Hydro testing

Hydro Test is done at low (ambient) temperature, does not affect properties of material.

HTP= 1.5 times design pressure, one hour holding.

Use water not air

If air is used TP = 1.1 times design pressure. This need special authoraization.

The code does not give any specific time. I used to ask the manufac. to keep the pressure for an hour. When I witnessed the test pressure with the Code inspector, on one occasion, he said that if it does not keak within 15 minutes it will not leak and 15 minutes time is OK. May be he was in a hurry to go somewhere else to witness some thing else. But in my future purchases, I always asked the vendor to certify that the pressure was kept for an hour. Also with the updated versions of metals like SA-516-70 and others, with higher updated sresses, the Hydro test pressure could be taken as 1 1/3 of the design pressure instead of 1 1/2 times..

Regards;

Nadeem Butt

07092007

Only for information.

ASME material SA-516 Grade 70 is a pressure vessel plates, not for piping. And according to ASME BPVC, Section VIII, Division 1, the current hydrostatic test pressure is 1.3 times the design pressure* (not 1 1/3) instead of 1.5 as stated in the previous code editions.

Note *: Taking into consideration the factor used for temperature at test.

According to ASME B31.3, Process Piping, Para. 345.4:

345.4.1. Test Fluid. The fluid shall be water unless there is the possibility of damage due to freezing or to adverse effects of water on the piping or the process. In that case another suitable nontoxic liquid may be used. If the liquid is flammable, its flash point shall be at least 49^oC (120^oF), and consideration shall be given to the test environment.

345.4.2. Test Pressure. Except as provided in para. 345.4.3, the hydrostatic test pressure at any point in a metallic piping system shall be as follows :

(a) not less than 1.5 times the design pressure;

(b) for design temp. above the test temp., the min. test pressure shall be calculated by Eq. (24), except that the value of S_T/S shall not exceed 6.5.

P_T = 1.5 P S_T/S ................ (24), where

P_T = Min. test gauge pressure

P = Internal design gauge pressure

S_T = Stress value at test temp.

S = Stress value at design temp.

345.5. Pneumatic Leak Test. (There are a lot of precautions). Shall be 110% of design pressure.

It looks as though the answer is in the question as posted:

...required test pressure is 100 bar...

The difference between this and the system operating pressure, expressed as a ratio, gives the percent overpressure.

-0-0-0-

[For background information, steam locomotive boilers that may be found in the heritage railway sector in the UK can be tested on cold water typically to 1¹/₃ or 1¹/₂ times the safety relief valve operating pressure, as may be required by the insurance examining body. The test is done against a certified pressure gauge, typically with a hand-pump or a small air-driven pump in the case of the larger boiler. Minor weeps at the tube plates and foundation ring are acceptable and are usually 'caulked' with a hammer and chisel or a limited amount of re-expansion of the tube; distortion of any structural member during the hydro test is not. Another way of sealing a minor leak is traditionally a thick aqueous suspension of shredded straw, oatmeal and fresh pig manure, added to the boiler contents prior to the fire being lit for the steam test. Personal experience of carrying out this prractice is a valuable, and unforgettable, learning exercise! The hydraulic test will be follwed by a steam test at the operating pressure, during which test the setting and behaviour of the safety relief valve will be assessed and, if satisfactory, an insurance test certificate will be issued by the examining body. The steam test will follow typically a few days after the hydro test to give time for the fittings that were configured for the hydro test to be re-configured for steam. Superheater elements assembled by a coded welder are tested hydraulically up to boiler operating pressure as, being downstream of the regulator valve, there is an ability to shut them off in an emergency.]

The Standard is 1.5 times working pressure or in some applications 1.3. Test duration can very from 3 min. to 4 hours depending on the application. A wetting agent could be needed.

If the material is austenitic stainless the Coloride content of the test liquid should not exceed 50 ppm, test liquid temp. should be within the operating range of the system. the data sheet should have all required information

I used to do hydrostatic testing on castings with a previous employer. We would do proof testing (it could not leak before a certain pressure) and burst testing (it couldn't crack before a certain pressure). As stated above, make sure all of the air is evacuated when performing the test. Compressed air will tend to send chunks of things flying if the part fails due to the stored energy in the compressible fluid. Water is generally considered incompressible and doesn't release as much energy if the part fails (which makes a nice Bellagio wanna-be).

The advice prior is all good. What is the material you are testing? What is operating pressure? What is operating temp? There are many variables. Some industries require specialized testing. For instance - some chip plants want an ambient test, followed by a flow test at system temp and pressure for HUPW (hot ultrapure H2O), and again an ambient hydrostatic. But as for general industry,PIPING, the ASME advice above is good.

