Slant cut on Relief Valve Outlet Piping
Slant cut on Relief Valve Outlet Piping
(OP)
Does anyone know why there is a slant cut on RV outlet piping to atmosphere? Is it supposed to "direct" the gas stream or is it for increased area? Is it related to wind direction or should just be pointed away from personnel/equipment?





RE: Slant cut on Relief Valve Outlet Piping
RE: Slant cut on Relief Valve Outlet Piping
RE: Slant cut on Relief Valve Outlet Piping
RE: Slant cut on Relief Valve Outlet Piping
RE: Slant cut on Relief Valve Outlet Piping
It is recommended that all discharge lines exhausting to atmosphere be square-cut for our plants.
This also helps to increase dispersion to the atmosphere. Condensate for non-hazaradous fluids can be removed via a small drain line at the bottom of the stack; large amounts of liquid may require a KnockOut Pot or other separation method.
Also, with the slant-cut it is more difficult to prevent rain from entering the vent pipe. Plastic caps are sometimes used on the end of a vent pipe to prevent rain from entering. The problem is that people forget they are there and do not replace them if there is a release.
With a square cut it has been reported that the discharge pressure and noise is less than with the slant-cut; but I do not have the theoretical basis for this observation.
Hope this helps, bottom line, you can slant-cut the line if you wish; but it results in nothing but negatives which you must then over-come.
The only situation I can envision where I might want to consider a slant-cut would be to help direct the discharge away from a working area where I did not have enough building steel to exhaust the discharge at a safe elevation and location. Of course, installing the needed steel may be the beter option.
Regards,
Charlie
The more you learn, the less you are certain of.
RE: Slant cut on Relief Valve Outlet Piping
The slant cut would be a diaganol directed away from the RV (and inlet nozzle). To try and describe it graphically, consider (./\). The period is the inlet nozzle connection at vessel. The back-slash is the slant cut directed away from the RV. As CHD01 noted above this produces a lateral reaction force component and combined with the vertical component the net force (the front-slash in the graphic) being directed back to the nozzle rather than just a lever moment directed down if it were just a square cut end on the outlet.
Of course, this shouldn't be taken out of context and unfortunately I can't remember all the details and circumstances of the reference. As always, taking things out of context can lead to unintended practices. Seems like a square cut end with proper vertical support would be better but my job function is not piping design or stress analysis.
If no one at your plant can answer the question, this may be an unintended application of the practice. You may want to confirm the piping design is adequate for your installations. I know of one company's practices which prohibit slant cuts to avoid the horizontal reaction component unless piping stress analysis has been performed.
RE: Slant cut on Relief Valve Outlet Piping
Some folk use the tapped connection above the inlet nozzle (actually connects to the body outlet) for a rainwater drain as even a weephole in the outlet pipe tends to plug. I think that this was originally intended as a pilot warning connection to show the operator that the relief valve was blowing, but its use appears to be lost.
RE: Slant cut on Relief Valve Outlet Piping
RE: Slant cut on Relief Valve Outlet Piping
The more you learn, the less you are certain of.
RE: Slant cut on Relief Valve Outlet Piping
One thing is known, it increses the cost of the discharge pipe. BTW, don't forget the weep hole on the bottom side of the discharge pipe.
RE: Slant cut on Relief Valve Outlet Piping