# Tanker Hydro Testing Valves and Lines



## handybilly7

Ref the hydrostatic testing of cargo pipelines and valves-- does anybody know of any "written instructions" or company procedures? Grateful any lead or web site I can visit.
Thanks


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## Billieboy

Basically, the following applies to tankers:-

Ballast system valves and lines to be tight at 25BAR 

Cargo Valves and lines to be tight at Working pressure plus 50%

The 25BAR for ballast lines is to allow for corrosion, erosion, cavitation and possible hydraulic shocks generated in the system.

*1BAR = 14.7ppsi*

When the Cargo and/or Ballast valves are butterfly type, then it is advisable to maintain the closing time of the valves at a minimum of 1second per centimeter or two and a half seconds per inch of nominal diameter; this should then vastly reduce the possibility of hydraulic shock wave generation. As a rule of thumb, a hydraulic shock wave is generated in a system when a valve is closed instantly, the value of the standing pressure wave will be equal in BAR to the velocity of the fluid passing through the valve in Meters per second times 10. Thus a shock in a line running at 2.5 M/Sec will equal 25BAR above working pressure.

If you have any further queries let me know.


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## Satanic Mechanic

I have a few official procedures I can send you - problem is I don't fully agree with any of them.

Are you wanting to strength test or leak test?

The general rules of thumb I tend to stick to are 

a) Never use air as a medium above 2.5 bar
b) Never use oil as the test medium
c) Cargo lines - law is 1.5 times nominal but not less than 10 kg/cm2
d) Ballast - 1.5 times nominal


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## BlythSpirit

Hydrotesting is a mechanical integrity test of piping systems including valves, instrument tappings, gaskets, etc. This follows construction of the components of a system. The hydrotest procedures and requirements of insurance groups should not be confused with service testing for operational reasons. The rule of thumb for hydrotesting is 1.1 times the design pressure of the system. The design pressure is completely different to the operating pressure. 
Try the ASME Code for pressure piping, B31.4 - 2002 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids, for reference.


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## Derek Roger

While supervising the construction of some product carriers in a shipyard which shall remain nameless I was called to witness a hydro test of the deck cargo lines . It was pouring with rain and when I refused to witness the test for obvious reasons the shipyard people became very indignant until the penny dropped .

Derek 
As an aside ; a hydro test is also very important in checking that the pipes are correctly supported particularly in way of right angle bends . If they are not properly supported they will move .


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## Satanic Mechanic

Derek Roger said:


> While supervising the construction of some product carriers in a shipyard which shall remain nameless I was called to witness a hydro test of the deck cargo lines . It was pouring with rain and when I refused to witness the test for obvious reasons the shipyard people became very indignant until the penny dropped .
> 
> Derek
> As an aside ; a hydro test is also very important in checking that the pipes are correctly supported particularly in way of right angle bends . If they are not properly supported they will move .


Erm - why not hydro test in the rain??????


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## BlythSpirit

SM - I think he meant if it is peeing down -how could you see minor leaks!(Jester)


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## Satanic Mechanic

BlythSpirit said:


> SM - I think he meant if it is peeing down -how could you see minor leaks!(Jester)


Why are you looking for leaks during a hydro test. At least not these days

150% hydro test are strength tests not leak tests. you can do a leak test at low pressure and my preference is to do it using air these days (ultrasonic mic - great invention)

People get a tad nervous about you inspecting pipes that are at test pressure - espescially if the test already indicates a fault.

HSE - gone mad?. I personally agree with this one 100% - hydro testing may not involve the same amount of energy as gas testing but that is not the same a no energy and I have seen some pretty spectacular parting of pipes under hydraulic pressure. There is absolutely no need to use high pressure to test for leaks.

I much prefer to do a leak test first with LP air then if all is clear do a hydro test and hold - if nothing parts and the pressure holds its good to go. Pressure dropping - back to the leak test.


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## BlythSpirit

It is common when preparing subsea pipelines for service to perform a helium/nitrogen leak test progressively up to normal operating pressure, (+/- 70bar g). 

This can save a fortune in loss of production if a pipeline has to be depressured and gas freed to fix a small leak.

