An engine can have an emergency shutdown system and still rely on someone being there to activate it. But what happens when no one is around?
For gas and chemical plants, engines power everything from service vehicles and compressors to generators and pumps. Not all of this equipment operates under the same conditions, and not every shutdown system works the same way.
So, when is an automatic air shutoff valve necessary, and when is manual activation enough? It comes down to how the engine is used, who’s operating it and the safety requirements that apply.
Do All Industrial Engines Require Automatic Air Shutoff Valves?
The short answer is no. Not every industrial engine is subject to the same automatic shutdown requirements.
It depends on:
- Where the equipment operates
- Whether someone is always with it
- Whether it could be exposed to combustible gases
- Which safety rules apply to the site
Offshore drilling and onshore refineries are a good example of how different those rules can be. For example, federal rules for US offshore drilling (30 CFR Part 250) treat attended and unattended diesel engines differently.
Onshore refineries operate under different regulatory and site-specific safety requirements. Equipment entering potentially hazardous areas may be subject to facility rules that determine whether positive air shutoff protection is needed.
Having an engine shutdown system doesn’t automatically mean you have positive air shutoff protection.
How Does an Automatic Air Shutoff Valve Work?
During a diesel runaway, an engine starts pulling hydrocarbons from the surrounding air through its intake. Those vapors act as a second fuel source, so closing a fuel shut off valve may not stop the engine.
A positive air shutoff valve solves that by cutting off the engine’s air supply. No air, no combustion, and the engine stops.
ShockerPASS provides positive air shutoff protection for internal combustion diesel engines. It comes in two activation configurations:
- Automatic: The valve closes on its own when the engine overspeeds. No operator needed.
- Manual: An operator triggers the shutoff with a switch.
See More: Automatic vs Manual Engine Shut-Off Systems
Both protect the engine. The right choice depends on the equipment and how it’s used.
Not sure which configuration fits your equipment? Talk to our team about ShockerPASS, and we’ll help you sort it out.
Where Are Automatic Air Shutoff Valves Used Onshore and Offshore?
Onshore Refineries: Vehicles, Stationary and Mobile Equipment
Refineries run a mix of permanent equipment, mobile fleets and temporary machinery. During a turnaround, contractors bring in even more, including:
- Service vehicles
- Portable compressors and pumps
- Generators
- Light towers
These engines can have different shutdown setups, and they often move between areas with different rules. That raises a simple question for refinery safety teams: Does every engine entering a designated area meet the facility’s air shutoff requirements?
An automatic air shutoff valve makes sense for equipment that runs without constant supervision, or anywhere the site calls for an automatic response to overspeed.
Pay close attention to contractor equipment. A machine that meets one site’s requirements may not meet another site's. Checking air shutoff requirements during turnaround planning leaves time for any changes or retrofits before work begins.
Planning a turnaround? Get a ShockerPASS quote early, so retrofits are done before contractors roll in.
Offshore Drilling: Unattended Engines and Shutdown Requirements
Offshore, many engines run with no one standing beside them. Generators, compressors and other equipment can run for long stretches, so whether a shutdown is manual or automatic matters.
In the U.S., Federal Outer Continental Shelf regulations (30 CFR 250.405, 250.510, and 250.610) require diesel engines used in drilling, well completion, and well workover operations to have air intake shutdown devices. The rules split engines into two groups:
- Continuously attended engines: Remote manual or automatic shutdown devices are allowed.
- Unattended engines: Automatic shutdown devices are required.
Some engines are exempt, such as those powering firewater pumps or emergency generators.
For offshore equipment specifiers, that means looking past whether an engine has an emergency shutdown device. How it’s activated, what the equipment does, and which rules apply all determine whether an automatic air shutoff valve is the right fit.
What Should You Consider When Choosing an Automatic Air Shutoff Valve?
- Engine compatibility: Does the system suit the engine type, size and setup?
- Activation method: Does the job call for manual activation, automatic overspeed response or both?
- Operating conditions: Is someone always with the equipment, or does it run on its own?
- Installation: Can the positive air shutoff valve fit into the existing engine setup?
- Site requirements: What shutdown rules apply to the facility, the equipment and its location?
Get the Right Air Shutoff for Every Engine on Site
Whether it’s a generator on a rig or a contractor’s light tower during a turnaround, we’ll help you match each engine with the right ShockerPASS configuration. Tell us what you’re running and where, and we’ll take it from there.