HRW vs Arc Welding

[TheSlash]

Afternoon all

I had my first look at an HRW last night {Head Repair Weld}. I'm really struggling to see the point of it. We've survived on Arc Welding all these years, and Arc welding is alot quicker. I was was talking to the welders about the time it takes. They recalled that on one night, they managed one HRW between two of them. The following night one welder did three defects using Arc welding. :roll:
Managers are sitting on a ticking time bomb with this. They send out one person to COSS for the welders and take the clamp plates off. The welder then proceeds to cut 90mm x 25mm out of the railhead
If something had gone wrong, especially the weld running out, the nearest set of men were engaged on a a stress job thirty miles away.

 

[Old Timer]

The Manual Metal Arc (MMA) weld repair process is heavily dependent upon the competence of the welder. The repair process is time consuming and historical data from most railway networks suggest that this process is prone to internal defects that eventually lead to 'Tache Ovale' type or vertical-transverse rail breaks.

The total repair time for a defect 60mm x 25mm deep is specified as being in the area of 75 to 95 minutes, with the benefit of removing the potential for internal defects, without the necessity to change the rail, with the need for additional welded joints.

It sounds as if Network Rail have not bothered to explain the longer term benefits to the staff who are doing the work, or if they have, they have not been able to convince them suggesting the briefing was of poor quality.

HRW is being used by many other Railways, although I understand Corus is working on a slightly different technique as follows :-

The defect is removed using a portable three-axis rail milling machine that clamps onto the side of the rail head.

The weld area is then preheated with a conventional burner, the temperature is adjusted to match the rail type so as to ensure that it remains above the Martensite Start (Ms) transformation temperature.

The rail head material is replaced by a process that involves a semi-automatic weld repair using an open arc welding process.

The top weld layer is removed by profile grinding.

The transverse and longitudinal rail profile is restored and blended by grinding, using conventional rail grinders.

 

[TheSlash]

OT

I'm just worried that Section Managers are putting all their eggs in one basket with this. If you do a conventional thermic weld, you normally have a Gang there to help the welders on and off the track. Then they carry out other work nearby while the welders work. That way people are already on site should something go wrong and you need to put a rail in.
Meanwhile, Section Managers are quite happy for you to cut a huge hole in the railhead and have no back up plan

 

[Old Timer]

I guess they are willing to run that risk.