Up to 160 SMRT staff took advantage of the full-day closure of 19 stations on the East-West Line (EWL) and North-South Line yesterday to squeeze in as much maintenance as they could - testing a new signalling system, replacing track circuits or cleaning the fans at train stations.

At Jurong East station, seven workers were spotted replacing a track circuit that spans 150m.

There are about 1,300 track circuits along the two lines that train operator SMRT said it will be replacing. So far, 40 to 50 have been replaced.

It usually takes two to three nights during non-service hours to replace just one.

Mr Keith Lim, principal fellow for signalling and communications at SMRT Trains, said he has two teams of about 10 men each working to replace three track circuits during 51/2 hours of the closure.

"With these extended engineering hours, we can shorten the time required for replacement," he said.

The 19 stations on the two lines will be closed all day again next Sunday.

They are also being closed earlier at 11pm on Fridays and Saturdays, and will open later at 8am on Saturdays and Sundays till Dec 31.

Compatibility issues between an old signalling system and a new one caused two MRT trains to collide on Nov 15.

SMRT said last month that the closures are being done to accelerate resignalling works and move the EWL to a new signalling system by June next year, instead of the end of next year.

It tested the new communications-based train control system from Redhill to Tuas stations from 11pm on Saturday till about 8am yesterday.

The system will allow trains to run closer together, and arrive at intervals of up to 100 seconds during peak hours, instead of 120 seconds currently.

Cleaning works that would obstruct human traffic, such as the cleaning of fans on platforms, were also done yesterday.

Mr Siu Yow Wee, director of building and facilities at SMRT Trains, noted that even non-track maintenance work, such as the replacement of components in platform doors and the clearing of rubbish from tracks, requires track access.

"Everybody is competing for track access, so today we have the opportunity to do peripheral work," he said yesterday.

Without closure, maintenance work on the building and facilities is done either monthly or once every three months, depending on the type of maintenance.

"We can't do much during the normal engineering (non-service) hours from 1.30am to 4.30am. Station closure helps us to hasten the corrective maintenance," said Mr Siu.