SAFETY ADVICE WHEN EXCEEDING MFG RECOMMENDED AIRLINE SETUP
There’s nothing more important to life than oxygen. Compromise the flow of oxygen to one’s blast helmet and you literally put life at risk.
BlastOne received a call from a client whose team was working within a penstock, 457 meters (1500 feet) from the breathing air filter. The crew were complaining about the lack of air flow. Manufacturers recognize 91 meters (300 feet) as the maximum recommended distance for one’s breathing air-supply hose. So what happens when you find your project conditions extending beyond the optimal manufacturer’s recommendations?
WARNING: If for some reason it’s impossible to comply with the manufacturer’s limit on hose distance – there are some general safety measures that must be adopted. The following information is a general workaround for situations where contractors are unable to comply with mfg recommendations – but our suggestions may not be applicable or safe for all scenarios. Always consult expert advice for your particular situation.
First, use caution and have a knowledgeable supervisor test pressures to the operators’ helmets to ensure sufficient air flow is reaching your team.
Next, understand the flow rate capacity of the air filter. We recommend drawing a flow rate through the breathing air filter no higher than 50 CFM.
• If you’re using a standard flow control device without cooling or heating your air, you can potentially run six operators off one breathing air filter. This is because each operator requires approximately 6 CFM to breathe easily.
• If using core tubes (heating/cooling) – which is common practice in the field – you need to allow 25 CFM per operator; which means 2 operators are maximizing the capacity of a single air filter.
Finally, understand the significance of hose diameter when exceeding mfg recommended distances from the air supply. Typically, in traditional set-ups, we always recommend running a 19-25mm (¾ – 1″) air hose through the breathing air filter – then a maximum of 91 meters of 10mm (300 feet of 3/8”) breathing air hose to the operator. However, when exceeding the maximum 91 meters distance, we recommend running a larger sized breathing air hose for those long lengths. In our client’s penstock situation (457 meters) we’d recommend using a 25mm food grade hose to cover the span. It needs to be food grade to avoid breakdown of the lining, which feeds toxic smells and odors to the operators. Again – even with this larger hose, a knowledgeable supervisor still needs to test air flow pressures to the operators’ helmets.