Pneumatic lockout is more than closing the air valve. The air already in lines, receivers and cylinders can still move the machine: a standard 100 mm cylinder at 6 bar pushes with 4,712 N, about the weight of 480 kg.[1]
Four questions decide every pneumatic lockout:
- Where does air enter the machine, and is there more than one supply?
- Which valve isolates each supply, and can it be locked?
- Where is air trapped once the supply is shut: receivers, lines, hoses, cylinders?
- What moves or drops when that air is released?
Part 1: What Pneumatic Lockout Must Cover
Closing the supply valve stops new air. It does not remove the air already in the machine. After shutdown, residual pressure stays in receivers and throughout the system, in cylinders, pipes and hoses, and it can start a dangerous movement on its own.[2]
The same air may also be holding something in place: a vertical cylinder keeps a tool raised, a clamp grips a part, a gripper holds a load. Bleed the air and they drop or let go. DGUV therefore asks you to check both what the pressure can drive and what it prevents, before you release it.[2] Lower or block those parts first.
Two more traps. A jammed mechanism can build up pressure that is released at once when the jam is cleared.[2] And a closed directional valve can keep air locked in a cylinder after the supply line already reads zero.
EU machinery law sets the frame: lockable isolators, and a safe way to dissipate stored energy.[3] Our pneumatic lockout devices keep those points closed or disconnected.
Part 2: Pneumatic LOTO Valves and Devices
Compressed air is isolated at one of four kinds of point. Each needs its own device.
| Isolation point | Locked position | Device |
|---|---|---|
| Ball valve on the supply line or branch | Handle closed | Ball valve lockout and padlock |
| Lockable shut-off and exhaust valve (dump valve) at the machine's air service unit | Supply closed, downstream air vented | Padlock through the valve's own lock point; hasp for a group |
| Quick coupling or plug-in hose | Disconnected, cannot be reconnected | Plug lockout box or air source lockout |
| Bleed valve on a receiver or manifold | Open | Valve lockout or the valve's own lock point |
Where the machine has a lockable dump valve, use it as the main isolation point: one movement shuts off the supply and vents the air downstream. INRS asks for exactly this pair: isolating valves locked closed, bleed valves locked open.[4]
For couplings, the Pneumatic Air Isolation Box encloses plugs of 9 to 20 mm and takes up to four padlocks. The Pneumatic Male Air Lockout fits screwed joints of 12, 13 and 16 mm. For ball valves on the air line, the Universal Ball Valve Lockout fits valves from 6 to 101 mm (1/4" to 4"). Our guide to valve lockout methods compares the options for gate and butterfly valves.
Best Practice: Lock the bleed open, not only the supply closed. A supply valve that leaks slowly refills the line, and a bleed that someone closes again lets that pressure build. Leave the gauge at the work point where everyone can read it.
Part 3: The Procedure, Step by Step
EN ISO 14118 defines isolation and energy dissipation as four actions: isolate, lock, dissipate stored energy and verify.[5] For compressed air they become seven steps, written into the machine's own lockout tagout procedure:
- Prepare. Read the procedure, tell the operators, stop the machine with its normal controls.
- Secure what the air holds. Move vertical axes to their lower end position or support them; take parts out of clamps and grippers.
- Isolate every supply. Close the shut-off valve or disconnect the coupling. Include auxiliary circuits and any gas cylinder feeding the machine.[4]
- Lock and tag. Each person fits their own padlock and tag to every isolation point; a hasp takes several locks.[2]
- Bleed. Open the exhaust or bleed valves slowly, with the outlet pointing away from people, and lock them open. Vent any receiver on the machine.
- Verify. Read the gauge at the work point, not only at the supply. Try the start controls. Release air trapped between valves and cylinders as the procedure describes. Every system must be depressurised and checked for zero pressure before maintenance.[2]
- Restore. Tools out, people clear, each person removes their own lock. Close the bleeds, then apply air slowly: a cylinder with an empty chamber can jump when pressure returns.
Real-World Case: In a refinery, a pump was isolated, its valves closed and the section drained. One valve could not close fully because of deposits, so hot product under pressure flowed back. Nobody checked again before the cover came off, and the fitter was doused.[2] A closed valve is not proof; the reading at the work point is.
