A method we can utilise to clean gaseous systems is via blowing, my blog today looks at this process.
Prior to me describing the main stages here, please let me stress that an engineering professional should always evaluate the stored energy scenario for the blows that are about to take place, so safety margins for the piping or vessel system are not compromised, if in doubt please seek professional guidance and advise.
Blowing by its nature has elements of risk, hence any blow to clean construction and or other potential debris from piping systems must have safety implications given to it first and foremost. I do not profess to know answers to all scenarios and you must in your blowing activities, access each blow on its own merit, however key safety considerations should be:
- The depression point from pipe system must be secure and clamped/fastened down
- None essential personnel must be removed from the area
- Adequate PPE must be worn, consider a duel line of ear protection, and face visors
- The blowing activity should be well demarcated and signed posted
- Adequate stand-by men and area access supervisors must be in position
- Communicate well to local other work parties and departments the pending blow.
- Indicate by the sounding of a horn the imminent blow procedure
… there are other considerations, the above is a typical guide.
When blowing a line clear of debris there are some other general factors to consider…
- Can I use the process medium or do we use a temporary source of clean energy, if an air make sure the air is clean, dry and oil free!)?
- Are we going to utilise the “piston blow” method for of cleaning, e.g. the line to be cleaned is pressurised and then rapidly depressurised to blow out dirt and debris or…
- … do we us a reservoir type blow where a vessel is pressurised and then the pressure rapidly released into and out of a pipe system to remove the debris?
- I would recommend using either method to blow as a minimum three separate times, monitoring the outlet for signs of debris. If dirt is still coming out, keep the blows going until it is clean.
- Always inform the source provider for the energy, so when you are pressurising your line, their overall system pressure is maintained, you may have to pressurise over a short period of time?
- A good practice is never to blow into a plant item or vessel, always blow away
- Blow down to encourage debris out, avoid blows which require the debris to go up as an exit route.
- Blow from as many extremity and low points as possible
So how do I know a line is really clean, especially on a delicate duty such as Instrument Air? Well there are two methods we could consider, 1. Blow to a target plate, we can monitor the impressions on a soft metal faced bar, such as brass and blow until we see limited or no impressions, or 2. A much less complicated process is to blow onto a white rag and blow a line until no more dirty marks appear on the rag.
So something as simple as a blowing activity has a number of implications which must be consider, plan for and incorporate, just another aspect to our important work.
Safe and successful commissioning always…
