Hydrotest Pressure difference in Higher points 1

[mtv3180]

Hi Guys,
Can you please explain, why there is an pressure difference at elevated points(higher elevation) during testing the pipes or boiler. As per the code, for 10M height 1bar pressure will increase.., According to my view on the pump end (lower point) must have high pressure.

 

[BigInch]

I don't understand the question.

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[mtv3180]

Hi Sir,(BIG INCH)

During testing the pipelines and boilers.., we have to Fix the pressure gauges at Lower point and at Higher point as per the codes.

Now the question is, why there is an pressure difference between the lower point(0Mtr) and Higher point(50Mtr)

For example the pressure at 0mtr level at 50bar and in 50mtr level of the same pipeline as 58bar

 

[BigInch]

There is a change in elevation, so the density of the fluid x elevation change equals the change in pressure.

Are you saying there is a pressure change of 8 barg in 50 m of elevation difference?

maybe you can find somebody to help you write the question with enough explanation so that we know what's going on there.




We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[europipe]

Did you use calibrated pressure indicators?
I should say 8 bar difference is impossible in this case.

 

[zdas04]

An engineer should realize that liquid has mass and when you stack liquid on top of itself it exerts a force.

Citing the code was a bit scary. The equation for hydrostatic pressure is rho*g*h, and 10 m with SG 1.0 water (1000 kg/m^3) 0.968 bar, but I guess the code is for people who can't multiply. I wonder if it calls pi=3.0?

50m elevation difference is 4.8 bar pressure difference, not 8 bar as you said or 5 bar as the "code" would predict.

David

 

[StephenA]

According to my understanding, the question siva3180 is asking is "why is the pressure higher at the higher elevation?"

I cannot explain it and he also thinks that it is the wrong way around (as do all the other responses).

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[BigInch]

Let's let Siva explain what they meant rather than starting the 20 question & guessing game.

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[Duwe6]

Everybody puts their Test Gauge at or near the bottom of elevated items, for convenience. ASME requires that you to compensate for the weight of the water column that that lower gauge will see.

At the top of a fully filled and unpressurized 200-ft tall column, the pressure is zero. At the bottom, the pressure will be 0.422# x 200-ft = 86.6 psig. If your required Test Pressure is 100 psig, your gauge down at the sidewalk must read 186.6 psig to have the ASME mandatory full hydro pressure at the top of the vessel [or boiler]

Your alternative is to actually put the test gauge at the top-most point of the item being hydro'd, and climb all the way up to read the official Test Gauge. I prefer to just document the compensation pressure and stand on the sidewalk.