water sampling line

Dear,


I need to take water sample for water quality measurement from a buried pipe, the pipe is buried in the sand, so the contractor will have to open the trench and then include a tapping point on the main line. please advise if this is feasible.


Second option, I can take water samples from downstream an electromagnetic flowmeter located on a flowmeter chamber, however, I am not sure if this sampling will affect the reading of the flowmeter, so to be safe, I guess it is better to keep the sampling line at least 3D downstream the flowmeter.


Please advise which method to you find it more suitable considering that in the first option, the buried pipe will be closer in distance to the water quality analyzer.


thank you, any thoughts on this issue are really appreciated.


Charbel

If you are going to use the sample point to close a control loop, you want the lag time as short as possible. You also want it far enough downstream to ensure that any chemical feed points have adequate mix time to ensure they don't interfere with your analysis.

I have some closed loop chlorine controls that are really hard to dial in because it takes ten minutes for a step change in CL2 feed rate to make its way back to the analyzer. If you are not automating this, then the long lag time is typically not a big deal.

Most sampling analyzers flow at a very low rate, so depending on the size of the main line, it is unlikely to affect the magmeter, but it is good to follow their guidelines and keep all disturbances outside the specified minimum diameters like you stated. If the flow meter comes into question later for any reason, you don't want to give them any reason to point the finger back at you. You didn't say if this sampling point will be a constant flow inline type of instrument, but that is what I envisioned.

Whether you can put a tapping point on the pipe depends on what the pipe is made of.

BryanG said:

Whether you can put a tapping point on the pipe depends on what the pipe is made of.

Click to expand...

I have seen it done on just about every type, they call it hot tapping, some water systems use can freeze them with liquid nitrogen, you can also use a saddle type and drill out a plug... the guys that are nuts are the ones that do natural gas lines