Clamont
Mechanical
- Dec 10, 2012
- 40
I have a couple of questions relating to cooling of atmospheric storage tanks as per API RP2030.
1. Section 7.3.13 states;
When reviewing an atmospheric storage tank’s protection
from an external fire the design personnel should
recognize that cooling water is of potential benefit only for
the exposed portions of the roof and for those portions of the
shell that are not in contact with the liquid contents. Those
portions of the tank most likely not to be in contact with liquid
include the roof of cone roofed and covered floating roof
tanks and the upper portion of the shell on all tanks. If spray
is used, typically only the upper 12 to 24 ft (3.7 to 7.4 m) of
shell is sprayed; up to 12 ft (3.7 m) of rundown is allowed on
inclined and vertical surfaces
I understand this that only the top 7.4m of shell (maximum) should be sprayed unless there is a wind girder or something blocking the permissible 3.7m rundown?
2. The same section then states for adjacent tanks the following;
Where water spray protection is used the system should
be designed to provide an application rate of 0.10 gpm/ft2
(4.1 lpm/m2) of protected surface. Generally between onequarter
to one-half of the total tank surface could be
exposed when a fire is in an adjacent tank. Since the exact
location of the exposing fire or the amount of liquid in the
exposed tank may not be known before the fire occurs, total
protection would require that the entire tank be sprayed.
However, water sprayed on surfaces that are not being
exposed to fire is wasted and takes resources from other fire
suppression efforts; sectionalization of fixed spray systems
can help ensure efficient use of firewater. Application of
water by hose streams and monitors has the potential for
more efficient use of available water
I understand this as the tanks adjacent to the one in question for which we are only cooling the top 7.4m the remaining tanks should have cooling across the entire surface area of the tank?
3. My final question is how to determine the volume of water required in the bund area? The only source I can see for this would be in NFPA 15 section 7.3.3 Flammable and Combustible Liquid Pool Fires. This however gives a water rate of 12.2L/min/m2 which is even higher than what is required on the tank shell in NFPA 15. Is it permissible to not consider water in the bund area and just on the storage tanks?
1. Section 7.3.13 states;
When reviewing an atmospheric storage tank’s protection
from an external fire the design personnel should
recognize that cooling water is of potential benefit only for
the exposed portions of the roof and for those portions of the
shell that are not in contact with the liquid contents. Those
portions of the tank most likely not to be in contact with liquid
include the roof of cone roofed and covered floating roof
tanks and the upper portion of the shell on all tanks. If spray
is used, typically only the upper 12 to 24 ft (3.7 to 7.4 m) of
shell is sprayed; up to 12 ft (3.7 m) of rundown is allowed on
inclined and vertical surfaces
I understand this that only the top 7.4m of shell (maximum) should be sprayed unless there is a wind girder or something blocking the permissible 3.7m rundown?
2. The same section then states for adjacent tanks the following;
Where water spray protection is used the system should
be designed to provide an application rate of 0.10 gpm/ft2
(4.1 lpm/m2) of protected surface. Generally between onequarter
to one-half of the total tank surface could be
exposed when a fire is in an adjacent tank. Since the exact
location of the exposing fire or the amount of liquid in the
exposed tank may not be known before the fire occurs, total
protection would require that the entire tank be sprayed.
However, water sprayed on surfaces that are not being
exposed to fire is wasted and takes resources from other fire
suppression efforts; sectionalization of fixed spray systems
can help ensure efficient use of firewater. Application of
water by hose streams and monitors has the potential for
more efficient use of available water
I understand this as the tanks adjacent to the one in question for which we are only cooling the top 7.4m the remaining tanks should have cooling across the entire surface area of the tank?
3. My final question is how to determine the volume of water required in the bund area? The only source I can see for this would be in NFPA 15 section 7.3.3 Flammable and Combustible Liquid Pool Fires. This however gives a water rate of 12.2L/min/m2 which is even higher than what is required on the tank shell in NFPA 15. Is it permissible to not consider water in the bund area and just on the storage tanks?
