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I want my system to be cleaner. Can new generation hydraulics help me with that?
Yes. To achieve a lubricant’s anti-wear properties, different types of additives are used. Normally a zinc additive is the most typical and easiest method of giving lubricants their anti-wear characteristics.
While zinc helps form a protective film on the machinery’s metal surface, sometimes in harsh conditions, the zinc can degrade to form a sludge which can impair the clean and smooth operation of the machinery.
Therefore, leading lubricant suppliers such as ExxonMobil have started to use zinc-free additive formulations in its new generation hydraulics. These formulations provide an equally robust protective film but do not have any of the sludge issues associated with zinc – therefore ensuring a cleaner system.
Our plant is in a warm climate and can reach up to 50ºC ambient temperature in the summer. We are having difficulties in cooling the system. What do you recommend?
On average, pump manufacturers recommend a minimum hot viscosity of 10 cSt. Due to its high viscosity index, Mobil DTE 10 Excel can operate effectively at higher operating temperatures compared to standard hydraulic oils before exceeding OEM limits – the higher viscosity index and ability to withstand higher temperatures means Mobil DTE 10 Excel avoids shearing and continues to protect equipment where others would fail.
Control/servo valve and pump expenditures are the major part of our maintenance budget and I have targets to reduce the number of spare part consumptions per year. What do you recommend?
Valves are the brains and pumps are the hearts of hydraulic systems. Therefore companies should insist on regular equipment maintenance procedures to keep the machinery in good health.
Lubricants play a huge role in this health check. Lubricants that don’t control oxidation can lead to contamination and varnish on valves, and varnished valves have a tendency to remain open. Therefore, the servo has to work harder, issuing repeated commands to close the varnished valve. Repeated commands and barely moving valves may lead to servo failure.
Oxidation can be held in check – and valves easily closed and kept clean – through the use of a new generation zinc free hydraulic oil such as Mobil DTE 10 Excel.
In addition, Mobil DTE 10 Excel’s high viscosity index helps avoid the problems associated with cold starts. The increased air release properties of high quality base stocks also prevent foaming which eventually leads to pump gear pitting. Tests show that Mobil DTE 10 Excel can reduce foaming by up to 20 percent(3)
time and noise.
Some of the equipment, especially those working with very high pressure levels, face a permanent viscosity drop after a few months, leading to me having to change the oil very frequently. What is the reason behind this phenomenon? How can I overcome this issue?
There are four types of stresses in material physics; tensile, compression, torsion and shear.
In hydraulic systems, lubricants are generally exposed to compression and shear stresses. These stresses, caused by working under high pressures over a long period of time, can cause the lubricants to exceed the plastic flow boundary and permanently lower their viscosity properties. This phenomenon is called ‘degrading’. Generally viscosity degrades one level; for example; from ISO VG 46 to ISO VG 32.
That kind of degradation can lead to unscheduled downtime and increased maintenance costs due to increased wear, heat generation, volumetric efficiency loss and leakages. To overcome this issue, it is important to use a lubricant with a high quality base stock, high shear stability as well as a high viscosity index.
In a severe shearing test, Mobil DTE 10 Excel maintained its viscosity level by up to 30 percent(4)
more and resisted rapid
shearing. Not every high viscosity index mineral hydraulic oil has such high performance shear stability.
Our plant is in a cold climate and we are having difficulties in starting the system after maintenance related downtimes. What do you recommend?
As well as consuming considerably more energy than at any other time of the cycle, a cold start is also the cause of most pump failures.
The pumpability of a Vickers pump test for example has a flow rate limit of 0.76 litres per minute. New generation hydraulic lubricants like Mobil DTE 10 Excel ISO VG 46 may reach that limit at 8ºC lower than standard hydraulics oils. Even if you never experience such low temperatures, improved cold flow properties will save energy at low temperatures up to 40ºC.
Mobil DTE 10 Excel has been designed to perform in extreme environments, with some grades operating successfully in temperatures as low as -34°C as well as offering excellent ‘start-up’ protection.
LINK
www.mobilindustrial.com
over standard hydraulic oils, helping to reduce resting
1 Energy Efficiency of Mobil DTE 10 Excel relates solely to the fluid performance when compared to ExxonMobil’s standard hydraulic fluids. The technology used allows up to six percent increase in hydraulic pump efficiency compared to Mobil DTE 20 series when tested in standard hydraulic applications under controlled conditions. The energy efficiency claim for this product is based on test results on the use of the fluid conducted in accordance with all applicable industry standards and protocols. In case of queries, please consult
TechDeskEurope@exxonmobil.com. Results may vary depending on operating conditions.
2 Based on in-house bench tests at ExxonMobil Research and Engineering Company
3 Based on in-house bench tests at ExxonMobil Research and Engineering Company
4 Based on in-house shear stability tests at ExxonMobil Research and Engineering Company
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LUBE MAGAZINE NO.127 JUNE 2015
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