Piping inside box culvert vs buried pipe
Piping inside box culvert vs buried pipe
(OP)
Hi All,
I am currently designing uPVC Sch80 chemical dosing lines containing Sodium Hypochlorite (0.8%) and am trying to understand how to properly derate the PVC (and find the temperature rise in the pipe) for the following options:
The ambient temperature will be around 49degC, so I am currently unsure how to calculate the rise in temperature inside the box culvert. Am I right to assume that the temperature in the box culvert will eventually rise to the ambient air temperature, or will the box culvert alleviate the temperature slightly?
I have been quoted that the soil at the 750mm burial depth will be a constant 35degC. So believe that the max fluid temperature the second option would rise to is also 35degC.
Any help or direction in this matter would be greatly appreciated.
I am currently designing uPVC Sch80 chemical dosing lines containing Sodium Hypochlorite (0.8%) and am trying to understand how to properly derate the PVC (and find the temperature rise in the pipe) for the following options:
- Buried concrete box culvert - nominal depth 450mm
- Direct buried - nominal depth 750mm
The ambient temperature will be around 49degC, so I am currently unsure how to calculate the rise in temperature inside the box culvert. Am I right to assume that the temperature in the box culvert will eventually rise to the ambient air temperature, or will the box culvert alleviate the temperature slightly?
I have been quoted that the soil at the 750mm burial depth will be a constant 35degC. So believe that the max fluid temperature the second option would rise to is also 35degC.
Any help or direction in this matter would be greatly appreciated.





RE: Piping inside box culvert vs buried pipe
Soil temperatures at 1m below ground will not reach maximum air temperatures, unless the sun doesn't go down for about a month. "750mm burial depth will be a constant 35degC." so at 450mm depth, expect roughly a maximum tempearure of around the average of 35 and 49, or 42 deg. The minimum temp at 450mm depth will be roughly the average of 35C and the minimum surface temperature you can read at night.
Reaction to change doesn't stop it
RE: Piping inside box culvert vs buried pipe
Sodium hypochlorite will also outgas.
Assume that is the reasoning for the 0.8% solution as well as your installation questions.
Have you considered using PVDF pipe? Have you considered adding insulation?
https://plasticpipe.org/pdf/tr-19_thermoplastic_pi...
https://www.zeusinc.com/materials/pvdf-polyvinylid...
750mm burial depth will be a constant 35degC. Agree at 450 mm depth, expect the temperature to be the average temperature between daytime and nighttime.
RE: Piping inside box culvert vs buried pipe
RE: Piping inside box culvert vs buried pipe
Might / should be < 5 minutes for that sort of distance, but might be 2 hours, might start and stop - we haven't been told.
worst case is 49 C - if de-rating doesn't impact design then use that and move on.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Piping inside box culvert vs buried pipe
RE: Piping inside box culvert vs buried pipe
Without knowing the consequences of failure, taking the worst case is not unreasonable.
RE: Piping inside box culvert vs buried pipe
Thank you for all the responses. I'm in Australia, so I apologise that I could not reply in a timely manner.
To add more information, the rate of dosing is approximately 10L/min, so the velocities in the line are extremely low. The dosing is expected to be continuous, as this is dosing into a main supply line.
The piping is envisioned to be double contained, though am currently unsure about insulation. Will double containment of pvc-pvc, have a resounding effect on this temperature?
RE: Piping inside box culvert vs buried pipe
Reaction to change doesn't stop it
RE: Piping inside box culvert vs buried pipe
Velocity?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Piping inside box culvert vs buried pipe
slow
Reaction to change doesn't stop it
RE: Piping inside box culvert vs buried pipe
According to the linked article- http://www.pipa.com.au/sites/default/files/documen... even at 40oC, the derating factor would be 0.7. Is that sort of pressure derating a problem? If it is then best to go for the buried option where the derating factor would be 0.78.
RE: Piping inside box culvert vs buried pipe
RE: Piping inside box culvert vs buried pipe