Corrosion pushes a fibre glass makeover for Howrah bridge

Howrah Bridge, which is one of the largest cantilever in the world connecting the twin cities of Kolkata and Howrah, will soon go for one of the major maintenance works since its inception to tackle corrosion, including a cosmetic makeover.

Kolkata Port trust (KoPT) — which is in charge of the bridge, popularly known as Rabindra Setu — is inviting bids for installing fibre glass casing on the 74 columns of the bridge hanger base to protect it from human spitting.

Sources said, this may also lead to a partial colour change for the bridge as KoPT may go for a dark coloured fibre glass. However, authorities refused to confirm on whether it is part of chief minister Mamata Banerjee’s effort to change the city’s colour to “blue”.  According to a recent report, spitting had reduced the thickness of steel hoods covering the pillars from six to less than three millimeters since 2007.

“We have already started painting primer zinc chromate, which is yellow in colour, as a temporary measure. Though it is not a cause of concern for the bridge now, unless we take these steps, damage to these hoods at the base can affect the safety of bridge in the long run. We are yet to decide on the colour, once the bids are finalise we would superimpose various colours and will decide after that,” said A K Mehera, chief engineer, KoPT.  

The port trust is likely to spend more than Rs 20 lakh for this makeover.  A similar effort was done in 2004 also when KoPT shelved out about Rs 65 lakh to repaint the bridge with two coats of aluminium paint, in order to deal with corrosion happened due to bird droppings.  Every year about Rs 2-3 crore is spend for the maintenance of the bridge, while about 25 people work for it on a daily basis.

Sources said that as per a survey conducted by KoPT in 2007, more than 1,20,000 vehicles cross the bridge on a week days, while the number of vehicles decrease to about 90,000 on weekends.  More than 500,000 pedestrians are also taking the bridge daily.

“As of now corrosion is not a cause of concern for commuters. The rust may be because of urinating, spitting and also bird dropping. To a minor extent, salt content in air can also affect. However, since the bridge is made of high-tensile alloy steel Tiscrom, there is nothing to worry about for now if the authorities are taking proper action,” said S K Nandy, metallurgy expert and chairman of Indian Institute of Metals, Kolkata chapter.

The bridge was commissioned in 1943 and was rechristened to Rabindra Setu in 1965. It was Tata Steel which supplied steel for about 23,000 tonnes of tiscrom for the bridge. However, Tata  Steel did not respond to the queries by the Business Standard.

The bridge has a central span of 1500 feet between centers of main towers, it is at the bridge deck with 71 feet width with two footpaths of 15 feet either side which mainly facing threat of corrosion now. In order to ensure the safety of the bridge, authorities have banned big trucks from plying on the bridge from 2007 onwards. 

Six high tech surveillance cameras were also installed for the safety of the bridge on different location after that.

Though experts and KoPT believe that there is nothing alarming, this can well be considered as a stitch in time to save Kolkata’s iconic structure.