Vent and darin for pipelines
Vent and darin for pipelines
(OP)
Normally high point vents and low point drains are provided for geas venting and liquid darining for hydrostatic testing in pipelines.This is not required after the hydro test unlike in piping within stations, where due to operations requirements, vent and drains are required afterwords also.
In the case of pipelines, containment of the fluid coming out of the vent/ drain is an issue as providing containers/ tanks or venting to atmosphere could cause envronmental issues and loss of product and sometimes even fire hazards.
I am refering to a case of a suggestion to provide a vent / drain point in a liquid sulphur pipeline, to contain the expanded liquid sulphur during remelting ( sulphur expands 10% during re melting) to avoid possible burst of pipeline due to abnormal increase of internal pressure.
Coul any body having similar experience comment on this, whetehr providing vents and darins is an acceptable solution inj this case?
In the case of pipelines, containment of the fluid coming out of the vent/ drain is an issue as providing containers/ tanks or venting to atmosphere could cause envronmental issues and loss of product and sometimes even fire hazards.
I am refering to a case of a suggestion to provide a vent / drain point in a liquid sulphur pipeline, to contain the expanded liquid sulphur during remelting ( sulphur expands 10% during re melting) to avoid possible burst of pipeline due to abnormal increase of internal pressure.
Coul any body having similar experience comment on this, whetehr providing vents and darins is an acceptable solution inj this case?





RE: Vent and darin for pipelines
The location (country) may influence the answer.
Where is this pipeline?
Sometimes its possible to do all the right things and still get bad results
RE: Vent and darin for pipelines
The pipeline is in one of the Middle east ( persian gulf) countries. It laid on the undulating sand dunes.
My concerns ( if this solution is adopted) are that to introduce the vent/ drain, there should be:
[i]Additioanl heating and insulation to make up heat loss.
[ii]Again to collect the spills, containment will be required- may be with heating and insulation.
[iii) I am not able to decide how many locations this facility should be there
RE: Vent and darin for pipelines
First, your comment "Normally high point vents and low point drains are provided for gas venting and liquid draining for hydrostatic testing in pipelines", Errr, no this is quite unusual. Normally pipelines, not piping, is swept through with one or more pigs (scrapers) with water to remove the air. fitting vents and drains is only valid for some water lines with low velocity.
Liquid sulphur lines need insulation and often trace heating to keep contents at 125 to 150C.
Re heating sulphur from a solid condition is a difficult operation and needs careful monitoring due to the large contraction / expansion and the particular properties of sulphur (very low heat transmission apparently). Vents or any taps would be virtually useless for this sort of product as you would need to pre-determine where the cold spots / solid parts were which could even be within one pipe length. Then you need to deal with liquid sulphur at 125C coming out from any vents. Your vents and drains would need to be heated to this level to avoid blockage.
This sounds like a very early concept issue to me, but you need to know what you're doing with liquid sulphur or you can very easily break the pipeline.
See this report on a sulphur pipeline break in Canada and what they did to avoid it in future. http://www.neb-one.gc.ca/sftnvrnmnt/sft/pplnrptr/a...
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Vent and darin for pipelines
Thanks for your very useful commnet. I agree to your point on pigging to remove air from pipelines.
Also to see the report on the incident on the sulphur pipeline failure, and I can foresee the situation.
This particular pipeline, is in laid among sand dunes with undulating terrain. It is difficult to decide the cold spots, though normally anchor supports are the heat sinks due to metal inserts. I understand that providing vents and darins will not be an easy solution, due to requirement of haeting , insulation and selecting the location and providing containment.
After having read the report on the failure (and also heard about incidents at other lcoations)of pipe burst during remelting, I am curious to know whether slower heating near the transition temeprature will be a better soultion to prevent / rule out the possible rupture while remelting.Or is there any other way to prevent the disaster.
I am requesting your valuable opinion, as I understand from your above comment that you are experienced in this field.
Thank you very much once again.
RE: Vent and darin for pipelines
Good temperature measurement throughout the line (fibre optic cable in contact with the pipe) is required / vital to understand what is going on.
It seems one option is then to rapidly heat the pipe top section near the heating cable to create a continuous channel where pressure can equalise / flow into areas where there are now voids due to the contraction of the sulphur. Once this is established, then slower heating can occur. However it seems there is always possibility of a shock or rapid rise in pressure.
Clearly the best option is not to get to that point and have sufficient reserve power supplies and Nitrogen to completely clear the pipeline inot the downstream plant if the upstream plant stops.
However some sort of plan is very much required for re-heat and at bigger cold spots you might need to provide extra heating.
Some of the trace heating companies seem to have good experience of this - look up Pentair and thermon.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Vent and darin for pipelines
In fact, on a query to Pentair, I got two suggestions
i) to install vents and darins at stretegic locations, with proper insulation
ii) to provide pressure relief valves and gauges at strategic locations.
I am not convinced with both the suggestions, as deciding the startegic location is not easy.There are so many high and low points. Containment is a problem. The line is outside station, as always teh case, not minitoired.
RE: Vent and darin for pipelines
The report from Canada has some good recommendations - I would see if you can find anything more about their procedures if I was you. They got it wrong before so what they have now will be informed by reality and hence should be much better.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Vent and darin for pipelines
I heard that there are about 40+ sulphur pipelines in the world, some of them are operating well, others are having problems when power fails, and insulation issues and eventually leading to rupture of pipeline. In most of the cases, failure occurs at the bends of expansion loops.
RE: Vent and darin for pipelines
and http://www.pentairthermal.com/Images/GB-SulfurTran... where they talk about their "proprietary sulphur re-melt program.."
Maybe you need to speak to the right person....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Vent and darin for pipelines
you must get smarter than the software you're using.
RE: Vent and darin for pipelines
you must get smarter than the software you're using.
RE: Vent and darin for pipelines
RE: Vent and darin for pipelines
From the above discussions, I understand that the alternative seems to be for incorporating containment of the excessive volume during remelting and allowing to glow to empty spaces ( created during solidification) and controlled heating with close monitoring of the DTS temperature monitoring system.
RE: Vent and darin for pipelines
I am bringing this point because, 31.4 do not specifically mentioning about liquid sulphur.
RE: Vent and darin for pipelines
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way