Re: [MW:16946] Pressure Drop During Hydro test due to temperature difference

[madhan chozhan]

Hi DESAI,

As you mentioned temperature difference does make a difference in pressure. Also kindly check the pump in line to the spool is closed and the line is isolated from pump.

Engage another pressure gauge in the highest point and lowest point of the line and note down the pressure difference.

Try to vent the line from the highest point and then pressurize to the test pressure gradually in 3 or more steps to stabilize the pressure.

As far as ug99 is concerned there is nothing mentioned about the pressure drop without visual leakage.

Regards,
Madhan

On Mar 5, 2013 4:57 PM, "hard" <hvdes...@gmail.com> wrote:

Dear Experts,

                      I have gone through the Hydrostatic test @ 32 kg test pressure, on site, for Piping spool(Line size - 4" X Sch 40).

                      Holding time - 1hr.Spool was having total 32 Groove weld joint & some portion of spool is in upstream side (Directing towards upward oppsite gravitation)

                      Test start time at 32 kg pressure - 1:20 p.m.

                     

                      After 1 hr (at 2:20 p.m.) pressure went down to 30 kg? - There is no leakage observed visually (or felt during direct check by rubbing the hands on the joints) on the welded joints or on the temporary joints. First of all can it be acceptable (Any small amount of pressure drop, like this, is acceptable as per code? is code specifies some tolerance for this kind of conditions? May be due to Temperature difference)

                     

                      We have continued the test for additional 1 hr in order to find the exact reason for this 2 kg pressure drop.After 3:20 p.m. we have observed the pressure dropped up to 22 kg? and all the other conditions were remain same.No visisble leakage observed or felt.Only differece between conditions is the Temperature difference during 1:20 p.m. and 3:20 p.m.This difference might be 5-7 deg.So This Temperature difference will effect this condition in this manner i mean it is possible to have around 10 kg pressure drop due to Temperature drop (if we consider here 10 deg Temperature drop then also this amount of pressure drop) can be expected?

                       

                      Can we use any valve as a temporary joint during Hydro Test?  i think code is not denying for the use of valve as a temperary joint? (Instead of Flanges).

                      

                      Last but not the least, During this type of conditions, can we accept the test on the bases of no leakage found during visual inspection.I think UG-99 and ASME B31.3 chapter VI clause 345 is not exactly specifying the acceptance criteria. can any one guide me for any interpretation with respect to ASME? or can any one suggest me any other code or standard which is specifying the exact acceptance criteria for Hydeo test?  

 

Regards,

Hardik Desai

 

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[Shashank Vagal]

Hardik, This is not uncommon. Please see attached sheet giving relationship between temp and press during similar conditions. Shashank Vagal --- On Tue, 5/3/13, madhan chozhan <madhan...@gmail.com> wrote:

[lakshman.bayyana]

Dear Friends,

if any leakage is not observed then how pressure was dropped?

simple check for confirming the affect of temperature is continue the test for 24 Hrs - any affect of temperature the same will be traced.

further - any chances of leakage through pressure pump system line - so disconnect the pump after pressuring.

you may have the option of to use valves - and no need to look for code provision for this same - as you have to isolate the section -but valve ratings shall be higher rated than your test pressure.

any code will not accept these much pressure drop - defiantly some leakage will be their.

please conclude any branches, valves and any more fittings in the line.

and also look in to the pressure gauge capability and range of operation for the same.

 

                     

[Naveen Batchu]

May be slight change in dimensions or minor side leaks also lead to pressure drop.

Regards,

Naveen

---

From: lakshman.bayyana <lakshma...@gmail.com>
To: material...@googlegroups.com
Sent: Tuesday, March 5, 2013 10:13 PM
Subject: Re: [MW:16959] Pressure Drop During Hydro test due to temperature difference

[para...@gmail.com]

Dear Hardin,

10 kg/cm^2 is definitely a higher pressure drop and could not be attributed/ compensated for the temperature rise. Few thing I would like to know before arriving on the conclusion.
1. Have you carried out proper cleaning and flushing of the piping spool / loop.
2. Are their two numbers of pressure gauges used in the piping spool, one at the highest and another at lowest elevation respectively.
3. Does any valves were involved in the piping test loop.
4. Are the pressure gauges were attached in the piping loop after complete flushing was carried out and the water was seen coming out from the highest point of the piping loop.

If you have not carried out the above activities properly then their are chances of leakage and the pressure may drop due to AIR Entrapment.

Pl. Provide the above details.

Regards,

PARAG PANSARE

Sent from my HTC

[Sudharsanam Goodrich Flosil]

Dear madhan,

 

                Thank you very much for your reply.  The pipe O.D is 914mm and the wall thick is 32.5mm.  And which standard having the below formula for max. pressure. Kindly

Send me soon.

 

Thanks&Regards,

 

B.Sudharsanam

Design Department

Goodrich Gasket Private Limited

Tel.+91-44-27498033

Fax: +91-44-27498055

Email Id: m...@flosil.com

Web: www.flosil.com

P Please consider our environment and think before you print. Thank you! q

 

From: madhan chozhan [mailto:madhan...@gmail.com]
Sent: Wednesday, March 06, 2013 5:43 PM
To: Sudharsanam Goodrich Flosil
Subject: RE: Spam : Re: [MW:16955] Pressure Drop During Hydro test due to temperature difference

 

Hi sudarsanam,

Can you please provide the OD and wall thickness of the pipe which you are about to test.

The formula to calculate the Max working pressure is

P = 2ST/ (d x SF)

P - Max working pressure
S - material tensile strength (psi)
T - wall thickness (in)
d - od of pipe
SF - safely factor (usually 1)

On Mar 6, 2013 9:29 AM, "Sudharsanam Goodrich Flosil" <m...@flosil.com> wrote:

Dear friends,

 

                Am doing the pipeline projects like joints and union connections.  And I need the details for the BUSTING Test pressure for the ASTM A333 Gr.6. pipe material.

Kindly help me soon. The pipe length is 1500 mm.

 

Thanks&Regards,

 

B.Sudharsanam

Design Department

Goodrich Gasket Private Limited

Tel.+91-44-27498033

Fax: +91-44-27498055

Email Id: m...@flosil.com

Web: www.flosil.com

P Please consider our environment and think before you print. Thank you! q

http://www.linkedin..com/groups/MaterialsWelding-122787?home=&gid=122787&trk=anet_ug_hm

[hardik desai]

Mr.Parag,

               First of all thanxs 4 ur reply.

     1. yes,proper cleaning was done.

     2. yes,two gauges at different elevations were used.

     3. Yes,two valves were involved and i have ensured its condition before and after the test.

     4.  yes, we have ensured the water coming out from the highest point on both the times at time of water filling and draining. 

          Actually this line is too long (Around 55-60 meter long) so surface area is very large.

          I just want to ask u all, Three basic questions.

          1. is there any criteria for limiting joint nos. or piping length for Hydro Test as per code or any spec.Because here we often perform Hydro test for so long spools/lines ( say up to 300-350 meters line having 150 to 160 joints). it depends on only practical convenience?or code specifies something for the same?

         2. Some time on site Hydro test, we observe pressure drop of around 1-2 KG, without any justifiable reason. such small amount of pressure drop during 1 hr holding time is acceptable? 

         

         3. Some time on site Hydro test, we observe pressure gain (Most probably due to temp rise) of around 3-4 KG, Is it acceptable?is there any justification in codes 4 theses issues?

[khalidzu...@gmail.com]

yes the same case is happen with my testing also. Can any one give the exact reason for this