API RP 67 Third Edition: Why the Standard Exists

The dangerous moment in a perforating job is not the shot. It is everything that happens before it.

Guns on the surface. Initiators in proximity to electrical systems. A wireline cable that runs from a firing panel through the wellhead to a detonator sitting inside a loaded gun string. Any one of a hundred steps between rigging up and firing, each one carrying the same fundamental risk: unintended initiation before the gun is where it is supposed to be.

API RP 67 — Recommended Practice for Perforating Safety — exists because of that risk. The standard covers the full perforating operation from the moment explosive equipment arrives on location to the moment it leaves. It addresses equipment design, handling procedures, pre-job electrical testing, arming sequences, and the accountability of the people involved. It is not a regulatory requirement, but it has become the closest thing the industry has to one for perforating operations.

The third edition updated that standard. Four changes are worth understanding in detail.

1. The Stray Voltage Limit

Unintended initiation from stray electrical current is one of the documented causes of perforating accidents. Current from power lines, generator returns, or other surface sources can reach a detonator through the wireline cable if the system is not properly isolated and checked.

The third edition introduced a defined limit for stray voltage: 0.25 volts. Surface electrical testing before arming must confirm that stray voltage at the firing panel is below this threshold. The limit provides a measurable, testable threshold rather than a general instruction to check for stray current.

2. Electrical Verification Before Ballistic Arming

The third edition formalised the sequence: complete all electrical testing and verification steps before any ballistic arming occurs.

This is a sequence requirement, not just a checklist item. The arming of a perforating system has two distinct stages — electrical and ballistic. Electrical arming connects the firing circuit. Ballistic arming makes the detonator live. The standard requires that the electrical stage is fully verified before the ballistic stage begins.

The practical effect is to create a defined gate in the procedure. You cannot move from electrical to ballistic until the electrical check is complete and documented. Informal practice in many operations already followed this sequence, but the third edition made it a named requirement with a defined order.

3. Initiator Categories: Group 1 and Group 2

The third edition formalised the segregation of initiating devices into two safety categories.

Group 1 initiators require a relatively low energy input to function. They offer less inherent protection against stray current, radio frequency energy, and electrostatic discharge. They require more stringent handling procedures and additional protective measures during use.

Group 2 initiators require a higher energy input. They provide greater inherent resistance to unintended initiation from stray current and RF. They are considered the safer default for general perforating operations.

The categorisation matters because it links the initiator type to the required handling procedure. A Group 1 device on location triggers specific precautions that a Group 2 device does not. Before the third edition, this distinction existed in engineering practice but was not formally codified in the standard.

4. The Explosive User in Charge

The third edition introduced the named role of Explosive User in Charge (EUIC): a single identified individual who holds operational accountability for the safe handling, use, and disposal of all explosive equipment on location.

This is a named accountability requirement. The EUIC is responsible for ensuring that all personnel involved in the perforating operation understand their roles, that procedures are followed correctly, and that deviations are recorded and addressed. The role formalises what competent operations already assigned informally to the senior wireline engineer or shooter.

The significance is that named accountability creates a clear line of responsibility that can be documented, audited, and trained to. Accountability that belongs to everyone belongs to no one.

Why These Four Changes Together

The changes are not independent. They form a coherent safety architecture.

The stray voltage limit gives personnel a measurable pass/fail criterion for a hazard that was previously assessed by judgement. The sequencing requirement creates a procedural gate that prevents ballistic arming before electrical safety is confirmed. The initiator categories link device selection to handling procedure, making the required precautions proportionate to the actual risk of the device being used. The EUIC requirement assigns clear human accountability for all of it.

Taken together, the third edition moved API RP 67 from a set of recommended practices toward a structured safety management system for perforating operations. The standard still does not carry regulatory force in most jurisdictions. Compliance remains voluntary. But for any operation that uses wireline perforating — and for any service company that wants to demonstrate it operates to the industry standard — the third edition is the reference.

The Source Behind This Post

The specifics of the third edition changes referenced here are drawn primarily from SPE-187206-MS, presented by David Ayre of BP Americas at the SPE Annual Technical Conference and Exhibition in 2017. Ayre was directly involved in the development work feeding the third edition and the paper documents the technical and procedural rationale behind the proposed changes.

If you are working in perforating safety or sitting on a task group, the paper is worth reading in full. The published standard itself is available directly from API.

The surface system used during a perforating job does not make the job safe on its own. Safe perforating is a procedural discipline, and API RP 67 is the document that defines it. What the surface system can do is give the people running the procedure the clearest possible picture of what is happening between the panel and the gun — and the time to act on it. That is what Warrior is built for.