control valves and piping hydrotest
control valves and piping hydrotest
(OP)
In the past we have hydrotested systems prior to installing control valves by installing a short spool in lieu of the valve. I have a contractor who is insisting that this is unnecessary. The system is ANSI 600#, Class Location 3, per B31.8 2007. The design pressure is 1440 (not 1480)and the test prtessure is 2016. The valve is by Mokveld.
Any advice will be appreciated.
Any advice will be appreciated.





RE: control valves and piping hydrotest
So in my opinion it depends on the specific valve you're using...I would remove it if:
--it has internal noise trim or any ports that can be plugged by sand, grit or welding slag. (in this case it should be left out until your gas purge is complete or install an upstream strainer)
or
--it is a globe valve type control valve (i.e. with a rising stem).
There are probalby some more instances where it would be prudent to remove it, but these are the two main instances I've had to deal with.
Now we have some folks in our company who consider any valve that has an automated pneumatic actuator on it, a control valve, and require them to be taken out of the line for testing, which is ridiculous.
RE: control valves and piping hydrotest
RE: control valves and piping hydrotest
I would also ask advice to the valve vendor.
"We don't believe things because they are true, things are true because we believe them."
RE: control valves and piping hydrotest
Unless, of course, the contractor is willing to take full responsibility (in writing) for procurring and installing a new control valve if you follow his advice.
Patricia Lougheed
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RE: control valves and piping hydrotest
That was the first thing we did, unfortunately the vendor wasn't any help. Hence my question in this forum.
Industry standard seems to be to replace them with a spool during pressure testing, which jives with my experience.
Chris
RE: control valves and piping hydrotest
"We don't believe things because they are true, things are true because we believe them."
RE: control valves and piping hydrotest
§ 192.505 Strength test requirements for steel pipeline to operate at a hoop stress of 30 percent or more of SMYS.
(a) Except for service lines, each segment of a steel pipeline that is to operate at a hoop stress of 30 percent or more of SMYS must be strength tested in accordance with this section to substantiate the proposed maximum allowable operating pressure. In addition, in a Class 1 or Class 2 location, if there is a building intended for human occupancy within 300 feet (91 meters) of a pipeline, a hydrostatic test must be conducted to a test pressure of at least 125 percent of maximum operating pressure on that segment of the pipeline within 300 feet (91 meters) of such a building, but in no event may the test section be less than 600 feet (183 meters) unless the length of the newly installed or relocated pipe is less than 600 feet (183 meters). However, if the buildings are evacuated while the hoop stress exceeds 50 percent of SMYS, air or inert gas may be used as the test medium.
(b) In a Class 1 or Class 2 location, each compressor station regulator station, and measuring station, must be tested to at least Class 3 location test requirements.
(c) Except as provided in paragraph (e) of this section, the strength test must be conducted by maintaining the pressure at or above the test pressure for at least 8 hours.
(d) If a component other than pipe is the only item being replaced or added to a pipeline, a strength test after installation is not required, if the manufacturer of the component certifies that—
(1) The component was tested to at least the pressure required for the pipeline to which it is being added;
(2) The component was manufactured under a quality control system that ensures that each item manufactured is at least equal in strength to a prototype and that the prototype was tested to at least the pressure required for the pipeline to which it is being added; or
(3) The component carries a pressure rating established through applicable ASME/ANSI, MSS specifications, or by unit strength calculations as described in §192.143.
(e) For fabricated units and short sections of pipe, for which a post installation test is impractical, a preinstallation strength test must be conducted by maintaining the pressure at or above the test pressure for at least 4 hours.
[35 FR 13257, Aug. 19, 1970, as amended by Amdt. 192–85, 63 FR 37504, July 13, 1998; Amdt. 192–94, 69 FR 32895, June 14, 2004; Amdt. 195–94, 69 FR 54592, Sept. 9, 2004]
RE: control valves and piping hydrotest
This plant is overseas and built to B31.8 2007 ed. All valves, flanges and fittings are normally all hydrotested together, in this case to 1.4 times MAOP. However, control valves are not covered by API 6D, so we normally install a dummy spool prior to FGT operations and install the control valve later with a witch's hat.
C.
RE: control valves and piping hydrotest
The only problem other than warranty will be packing leaks. Bring the test pressure up to Operating, and adjust the packing to be leaktight. Don't touch the packing during the overpressure portion of the Hydro, otherwise you will have the packing WAY too tight. Identified leaks of this nature are acceptable in a Code hydro, even at nuclear plants.
RE: control valves and piping hydrotest
We are going with the spool piece since it's not practical to gauge a pipeline with a control valve installed !!
Thanks anyway.
C
RE: control valves and piping hydrotest
RE: control valves and piping hydrotest
RE: control valves and piping hydrotest
Just doing up a hydrostatic test procedure for piping on the $50 billion Gorgon LNG Project in Australia.
The client is Chevron and this is an excerpt from the clients project specifications.
a. Tests through control valves will be permitted provided there is no internal cage assembly or possibility of damage. A list shall be created identifying those not suitable for testing through; these will be tagged and removed.
b. Pressure balanced type control valves and their pressure connecting leads shall be isolated from the test pressure. The valves shall be bypassed and blocked off with the drain or vent open and the pressure connection to the diaphragm closed or
disconnected.
Hope that helps,
Regards,
Kiwi
RE: control valves and piping hydrotest
"Pre-test preparation
.... Remove or spade off any control valve or instrument liable to damage under test pressure, replace with spool or make good joint and open any by pass vale"
RE: control valves and piping hydrotest
"We don't believe things because they are true, things are true because we believe them."
RE: control valves and piping hydrotest
The pipeline system was successfully flooded, gauged and hydrotestedand the contraol valves were reinstalled this morning.
Regards,
Elijah C
RE: control valves and piping hydrotest
RE: control valves and piping hydrotest
RE: control valves and piping hydrotest
Remember the hoop stress for design purposes is governed by the class locations and 80% SMYS is the limit for gas. However, when it comes to hydrotesting, as long as one does not yield the steel, its ok up to 100% SMYS. So the non steel internals are what one must be careful with, like seals etc. and thois is why valves are tested in the half open position.
RE: control valves and piping hydrotest
Methinks you may be undertaking some wishful thinking.
A quick review of ansi b16.34 , par 2.5.3 "Pressure test limitations", 2.5.3.1 "valve in the closed position", and 2.5.3.2 "valve in the open position" makes it explicit, that any pressure test that occurs at a pressure above its 38 C ( 100 F) pressure rating or differential pressure rating is soley at the risk of the user. So that is , zero overpressure is permitted , based on 100 F rating. So, it may be an issue for valves that noomrally operate at 100 F.
It is true that B31 allows 10% overpressure during transients, but if a valve were to fail durig hydrotest, and you were to try to get a free replacement from the vendor, it is likely that he will take refuge in the B16.34 statements.
RE: control valves and piping hydrotest