This article is a buyers' guide to the Y-Parts used on Tunnel Boring Machines (TBM). Y-Parts are the spare parts used on the TBM's Cutter Head. These are the parts which are worn most and need replacement most often during the boring operation.

The purpose of this article is to give an overall information about the TBM Y-Parts to help buyer with their buying process.

Y-Parts, Cutters, Collectors & Supports

The parts which do the actual cutting on a TBM Cutter Head are called TBM Cutters. Or simply Cutters. A typical Cutter Head also contains the support parts which we here call 'Supports'.

Here are the categories which together make up the Y-Parts:

TBM Y-Parts

• Disc Cutters (also called: Roller Cutters)
• Bica Cutters
• Collectors
• Supports

General Buying Advice

When you buy a TBM for a tunnelling project, you are right in expecting that the TBM manufacturer provides you with some sort of warranty (spare parts etc) during the whole project run for your TBM that you paid millions of Euros.

In addition to this, often a good contract stipulates that the TBM manufacturer takes the supervisory responsibility for the first X-meters (500 meters or so) of the boring operation. During this 'first X-meters' (often with a time constraint as well), your TBM team is still in charge. But the TBM manufacturer will be there to direct and help your TBM team to counter the early assembly & operation problems and attain a certain performance level.

These "first X-meter" clauses often require that the TBM uses the Y-Parts supplied/sold by the TBM manufacturer during this suprevisory period of operation. There are two reasons for this requirement. The first one is that, the TBM manufacturer wants to operate in a relatively controlled environment in this supervisory period by fixing some of the variables, ie in this case by working with Y-Parts that they are familiar with, rather than some Y-Parts you throw in from of them. Basically if you are telling them "500 meters of boring within 30 days", they have the right to set some counter constraints. Often the Y-Parts that the TBM manufacturers like to call "Original parts" is one of them. Secondly, the TBM manufacturer bets on your inertia (your lack of action). They hope that, rather than taking the (supposedly) "risky" decision of changing the sourcing of Y-Parts, you will simply be inclined to continue buying their Y-Parts.

Now comes this question:

Do Y-Parts of TBM Manufacturers Perform Better than that of Independent Producers?

Not necessarily.

The so-called "original" Y-Parts supplied by TBM manufacturers will almost always cost you more and often will not perform as well as Y-Parts of the independents. In general, it is safe to say that they will often deliver and average to good level of performance. This means: they will almost never perform too lowly or highly. With TBM manufacturer Y-Parts, you will be buying an average-to-good performance guarantee. At a price!

In the past, this has helped the revenues of the TBM manufacturers a lot. A bit like Gilette model (selling the razor cheaply and then making money on repeat selling replacable blades). Except that the TBMs themselves were also very expensive as well as the expensive Y-Parts. A true win-win (both wins for the TBM manufacturers).  Basically it was not really in the interests of the TBM manufacturers to sell high-performance Y-parts. The system was based on selling the TBM and then selling as many spares (Y-Parts etc) as possible during the course of the project.

As a matter of fact, it is safe to assert that the quality of the Y-Parts supplied by TBM Manufacturers have gotten better over the years thanks to the competition from the independent Y-Parts producers.

When it comes to the Y-Parts of the independents -unlike the those of TBM manufacturers- they can be Y-Parts from a bad manufacturer performing very badly or Y-Parts from a good manufactuer performing over the top.

To compare both sources of TBM Y-Parts:

Y-Parts from TBM Manufacturers

+ Often with an expected level (average-to-good) of performance

+ Lazy sourcing. Just use the same manufacturer.

- Performance is average-to-good

- Expensive

Y-Parts from Independent Producers

+ Almost always cheaper.

+ Great price/performance ratio from good manufacturers.

- Need to investigate to find a good manufacturers.

• Disc Cutters (also called: Roller Cutters)

Also called 'Roller Cutters', becase they turn when they are cutting the "wall" that the TBM is boring.

Disc Cutters are used for boring the hard surfaces like rocks. Their working method is causing cracks on the "wall" by applying pressure on it.

• Bica Cutters
• Collectors
• Supports