Vinzzzz
Materials
- Mar 24, 2009
- 21
Dear All i have a question about the protection about an underground plant piping system.
I have to protect 18 Km of plant piping in a congested area where there is the presence of great aboveground structures like cooling towers and process equipments with concrete foundations.
The minimum pipe diameter is about 4 inch and the maximum diameter is 76 inches running in the center of the plant.
Along plant boudaries i have the presence of an underground 10 Inch pipe used for fire water system while in the center i have 76" UG pipes for water supply and return running in parallel.
My idea is to use a Deep well system to protect the entire plant.
Plant is located near the sea so i expect a low resistivity soil and deepwells are located inside the plant and on plant boundaries in order to create a uniform current distribution on the entire plant. I'm considering a spare on current of about 50% due to dreinage due to UG structures not protected, a spare for UG electrical grounding (made in galvanised steel) of about 20 mA per square meter and a coating breakdown factor of about 1.5% per year with an initial damage of 5% (coating is made by epoxy sysstem of about 1.5 mm in thk).
deepwells should be placed at 40m of depth with an active section of about 19 m the total number is about 44 with a soil resistivity supposed to be 20 ohm *m with an anode voltage not greater than 18V.
My question are:
1- this system is ok or have I expect some problems to be considered in the design phase? This system permits me to avoid a large ammount of shallow anodes sited along the pipes and a large ammount of cables to be positioned in a congested area with a great difficulty in finding spaces. My total calculated ammount of current is about 390 Amps at the end of life.
2- I want to use a von baekman equation to verify the mutual interference between anodes could anyone suggest me equations to use and a way to place anodes in the plant in order to guarantee a correct distribution?
3- i have used the Von baeckma formulas indicated by nace but the problem is if i increase current or resistivity increase also the radius of protection by one anode with difficulty to place 44 anodes in a space of about 800 * 500 meters? Is there a solution in spacing the anodes
4- Is there the possibility of a shielding effect caused by concrete foundations that could create problems to pipes protection?
Many thanks
vincenzo
I have to protect 18 Km of plant piping in a congested area where there is the presence of great aboveground structures like cooling towers and process equipments with concrete foundations.
The minimum pipe diameter is about 4 inch and the maximum diameter is 76 inches running in the center of the plant.
Along plant boudaries i have the presence of an underground 10 Inch pipe used for fire water system while in the center i have 76" UG pipes for water supply and return running in parallel.
My idea is to use a Deep well system to protect the entire plant.
Plant is located near the sea so i expect a low resistivity soil and deepwells are located inside the plant and on plant boundaries in order to create a uniform current distribution on the entire plant. I'm considering a spare on current of about 50% due to dreinage due to UG structures not protected, a spare for UG electrical grounding (made in galvanised steel) of about 20 mA per square meter and a coating breakdown factor of about 1.5% per year with an initial damage of 5% (coating is made by epoxy sysstem of about 1.5 mm in thk).
deepwells should be placed at 40m of depth with an active section of about 19 m the total number is about 44 with a soil resistivity supposed to be 20 ohm *m with an anode voltage not greater than 18V.
My question are:
1- this system is ok or have I expect some problems to be considered in the design phase? This system permits me to avoid a large ammount of shallow anodes sited along the pipes and a large ammount of cables to be positioned in a congested area with a great difficulty in finding spaces. My total calculated ammount of current is about 390 Amps at the end of life.
2- I want to use a von baekman equation to verify the mutual interference between anodes could anyone suggest me equations to use and a way to place anodes in the plant in order to guarantee a correct distribution?
3- i have used the Von baeckma formulas indicated by nace but the problem is if i increase current or resistivity increase also the radius of protection by one anode with difficulty to place 44 anodes in a space of about 800 * 500 meters? Is there a solution in spacing the anodes
4- Is there the possibility of a shielding effect caused by concrete foundations that could create problems to pipes protection?
Many thanks
vincenzo
