Expanding popularity of microturbines (micro-turbo-generators) is due to electronics development that makes possible for equipment operating without human interference.
By means of micro turbines the fuel combustion energy transforms into electric energy and heat. These devices have high productivity, and at the same time they are space saving and environmentally safe.
The intervals between scheduled maintenance and current repairs for the microturbines are much longer than those for gas-and-piston units. They require no oils or cooling liquids to be applied which makes microturbines a profitable alternative for the power stations of other kinds.
The microturbines are supplied to malls, data centers, construction sites, pharmaceutical stocks, oil platforms, agricultural sphere facilities. They are used in the most complex autonomous power supply projects, including those operating under Extreme North conditions.
Wide spread of the microturbines has become possible due to developing contactless supports with gas lubrication, namely, petal gas-dynamic bearings (PGB). They are operable under conditions of significant temperature drops and external heat inflows, have high damping properties and resistance to vibrations.
The petal gas-gas-dynamic bearings exactly are what are paid special attention to at microturbine repairs. The most technologically complicated challenge is providing petal-shaft tribo-pair operability (see Fig.1).
Fig. 1 Petal gas-dynamic bearing and its schematic image: 1 – petal, 2 – shaft, 3 – body.
This pair should have
- relatively low friction coefficient;
- anti-scuffing properties;
- wear resistance;
- Resistance to extremely high temperatures
It is possible to provide the friction pair with such parameters by using MODENGY anti-friction solid-film coatings. They are applied onto the petal carrying surfaces and protect them against premature wear, especially in the moments of contact with the shaft at starting and stopping the microturbines as well as in the transient and emergency operating modes of the equipment.
Extreme thermal tension of the modern gas-turbine machinery elements requires using the coating that doesn't damage at +400 to -500 °C (in possible future at +650 to 700 °C).
Besides, materials must have high adhesion to metals, little wear, very low friction coefficient, and fast running- in capacity.
MODENGY anti-friction solid-film coatings that have been applied in the sphere of energetics meet these requirements. They are used at Russian microturbines production, and foreign devices repairs (particularly, ones of the well-known Capstone brand).
The classic anti-friction coating are made on basis of solid lubricating materials that have layered crystal structure – as a rule, it’s molybdenum disulfide. The organic resins including epoxy, phenolformaldehyde, acrylic, and other ones are used as a binder.
Due to the solid lubricating particles properties, such materials effectively reduce friction and protect the parts against scuffing forming. Molybdenum disulfide gives the treated surfaces a distinctive grey colour with a metallic glare (see Fig.2).
Fig. 2 Appearance of MODENGY coatings on the different parts
There are both the materials based on conventional solid lubricants (such as molybdenum disulfide, polytetrafluorethylene, graphite, and the others) and the compounds containing other components in MODENGY coating line.
Let’s take as an example MODENGY 2560 coating with tungsten disulfide and non-organic binder based on metal salts combination.
In addition to tungsten, specially synthesized graphite, and reinforcing and stabilizing elements are also included into this material composition.
MODENGY 2560 coating is notable for…
- its thermal stability up to +500 °С
- resistance to acids
- increased adhesion and wear resistance
- effectiveness at both low and high sliding speeds (0 to 20 m/s)
MODENGY 2560 is successfully used in the turbine petal gas-dynamic bearings to reduce friction and wear at the moments of equipment starting and stopping.
For the bearings operating in other temperature ranges, MODENGY 1007 and MODENGY 1014 coatings are also use.
MODENGY 1007 based on graphite, and polyamide-imide binder has high adhesion, high wear resistance, and the properties of an emergency lubrication.
Coating Typical Characteristics:
- Colour: grey-and-black
- Service temperature range: -50… +350 °С
- Standard consumption: 65 g/m2
- Polymerization temperature/ time: +200 °С / 20 min
MODENGY 1007 forms an especially strong and heat resistant polymer film with integrated solid lubricant on the petal surfaces. The coating is excellent at protecting the parts under conditions of increased humidity.
MODENGY 1014 based on polytetrafluorethylene (PTFE) and molybdenum disulfide has low friction coefficient, chemical stability, excellent separating properties, capability to prevent stick-slip motion of the contacting surfaces. After being applied and cured, it form a layer with very smooth texture what is important to provide a gas-dynamic mode in the bearing.
Coating Typical Characteristics:
- Colour: Gray
- Service temperature range: -75 … +255 °С
- Corrosion protection: >672 hours (acc.to DIN EN ISO 9227)
- Standard coating consumption: 55 g/m2
- Polymerization temperature/ time: +200 °С / 40 мин.
All MODENGY coatings that are used at microturbines production and repairs provide longterm lubrication for the petal gas-dynamic bearings, and enable to create the friction units that require no maintenance.
The Modengy company is engaged in developing the coatings to solve their customers’ specific challenges as well as provides services on applying materials onto the components given by the customer.
For more detailed information, and to get a consultation, please contact our experts.
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