This seems like a piping question to me, but if it's in the wrong area, please let me know.
At my company, we've been working on refurbishing and repackaging a couple Ariel recips that originally started as gas compressors and are being turned into higher-pressure syngas compressors. One is an Ariel JGK/4 taking gas from about 280 psi to 2000 psi in 4 stages, and the other is a JGH/2 taking mostly hydrogen (~70 mol%) with some other components from 2000 psi to 2200 psi in two stages. We've replaced most of the parts including the cylinders, pistons, and pulsation bottles on both.
Since I haven't been supervising the refurb and I haven't spent much time with recips, I just noticed that all of the cylinders have flat faces where they mate to their inlet and discharge bottles. The bottles all use standard ASME 16.5 raised-face flanges for the mating flange. Currently, someone has sandwiched spiral wound gaskets between all of the bottles and their cylinders, so we've got a spiral-wound gasket between a flat face and a raised-face.
I've always thought and read various places that flat-to-RF pairings are not to be done. I know the ASME Code says that it's okay to mate RF flanges to Class 125 or 250 flat-face cast-iron flanges IF you shave off the raised face on the RF flange and use a full-face gasket. However, those flat-face Class 125 and Class 250 flanges are for much lower pressures than I'm dealing with in most stages of these compressors. (All the cylinders are ductile, not cast, iron by the way and rated for the pressures we need.) Further confusing me is the fact that the tapped bolt hole circles on the cylinders perfectly match those for the Class 300, 600, 900, and 1500 raised-face flanges being used for the bottles. It's like Ariel is saying, "It's okay to treat the cylinders like standard RF flanges and use RF gaskets like spiral-wounds."
What is going on here, though, and is this reasonable and safe? I already have my compressor technician calling Ariel to find out more about this, but he says that ALL of their cylinders are flat-faced from what he's seen over the years. Ariel's website seems to confirm this. However, these are very high pressures and a lot of hydrogen we're talking about. I've had other engineers suggest I should be using RTJ flanges for these types of conditions for other equipment. In fact the pulsation bottle designers had us put RTJs on the inlet and discharge nozzles of each bottle-cylinder-bottle assembly, but still specified standard raised-face flanges for the bottle-to-cylinder pairings. I just don't want any leaks because of improper flange matings, and what I'm seeing goes against everything I've previously learned about the subject. I could really use some help sorting this conundrum out. Thank you.
At my company, we've been working on refurbishing and repackaging a couple Ariel recips that originally started as gas compressors and are being turned into higher-pressure syngas compressors. One is an Ariel JGK/4 taking gas from about 280 psi to 2000 psi in 4 stages, and the other is a JGH/2 taking mostly hydrogen (~70 mol%) with some other components from 2000 psi to 2200 psi in two stages. We've replaced most of the parts including the cylinders, pistons, and pulsation bottles on both.
Since I haven't been supervising the refurb and I haven't spent much time with recips, I just noticed that all of the cylinders have flat faces where they mate to their inlet and discharge bottles. The bottles all use standard ASME 16.5 raised-face flanges for the mating flange. Currently, someone has sandwiched spiral wound gaskets between all of the bottles and their cylinders, so we've got a spiral-wound gasket between a flat face and a raised-face.
I've always thought and read various places that flat-to-RF pairings are not to be done. I know the ASME Code says that it's okay to mate RF flanges to Class 125 or 250 flat-face cast-iron flanges IF you shave off the raised face on the RF flange and use a full-face gasket. However, those flat-face Class 125 and Class 250 flanges are for much lower pressures than I'm dealing with in most stages of these compressors. (All the cylinders are ductile, not cast, iron by the way and rated for the pressures we need.) Further confusing me is the fact that the tapped bolt hole circles on the cylinders perfectly match those for the Class 300, 600, 900, and 1500 raised-face flanges being used for the bottles. It's like Ariel is saying, "It's okay to treat the cylinders like standard RF flanges and use RF gaskets like spiral-wounds."
What is going on here, though, and is this reasonable and safe? I already have my compressor technician calling Ariel to find out more about this, but he says that ALL of their cylinders are flat-faced from what he's seen over the years. Ariel's website seems to confirm this. However, these are very high pressures and a lot of hydrogen we're talking about. I've had other engineers suggest I should be using RTJ flanges for these types of conditions for other equipment. In fact the pulsation bottle designers had us put RTJs on the inlet and discharge nozzles of each bottle-cylinder-bottle assembly, but still specified standard raised-face flanges for the bottle-to-cylinder pairings. I just don't want any leaks because of improper flange matings, and what I'm seeing goes against everything I've previously learned about the subject. I could really use some help sorting this conundrum out. Thank you.
