I’ve run enough wireline strings to know when something feels off. You get that subtle tension shift, or the switch test just doesn’t sit right, and you know deep down: something’s not right inside the string. But this one had me scratching my head.

We’d done everything by the book—gunstring checked, logging cable verified, switch test completed. It wasn’t until we lifted the wireline tools off the ground that the issue showed up. A switch test that passed seconds before began to fail intermittently.

I’ve learned the hard way that in wireline and perforating, intermittent failures are worse than outright ones. They lead to second-guessing, wasted time, and misruns. What we eventually uncovered was a sneaky problem inside the weight bar—one that’s now part of every rebuild and every training course I teach.

The Problem: A Loose Lock Ring Inside the Weight Bar

During the breakdown, we found the root cause: a loose lock ring inside the weight bar. It had backed off a few turns over just 3–4 runs. This lock ring, which holds the internal components—or “guts”—in place, wasn’t seated properly during its last rebuild.

Some of our wireline units still used older weight bars without locking collars, so the crews weren’t familiar with how to secure them. And that unfamiliarity led to a failure we couldn’t see from the surface.

That ring was supposed to prevent the internal rod and contacts from sliding within the bar body. Instead, they were moving just enough to cause intermittent contact—clean on the bench, faulty once hanging from the wireline truck.

This issue, though minor in appearance, caused misruns and several hours of non-productive time. In a high-efficiency cased hole wireline environment, that’s unacceptable.

Where It All Went Wrong

The reality is, most crews only tear down the weight bar if something’s obviously wrong. That mindset works… until it doesn’t. With horizontal wireline jobs pushing the limits of string length and complexity, the smallest misalignment can stop a run cold.

And here’s the thing about intermittent gunstring failures: they never fail on the test deck. They wait until you’re 5,000 feet in and fully committed. That’s when the wireline control systems flash a red flag, and you’re left guessing whether to pull out or go for it.

That uncertainty costs time, trust, and money—especially in the current wireline services market, where clients are watching every run, every minute, and every shot.

What We Changed: New Lock Ring Inspection SOP

After identifying the issue, we rolled out a detailed standard operating procedure for weight bar lock ring inspection and rebuilds. It’s now a required part of every job, not just perforating services, but also during:

• Production logging services

• Cased hole logging

• Plug and abandon operations

• Formation evaluation jobs

• Fishing wire line and pipe recovery operations

• Even when preparing for CBL logs or downhole camera use

Here’s how we do it now:

Step-by-Step: Weight Bar Lock Ring Rebuild and Verification

1. Full Tool Breakdown

• Remove all subs.

• Slide the internal rod out completely.

• Visually inspect the insulation, pin contact, and wear surfaces.

2. Lock Ring Identification

• Confirm if the weight bar uses lock rings (not all do).

• If yes, use the lock ring removal tool to back the collars off completely.

Tip: Lock rings typically have four tool slots. Some require specific tools, so each wireline trailer is now stocked with the correct set.

3. Component Rebuild and Inspection

• Remove internal rod and contacts.

• Check for electrical continuity, exposed wiring, and contact length.

• Replace all worn insulation or damaged collars.

4. Lock Ring Reinstallation

• Tighten both lock rings firmly.

• Understand that tightening one does not automatically seat the internal rod. Both rings must bottom out, securing the guts in place.

Important: The rod must not slide within the weight bar after both collars are torqued. If it does, disassemble and retighten.

5. Document and Verify

• Record rebuild in job prep sheet.

• Sign off by lead operator and engineer before use.

• Repeat this process before any pump down perforating or wireline perforating job.

Why This Matters for the Wireline Oilfield

In today’s wireline oilfield, where cased hole well services are under pressure to perform flawlessly, problems like this can’t be tolerated. A loose lock ring might not seem like much—but it can:

• Prevent perforating guns from firing

• Lead to short or open circuits in the gunstring

• Cause costly delays in perforation well execution

• Trigger unnecessary fishing operations

• Damage client confidence in the wireline provider

Adding This to Wireline Courses and Crew Training

This issue has become a core part of our wireline courses and crew onboarding. New engineers and operators learn:

• How to identify weight bars with and without lock rings

• How to use the removal/insertion tool correctly

• How to test for movement in the rod

• Why intermittent contact is worse than complete failure

• How rebuild quality affects well integrity and wireline service reliability

We use real field photos, failed run data, and mock tools in class to reinforce these lessons.

Building a Better Wireline Business Starts With Details

As a wireline company, we’ve learned that the biggest threats to operational success are often the smallest parts. Not the pressure control equipment, not the wireline gun, not even the logging cable—but something as simple as a lock ring.

If you’re trying to scale your wireline services, expand into new cased hole logging markets, or maintain a high-performing wireline truck fleet, this is where it starts: rebuild discipline, inspection culture, and tool ownership.

Final Thoughts – Secure the String Before You Run

Every run begins with a check. Every success begins with preparation. And every misrun usually starts with something someone assumed was fine.

Don’t assume.