Alphatec – Grouting Specialists a case report by
Work Report – Foundation Repair, Compressor and Motor Regrout Bayernoil, Vohburg Refinery, Bavaria
Customer: BayernOil Raffinerie GmbH End User: BayernOil Vohburg Refinery Location: Vohburg, Bavaria, Germany Project: J-602-A gas compressor foundation repair, compressor regrout and electric motor grout baseplate regrout. Work Period: 18 – 29 June 2007
Original Conditions
The machine in question is a Worthington Type BDC 1-1, gas compressor in Process Unit 6, powered by a direct coupled Siemens electric motor of 410 kW at 422 rpm. An inspection of the compressor was carried out on 14 June 2007 by Alphatec and BayernOil engineers, to evaluate the existing problems and discuss outline repair methods.
The compressor was manufactured and installed in 1967 and was grouted in place with a cementitious grout material. The machine had been shut down because of high vibrations, so it was not possible to see the degree of movement of the crankcase within the grout. The grout was seen to be thoroughly oil soaked, and several cracks and separations were visible.
The motor baseplates were very poorly supported by the surrounding grout, with evidence of voids over large areas.
The grout must be replaced by a modern epoxy-based grout product, correctly mixed and installed by a competent and experienced contractor.
The motor baseplates were very poorly supported by the surrounding grout, with evidence of voids over large areas. The possibility of corrosion of the baseplate was also considered, which can often be caused by induced currents within the concrete and the cement-based grout material. For these reasons, a regrout using epoxy grout was recommended.
The secondary supports, under the intermediate bearing, the crossheads and the cylinder heads, were all seen to be in bad condition due to oil contamination, and a regrout was recommended.
Many of the piping supports were also in bad condition and a regrout of those closest to the compressor was recommended.
From the foundation drawings, it was calculated that the above-ground plinths had a combined volume of around 22 m3, giving an estimated
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mass of 54 tonnes. Based on the foundation-mass-to-power rule of 100 kg/kW, this should be enough to damp out the vibrations. However, another rule suggests six times the weight of the compressor train and it is unlikely that this requirement is met. Injection through the foundation
Several deep holes were drilled from the foundation top through the main block and into the pile cap.
and into the underlying mat was therefore recommended, with an exploratory core hole drilled before the main drilling to establish the depth of this mat.
There was some discussion about the connection between the compressor anchor bolts and the concrete foundation, and a secondary injection to deal with this problem was planned.
Repair Work Carried Out
Because of the poor state of the foundation, a decision was made to carry out the recommended work immediately, and the Alphatec team mobilised in record time. Materials and equipment were delivered to site on Monday 18 June and work started the same afternoon.
There are four main components of the repair work effected: injection repair of the foundation; grout removal and support of the machine; alignment of all components; and forming and regrouting of all machine bases.
Injection Repair:
A preliminary core was drilled from ground level to determine the depth of the underground mat. Including the final floor thickness, there was 900 mm of concrete to be added to the foundation’s mass.
Several deep holes were drilled from the foundation top through the main block and into the pile cap. These holes were drilled with a diamond core drill, with a 60 mm ø bit and with a rotation-percussion rock drill.
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Case Report
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