Monolithic joint location
Monolithic joint location
(OP)
Hi everybody. I have to design the last kilometer of a pipeline but I don't know the order to locate a monolithic joint and an anchor block. Please, someone could tell me if the order is mono - block - receiver or block - mono - receiver. Thanks.





RE: Monolithic joint location
RE: Monolithic joint location
RE: Monolithic joint location
RE: Monolithic joint location
I agree with you that anchor block should be avoided as far as possible, and in all caeses of pipeline where I was involved there was no anchor block. My comment was not on the requirement of anchor block, but on the location, if at all is required, as the query was that the Op does not know the location of "IJ and Anchorblock".
RE: Monolithic joint location
You are correct that the "normal" position of IJs , i.e. a few meters after it gets above ground, is often at a high stress location, but once you allow a support or some instrument on the pipeline side, the chance of insulation of the supports and instruments is low and hence the risk of current leakage to ground increases. Also the pipeline is then at a potential relative to earth and there is a spark and touch issue with bare or painted pipe.
Therefore you will fnd most IJs on the first level bit of pipe after it comes above ground as the least worst place. I'm not aware of systemic failure of IJs in these locations, but am open to more information...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Monolithic joint location
IMO there are far better locations for most instruments requiring connections back to plant, except perhaps for a pigsig. Most other instruments can be moved to station suction and discharge lines, on the station side of isolation joints, thereby being kept off the pipeline entirely.
The isolation joint itself may be responsible for creating the high voltage potentials. Isolation joints, when used, should be used with cathodic isolators and spark gaps, which prevent dangerous voltage level build-ups across isolation joints and flange kits. 2005 NEC had some significant changes to plant grounding requirements. Launchers/receivers should be earthed like this http://ecmweb.com/design/cathodic-protection-syste..., including a cathodic isolator where applicable. More info on that equipment at, http://www.cathodic.co.uk/files/124280955112186137...