What he said, plus the pitot pressure tables in NFPA #291 are titled "Theoretical Discharge Through Circular Orifices" emphasis on Theoretical. It's yet another case of, "calc with a computer, measure with micrometer, mark with chalk and chop off with axe".
Ron Fletcher Aero Automatic Phoenix, AZ 114F = HOT -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Davidson Sent: Friday, August 01, 2008 2:02 PM To: [email protected] Subject: RE: Gauge Calibration Gentlemen, If you reference Fluid Power 3rd Edition, Sept., 22, 1966, Chapter 18 "Pressure Gages", page No 75, Figure 4 "American standards of accuracy" states that for a gauge with a typical face scale of 0 to 100 psi the error in psi ranges from + or - 2 to 3 psi on a calibrated gage, however the gauge repeatability may be 1%, For a gage with a face scale of 0 to 500 psi the error in psi ranges from + or - 10 to 15 psi on a calibrated gage. Who are you fooling by the false accuracy reading? A pressure gauge should be read to the decimal point not to the right of the decimal point. Any AHJ who is making the contractor read to the right of the decimal point on any gage and any contractor who submits hydraulic calculations to the tenths and hundredths of a pound or GPM needs to understand the accuracy of the equipment being used to measure water flow and pressure. Inaccuracies are also introduced in the pressure and flow reading by the orifice and condition of the orifice of the pitot tube and nozzle coefficient of the flowing orifice all of which is considered to be +or- 5% to 10%. Regards Jim James S. Davidson, Jr. PE Davidson Associates 302-378-7600 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Matt Willis Sent: Friday, August 01, 2008 2:00 PM To: [email protected] Subject: RE: Gauge Calibration I used to be qualified to calibrate gauges, courtesy of the U.S.N.. I had a nice little book with knowledge questions and tasks to perform under supervision. I Doubt there is that level in use out here. The "new guy" hired last week may know how to run the machine and is now placing little labels saying they are calibrated. Not even sure if there is a liability issue if it is out 3psi or so. I would think, if you have the equipment, we could calibrate our own. Bottom line is to show the numbers "almost" match. R/ Matt -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ron Greenman Sent: Friday, August 01, 2008 11:56 AM To: [email protected] Subject: Re: Gauge Calibration What actually qualifies someone to calibrate a gauge? Is the calibrator certified? Is it someone that knows how to do it? Is it someone that does it regularly? Is it someone that works for a company that sells lots of instruments? Is it someone other than you? I've got a device to do this that I use in class to demonstrate relationships and measurements. Am I qualified or not? I've watched the guy at the instrument company certify gauges for me and his regular job is working the will call counter. Now that doesn't mean he doesn't have some special qualification beyond knowing how to be able to put that tag on the gauge but I don't know. And if you need to be certified who regulates it and what's the standard of care? Seems to me that any one of us could calibrate our own gauges. On Fri, Aug 1, 2008 at 8:59 AM, Thom McMahon <[EMAIL PROTECTED]> wrote: > RE-testing a fire pump for not using calibrated gauges, is an AHJ issue. > Calibration is only required once a year as far as I can see, for any > testing device. By doing that it doesn't mean that your gauges are > correct or in spec.(it means they were when they were tested.) Just as > with BFP you can test and pass a device, and then disconnect and > re-connect your gauge, and it will fail. Was the first test wrong or a > failure? NO. At the time of the test it passed. Does that indicate or > mean anything about any other time? NO. Calibration for Fire > protection is more Just A "Warm Fuzzy" than an indication of the > exacting science of our profession. As you said on a fire pump test > your matching a pre-determined curve, any large variation would alert you to an issue such as a bad gauge. > > Thom McMahon, SET > Firetech, Inc. > 2560 Copper Ridge Dr > P.O. Box 882136 > Steamboat Springs, CO 80488 > Tel: 970-879-7952 > Fax: 970-879-7926 > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Ken > Holsopple > (forum) > Sent: Thursday, July 31, 2008 8:20 PM > To: [email protected] > Subject: RE: Gauge Calibration > > Tom, > > Fortunately it was a small pump and the gauge in question was the one > used on the single hose monster. Fortunate our pump rep. had one in > his van with the calibration paperwork. > > Why