Hydro power is the most widely used source of renewable energy. Just under 20% of the world’s total electricity production originates in hydro power plants. These plants play a crucial role in the electricity mix of all but the most arid countries; consumers and utilities alike have been relying for decades on the very dependable power that they provide.
In order to ensure that the plants remain reliable and efficient over their entire life time, regular outages are performed. QuantiServ is assisting hydro power plant owners and operators across the globe to reduce the cost and time of these outages by providing specialist services such as
- runner refurbishments (blasting, welding, coating, balancing)
- in-situ machining of the various sealing surfaces on main inlet valves, butterfly valves, spiral casings, etc.
- bearing refurbishments and repairs
- shaft-seal re-designs
- turbine alignment checks and re-alignments
- equipment overhauls
- metal stitching and welding repairs
The services that we provide are flexible, economical and reliable. We particularly excel in special machining and in the professional and rapid reconditioning or manufacturing of made-to-order parts, such as for example white metal bearings.
Re-machining (skimming) of the various sealing surfaces is usually performed during major outages to ensure proper sealing and to eliminate water leakages. This work is usually done in-situ, by employing portable machinery. Most in-situ machines are of the conventional type, meaning that they consist of a central vertical shaft, around which a horizontal boom rotates. A milling or grinding machine is attached to the horizontal beam, hovering close to the surface that is to be machined.
The problem with such an arrangement is that the further the machine from the central vertical shaft, the larger the bending moment and deflection in the horizontal boom. This inevitably makes it very difficult to control machining tolerances and surface roughness. Geometrical inaccuracies and vibration marks are all but inevitable.
For this reason, QuantiServ has developed a revolutionary new generation of in-situ machines in 2016. These machines do not suffer from the problems described above as they do not have a central shaft nor a horizontal boom. They are centreless. The bearing of these machines is not located at the centre, but adjacent to the surface that is to be machined. This makes these machines ideal for large diameters, such as the ones typically found on hydro turbines.
Our new, centreless machines have the following advantages over traditional, boom-type ones:
- very high precision
- ability to adhere to tight machining tolerances
- superior surface finish
- higher machining speed, resulting in big time savings
After extensive testing we have started to use these machines in the field in early 2017. The results are very good. We are now able to carry out a superior machining job in less than anyone else.
Bearing refurbishments and repairs
We specialize in the refurbishment of any kind of white metal bearing and deliver top quality products with fast turnaround times. Depending on the bearing’s geometry, specification and application, we either use static or centrifugal casting processes. Generally speaking, bearings with complex shapes lend themselves well to centrifugal casting, while large bearings are usually statically cast.
There are virtually no size limitations, neither in diameter nor in width. We have been re-babbitting bearings as small as 80 mm and as large as 2000 mm diameter.
A good quality bond between the bearing material and the shell or housing is of paramount importance for good bearing performance and reliability. We therefore always verify the bond with non-destructive testing (NDT) methods such as dye-penetrant, ultrasound or galvanometer.
Our engineers and technicians are very experienced and well trained and they are usually available on short notice, particularly in emergency situations. Read more about the services that QuantiServ provides to hydro power plant owners and operators all over the world by clicking on one of the links below.
The following photos show in-situ machining work that we have recently carried out in a hydro power plant in Romania. The work consisted of the skimming of various surfaces on a 50 MW Francis turbine.
The next case comes from Quebec, Canada, where we metal stitched a long crack in the inlet flange of an 11 MW turbine casing. The crack was the result of excessive forces originating from the pen stock.
The total length of the crack was 2160 mm, which means that the crack extended to over half of the pipe’s circumference. All repair work was carried out in-situ. The crack was sealed with stitching pins from the outside while from the inside locks were added for extra strength.