Flow nozzle in thermal powerplant piping.

[Raai2015]

Just need a guidance , Flow nozzle location for Feed water pipe and Main steam pipe. It is a argument between Vertical or horizontal. i am just looking for any supporting writeup to support the argument. for eg something given on this book Power plant control and instrumentation, unfortunately it is costly for me to download. Is there a help?

 

[CGonsalves]

From my experience, customers normally prefer that flow elements be inserted in horizontal pipes, though we're not really given reasons. If they are inserted in vertical pipelines, however, it's recommended that the flow is in an upward direction.

 

[danw2]

The installation needs access to the DP tap/ports, impulse tubing to the DP flowmeter and drop legs and condensate pots if on steam.

Many flow nozzles are sold as meter run assemblies with 20D pipe diameter of pipe. A nozzle by itself needs sufficient upstream piping to meet the accuracy requirement.
No vertical downflow for liquids.

From Liptak's 2003 Instrument Engineers Handbook: Process Measurement and Analysis

[link ftp://ftp.unicauca.edu.co/Facultades/FIET/DEIC/Materias/Instrumentacion%20Industrial/Instrument_Engineers__Handbook_-_Process_Measurement_and_Analysis/Instrument%20Engineers%27%20Handbook%20-%20Process%20Measurement%20and%20Analysis/1083ch2_29.pdf]Link[/url]

Flow Nozzles

Tap installation precautions are the same as for orifice plates. The preferred installation position for flow nozzles is horizontal, but they can be installed in any position. However, a vertical downflow position is preferred for wet steam or for gases and liquids with suspended solids. In general, up stream and downstream piping requirements are similar to those required for orifices. Because of the width, nozzles installed between flanges are difficult to remove. Common practice is to provide a flange in the downstream piping to allow the nozzle to be removed as part of a spool section for inspection at regular intervals. Sometimes, inspection openings are placed just upstream of the nozzle so that frequent inspections can be made without removing the nozzle from service.

2.29 Venturi Tubes, Flow Tubes, and Flow Nozzles Installation

A venturi tube may be installed in any position to suit the requirements of the application and piping. The only limitation is that, with liquids, the venturi is always full. In most cases, the valved pressure taps will follow the same installation guidelines as for orifice plates.

Upstream piping should be as long as needed to provide aproper velocity profile (Figure 2.29g). However, in most installations, shorter upstream piping is required than for orifices, nozzles, or pitot tubes, because the venturi hydraulic shape itself provides some flow conditioning. Often, the combined length of a venturi and its upstream piping is less than the overall amount of piping required for an orifice or nozzle. Figure 2.29h shows typical upstream pipe diameters required for various elements at 0.7ß ratio and one elbow upstream. Straightening vanes can be used upstream to reduce the inlet pipe length.

In Fluid Meters, the ASME recommends the use of tubular straightening vanes (19 tubes and 2 diameters long) upstream of the venturi to reduce the inlet pipe length. The vane installation should have a minimum of 2 diameters upstream and 2 diameters downstream before entering the venturi.

There is no limitation on piping configuration downstream of the venturi except that a valve should be no closer than two diameters. Valves on other devices that protrude into the flow stream should not be mounted upstream of the venturi, if possible.

 

[JGard1985]

Also...related to any sort of pressure instrumentation, make sure your instrument sensing lines are properly pitched depending on service conditions

Jeff
Pipe Stress Analysis
Finite Element Analysis

http://www.xceed-eng.com

 

[georgeverghese]

As with all other gas streams that can condense, the following would be applicable to the FE in steam service:
a)FE should be at a high point and downstream section should continuously slope down towards system where steam condensate is collected / drained away.
b)FE impulse lines should be top tapped on the pipe and self draining(into main pipe). If self draining is not possible or not practical, then use remote seals.