Traffic Impact Testing on Fire Hydrants 2

[buyamericaniron]

The City of Houston requires traffic impact testing on live fire hydrants. Has anyone heard of such tests? Does anyone know of a lab that would perform such a test? We currently do only hydraulic and flow tests as required by AWWA.

 

[cr1973]

Are you speaking of impact testing on newly installed hydrants that are live and in service? Sounds a little crazy to me.

 

[civilsid]

This sounds like mixed up communication somewhere. To the best of my knowledge, fire hydrants don't move an, unless placed in a lane of traffic, should not in any way impact traffic patterns. (And who said engineers don't hjave a sense of humor!)

In reality, if someone were to actually hit or "impact" a "live" fire hydrant, the water would not spurt up like it does in the movies. The valving is actually sub-surface and nothing you did to the exposed fire plug itself would matter as fart as pressures and water release. I don't know if older fire hydrants were different or not.

I would get in touch with your municipality and find out what they are looking for. I don't see the engineering connection between water service infrastructure and TIA's.

 

[CarlB]

as fart as pressures and water release

civilisid, you do have a sense of humor!

 

[Maury]

I an going to assume that the testing is in reference to breakaway hydrants and their impact resistance to vehicles. This brings up an excellent question that hadn't occurred to me. I looked for a reference to a standard for the design of breakaway connections and was surprised to not find any, either in any hydrant manufacturer's catalog or in FHWA, Underwriter's Laboratory, Factory Mutual, or AWWA. There are many references to requirements that breakaway connections be provided, but nothing that I have found that says what makes an acceptable design. If anyone else has come across a standard, I'd like to know.

If the City wants testing, then somebody would need to provide a design standard and a test criteria for controlled testing of a sample of the hydrant being used. To do this on live hydrants seems strange, and not practical. Are you sure you understand what they are asking?

 

[AegisFPE]

civilsid - in Texas they may not have freezing issues, such that wet barrel hydrants would be installed (rather than dry as you describe). Therefore, it would be possible to truly evaluate the system head pressure!

 

[rconner]

Just a clarification. Some contemporary break-away hydrant designs e.g. for even high water tables or without built-in drain mechanisms etc.(and maybe particularly prevalent in the South/West where freezing is not an issue), are also provided with valve mechanisms that "close with/in the direction of the flow". I think this sort of design whether or not there is initially at least unpressurized water in the barrel is intended to minimize the chance of the media popular "geyser" in a traffic event.

 

[JStephen]

I would take the requirement to mean a sample of the hydrant is or has been tested in an actual impact, not that a hydrant has to be tested there at the city. Probably at least one hydrant manufacturer has done so and sold the city on the idea that it needs to be done.

So far as I know, all the Texas cities use the same types of dry-barrel hydrants that everyone else does. Houston doesn't get a lot of freezing whether but busting all your hydrants once every 20 years would be enoough reason to use them.

As far as the geyser, I think I've seen enough of them on the news to know that hyrants don't always work like you want them to when they get hit.

 

[fel3]

buyamericaniron…

I am ashamed to say that I have professionally "whacked" three hydrants for the City of Houston. Here's my story:

Several years ago I got a call from American AVK, which has a fire hydrant and valve manufacturing plant here in Fresno, CA. They were trying to get their hydrants certified in Houston, and had pulled our firm (Boyle Engineering) out of the phone book.

At first, AVK was told that only hydraulic testing was required. A licensed civil engineer (non-Texas OK) had to witness the tests and write a short report. AVK arranged to do the hydraulic tests at the Center for Irrigation Technology on the campus of California State University, Fresno. I witnessed the tests, took some photos, did some calcs, and wrote a short report.

When AVK submitted the report to Houston, they were told "by the way, we now also require traffic impact tests" (or something like that). Houston provided the test criteria: whack hydrants at three different kinetic energies and prove that the repairs will be less than $100 and that leakage will be less than the specified amount. AVK had never performed traffic impact tests and neither had I. We batted around a bunch of ideas, including the lab where the crash test dummies live. In the end, AVK arranged with the City of Fresno to perform the tests at Leaky Acres [sic], which is a groundwater recharge facility consisting of several hundred acres of ponds. Leaky Acres had the advantage of being close to AVK's plant and being unpopulated and secure. The City of Fresno was intrigued and had several representatives present.

AVK hired a contractor to construct a hydrant assembly on the widest berm at Leaky Acres. The assembly consisted of the hydrant head, bury, and about 20 feet of lateral piping. At the far end of the lateral was a riser with a tap for pressurizing the system. AVK supplied a large flatbed truck (nicknamed "Snowball"), to which they had welded a "whack bar" at the correct height. We then proceded to run over the hydrant at three different speeds that resulted in kinetic energies meeting or exceeding the required values. Speeds were measured with both a radar gun and a GPS. More damage was done to Snowball than to the hydrant, and the amount of leakage was minimal. Success!

Fred
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"Is it the only lesson of history that mankind is unteachable?" Winston S. Churchill

 

[buyamericaniron]

Thank you fel3 for your information.

These are the specific requirements of the test for the City of Houston. We are searching for a lab to perform the tests described below. So far, we have not found an engineering lab that will agree to conduct such a test.


A certified test report shall be provided which outlines the results of a traffic impact test involving standard production run models (not exceeding 5 foot bury depth) of the fire hydrant with a breakable barrel of the same in design of that proposed for certification. These hydrants shall be installed in accordance with the requirements of this standard, and shall be struck at a point eighteen (18") +/- (2") two inches above the designated ground line. The proximate point of impact on the hydrant barrel shall be within two (2") of the line perpendicular to the base and equidistant from the pumper nozzle and one hose nozzle.

Successive tests shall be conducted to simulate the impact of vehicles with the gross weights of 3,500, 5,500, and 10,500 pounds. An impact speed of 35 mph is to be simulated for each vehicle weight.

The test report shall include the following elements:

1. Detailed schematic drawings of the test facility

2. Complete description of mechanical testing equipment used.

3. Complete list of hydrant parts and materials damaged in each mechanical impact test and currently published price schedule.

4. Photographs, including scale references as appropriate, are to be provided to show hydrant thrust restraint, bedding and backfill lifts, fabricated impact bumper if used (Note that this is to be parallel to standard vehicle bumper) and to show condition of hydrant before and after impact test to document damage caused by each test.

5. The size and static pressure of the line to which the hydrant is attached. (minimum to be 45 psi on impact)

6. An estimate on how much water discharged from the hydrant within the thirty (30) minutes immediately following the collision.

7. Hydrants to be inspected and tested for damage after each impact test

A. Perform visual inspection of the hydrant assembly for cracks, breakage, and disfiguremnet.

B. Verify upper valve rod is straight and true and still meeting manufacturer's published assembly specification limitations.

C. Verify hydrant operating and nozzle cap nuts are still fully functional and will accept a standard operating wrench

D. Verify hydrant pumper and nozzle locking devices are functional and that the threads will still fully accept a hose coupling which is AWWA standard C502-95

E. Replace all "damaged" partes and reassemble hydrant on existing lower section. Perform mechanical and hydrostatic tests in accordance with AWWA C502-85.

 

[fel3]

buyamericaniron…

As far as I can remember, those are the exact same requirements we had. We couldn't find a lab either, which is why the hydrants were whacked in situ.

See my URL above to make contact for photos, video, a report, etc.

Fred