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Extend of high or ultra high sprinkler heads above oven

Extend of high or ultra high sprinkler heads above oven

(OP)
Hello all,

I came across the following issue and I would appreciate any help or recommendations.

I have a rectangular shaped industrial oven which has some maintenance doors on the side, around every 50 to 60 ft. There are cases where these doors may be open either accidentally or for any other reason.

The oven operates at 480F. The sprinkler ceiling system right above, some 15 ft higher from top of oven, is to cover a much more wider area with standard 165F sprinklers. The ones above these open doors would need of course to be of higher temp. classification. NFPA 13 commentary says the following



How would you interpret the term "immediately above equipment"? Personally I wouldn't trust having only one or two heads right above these doors. How large would that area with high or ultra high temp. sprinklers normally have to be?

The other question here is what kind of temperature class would the heads need to be?

Any comments are welcome. Thank you.

RE: Extend of high or ultra high sprinkler heads above oven

Further on in Chapter 8, we are told in a footnote, that the use of a thermometer may be required to verify job conditions.

Then we can go back to the temp chart in Chapter 6 for maximum ceiling temp.

R/
Matt

RE: Extend of high or ultra high sprinkler heads above oven

(OP)
How could you verify an installation which at the moment does not exist and the oven will definitely come after the sprinkler system? You probably mean emptying and putting the system out of commission, running the oven with no protection, measuring with thermometer(s) and then replacing the necessary heads? That s not practical. If there was a chance to do it like that, I 'd rather let just the sprinklers and see how many they will get activated. I doubt however this is the way of things. I was kinda hoping for experience from similar cases.

RE: Extend of high or ultra high sprinkler heads above oven

Uft

To help answer the question

Are you mechicanical contractor

Sprinkler, general contractor or other

RE: Extend of high or ultra high sprinkler heads above oven

(OP)
Mechanical engineer. We are installing the oven but have a good knowledge about NFPA codes. We will contract a sprinkler contractor but this comes quite later and we ve been asked from the customer to provide outline designs for various trades, among others, information about sprinklers. I believe (without having confirmed), he may have had bad experience from the past about this issue.

We will confirm with an expert but at the moment I just wanted to know if there was some similar experience on the issue.

RE: Extend of high or ultra high sprinkler heads above oven

I wonder if the oven maker has some temp numbers , when the door opens??


You cannot be the first person with the question.

RE: Extend of high or ultra high sprinkler heads above oven

Actually, I did not mention taking a system out of service.

"Immediately above", means just that. Project the foot print to the ceiling and that is the area.
We all know that isn't good enough. We also know that Chapter 1 tells us the standard represents the Minimum requirements.

My suggestion is based on providing sprinklers for several rings out from the equipment in question. THEN you temp it with a thermometer.
You can then document the areas, and provided lower temps based on results.
Yes, this is an extra step/trip to provide protection. But we are required to provide the lower temps by the standard to minimize operation time for the sprinklers.

R/
Matt

RE: Extend of high or ultra high sprinkler heads above oven

Looks like Ultra-high temp heads should be used above the access doors. +50F above maximum oven temp setting as per A.8.15.12 below.
Care should be taken when determining the maximum ceiling temperature. Should be measured as Mr. Willis has said.
As far as how far the higher temp class should extend, that is not clear.

Some relevant code:

A.8.15.12 The combustible materials present inside indus­
trial ovens and furnaces can be protected by automatic sprin­
klers. Wet sprinkler systems are preferred. However, waterfilled
piping exposed to heat within an oven or furnace can
incur deposition and buildup of minerals within the pipe. If
the oven or furnace could be exposed to freezing tempera­
tures, dry pendent sprinklers are an alternative to wet pipe
systems. Another option is to use a dry pipe system.
The preferred arrangement for piping is outside of the oven;
the sprinkler should be installed in the pendent position. The
sprinkler temperature rating should be at least 50°F (28°C)
greater than the high-temperature limit setting of the oven or
applicable zone. As a minimum, the sprinkler system inside the
oven or furnace should be designed to provide 15psi (1 bar) with
all sprinklers operating inside the oven/furnace. Sprinkler spac­
ing on each branch line should not exceed 12 ft (3.7 m).

8.3 Use of Sprinklers.
8.3.2 Temperature Ratings.

8.3.2.5* The following practices shall be observed to provide
sprinklers of other than ordinary-temperature classification
unless other temperatures are determined or unless high temperature
sprinklers are used throughout, and tempera­
ture selection shall be in accordance with Table 8.3.2.5(a),
Table 8.3.2.5(b), and Figure 8.3.2.5:

(7) Sprinklers protecting commercial-type cooking equip­
ment and ventilation systems shall be of the high- or ex­
tra high-temperature classification as determined by use
of a temperature-measuring device. (See 7.10.6.)

7.10.6 Sprinkler and Automatic Spray Nozzle Temperature
Ratings and K-Factors.

7.10.6.1 Where the exposed temperature is expected to be
300°F (149°C) or less, sprinklers or automatic spray nozzles
being used in duct, duct collar, and plenum areas shall be of
the extra high-temperature classification [325°F to 375°F
(163°C to 191°C)].

7.10.6.2 When use of a temperature-measuring device indi­
cates temperatures above 300°F (149°C), a sprinkler or auto­
matic spray nozzle of higher classification shall be used.

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