pigging pipelines with Air Compressor 1

[Cyrius]

1.Does any one know of a way to calculate the movement of a pig, such as a construction pig through a line when being pumped with an air compressor with a max. operating pressure of 125psi and a displacement of 150 CFM.
2. Also how would you calculate the time it would take to run the pig through the line when pushing it with such a compressor?
I have come across a problem with using the ar compressor to push a 6" pig through a line that is 15 km long. The compressor is maxed out at 125 psi and I do not know how to determine whether the pig is stuck or whether the compressor is not large enough to complete the task due to length of line and pressure loss.

Any help on P drop in pipeline or Pigging experience is greatly appreciated.

 

[saxon]

Cyrius, Is the compressor going into the unloaded mode when you reach the 125 psi set, or does it cycle between the loaded/unloaded modes? This will tell you wether or not the pig is moving in the line (volume change occuring with pressure drop). If the pressure hits the 125 set and the comp. unloads and stays that way, you either don't have enough force behind the pig or it's stuck. If it's cycling the pig is probably moving,or you might have, line leaks or a pressure drop below the needed movemnt force to drive the pig causing a discontinous pig movement.
As for the driving force on the pig use the following formula:

F=pA
Where: F= force, lbf
p= pressure, psi
A= pig seal area. in^2

As for the length of time required to move/fill the pipeline/pig (provided there is enough force to move the pig continously or it's not hung up) can be estimated as follows:

t= v/Q
Where: t=time to fill pipeline, min.
v= system volume, ft^3
Q= Comp. output cap., ft^3/min.
Hope this helps.

saxon

 

[Cyrius]

Thank you saxon.
This has given me some more insight into the behavior of filling a pipeline and is greatly appreciated.

Another question:
Does anyone know where I could obtain displacement vs discharge pressure graphs for an Ingersoll-Rand industrial compressor. I cannot find on at the IR website. Originally I was hoping that the relationship between backpressure and compressor displacement was linear but from first hand experience I believe it to be exponential. Does anyone know the true relationship between the backpressure a compressor would experience from a pipeline during pumping a pig and the displacement of the pump at the relavent pressure

 

[macfa1]

cyrius,

to work out the time it will take the pig to travel through the line, simply find the flowrate through the line multiply by 3600 and divide by 1000 to get the answer in km/hr and then you can work out how many hours it will take fo your pig to go 15km's (as long as you work out your flowrate in m/s).
By the way if you have valves along the line that are not fully open the pig could get trapped, especially if they are cavity valves. I know this because it happened to us in '96.
Take care,
A

 

[pardal]

try here

http://air.irco.com/

and do not forget to use searcher engines Pardal

 

[svanels]

The back pressure is related to the system resistance, thus the manufacturer has no way to construct graphs relating the 2 things. Steven van Els
SAvanEls@cq-link.sr