When the chart of one stock within an industry starts to raise a red flag, it’s noteworthy. When the majority of the stocks in an industry wave similar flags with their own charts, however, action may be merited, as there’s likely a bigger underlying reason for the group’s troubles.

That’s what makes recent red flags in the oil equipment sector from Baker Hughes (NYSE: BHI), Schlumberger (NYSE: SLB), and Halliburton (NYSE: HAL) so alarming. It’s not that one of these stocks is simply going through a rough patch – it’s the entire oil well services and equipment group under serious  fire, indicating a widespread challenge that may not be easily shrugged off.

For Baker Hughes stock, the problem became evident in early June when we saw the first lower high (see the descending yellow line). But shares became downright worrisome on Friday with the move under an important support line (orange). Now, with no other floor to lean on — BHI already is under most of its key moving averages — there’s not too much to prevent more downside. The bulls are hoping the 200-day moving average line at $60.83 can serve as a landing pad, but that’s still a long way off.

Halliburton’s chart looks a little different, but equally troubled. We actually saw a double-top (two peaks at essentially the same price) at $51.32 as of the end of May. Each peak followed what we now can see were the two troughs of a double bottom at $44.50.

Those two lines still are established as horizontal resistance and support, and framed in black on our chart of HAL below. As you can see, the stock has yet to break under that lower line at $44.50. However, we have seen a move under the 100-day moving average for the first time in months. And with the 20-day line now back under the 50-day line, the short-term momentum, as well as the intermediate-term momentum, is confirmed as bearish. A move under $44.50 would seal the deal, but such a trend confirmation isn’t really necessary for most traders at this point.

Given what we know now about two major oil service and equipment stocks, it should come as no surprise that Schlumberger is in technical trouble, too. In fact, SLB might be closer to a meltdown than the others.

Like Halliburton and Baker Hughes, Schlumberger met resistance a few days ago at its 50-day moving average line, which just so happens to align with a longer-term — and falling — resistance line (yellow). Unlike the other two names on the radar, though, Schlumberger is in a descending wedge, where both the support and the resistance side of a trading range are pointed lower. This is doubly troubling.

Although SLB has yet to slide under that lower line (orange) of the wedge yet, the support and resistance lines are coming to a point; the stock will have to move outside of it soon, one way or another. Many traders are expecting a bearish move under the support side of the wedge shape, in light of the overall momentum. If that’s the case, it also will mean a move under the important 200-day moving average line at $80.71. The technical fallout from such a move could start a firestorm of selling.

Conclusions? Were it only one or two of these stocks under attack now, it might be easy to dismiss. It’s not just a few charts, however – most of the names in the oil equipment and services arena are painting the same picture. Weatherford International (NYSE:WFT) is off over -20% so far in 2011. Cameron International (NYSE:CAM) is down -10%. The list goes on.

The problem is, a pullback with this much breadth and depth is apt to last awhile, as it points to doubts about the industry at large – a much tougher hurdle to get past than a little volatility for an individual stock. It’s also unlikely any individual stock would be able to resist an industry-wide selloff like the one that seems to be brewing here.

Until the group as a whole decides to recover, none of these stocks are worth taking a swing on.

As of this writing, James Brumley did not own a position in any of the stocks named here.