Connect tube to pipe
Connect tube to pipe
(OP)
Hi there
We just had an incident where a tubing connected to an end flange snapped and caused a chemical burn to the operator? Does anyone know what is the design/fabrication standard on tube to pipe/flange connection?
Tq
We just had an incident where a tubing connected to an end flange snapped and caused a chemical burn to the operator? Does anyone know what is the design/fabrication standard on tube to pipe/flange connection?
Tq





RE: Connect tube to pipe
Generally a tubing compression fitting male connector is attached to the pipe by any joining method permitted in the piping code and your piping specification. Generally a valve is installed at transitions like this such that leaking tube joints can be repaired without draining the piping.
Making the connection at a threaded or flanged joint allows you to easily renew the male connector when it is beyond its service life. All compression fittings have a limited number of assembly/disassembly cycles before they start to leak in a way that can't be repaired just by tightening. Tube fittings welded directly to pipe or to pipe tees can be used where permitted by piping specifications and code, but repair of the tube fitting will then require the fitting to be cut out and a new one welded in place.
Some vendors of fittings sell flange adapters which consist of a flange and male connector body machined from a single forging. It is not necessary to buy these but they are convenient if you have no access to welding and threading is not permitted. Instead, you can use a threaded or socket weld reducing flange, or if the flanged joint is large enough relative to the tube fitting to fall within the limits imposed by ASME B16.5, you can drill and tap or weld to a blind flange.
In addition to the block valve to isolate the tubing from the pipe, a check valve immediately at the injection point is a good idea in cases where the tube is being used for chemical addition. That's of no use for sample points or instrument taps though.
Tubing needs to be physically safeguarded against mechanical damage in areas where such damage is likely. Physical safeguarding is essential if the tubing is plastic.
RE: Connect tube to pipe
In terms of design and fitting good workmanship requirements come into play more than a set standard or "code".
The individual fittings are more of a vendor specific design and generally accepted methods of installation. Instrument tubing is not strong and care needs to be taken to ensure the connections are not subject to excess stress, either axial, sheer, fatigue / vibration etc.
It's a big pity the operator has been injured, and hopefully a root cause analysis will show why and then an inspection of other similar connections undertaken to identify any others where poor design or installation has taken place which could overstress the tubing.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Connect tube to pipe
RE: Connect tube to pipe
RE: Connect tube to pipe
The fittings though are normally much thicker and stronger than their connecting pipes hence why there is nothing more than the type testing from reputable vendors.
You do need to be aware of potential fake fittings though - might be worth trying to find where they came from.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Connect tube to pipe
If you are injecting 98% sulphuric acid into water in an arrangement like that, you've had a corrosion-related failure that has nothing to do with galvanic corrosion and everything to do with heat of dilution/hydration of the acid and the lack of resistance of either carbon or stainless steels to intermediate strength sulphuric acid. You need a proper dilution spool and injection quill, made of materials of construction resistant to what you're producing in that spool.
RE: Connect tube to pipe
RE: Connect tube to pipe
RE: Connect tube to pipe
Too much damage and unclear what the original fitting was to really judge from afar.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Connect tube to pipe
RE: Connect tube to pipe
Leakage rapidly leads to dilution due to pulling water from the atmosphere which causes dilution and rapid external corrosion.