Compressor gets hot and blows line

[bachster]

Originally Posted by FrankJ

Not only is it good practice, but the relief valve is required to be teed to the compressor with a metal fitting by rule.

Technically, R87 states:
The relief valve must be attached directly to the compressor or attached by legal fittings connected to the compressor output port. If using an off-board compressor, an additional relief valve must be included on the ROBOT.

I agree a metal tee fitting is the best here. However, I think I had a RI or LRI last year state that tubing and plastic fittings would be allowed between the compressor and relief valve as these are considered "legal fittings." Of course, "legal fittings" are not explicitly defined anywhere I can tell.

R77 explicitly allows only:
A. Items available in the 2014 KOP,
...
E. Additional pneumatic tubing, with a maximum 0.160 in. inside diameter, functionally equivalent to that provided in the KOP,
F. Pressure transducers, pressure gauges, flow control valves, and connecting fittings,
...

There is also R75:
All pneumatic items must be COTS pneumatic devices rated by their manufacturers for working pressure of at least 125psi (with the exception of R77-D).

I don't read this combination of rules to mean that tubing would be a "legal fitting" to be used in between the compressor and relief valve (it's tubing, not a fitting). I did inspect a robot last year which had a flow control fitting (and tubing I think?) in between their compressor and relief valve. This is clearly an unsafe condition to me - if the flow control fitting was closed, it would prevent the relief valve from doing its job, instead allowing the compressor and fitting to reach higher than 120 psi. I think I had another team using their vent plug in between the two, which presents the same issue. I did require both teams to switch to the standard metal tee implementation (which they had to borrow - maybe part of the problem is these brass fittings are no longer included in the KOP).

To me, using normal push-connect fittings and tubing in between the compressor and relief valve is still potentially unsafe (and in my interpretation illegal), as any sort of blockage (floating thread wrap, melted tubing, etc) which could present itself in this path would prevent the system from venting at 120 psi. The heat from the compressor affecting the integrity of the tubing is another great point.

Al, would you say that the proper interpretation of R87 is that "legal fittings" are only metal tees? Or is the fall back to R8, for unsafe condition? Thanks!

Katie