ME Air Compressors

'tried to get a thread going on this a short while ago, but haven't been able to follow up due to pc probs:- I have a small air compressor in the workshop. It's one of those cheap
ones marketted under various names (Clarke, etc). I've had it about 7 years now and it's given no trouble. But the nagging doubt is the internal condition of the resevoir. I always remove the drain plug to 'blow it down' when the pressure has dropped to about 10psi to release the condensate. It's the thought of a resevoir tank failure at 100psi that prompts the question. . . . . . . What's good practice for these? Should they be hydraulically tested once in a while? Will the motor expire before the tank?
Any guidance/reassurance welcomed.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hi I can only talk from a company viewpoint.

Good and essential practice, I open the drain plug at full pressure, rather I crack the plug open.

The compressed air regulations state that I must appoint an qualified inspector to assess the equipment on a yearly basis. So far the inspector has only done a 'visual' ie remove the inspection plugs/mud hole doors and look inside the vessel for rust pits etc. Check that the safety valve works and that the pressure is within that stated on the original tank certifiate.

My compressors are now about 8 years old and so at some point I am expecting to have a hydraulic test, at that stage I shall probably buy new compressors. Bad news is the cost of the inspection was 135 for the first inspection and 'air schedule' report and then 80 (roughly) per year. I hope this helps. Cheers Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 7 Jan 2004 10:15:17 -0000, "Dave Jones"

My *understanding* is slightly different, but please don't act on it without checking first. When I last had my receiver checked, I was told that the rules had changed somewhat, and that the surveyor now had the discretion to recommend a survey interval, of up to 4 years. Perish the thought that the insurance companies & surveyors wouldn't want that too widely known. <g> This particular surveyor was about to retire, so wasn't worried about loss of work, & quite happily gave me a 4-year certificate, on a (very substantial) 30-year old receiver. Trouble is, that was about 4 years ago & he has retired now :-( Individual *Insurance company* requirements may still be for annual inspections, of course.
Cheers Tim Tim Leech Dutton Dry-Dock
Traditional & Modern canal craft repairs
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've asked myself the same question. I assume the tanks are proof tested when made, which means that any defects in welds must be small. If the designers have got it right, the cyclic stress levels in service will be too low for fatigue cracks to propagate and in any case for domestic use you probably won't be using it daily. So internal corrosion is the important degradation mode. Periodic blowdown will help keep it dry.In steel, the corrosion will take the form of localised pitting, and if it procedes to failure you will have a small pinhole (and will know about it). You shouldn't end up with the tank, or large pieces of it, flying around provided you don't overpressurise it. The compressor should "run out of puff" at a safe pressure even if the pressure switch fails. Also, with a pressure switch and a separate relief valve you need two simultaneous failures to overpressurise. In a fire, the rubber seal in the relief valve should fail before the tank even if the valve is stuck.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks to all for replying. I suppose I'm reassured ! Blowing down seems clearly helpful and I always leave the resevoir plug out during periods of inactivity. No one (so far!) has reported any catastrophic failures with these little units, so that's consoling.
IanC.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.