In the gas production industry it is not the cost of the repair but the loss of production that really hurts. An air test at 50 -70 bar g. on a 1500 km pipeline would be some ticking bomb! 

The highest leak test pressure I have supervised in commissioning gas plants was 420 bar g on a 24" gas reinjection pipeline in Qatar in 1990, and yes we inspected all the gaskets etc for leaks!


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## Satanic Mechanic

BlythSpirit said:


> It is common when preparing subsea pipelines for service to perform a helium/nitrogen leak test progressively up to normal operating pressure, (+/- 70bar g).
> 
> This can save a fortune in loss of production if a pipeline has to be depressured and gas freed to fix a small leak.
> 
> In the gas production industry it is not the cost of the repair but the loss of production that really hurts. An air test at 50 -70 bar g. on a 1500 km pipeline would be some ticking bomb! To say the least!!!
> 
> The highest leak test pressure I have supervised in commissioning gas plants was 420 bar g on a 24" gas reinjection pipeline in Qatar in 1990, and yes we inspected all the gaskets etc for leaks!


Bearing in mind I am talking about ships pipes, I was doing a 300bar test using helium on a new build line, done a low pressure leak test 0.5 bar - nipped up everything - everyone off the vessel and the instrumentation and controls led down to the jetty, pressed it up and held the pressure - wasn't holding. Lowered the pressure again and another leak test - found it easily enough - a cracked weld. Now this was a strength failure and the very reason why I had evacuated the vessel.

Now whats your opinion on this? I contend that a leak is a leak and will show up at low pressure - if after checking and repair we are happy enough to raise the pressure (hydro or otherwise) and something starts to leak this represents a material failure under pressure and requires investigation.

Incidently I am not decrying other ways of doing this, there are many ways of doing things, but I have sort of settled into a procedure that seems to cover everything. But I do like a second opinion from time time - just to keep me on my toes


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## Billieboy

Surely a 300Bar weld will have been x-rayed and/or U/S inspected? Otherwise the crack probably came up on strentgh test or when the line moved during the test!


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## Satanic Mechanic

Billieboy said:


> Surely a 300Bar weld will have been x-rayed and/or U/S inspected? Otherwise the crack probably came up on strentgh test or when the line moved during the test!


Yup - it had been x rayed and passed. It came up on the strength (150%) test. The point I am making is:

a)that is why we do the test
b) It could easily have failed explosively
c) why would I have anyone near a pipe at strength test pressure


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## Duncan112

Slightly different but I am currently involved in testing sub sea christmas trees for a deep water project..

The valve bodies are hydraulically tested to 15 000 psi
The valve gates are hydraulically tested to 10 000 psi

If this is successful then a gas test using nitrogen is carried out, all tests to 10 000 psi submerged.

Reasoning behind this is that a small liquid leak will produce a noticable drop in the recorder trace during the 15 min test duration, whilst if catopstrophic failure occurs the lack of compressibility of the inhibited water will limit damage whilst an even smaller gas leak (usually across the valve gate) will not produce a visible drop but the bubbles will be readily visible.

Needless to say the tests are carried out within shielded areas, watched by cctv.

The procedure that does give me the willies however is autofrettage where the valve bodies are taken beyond the yield point (some of the larger ones are taken up to 25 000 psi)

The completed tree then has a 1 hour gas test.

Needless to say there is 100% radiography on welds and extensive NDT before we even get that far!!


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## surfaceblow

In the U. S. the requirement for testing the Cargo Equipment is has follows:

§ 35.35-70 Maintenance of cargo handling equipment—TB/ALL.

The cargo handling equipment shall be maintained by the tank vessel's personnel in accordance with the regulations in this subchapter, including the following: 

(a) Cargo hose shall not be used in transfer operations in which the pressures are such that leakage of cargo occurs through the body of the hose. 

(b) Cargo pump relief valves shall be tested at least once each year to determine that they function satisfactorily at the pressure at which they are set to open. 

(c) Cargo pump pressure gage shall be tested at least once a year for accuracy. 

(d) The cargo discharge piping of all tank vessels shall be tested at least once each year for tightness, at the maximum working pressure. 


