Pressure Difference Observed in Pressure Gauge

Good grief, don't you know anything at all? (I haven't yet checked the conversion between meters of water column and kg/cm², but I will let the original comment stand.)

How much pressure difference did you expect?

28.4 psi is not a hell of an issue if the pressure gauge has a range of say 3000 psi then this within a tolerance of what 1%?

Is it just water or contaminated with process fluids?

10 meter of water amounts to 14.7 psi, did you know that?

Are both gouges of the same make? Did you try to swap them?

Whats the result?

Much more information is needed and I believe you would not ask if you had just done your homework!

but entertaing

Explain that please!

Complete nonsense. If that were true, submarines would be able to operate at infinite submersion depth.

Elevation difference 10m accounts for about 1 kg/cm². Whether the other 1 kg/cm² is significant depends on the actual hydrotest pressure hence the % error. Swapping the gauges as #2 is a good check.

Move the top gauge down to the same level as the bottom gauge, or move the bottom gauge up to the same level as the top gauge, or remove one of them.

Alternately, lay the system over on its side.

Delta P = weight of liquid between two gauges/Cross section of piping. (for vertical piping only)

That both complicates the formula and restricts it to a special case (vertical pipe with constant cross section).

ΔP in absolute units (Pa) = h*ρ*g where h = difference in height m, but doesn't have to be in a vertical line, ρ = density, kg/m³. There's no need to involve the weight of liquid and the pipe cross section explicitly.

You simply don't get the gravity of the problem at hand.

Please explain the perceived need for two gauges.

It's a test of operator intelligence.

Score:

Gauges----1

Operator---0

Kindly explain why the Pressure Test Procedure requires the use of two gauges.

No doubt about that. However, it doesn't answer the question, which is why two gauges are part of the test procedure. That bit defies explanation so far.

Look at the face of the gauges. Does one gauge, or other, both, or neither have a reasonably recent "calibration sticker", indicating they have been checked for accuracy with e.g. a deadweight tester in turn calibrated/traceable to recognized standards etc?

If not, might want to get at least one that is or have one or both so calibrated. Don't know any other obvious reason for your readings, unless of course you are dealing with high enough pressures that the 1 kg/cm^2 difference is not really significant (as another has already mentioned).

I know, I KNOW!!!

They are pressurizing the pipe from the bottom. That's why the bottom gauge reads higher!!!

Problem solved!

I feel good!