Where does it address the accuracy of test gauges in NFPA? 1

[ContractorDave]

I was having a discussion about the accuracy of test gauges and when I went to cite my source ... well I can't find it.

Anyone?

Thx
Dave

 

[NJ1]

For water based systems gauges must be within 3 percent of the full scale.
NFPA 25 page 25-13
Section 5.3.2

It is the same for hydrostatic gauges as well

 

[FFP1]

NFPA 25:

Chapter 8 Fire Pumps

8.3.5 Test Results and Evaluation.
8.3.5.1* Interpretation.
8.3.5.1.1 The interpretation of the test results shall be the basis for determining performance of the pump assembly.
8.3.5.1.2 Qualified individuals shall interpret the test results.
A.8.3.5.1 Where the information is available, the test plot should be compared with the original acceptance test plot. It should be recognized that the acceptance test plot could exceed the minimum acceptable pump requirements as indicated by the rated characteristics for the pump. While a reduction in output is a matter of concern, this condition should be evaluated in light of meeting the rated characteristics for the pump. [See Figure A.8.3.5.3(1).]
The test equipment should be of high quality and accuracy. All equipment should have been calibrated within the last 12 months by an approved calibration facility. Where possible, the calibration facility should provide documentation indicating the instrument reading against the calibrated reading. Instruments that pass the calibration test should be labeled by the calibration facility with the name of the facility and the date of the test.

Pressure gauges should have an accuracy not greater than 1 percent of full scale. To prevent damage to a pressure gauge utilizing a Bourdon tube mechanism, it should not be used where the expected test pressure is greater than 75 percent of the test gauge scale. Some digital gauges can be subjected to twice the full scale pressure without damage. The manufacturer’s recommendations should be consulted for the proper use of the gauge. To be able to easily read an analog gauge, the diameter of the face of the analog gauge should be greater than 3 in. (76 mm). Pressure snubbers should be used for all gauges to minimize needle fluctuation. All gauges used in the test should be such that a gauge with the lowest full scale pressure is used. For example, a 300 psi (20.7 bar) gauge should not be used to
measure a 20 psi (1.4 bar) pitot pressure. Equipment other than pressure gauges, such as volt/ammeters, tachometers, and flowmeters, should be calibrated to the manufacturer’s specifications. The readings from equipment with this level of accuracy and calibration can be used without adjustment for accuracy.

 

[b1ueshift]

It depends on what the pressure gauge is used for.

The pressure gauges on a sprinkler alarm valve or on the suction and discharge of a fire pump don't need to be particularly accurate. As NJ1 points out, they only need to be calibrated, or replaced once every 5 years. You can expect quite a lot of drift in 5 years, so these gauges could be quite inaccurate.

If you are using a guauge for flow testing hydrants, or fire pumps - then accuracy is much more important. You need to refer to the standard concerning testing of this equipment.

 

[FFP1]

Dave was asking specifically about test gauges.

System gauges should be replaced if they are inacurate by >3 percent regardless of the age (even if they are less than 5 years old).

 

[NJ1]

Well I know that test gauges for testing cylinders have to be calibrated yearly. I dont know what percentage of accuracy they required.

 

[ContractorDave]

FFP1 answered my question quite succinctly.

Thx

 

[NJ1]

Wow.
That is exactly what I answered in my first post.

 

[ContractorDave]

Wow? Really?

Let's see... I asked about whether NFPA addressed the accuracy of test gauges. You cited 25, 5.3.2 which addresses system gauges. You will note that what FFP1 cited specifically addressed gauges for testing.

Blueshift made a comment in the following post about the intended use of the gauges and FFP1 correctly replied that I asked about test gauges.

Your "Wow" post seems a little off base no?

 

[NJ1]

Whatever. The information still the same if you read. That is what I mean. I not looking to take credit. I just want to make sure I had it right.

 

[TyphoonK]

Flow test requirements refer to NFPA 25 2010 Section 5.3.2.

NFPA 25 Section 6.3.1.5.2 - "Pressure gauges shall be provided for the test and shall be maintained in accordance with 5.3.2."

It appears each type of test has their own standard on gauges, as b1ueshift pointed out. I wouldn't have known where to find the requirements if this question was never brought up, thanks lightecho

 

[TyphoonK]

correction, *NFPA 25 2011... still a beginner here!

 

[b1ueshift]

Yes, I'm always learning things from this forum, thanks to everyone who gives free advice.

 

[FFP1]

Chapter 6 outlines requirements for Standpipes & Hose systems; therefore, Section 6.3.1.5.2 is applicable to flow testing conducted on standpipe systems.

I only post this statement for clarity because the requirements for fire pump and fire hydrant flow test equipment is different than for standpipe flow tests. My overall intent is to be helpful and try my best to be completely accurate with my posts.....I hope everyone understands I mean well even when I contradict or state a previous post might be somewhat misleading.

 

[ContractorDave]

Coincidentally, I had been down to Peerless in Indianapolis and fire pumps were on my mind when I was asking the question, so your reply was most relevant to me. I would have mentioned that I was referring to fire pumps but I was not aware that you could have test equipment that was required to be more accurate for some systems than others, and of course this makes little sense really. If one is doing inspections to NFPA 25, one is (almost certainly) doing fire pump inspections. I won't be carrying around two or more sets of test gauges with differing rates of accuracy.

Your posts FFP1 are always helpful.

Regards
Dave

 

[b1ueshift]

Your assumption is probably correct that if a gauge is ok for pumps, it is ok for everything else you are likely to test. I doubt any standard will ask for better than 1% accuracy.

The reason for my comment was that if you want to quote a source to demonstrate compliance with a relevant standard, then the standard should preferably discuss the type of equipment that you are testing.

I don't know how many relevant standards there are, but I have come accross NFPA 291 for testing fire hydrant flow rates. As it happens, now that I look it up, it seems to mention the frequency of testing, but not the accuracy.

4.4.1 The equipment necessary for field work consists of the
following:
(1) A single 200 psi (14 bar) bourdon pressure gauge with
1 psi (0.0689 bar) graduations.
(2) A number of pitot tubes.
(3) Hydrant wrenches.
(4) 50 or 60 psi (3.5 or 4.0 bar) bourdon pressure gauges with
1 psi (0.0689 bar) graduations, and scales with 1?16 in.
(1.6 mm) graduations [One pitot tube, a 50 or 60 psi
(3.5 or 4.0 bar) gauge, a hydrant wrench, a scale for each
hydrant to be flowed].
(5) A special hydrant cap tapped with a hole into which a short
length of 1?4 in. (6.35 mm) brass pipe is fitted; this pipe is
provided with a T connection for the 200 psi (14 bar) gauge
and a cock at the end for relieving air pressure.
4.4.2 All pressure gauges should be calibrated at least every
12 months, or more frequently depending on use.