ASME U-Stamp for Surface condenser designed on FV 1

[franklin55]

We are procuring a surface condenser.The heat transfer area of the condenser is around 3500 m2.and one of our requirement mentioned in the RFQ is that the condenser should be U-Stamped. Some of the vendors have replied that since condensers are designed for negative pressure (Full Vacuum),and the design code is HEI not ASME, therefore U-Stamp cannot be applied to it. Can anyone advise whether this is a justified reason?

 

[MrBTU]

First, the cooling water side needs to be designed for positive pressure, and you can specify that the shellside be designed for FV/75, as in 75 psi positive pressure. That way both sides would be U designed to ASME Sect VIII Div 1 and the unit would be U stamped.

 

[rmw]

You basically buy condensers by weight. If designed to ASME, it will have to be designed for something greater than 15 psig which will dictate specific metal thicknesses for that requirement. Doubtful you will ever operate there. If you must, then by all means go with ASME.

HEI designs on the other hand do not consider positive pressure, only negative. Therefore square foot for square foot of heat transfer surface area, your ASME condenser will heavier and thus more expensive.

How much is a ASME nameplate with a stamp on it worth to you when an HEI design will give you a fine condenser?

rmw

 

[franklin55]

Actually we require ASME U-stamp for ensuring the quality and safety. Is there any other means in case the condenser is designed to HEI which we can use as a safeguard? (just like U-Stamp in case of ASME)

 

[rmw]

You can require that it be built to HEI standards using only ASME materials, techniques and welding procedures.

Years ago I designed low pressure vacuum equipment using all ASME design techniques but not stamped. The metal thicknesses were adequate for the service required (normally atmospheric to FV) but not to +15 psig. All other details of the design were right out of Section VIII.

rmw

 

[MJCronin]

Have you contacted the Steam Surface Condenser people and asked this question ?

It seems to me that they must have addressed this issue many times in the past.

The fine people at Graham have always helped me in the past

http://www.graham-mfg.com

Since the tubeside (only) would qualify for and ASME code stamp,(>15 psig design) doesn't that mean that the whole unit requires a stamp ?

 

[rmw]

Graham builds a complete ASME unit (in their round condensers that is and they don't build rectangular ones anymore). If someone wants a HEI design they don't try to compete with it - or that was their position a few years ago. There are some companys that specify total ASME designs and when that happens, they are in their sweet spot and the HEI design folks are at a disadvantage.

With a Graham condenser and a sherman tank you could win a war.

rmw

 

[rmw]

Oh yes,

And Graham is a backbone member of HEI so it isn't as if they don't know how to do it if they wanted to. Obviously they must have gone that route when they built the rectangular condensers for the CCGT plants.

rmw

 

[franklin55]

Is the ASME designed condenser heavier than the HEI design? I am asking this because the vendors has told us that if we want to build it as per ASME the weight will increase by 15 ~ 20%. Consequently it will affect the cost.

 

[rmw]

Absolutely is heavier. I thought I said that in the very first post I made in this thread. I think the vendor has given you just about the right number. And, as I mentioned there also, you buy it by the pound/kilo, whatever. So if you have need for that, then you can justify the cost. If it is just to satisfy a tick box on some ivory tower; never been out to the real world engineer's specification, then it is an expensive tick box.

Some condensers have the possibility of going well positive under certain (usually upset) operating conditions and if so the vessel better be built to do it. But if not, it is wasted effort IMHO.

Some industrial plants have standards for minimum vessel design and every vessel in the plant is designed accordingly so this may not be the only gold plated vessel in the plant.

rmw

 

[MJCronin]

Excellent information rmw........

 

[starfarooq]

The problem of U-Stamp is being faced when most of the Chinese vendors use non-astm material (as the U-Stamp requires ASTM specs material)

 

[SnTMan]

Condenser tubesides often are exempted under U-1(f)

Regards,

Mike

 

[rmw]

Thanks Mike,

Ever since I started reading this thread, I've been playing all the HEI condensers I ever touched back through my mind to see if I could remember even one that was code stamped on the tube side. Round ones, yes. And plenty of those in refineries, chemical plants, etc. Graham's, every (round) one I ever saw, but none of their rectangulars.

Another thought that has occurred to me re; this thread is that HEI is pretty much the standard in the power utility world while the industrial world worships ASME. The larger condensers in the power world are large enough to serve as livestock barns or small airplane hangars in another life while the condensers in the industrial world are generally quite smaller and mostly round.

Therefore it isn't beyond the stretch of reason that someone in an industrial environment would default to the more familiar ASME code as a standard while utility guys would never even consider it - for their condensers, that is.... Boilers and FWH's on the other hand...

rmw