Straight Length Before and After Strainer at Steam Turbine Inlet

[magreen]

Hi,
A manufacturer of steam turbine requires a long straight length at upstream and downstream of a strainer at steam turbine inlet.

The turbine is about 14MW and steam flow is about 85t/hr. Size of inlet pipe is 8in. The length of strainer is 650mm. The manufacturer requires 2500mm straight length at upstream and downstream of the strainer. Is this requirement necessary for such cases? Or does it have a technical reason?

Could you please share with me your experience.

Thanks in advance.

 

[byrdj]

Is this a “strainer” to prevent foreign materiel from passing through the valves and entering the turbine? All of the units I dealt with the strainers were part of the first turbine’s protection/control valve. Thus no straighten section prior or aft.
Straighten sections are normally associated with a flow measurement device like orifice or nozzle. And then measurement of steam flow in the pipe were rare.

 

[tbuelna]

A 650mm (25.6 inch) long "strainer" inside an 8 inch pipe would seem to present a flow situation that requires careful consideration. The long straight sections of pipe fore/aft of the strainer are likely required to ensure the pressure and flow conditions across the strainer are within the limits the turbine was qual tested for.

So in short, yes the design of the inlet pipe described by the OEM should be followed.

 

[JJPellin]

Our largest steam turbine was originally equipped with a centrifugal separator in the steam supply line. This separator would rotate the steam flow, throwing solids or liquid to the outside where they would be directed to a mud pot on the bottom od the device. This type of searator did require a straight run of pipe. Are you certain that this is not the sort of "strainer" that is being proposed?

Johnny Pellin

 

[JJPellin]

As noted by byrdj, the only strainers I have ever seen are built into the T&T valve and do not require a straight run of pipe.

Johnny Pellin

 

[byrdj]

JJP,
I learned something new today, THANKS
would this be the type of cyclone seperator of which you mentioned.

http://www.kelburneng.co.uk/pdf/Steam-Separation-Products.pdf

I can see they would be benificial in the industrial boiler / turbine application.
(and the need for straigntening sections prior and aft)

 

[JJPellin]

That is the sort of searator I was referring to. Ours was in the 8 inch supply line to our 17,000 HP drive turbine on our FCC main air blower. We elininated this separator because our steam quality is excellent and we wanted to reduce the pressure drop.

Johnny Pellin

 

[magreen]

byrdj & JJPellin,
The strainer is a common cone type one and not special, not cyclone type.

Thank you all.