Since the requirement is for the testing is once a year and in other part of the rules require that the pressure is to be maintained until the length of the system can be observed. In the past I have used the stripping pump to pressurize the Cargo System to the maximum working pressure listed on the ships plans and have walked the piping system for this inspection and entered the results in the log book. I can not remember any USCG witnessing the test but on one occasion ABS was in attendance during the testing but he was onboard for other testing and inspections.

The initial testing of the lines when build is 1 1/4 times the working pressure and is done when the ship is build.

Joe


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## Satanic Mechanic

Duncan112 said:


> Reasoning behind this is that a small liquid leak will produce a noticable drop in the recorder trace during the 15 min test duration, whilst if catopstrophic failure occurs the lack of compressibility of the inhibited water will limit damage.


Sound principles. My methodology is that before we get to hydro testing a low pressure leak test will show up any actual holes. I am of the opinion that these are potentially failure points during strength testing and it is best to find them and repair/examine them first. As you say any leak becomes easily apparent on a hydro test with out visual examination.

I caught Samsung hydro testing a line using gas oil as the test medium - worse in an active work area with welders and burners. It took a quite an effort on the part of the yard to release my hand from the piping foremans throat(Jester)


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## Derek Roger

When building the Bow Drill 3 the highest pressure Hydro test was the Kill and Choke lines . It was a complicated procedure and necessary to make sure there was absolutely no air /oxygen in the system before raising the test pressure ( oxygen becomes explosive at a certain pressure; I forget the actual figure ) The test required evacuation of the rig .

Current kill lines have a working pressure up to 20,000 psi and the test units are capable of pressures up to 30,000 psi .

Not pressures for the uninitiated to play about with .

Regards Derek


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## Satanic Mechanic

Derek Roger said:


> oxygen becomes explosive at a certain pressure; I forget the actual figure


now thats interesting - not heard of that. Have you got any further details? Its not a gas I would use as a test medium of course but are there interactions and ratios to beware of?


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## Derek Roger

Satanic Mechanic said:


> now thats interesting - not heard of that. Have you got any further details? Its not a gas I would use as a test medium of course but are there interactions and ratios to beware of?


The test medium is water ( hydro test ) my comment is that it was important to remove all the air in the system before raising the pressure because of the oxygen content in the air . It is the oxygen content which becomes explosive at a certain pressure ; the nitrogen content being inert .

I don't recollect the test pressure on Semi Submersible Bow Drill 3 but imagine that the Kill & Choke lines would have been at least 3000 to 5000 psi working pressure . I will try and check .

Derek


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## Derek Roger

Cant find the Bow Drill 3 spec but a deep water drill ship design we at Irving Shipbuilding had a 15000 psi Blow out preventer so the Semi would more likely be in that range .


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## Satanic Mechanic

Derek Roger said:


> Cant find the Bow Drill 3 spec but a deep water drill ship design we at Irving Shipbuilding had a 15000 psi Blow out preventer so the Semi would more likely be in that range .



Did you add any scavenger to the water or anything like that?


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## Derek Roger

I dont recollect the details SM other than we brought in a squad with the test unit to conduct the actual operation as it was not equipment we had on hand in the shipyard ( 1984 if I am correct ) .

Derek


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## Derek Roger

Done a little investigating ; the explosion caused by air or other dissolved gases in a system under high pressure does not cause an chemical explosion but a mechanical one if there is a flaw which allows the pressure to drop quickly .

For example 10 cc of air in a hydro test at 30,000 psi ( 2000 bar ) would end up with a volume of only 0.005 cc but will have stored an enormous amount of energy while being compressed . Upon even a very small failure this would instantly expand releasing all the energy ( a mechanical explosion ) .

I take it the scavenger removes dissolved gases ; but would not remove air which has not been very thoroughly vented before raising the pressure .

An analogy would be opening your bottle of tonic for the G&T and although only at low pressure the dissolved CO 2 always tries to hit the roof .

A properly vented gas free hydro test liquid is almost incompressible and any flaw in the structure under test would allow it to almost instantly drop to atmospheric pressure without catastrophe .


Regards Derek


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## handybilly7

*Hydro Testing*

Gentlemen--many thanks for the replies and info which most helpful.(Thumb)


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