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# Fluid velocity limit

## Fluid velocity limit

(OP)
What is your recommandation for the maximum velocity of water  in a stainless steel pipe?

What are the limitating phenomena (abrasing, pipe vibrations, ...)?

Replies continue below

### RE: Fluid velocity limit

Checkout the NORSOK standards homepage

It includes a Process Design specification with general requirements for line sizing at

http://www.nts.no/norsok/p/p00104/p00104.htm

Regards
Mogens

### RE: Fluid velocity limit

Consider energy cost usage as a possible limiting factor.  AT \$.10 per kWH blended, I use 6 FPS as a good rule of thumb for standard black steel.  For SS pipe, the cost is much higher for materials, so your economic model would tend towards a faster flow rate as being optimal, based on installation cost and future energy usage.

Above 8 FPS, other factors such as valve erosion may come into play.  I am not a real expert as that stuff in a shoot from the hip way.

Steve

### RE: Fluid velocity limit

Higher the flow rate, higher the headloss and consequently higher the cost of pumping per cubic meter. In most of the installations, energy-cost is the governing criteria for limiting the velocity in pipes.

### RE: Fluid velocity limit

The limiting factor for velocity in a pipe line is the point where headloss equals vapor pressure of the liquid.  The higher the velocity, the greater the headloss, the quicker the liquid boils, the faster your system fails.

### RE: Fluid velocity limit

Don't know if this would help -- but for stainless heat exchanger tubing, TEMA says max flow velocity should be less than 12 fps.  Main concerns are erosion and tube vibration.

Patricia Lougheed

### RE: Fluid velocity limit

I am looking for a fitting similar to that used on automobile A/C compressors. It consists of the tube itself, which is a close fit in a deep (~2XD) smooth bore in the compressor casting, and a tab (probably brazed onto the tube) that has one screw hole.

I am trying to increase flow capacity in a situation where an NPT fitting was used and there is not enough material on three sides of the boss to go to a larger pipe fitting. Fortunately on the fourth side I have room for the hold-down screw on a fitting of this type.

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