would I need to re-test when the calibration is not required by > NFPA 20 (03)? > > Ken > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Thom > McMahon > Sent: Thursday, July 31, 2008 6:12 PM > To: [email protected] > Subject: RE: Water Supply > > Ken if you're doing BFP testing you get your test sets calibrated each > year, you can send your gauges in at the same time. Personally we keep > two sets and that way we are never without one as they expire one month apart. > Additionally if you run into this problem at test, I would offer to > run the test, then insert the gauge in an envelope addressed to the > calibration co, record the serial # of the gauge. (If it doesn't have > one write one on it in marker. Note that # on the test report. Offer > to let the AHJ stick it in the mail, and include a request that the > AHJ be copied on the Calibration report. When it comes back, if it's > within 1% your test is complete, if not you may have to re-test, which it sounds like you have to do anyway. > > Thom McMahon, SET > Firetech, Inc. > 2560 Copper Ridge Dr > P.O. Box 882136 > Steamboat Springs, CO 80488 > Tel: 970-879-7952 > Fax: 970-879-7926 > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Ken > Holsopple > (forum) > Sent: Thursday, July 31, 2008 2:41 PM > To: [email protected] > Subject: RE: Water Supply > > Ok guys and gals.....here's one for ya. > > Just did a pump acceptance test under 2003 edition of NFPA 20. The > inspector shows up on site and asks for calibrated gauges. Even though > we pulled out a gauge that came from the factory 3 months ago, he > wanted to see the paperwork. (I guess he didn't like the dirt that was > on the gauge either from a previous diesel pump flow test. Turns out > things get muddy when you do those) After reviewing NFPA 20 (03) I see > that there is not a requirement for gauge calibration except in the > appendix, to which no tolerance for the gauges is given. > > I questioned the inspector on the requirement and asked for a code > reference. What I got back was the re-write that appears in the 2007 > edition of the acceptance procedure that does note that gauges must be > calibrated and within +/- 1%. I'm fine with that, except for the fact > that here in Pennsyltucky and in his jurisdiction, the 2003 is the applicable standard. > > Now to take it one step further, the new NFPA 20 (07) mentions that > the gauges must be calibrated annually (depending on use...kinda open > ended don't ya think?). In speaking with some folks that supplied our shiny 4 1/2" > Glycerine filled gauges, they mentioned that we could get them > calibrated, but "what are you gonna do, get them calibrated after > every use?" They do mention in the literature for our gauges (that I > sent to the AHJ) that they are calibrated at the factory. Keeping in > mind that scientists are probably using their "top of the line" gauges > to measure the force of an atom bouncing of a cow's butt. > > I mentioned to the AHJ that in the meantime (till the 2007 ed comes > around), the township could purchase a calibrated gauge and use that > as a benchmark and throw the contractor's gauge(s) on a static point > of the system if they think something was tampered with. > > I would be curious to see how others would handle this. AHJs especially. > You'ins keep my life interesting. > > Getting calibrated gauge paperwork isn't a big deal (well it is if > they spring this on you at the time of test), but trying to enforce > rules that haven't been adopted yet kinda crosses the line in my book. > > By the way, I did check out NFPA 291 (forgot the edition), there was > mention of calibration, but no mention of tolerance. > > I have a headache from bouncing my head off the soapbox. > > Ken Holsopple > Design Manager & Gauge Calibration Coordinator Rowe Sprinkler Systems > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email > to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > > No virus found in this incoming message. > Checked by AVG - http://www.avg.com > Version: 8.0.138 / Virus Database: 270.5.10/1584 - Release Date: > 7/31/2008 12:00 PM > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email > to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email > to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > > No virus found in this incoming message. > Checked by AVG - http://www.avg.com > Version: 8.0.138 / Virus Database: 270.5.10/1585 - Release Date: > 8/1/2008 > 6:39 AM > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email > to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > -- Ron Greenman at home.... _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
