A pitstop model, similar to those used in Formula One motor racing, was used to fast-track the retrofitting of environment-protecting electrostatic precipitators at a large pulp and paper mill in Mpumalanga, Engineering News can today exclusively report.

The innovative model was developed by the slick engineering team at Sappi Kraft’s large Ngodwana pulp and paper mill with the aim of transferring the quick-fire mindset of pitstop operatives to Ngodwana site at which a new air-pollution-reducing electrostatic precipi-tator was being retrofitted.

The use of the pitstop concept involved each company within a specially-formed alliance being required to perform their functions in the shortest possible time, as is done in Ferrari pitstops, with points being deducted for failure.

This approach proved highly successful in that the duration of the retrofitting of Ngodwana’s fourth electrostatic precipitator, known as P4, was reduced from an initial 45 days to only 18,3 days, in what is believed to be a world record.

Moreover, the precipitator is cleaning the air to a level of 30 mg/Nm3, well below the legal requirement of 100 mg/Nm3.

The Engineering News team visited Ngodwana for an exclusive presentation on this and several other developments at the impressive forest products mill, where engineering manager Merten van Rensburg pointed out that two fields of innovation were involved in the P4 project, the first being commercial and involving novel performance bonuses for the construction team and the second being technical and involving the novel use of a jig, pre-assembled modules and special cranes.

Global company Alstom Power – the lead company in Ngodwana’s special ‘pitstop’ alliance, which includes post-construction mainten-ance company August General Servicing, rigging company Van-guard and electrical contractor Power Plant Electrical – reports that, to its knowledge, an electrostatic precipitator has never been installed as rapidly anywhere in the world.

“We have set an industry standard, which is an investment in the future, and we attribute the success to the alliance concept,” Ngodwana engineer Erwin Schroeder tells Engineering News.

However, not satisfied with the record 18,3 days, the alliance targeted an even more astonishing fourteen-day retrofit for the fourth electrostatic precipitator, P3, which was completed in 10,5 days, during the annual outage in March this year.

The fifth electrostatic precipitator, P5, will be entirely prebuilt and put into position using hydraulic jacks, during the up and coming outage in September.

Ngodwana’s great emphasis on speed is to ensure that pulp production is not lowered during the period of shutdown.

To this end, additional pulp is produced ahead of time to provide sufficient feedstock to the mill during the period of construction.

The capital cost of the five new retrofitted electrostatic precipitators is R83-million and, since 1990, Ngodwana has spent R200-million on protecting the environment. A retrofit involves a complete replacement of all the innards and control systems of the electrostatic precipitators.

There has been a deliberate invest-ment in intellectual capital, which has paid off as the same alliance has been engaged in precipitator projects three to five.

The P4 construction methodology involved the pre-assembly of a tall nine-compartment jig into which modular bundles were hoisted.

Initially, one bundle was hoisted at a time, but as confidence grew, four and five bundles were being lifted simultaneously.

Two 30 t cranes were used for assembly and a 550 t mobile hydraulic crane from Johnson Crane Hire carried out heavy 17 t lifts within a 54 m radius.

All the electrical equipment, installed on roof panels, was hoisted into position simultaneously to save time.

The old P4 plant was stripped away in two-and-a-half days, special scrap trucks removing the old equipment in bulk pieces.

Cleaning, preparation and dimension checks were completed in three days; installation of the modules and rapping gear in eight days; installation of the hot roof and the cold roof in two days; installation of electrical equipment in a day; and testing and commissioning took 1,8 days, totalling 18,3 days.

There was 18 hours of rain when work could not take place, extending the actual outage to 21 days.