Team News Riveting
Raipur, December 26
In a first of its kind job in SAIL-Bhilai Steel Plant, the Water Management Department Mechanical 1 team has successfully executed underwater repair and rectification job of corroded and damaged suction line in pumps P6 and P8 in Pump House (PH) 3A.
PH 3 and 3A handle water laden with mill scale from Rail and Structural Mill, Merchant Mill and Wire Rod Mill. There are a total of 11 pumps of around 2000 cub mt/hr and one smaller capacity pump. These pump the scale laden water to a Distribution chamber, from where the water is taken to Horizontal secondary settling tanks, where the water is allowed to remain static in large horizontal tanks. The clear decanted water thereafter flows to Maroda I reservoir and the settled mill scale is lifted out by grab crane and handled further.
Owing to the continuous flow of scale laden water, the suction pipes that convey water from sump to the suction end of pump had got badly corroded and had even broken off at places. The suction pipe inside the pump house had also become perforated, as a result of which leakage inside the pump house had set in. The suction pipe inside the pump house had to be encased in a block of concrete cast in-situ. Pump no 6 was lying in-operational owing to the suction line damage, for around a decade. Since the sump could never be available in a dry condition owing to operation of one mill or the other and the water was always heavily scale laden with near-zero visibility, repair work in conventional ways could never be taken up.
After brainstorming and exchange of ideas with organisations connected with underwater repair work, it was decided that the problem be addressed by inserting a marginally smaller diameter pipe inside the original corroded pipe and the annular space be sealed with epoxy at the ends and polymer modified cement along the length. The part of the suction wall around the suction on the sump side that had also got pitted was to be sealed with under-water-use epoxy putty. Since mill scale keeps on accumulating around the suction pipes in the sump, the suction pipe area for pumps P6 and P8 where rectification work was to be carried out would have to be kept free of mill scale by dedicated pumps, pumping scale to the downstream areas of the sump.
After inserting the smaller diameter pipe into the original corroded pipe from the suction end and sealing the annular ring from the sump end, and blanking the suction pipe from sump end, the suction valve inside the pump house were to be carefully removed to facilitate sealing of the annular space from the from pump house end.
Working as per the plan developed through brainstorming, the entire job was executed by M/s Abee Divecorp, an organisation employing underwater divers and offering engineering solutions including underwater cutting welding etc. The job that was being carried out for the first time in Bhilai Steel Plant was guided by CGM (Utilities) GA Sorte and GM and HoD WMD Utpal Dutta. The macro planning and co-ordination for execution was done by GM(WMD), A Banerjee and micro monitored by Bhaskar Prasad, Senior Manager (WMD) and his team led by Sripad Indurkar.
Working on similar lines, Pump no 8 of the same pump house that was not operable for some time owing to problems with suction valve has become operational after the repair / rectification operation. The suction line of Pump 6 is now free of leaks. Once pump 6 is overhauled, the same is expected to be healthy and operational soon. The experience gained through this pilot project will be useful for other plants of SAIL facing similar problems.
