Spray Nozzles Spaced for Entire Oil Tank Wall?

6/23/2026

When a water spray system is installed for outdoor vertical fixed-roof oil storage tanks, is every point on the tank exterior wall required to be within the coverage of water spray nozzles?

Or is it sufficient to arrange a ring of nozzles around the exterior wall, so that the sprayed water flows down the tank wall by gravity to achieve effective suppression?

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

5 Comments

Glenn Berger

6/23/2026 08:29:08 am

How tall is the tank?

With a fixed roof tank it may be satisfactory to provide one ring of nozzles with the applicable spray pattern achieved.

anthony

6/23/2026 08:40:44 am

This should be answered in NFAP 15 and or 30. The few times I have done fixed water spray the spray pattern needed to be examined very closely. So possible that a single row of sprinklers may work but its spray pattern dependent.

Dan Wilder

6/23/2026 08:42:50 am

If there is a way to perform and confirm the wetting is applied over all surface areas, you could use water run down as an acceptable discharge.....and pretty sure there would be no "suppression" especially with just rundown, just cooling, unless there is foam involved.

This is where a FPE should come in to provide guidance as to the end goal of the protection system.

Ryan Hinson

6/23/2026 12:59:47 pm

Assuming NFPA 15 (2022 cited) is applicable, then per Section 7.4.2.2, "Where rundown is contemplated, the distance between nozzles at different levels or elevations, protecting the vertical or inclined surfaces, shall not exceed 12 ft as measured along the surface." Section 7.4.2.4 adds, "Spherical or horizontal cyindrical surfaces below the vessel equator shall not be considered wettable from rundown."

Therefore, any protected surfaces are horizontal and sprayed from above or from any angle up to a vertical surface are allowed to be wetted with up to 12 ft of rundown. Per NFPA 15, any surface past vertical (inverted or below the a vertically curved vessel's equator are not wettable from rundown and direct impingement must be provided from nozzles in accordance with their listings (which are typically fixed angle dependent).

API Publ 2510A Section 5.3.2 differs significantly from what NFPA 15 requires and allows rundown...typically from a weir over spherical surfaces beyond 12 ft and even to surfaces below the vessel equator. It does become paramound to provide direct spray impingement beneath obstructions to rundown in this instance.

If this your project is for the Oil and Gas industry, the Owner likely has their own set of standards/engineering practices which must be adhered to. These will tell you whether you are to follow NFPA 15, API direction, or other guidelines...which will also be based on your tank's spacing/proximity to other facility/tank farm equipment, provided/planned containment, and anticipated realistic worst-case fire event involving this tank (exposure with/out direct flame impingement and tank's actual 'exposed' surface area anticipated to to be exposed...which may not be the entire circumference or height of the tank) which should be agreed upon by all the stakeholders.

As previously recommended, an FPE's involvement is recommended.

Jack G

6/23/2026 05:10:16 pm

My experience is the entire surface is to be wetted with the required density. My last two have been a .5 density for propane tanks 30 ft long, diameter required 4 rows. Open nozzles with detectors, strainer ( river water ).

Leave a Reply.

Home
Our Cause

The Blog
The Forum

PE Exam Prep
The Toolkit
MeyerFire University

Pricing
Login
Support
Contact Us

MeyerFire.com is a startup community built to help fire protection professionals shine.
Our goal is to improve fire protection practices worldwide. We promote the industry by creating helpful tools and resources, and by bringing together industry professionals to share their expertise.

MeyerFire, LLC is a NICET Recognized Training Provider and International Code Council Preferred Education Provider.
All text, images, and media Copyright © 2016-2025 MeyerFire, LLC

We respect your privacy and personal data. See our Privacy Policy and Terms of Service. The views, opinions, and information found on this site represent solely the author and do not represent the opinions of any other party, nor does the presented material assume responsibility for its use. Fire protection and life safety systems constitute a critical component for public health and safety and you should consult with a licensed professional for proper design and code adherence.

Discussions are solely for the purpose of peer review and the exchange of ideas. All comments are reviewed. Comments which do not contribute, are not relevant, are spam, or are disrespectful in nature may be removed. Information presented and opinions expressed should not be relied upon as a replacement for consulting services. Some (not all) outbound links on this website, such as Amazon links, are affiliate-based where we receive a small commission for orders placed elsewhere.

Spray Nozzles Spaced for Entire Oil Tank Wall?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES