Thread: Components of a Fire Sprinkler

8/9/2023

We had a tip last week about being able to comment and share ideas from our articles on the Blog and our hits series - and we love the idea. The hope is to open a thread once-a-week concerning the Blog topics so we can expand and discuss in greater detail.

My hope is that this doesn't take away from the Forum at all (again, just once a week), but allows opportunity for further discussion where it's wanted.

This thread is for Components of a Fire Sprinkler, with our high-quality image above (right-click to download and save).

Thanks everyone!

- Joe

9 Comments

Pete A

8/9/2023 12:09:32 pm

I was always under the impression that the orifice is the actual opening the plug seals in to. The larger the K-factor, the larger the opening. Nearly all the sprinklers I deal with have 1/2" NPT threads, but they have varying K-factors (up to 5.6) - meaning the plug opening varies. This picture, and all I found with a quick search, show the orifice at the threads, not the plug. Am I missing something?

Joe Meyer

8/9/2023 12:12:57 pm

Thanks Pete! I think you're right - I've tried to show the orifice as the actual opening (the most-constricted portion of the opening), but had trouble illustrating that concept. The orifice is the inside diameter so-to-speak, not at the threads, yep.

Janakkumar link

8/9/2023 12:13:25 pm

Though it is not a component, it would be very useful to show where the sprinkler ID #, UL/FM marking to look for on the sprinkler deflector.

James Art, FPE

8/9/2023 12:54:41 pm

NO!

The Orifice size refers to the actual Inside diameter of the opening.
This is INSIDE where the picture is labelled: Thread.

Pipe size is called by "nominal" INSIDE diameter of the pipe,
so the Outside Diameter of the pipe and so the threads are actually larger.
(To make things easier, and use the same fittings where they can, most OD's are the same. That means thinner wall pipe has a larger ID)

Most pipe fittings use at least what is called 1/2 in. openings,
SO often small diameter sprinkler orifices were mfr'd by making a "normal" 1/2 in diameter sprinkler, and then inserting a reducer shim down the opening.
This makes a small orifice sprinkler, with a K Factor less than 5.6.

A shame, but it used to be all sprinklers that were not K=5.6 had a "pintle", so you could tell they were different.
Old ones still have them, but they eliminated the requirement from the code.
Now you really need to see the SIM, or read markings on the sprinkler.

Joe Meyer

8/9/2023 01:56:16 pm

Thanks James! I appreciate the input - hard to show on this image but you've nailed it. I appreciate it!

Adam

8/9/2023 01:43:09 pm

In your newsletter, you list the correlation between K-factor and orifice size (pasted below). I had been looking for this information a while ago, and I thought it would be readily available, but had no luck finding anything.

Thank you for posting this information!

K2.8 → 3/8" Orifice
K4.2 → 7/16" Orifice
K5.6 → 1/2" Orifice
K8.0 → 17/32" Orifice
K11.2 → 5/8" Orifice
K14.0 → 3/4" Orifice

Joe Meyer

8/9/2023 01:55:18 pm

Thanks Adam! I wrote it down myself to matchup inspector's tests sizes for stocklisting - but I don't recall the source.

There's a chance it's in NFPA 13 somewhere, but I don't remember where. Glad it's helpful!

Joe Meyer

8/10/2023 07:42:32 am

Big thanks to Dan Wilder - who emailed a few references.

Nominal K-Factor is listed with Nominal Orifice Size in Table A.7.2.2.1 of NFPA 13, 2022 Edition.

8/10/2023 08:54:54 am

Not all sprinklers have threads on them. Victaulic uses grooved sprinklers in 1/2", 3/4", and 1" sized grooves, which attach to a grooved sprinkler outlet using a Style V9 Coupling as a part of the IGS system.

There is also the Tyco RIS sprinklers which have a special "RIS" thread and gasket to ensure a tight seal.

Not sure if these products will catch on enough to add to the detail, but it is worth bringing up to the discussion.

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Thread: Components of a Fire Sprinkler

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