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Case Study
BHILAI steel plant - Oxygen plant compressor noise control
BOC, MANNESSMAN DEMAG - GERMANY and DEMAG KIRLOSKAR were engaged in setting up a large oxygen plant for Bhilai steel plant. One of the major equipment for the oxygen plant is 2 Nos. large air compressor of capacity 1,47,800 kg/hr at 11.73 kg/cm2 discharge pressure driven by a 9500 KW motor supplied by M/S. MANNESSMAN DEMAG.

M/S.AIPL was approached to design, manufacture, supply and commission a suitable noise control scheme to control the noise level within 85 dBA at a distance of 1m around the compressor. The compressor package consists of a large multi stage compressor, 9500 KW motor, after coolers, intercoolers and moisture separator. The coolers are having a diameter of 2700mm and length of 9.7m.The compressor with motor was installed at an elevation of 4.5m.

The large after coolers and intercoolers are installed right below the compressor. It was also observed that the noise emanated from the coolers was much on the higher side.

The following noise level was observed from the compressor.
Freq(Hz) 63 125 250 500 1k 2k 4k 8k
Suction SWL dBA 113 117 116 119 121 121 118 107
Discharge SWL dBA 126 130 129 132 134 134 131 120
Blow off SWL dBA 109 113 112 115 117 117 114 103
Casing SWL dBA 114 108 107 110 112 112 109 98
 
AIPL's responsibility was to design a suitable noise control system to reduce the noise emanated from the compressor well within 85 dBA limit.

The temperature rise inside the acoustic enclosure is to be maintained below 50 C above ambient.

On careful analysis of the whole system involved in this project, it was observed that the coolers are posing problems not only from the point of temperature rise, but also emits very high noise from the casing. This necessitated suitable acoustic treatment by providing a brick walled enclosure for the cooler assembly package.
 
Fig.1
Acoustic Enclosure for the compressor
Fig.2
Inner view of the Enclosure for the compressor
 
If the cooler assembly package was to be covered inside an enclosure, then the temperature would shoot up inside the acoustic enclosure affecting the performance of the cooler. After a very careful analysis the following scheme was worked out.
  • Acoustic Enclosure for the blower with motor
  • Suction Silencer for the compressor
  • Discharge Silencer for the compressor
  • Blow off vent Silencer in the by-pass line
  • An Enclosure for the cooler assembly below 4.5m elevation
  • A ventilation package to remove the heat dissipated from the compressors, motors, after coolers, intercoolers and moisture separators.
Fig.3
Suction Silencer for the compressor
Fig.4
Discharge Silencer with Acoustic Enclosure
Acoustic insulation of the Suction, Discharge piping and acoustic treatment of various other piping in the lubrication circuit was done. The acoustic enclosure designed by us was having a dimension of 9.7m long x 9.2m wide x 3.4m height for the compressor/motor and the brick walled chamber of dimension 16m length x 10m wide x 6m height for the cooler assembly with adequate number ventilation inlet silencers and soundproof door assembly.
The ventilation air sucked through the intake silencers takes away the heat dissipated by all the coolers and moves up through the floor grills and gets inside the compressor acoustic enclosure to take away the heat from the compressor and motor and escape through the exhaust blowers mounted on the roof of the enclosure with ventilation exhaust silencers.

After installing the system, the noise level was found to be within 85 dBA around the enclosure. The temperature was measured inside the enclosure and found to be within 50 C above ambient.
Fig.5
By-pass blow off vent Silencers.
 
 
Silencers   Enclosures   Other Products   Noise survey
Silencers   Acoustic Enclosures   Other Products   Noise Survey
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