Maintaining water temp in hydrotest 1

[txcraig]

I have a question concerning hydrotesting pipe in cold conditions.

what will we need to look into when specifications call for water being used for a hydrotest be kept at no less than 60 degrees farenheit? I am thinking we will need a heated tank of some sort with temperature gauges at various locations.

I would appreciate any advice that could be given, specifically a name or brand name for the equipment or ideas on who furnishes this.

 

[davefitz]

you will also need to apply monitoring thermocouples on the part being hydrotested- both the water and the temperature of the metal part being hydrotested needs to be above 60F throughout the test and throughout the entire part being tested. For the case of an outdoor boiler in a cold climate, you might want to look into X-ray or the repair welds in lieu of hydrotest.

The purpose of the 60 F min limit is to ensure adequate ductility in the pressure part metal, to avoid a prompt brittle fracture of the part. For modern hi temperature creep resistant alloys , as applied on the HP main steam line ( P91, P92, P112), their ductility at 60 F is marginal at best, and a hydrotest could cause pre-existing cracks at welds to grow at the speed of sound ( in the metal) if the metal ductility is below some known minimum value. This is a big issue if the water is introduced at hi temp ( 212 f) at the economizer inlet and pumped thru a cold boiler to the HP main steam outlet ( where the P91 is) - by the time the water gets to the HP main steam outlet, it can be well below the 60 F min temp needed for a hydrotest.

 

[zerosum]

A few years ago this phenomenon caused a major problem in a west coast boiler installation during the attempted commissioning. Lots of litigation, too.

 

[metengr]

txcraig;
I am going to ask the obvious. Is this for new construction or are you installing replacement pipe sections in an exisitng line or what?

Hydrostatic testing has its limitations with one being cold weather service conditions. This is the reason for my asking you the specific application. If the pipe sections have been hydrotested by the mill, you can make shop welds and hydrotest completed pipe spools under controlled conditions. In this case, final connecting welds of the shop fabricated spools can be subjected to volumetric examination in the field. However, this all has to be agreed upon between the owner and the installer, this is the reason for my asking the specific application.

 

[WBH]

txcraig,

If I read your post correctly this sounds like a costumer specification to maintain water temp at 60F. I would consult with the customer to see how this requirement has been meet in the past. Heating methods will depend on volume of water, location, and ambient temp and duration of test.

WBH