Machines with hydraulics as well need extra steps for accumulators, which store far more energy. Our guide to hydraulic lockout covers them.
Part 4: The Rules in the EU, Germany, Switzerland and France
- EU machinery law: Directive 2006/42/EC, Annex I 1.6.3, and from 20 January 2027 Regulation (EU) 2023/1230, Annex III 1.6.3: isolators lockable where reconnection could endanger people, stored energy dissipated without risk. Circuits may stay connected to hold parts only with special safety measures.[3]
- EN ISO 14118: the four actions above, for every energy type, pneumatic included.[5]
- EN ISO 4414: safety requirements for pneumatic systems on machinery. It excludes compressors and the factory's air distribution, receivers included, so your site procedure has to cover the network side.[6]
- Germany: BetrSichV §10(3) No. 7 requires devices that remove energy still stored after isolation, clearly marked.[7] DGUV Information 209-015 sets out the practice.[2]
- Switzerland: Suva's eight vital rules for maintenance include switching off and securing with your personal padlock (rule 3) and making stored energy safe (rule 4). Suva counts more than ten deaths a year in maintenance work.[8]
- France: INRS ED 6109 sets four operations for pressurised media: separate, purge, lock (isolating valves closed, purge valves open), verify.[4]
Part 5: Where The Lock Box Fits
Our pneumatic lockout collection holds the coupling and plug devices: the Pneumatic Air Isolation Box, the Pneumatic Male Air Lockout and the Stainless Steel Air Source Lockout (304 stainless steel, sources of 7 to 20 mm, two lock points), plus covers for gas cylinder valves. For shut-off valves, start with the Universal Ball Valve Lockout. Each person then adds a personal padlock and tag at every point.
Write each air isolation point, the bleed-down and the zero-pressure check into the machine's procedure with our free lockout/tagout procedure template (PDF, Word or Excel).
Not sure which device fits your couplings?
Send us the coupling type, plug diameter or valve size, ideally with a photo. Contact The Lock Box and we will suggest a device for each isolation point.
References
- Festo. Data sheet DSBC-100-80-D3-PPVA-N3 (part number 8165660): piston diameter 100 mm, theoretical force at 0.6 MPa (6 bar), advance stroke. https://docs.
rs- (accessed 2026)online. com/ 23f7/ A700000013130408. pdf - DGUV. DGUV Information 209-015: Instandhaltung an Maschinen und Anlagen, June 2026, pp. 50-51 (personal locks, valve lockouts) and section 5.2.3, p. 86 (residual pressure, accident example). https://publikationen.
dguv. de/ regelwerk/ dguv- informationen/ 338/ instandhaltung- an- maschinen- und- anlagen - European Union. Directive 2006/42/EC on machinery, Annex I 1.6.3, https://eur-
lex. ; Regulation (EU) 2023/1230 on machinery, Annex III 1.6.3, https://eur-europa. eu/ eli/ dir/ 2006/ 42/ oj lex. europa. eu/ eli/ reg/ 2023/ 1230/ oj - INRS. ED 6109: Consignations et déconsignations, 3rd edition, October 2020, chapter 6.1, p. 18. https://www.
inrs. fr/ dam/ inrs/ CataloguePapier/ ED/ TI- ED- 6109. pdf - ISO. ISO 14118:2017: Safety of machinery, Prevention of unexpected start-up, clause 3.3. https://www.
iso. org/ standard/ 66460. html - ISO. ISO 4414:2010: Pneumatic fluid power, General rules and safety requirements for systems and their components, scope. https://www.
iso. org/ standard/ 44790. html - Federal Ministry of Justice (Germany). Betriebssicherheitsverordnung (BetrSichV), §10 Instandhaltung und Änderung von Arbeitsmitteln. https://www.
gesetze- im- internet. de/ betrsichv_ 2015/ _ _ 10. html - Suva. Acht lebenswichtige Regeln für die Instandhaltung (84040.D), March 2022. https://www.
suva. ch/ 84040. d