lab blend for this product had passed all sequences, they were not using foaming as a release test. Further investigation revealed that the lab blend had been prepared with a motored paddle in a beaker overnight. Hardly representative of the SMB. Many of these issues can be resolved by capital expenditure or increasing working capital by holding more additive stocks, but no shareholder likes those ideas. The optimal solutions outside that envelope usually involve combinations of the scheduler, operator, engineer, lab chemist and health, safety and environment manager looking outside their working silo.ο
Trevor Gauntlett has more than 25 years experience in blue chip chemicals and oil companies, including 18 years as the technical expert on Shells Lubricants Additives procurement team. He can be contacted at email@example.com