Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
(OP)
First off I understand that Hydrotesting over any substantial time period is erroneous as ASME guidelines state ~15min.
Per General Contractor/Contract with owner, we have to run a 24hr Hydrotest. The problem arises when they claim we fail the test and can't listen to reason, (temperature is going to affect the system).
I NEED an/a set of equations that account for the Thermal Expansion of the Pipe and the H2O, that can show that the system hasn't lost water. An equation that produces either Delta P, new P or a pressure correction factor could work.
I have a copper line 2" Dia. (Copper Type L)
Temp. int. = 92 F
Temp. fin. = 81 F
Pressure int. = 166 psi
Pressure fin. = 156 psi
-Thank you, from a frustrated PM.
If there already is a post that encompasses my question please direct me to that area of the depths some call the internet.
Per General Contractor/Contract with owner, we have to run a 24hr Hydrotest. The problem arises when they claim we fail the test and can't listen to reason, (temperature is going to affect the system).
I NEED an/a set of equations that account for the Thermal Expansion of the Pipe and the H2O, that can show that the system hasn't lost water. An equation that produces either Delta P, new P or a pressure correction factor could work.
I have a copper line 2" Dia. (Copper Type L)
Temp. int. = 92 F
Temp. fin. = 81 F
Pressure int. = 166 psi
Pressure fin. = 156 psi
-Thank you, from a frustrated PM.
If there already is a post that encompasses my question please direct me to that area of the depths some call the internet.





RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
Also get a copy of BS PD 8010 pt 1. This has a substantial section on how to account for temperature change during hydrotest and hence is able to be quoted as an international standard approved by a standards body and not something found from the internet, though I think the FAQ is very good, it will never carry the "weight" of a code.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
One way that I've gotten around this on 24 hour tests is to fill the system the day before, pressurize it early in the morning, drain the excess pressure into a container, and use that same container for makeup to maintain test pressure the whole time. If you run out of water you let the pressure drift down. A successful test is one that ends at test pressure without adding any water from anywhere except the tank (you may or may not end up with water in the tank). This only works if the first temperature change is an increase. A clean chart and all liquid accounted for satisfies every client I've ever worked for.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
An 11F drop but only 10psi drip doesn't look right unless you are constantly tipping this up, but presumably measuring carefully the amount you're putting back in.
A goods stabilisation period (8 to12 hours) before you start the test is usually a good idea like zdas04 says, fill it one day and start the test the next day.
Pressure testing a low pressure 2" copper line for 24hrs sounds a bit OTT. How long is it?, is it all buried?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
(pipe is hung just below deck (ceiling) in an exposed/open building (not roughed in))
1. Fill line (from lowest point)
2. Bleed off the air at the high points
3. Pressurize the system using a water/air tank (air as the means of supplying the pressurizing force)
4. Take pressure and temperature readings (roughly no less than 30min since system was filled / ie system sat for 30min)
4.a. Temperature is taken with a laser gun aimed at the pipe, (in the shade as it is under a concrete deck)
4.b. Pressure is taken with a dial gauge tapped to a valve the is used on essentially all the tests
4.a.1. Temperature gun measures in increments of 1/2 a degree, aka 0.5s
4.b.1. Pressure measures in increments of 1 Psi (gauge is new for this job, and has been calibrated at the factory)
5. Wait 24 hrs
6. Take final temperature and pressure readings
*7. Per GC/Owner if the pressure drops - test fails! (GC/owner doesn't record/look at/read/measure temperature, only our QA/QC, because we understand thermo and fluid concepts)
*8. Wait another 24 hrs
*9. And wait again... for cryin out load this is TEXAS Weather temperature matters!!!
Yes the math of my original posts data may not exactly jive as inaccuracies in the equipments precision, and trapped air may/is still in the system (clung to the pipe walls).
@Zdas04 we are not allowed to bleed and fill water.
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
They waited 30min before taking the initial reading, not recording every 30min. Sorry for the confusion there.
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
Also I'm finding it kind of difficult to work out how you get the water to equalise with ambient air temp so fast. 92F is quite warm water.
For this size of pipe etc can't you use air?
Otherwise you might just need to wait until the temperature drops to the minimum and then start the test from then?
This does sound rather ridiculous though from your client.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
I have been researching this none stop and with the help here, I have come to the below.
Life is well.. just that "LIFE".. and trying to account for the temperature and pressure in the case is near impossible.
Unsolvable problems:
1. Testing the system over a 24 hr period with the outside temperature constantly changing.
2. Not being able to reach a point where we can confirm without any uncertainty that the system has reached a stable state.
3. Accounting for the different line sizes, tees, 90s, that would effect the "vessel". (temp. expansion/compression effects on the pipe)
4. The tight guidelines/procedures enforced by the GC/Owner.
5. Having a tolerance of "must be at least higher than the initial pressure to pass".
6. Throwing temperature out of the testing procedure (GC/Owner) does not include in their analysis.
7. The accumulation of air in the system that can not be purged via the air vents that are located at the high points.
8. The testing equipment accuracies.
9. (might be a stretch) but using city water in lieu of pure H2O.
Only reasonable solution: Test in a way that mitigates temperature, ie 15min-1hr tests.
Consensus... Since the GC/Owner's testing subcontractor is the one who holds final approval and responsibility on approving the test and whether it is passing... let them use fictitious/weak standing/unbackable values.
Thank you again for the help.
RE: Hydrotesting; Delta T, Delta P! Need formula that accounts for Thermal Expansion in Pipe and H20.
The "leaks" - if any at all! - were assumed through valve seats, because all joints and the new welds were monitored. No water through a joint at max pressure? No leak at that joint.