2 very important things: this advice is only good for piping. Vessels are a whole different story. Also; your test psi is restricted by the lowest rated component w/in the system and valves and gages are susceptible to failure at marginal psi increases over regulated psi. And most important: It is extremely important that as much air as possible is evacuated prior to testing/during pressurizing. As air compresses MUCH more than H2O, gage psi drops will be inevitable. If it is a tight tolerance test spec, a small amount of trapped air can be confounding at best. But, more importantly, the Kinetic, or stored energy of that compressed gas (air) can prove catastrophic even fatal. So, again for plastics; polypropylene, PVC (any sched), PVDF, PFA etc, make sure as much air as possible is evacuated for safety reasons and if you are testing a ferrous,or metal system as well, accurate gage readings are near impossible.

A few hours on the front can save thousands on the back. Lengthy systems should have vents engnrd in. Expansion rates of hot service systems are significant depending on material and possible obstructions should be noted and considered an integrity threat with temp increases.

Happy testing, I'll send you a bill!

C Rummel

Contact the pipe manufacturer or the manufacturer's representative for hydrostatic testing information. The technical staff there should have all the information you need to support your test requirement. Wish I could get away with a 15 minute hydro.

Manufactures specs are only good for ensuring that material is properly rated to fullfill system test reqs. How is system joined? Weldments, mechanical, compression fittings, pipe threads, faceseal, gaskets or sans? What is gasket material etc, etc, etc....

All US mfg pipe will have ASTM info and all packaged components should too...if not consider dumping your supplier!

Beyond material specifications I have found that many manufacturers provide very specific guidance for pressure testing specific piping systems as well as installation procedures. Many of the clients I provide services to specify test requirements, some of which are unrealistic and sometimes dangerous (i.e. air pressure tests for pvc piping systems). It is always much easier to provide mfg. recommendations as a solution when challenging such a requirement.

How is Austin? The Armadillo World Headquarters was still open last time I was there.

I'd like to differentiate between the two hydrostatic test pressures carried out for a pipe and for a piping system.

At mill every pipe shall be hydrostatically tested for a few of seconds, and the test shall be carried out even for seamless pipes (without any welding seam) in accordance with the code of material.

Another hydrostatic test pressure for piping system after welding completion and assembly of piping networks for a plant, where the test must be carried out based on the code used in design, inspection, and manufacturing, and the test shall be carried out by the erector or his subcontractor.

Good point sir.

Couldn't a said it better my own self.

A lot of details may not clearly specified in Code / Std, but from best practices. May consider the stabilization time of test fluid (norm, 15 minutes), fluid penetration time for fine leak / crack, surrounding temperature when testing (e.g. if increasing will compromise pressure drop of line) and walk the line time (for piping system) which will also help to ensure proper testing been conducted.

Cheers

Salam,

It is recommended to use shop hydrotest up to 1.3 times that of design pressure.

With regards,

Naveed

Holding time may be between 20 to maximum up to 60min but it does not have any direct effect on the piping

lovely thread,

how about sub-sea pipelines ? all this was regarding piping......

oh and by the way, when you say "mill"...what does this word mean ? i have read it many times ...what does it stand for ?

mill pressure test..mill i dont know what !!!

I'm assuming mill to be the manufacturing facility and the test to be a quality assurance procedure wheres as plant would refer to testing of the assembled piping system int the field.

As experienced before, they will carried out 100% RT and hydrotest as well for offshore subsea pipeline.

What about the leak test pressure if the piping system is design for only about 0.25 bar but flammable medium (gas)? Should that be test by pneumatic with only 0.275 (1.1 x Design pressure) or otherwise?

Yes the mill is the factory for producing the pipe itself, where a hydrostatic test must be carried out before shipping of pipes. Whereas the plant is the site where the piping fabricated (joined to each other with fittings, ... etc.) and assembled.

The good engg. practises - first the client tells you the working pressure which is basic need. 1.1 times the working pressure is the design pressure. 1.5 times the design pressure is the test pressure. However, the test pressure should not exceed more than 70% of SMYS {max. yield strength}. If you exceed beyond the permissible material strength, then the material is supposed to loosing its "memory" or its elasticity. {applicable when the pressure is held for longer durations...}

The hydrotest - pressure holding time is a subject of application. the time should be enough to inspection and conclude that the pipeline is free from any leakages. Incase of cross country pipelines, one has to consider the temperature effects. The pressure and temperature have directly proportional relationship. Hence, when the pressure is held over a 24 hrs cycle, the weather temperature variations effect the pressure and it can reach the corresponding pressure as referred by the temperature at the starting of the hydro-test process, excluding any temperature corrections between start and end of 24 hr cycle.

Generally seen it takes around 2 to 2.5 hrs for ambient temperature to effect the laid pipeline {underground with 1 mtrs. pipe cover } to reflect on the pressure variations.

However, all the pipepline standards simply mention time duration as NOT less than 30 minutes !!!