Hydrotest exemption for B16.5 flanges 1

[nipra03]

Accordiong to the B16.5, flanges are not required to be hydrotested as part of the manufacturing process. However flanged fittings are not exempt. Is there a specific reason ?

 

[XL83NL]

B16.5, para 2.6 states;

2.6 System Hydrostatic Testing
Flanged joints and flanged fittings may be subjected
to system hydrostatic tests at a pressure of 1.5 times the
38°C (100°F) rating rounded off to the next higher 1 bar
(25 psi) increment. Testing at any higher pressure is
the responsibility of the user, taking into account the
requirements of the applicable code or regulation.

Not sure where the exemption you mentioned comes from.

Only thing i could think of is flanged fittings where e.g. a WNRF is welded to the fitting, than that weld needs to be tested.

 

[LittleInch]

I think what you mean is why are the flanges themselves not tested. The failure mode of a flange is not from internal pressure, but bolt forces and bending. Thus a pressure test is next to useless in testing a flange, but needed in testing any fitting as the flange is only one part of the item and the other parts are able to fail from internal pressure or have welds needing to be tested.

That's my guess any way.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[moltenmetal]

A flanged fitting may be assembled from welded components, or may be a casting. In either case it needs testing. The flange itself is either attached to piping by means of joints which require testing (i.e. either welded or threaded) and hence will be tested when you test those joints, or it is a blind flange. A blind flange, as noted above, does not require testing because you're not really testing the flange in a meaningful way during a hydrotest- you're testing the bolting and the gasket.

 

[DekDee]

Guys,
The question from nipra03 comes from:
8.1
Each flanged fitting shall be given a hydrostatic shell test as specified in para 8.3.
8.2
Flanges are not required to be hydrostatically tested

I had no idea of the reason and that is why I didn't respond,
Cheers,
DD

 

[XL83NL]

Dekdee, I stand corrected, you're right.
Just checked the 2013 edt of B16.5, but in that version the references are the other way around, but in principle the same;

8 PRESSURE TESTING
8.1 Flange Test
Flanges are not required to be pressure tested.
8.2 Flanged Fitting Test
8.2.1 Shell Pressure Test. Each flanged fitting shall
be given a shell pressure test.
8.2.2 Test Conditions. The shell pressure test for
flanged fittings shall be at a pressure no less than 1.5
times the 38°C (100°F) pressure rating rounded off to
the next higher 1 bar (25 psi) increment.
8.2.3 Test Fluid. The pressure test shall be made
using water, which may contain a corrosion inhibitor or
kerosene as the test fluid. Other suitable test fluids may
be used provided their viscosity is no greater than that
of water. The test fluid temperature shall not exceed
50°C (125°F).
8.2.4 Test Duration. The test duration shall be as
follows:
Fitting Size Duration, sec
NPS ≤2 60
21⁄2 ≤ NPS ≤ 8 120
NPS ≥ 10 180
8.2.5 Acceptance. No visible leakage is permitted
through the pressure boundary wall.

 

[rconner]

I don't know the answer to this question; however, I notice that the passage language of apparent concern of course just refers to "flanges" (not e.g. specifically to "flanged joints", or even "blind flanges"). I guess it nevertheless would be easy for a specifier to take issue with this language, based some sort of perception of conservatism etc, and instead write just the opposite, "All flanges must hydrotested..."
However, what would this sort of counter- specification literally mean, as in many real applications after all the literal "flange" may be contacted little or none at all by the fluid in service? While I guess apparently unlike some politics, I think on the other hand most developers and maintainers of important consensus engineering specifications, e.g. for steel fittings that might be used for quite high pressures and temperatures in important services, generally want their words to mean something at least a little clearer. If there were some sort of dispute and the counter-specifier were to defend his briefly-worded spec with words like, "Well, it is clear I wanted them (the manufacturer or fabricator etc.) to bolt something to the flanges during the hydrotest like will be done in the field", this begs further questions. What kind of sealing mechanisms or gaskets are to be used in this Shop test (there are perhaps hundreds of different gasketing/test sealing types out there), and must the gaskets be new for testing of every flange, or can they be re-used? What kinds of bolts or studs? How many bolts or studs must be inserted? Must the bolts or studs be new for every test? How must the bolts be lubricated or non-lubricated? What means are to be used for tensioning or torquing bolting, how shouold the tensioning be measured, and in what pattern/procedure etc? What QA stuff must be recorded and/or maintained for all this, and for how long? The list and complexity/cost of interpretations goes on and on, and who knows in the end may bear little resemblance to where/how the flange may be used in the actual piping system.
I do not really otherwise know why the writers/maintainers of this particular standard in the fashion they have even bothered to comb this particular seemingly somewhat negative frog hair in the fashion they did (that I believe could have elicited the OP's reasonably honest question); however, if a fitting manufacture absolutely must bolt something individually to each and every flange of each and every fitting, then connect filling and pressurizing hoses, fill and pressurize same (it should be realized in effect having to build all these "mini-pipelines", before they are actually again assembled and tested in the field!) according to some specifier's detailed answer to all of these questions, it should be understood this would be extremely labor-intensive and time-consuming for a manufacturer in at least the developed/modern world, could require substantial time and purchase/coordination of joining materials etc., and I would think this could add greatly to manufacturer's cost and furthermore limit practical availability.
Even if cost and difficulty to manufacturer are perceived no object to a particular buyer, if quick delivery of e.g. common or standard small diameter fittings sitting on a warehouse shelf is needed, what are the chances that those particular fittings were tested exactly how the specifier wanted per answers to the second paragraph above? While I am not familiar with particularly modern smaller diameter steel fitting (near commodity?) manufacture, I wouldn't be surprised if many manufacturers are now for at least most common fitting and valve etc. configurations clearly satisfying at least the present standard verbiage/requirements in clamped specially designed modern hydraulic presses and blocking/mechanized water supply etc., that I would think makes this process much less labor-intensive, quicker and in the end perhaps more efficient for all?

 

[BigInch]

There are many uses for flanges, some not having anything to do with containment of pressure. A flanged fitting, on the other hand, would almost certainly be used for pressure containment.

What may abe more important is whether your pipe design code requires its components to be hydrostatically tested.

I hate Windowz 8!!!!