English to German Tech/Engineering Petroleum Eng/Sci Pipeline engineering

Can anyone help out with a German translation of "back acter"?

Unfortunately I only have a limited amount of context, as follows:

It was reported that approximately 33% of all pipeline faults were caused by third party activity and that the
worst external interference hazard resulting in a loss of gas was due to the use of earth moving equipment. BG Transco's interference fault database recorded details of:

- the type of machinery causing damage to pipelines
- the type of third party activity being undertaken
- the method of detection.

Table 32 reports on the type of machinery causing damage to pipelines.

Type of machine:

Back Acter
Bull Dozer Blade
Digger
Dragline
Drain Layer
Power Drill
Scraper
Spike
Tracks
Trencher
Unknown

The use of Back Acters and Diggers accounts for approximately 54% of all recorded damage incidents and 28% of pipeline failures.

Any help will be appreciated!

Thanks,
Croc