PGW SCHIELE GX-420 TURBO AERATION BLOWER Major Repair
Near a city of millions in southern Europe, a water treatment plant is equipped with a series of PGW Schiele turbo aeration blowers. One of these blowers was out of operation, which meant that the reserve capacity was lost. The blower was seriously damaged at the level of the impeller, further investigation revealed that the bearings and the pinion were badly damaged.
An examination revealed that the impeller cap had come off during full operation. The reason why this could happen became clear after the bolt connection was recalculated and we came to the conclusion that the bolt connection was designed too weakly. There were shortcomings in both dimensions and choice of materials.
Our field team came on site and disassembled the complete compressor to transport it to the workshop. During these works, the first damage reports were drawn up. Arriving at the workshop, the inspection was continued to clearly report all calamities and to propose a suitable action.
Several parts were heavily damaged. The impeller was irretrievably lost as well as the fast spinning pinion, that was completely bent along with the tension bolt.
Fast-turning pinion , strongly bent by the shock caused by the impeller cover coming loose severely damaged hirt connection.
The bearings of the fast-spinning rotor were also damaged. The bearings of the slow-turning gear were worn and therefore out of specification.
The system of the inlet guide vanes clearly needed maintenance and the variable diffusor blades were also damaged here and there.
IGV system completely overhauled and new wear parts mounted.
Variable diffusor vanes partly renewed by using reverse engineering method. After the inspection was completed, a plan was drawn up to carry out repairs and to make new parts.
Very little documentation was available and no production drawings were available at all. That is why we designed a completely new impeller according to the necessary and available parameters. The impeller was designed with a computer flow design software and the parameters were tested by means of simulations.
By using 3D programs we went from CFD design to hard metal design and moved to production by means of cam software and fast cutting machines.
The certified material was first given the correct thermal treatment and after the first machining step was tested for operational speed + 10%. Afterwards the impeller was fully re-machined. The NDT test was negative.
A completely new pignion was manufactured taking into account the toothing, which was checked with a gearload program.
The trust discs were hardened and ground. The pinion is nitrided.
Both the pinion and the impeller were fitted with a ground hirth connection. The combination was first balanced dynamically and incrementally at low speed to check possible imbalance at operational speed afterwards.
The oil labyrinths were also damaged by the ash run-up and have been re-manufactured.
The bearings of the pinion were very badly damaged and were completely re-manufactured after design. A bearing-load calculation and simulation program was used for this. The engineering and production line of white metal bearings within our company worked closely together for this. Not all bearings were made new . Those that were repairable like the bull gear bearings were therefore repaired.
Inhouse production of new tilting pads
The counter impeller piece was provided with a new profile and the clearance was adjusted during assembly in our mechanics hall.
Installation on site.
Special hydraulic tool is used to extend the stretch bolt in steps. The extension lengths and applied forces are calculated by our engineering in preparation for the assembly carried out by our technical people on site.
The blower has been operational for over a year now without any calamities. Not only was an extensive report drawn up, but a 3D model and a 2D drawing with production data and tolerances were made of all parts by reverse engineering method. This is to prevent the operation of this blower from being endangered by obsolete spare parts.