Flushing pump sizing for turbulent flow

Try this site http://www.penberthy-online.com/jet5c.asp

Depco Pump also has several pump engineers that can help with application assitance

800-446-1656 www.depcopump.com

Hi Guest,

Many thanks for your response,

I have emailed Depcopump.com to see if they have UK / EU agents.

FYI, see my reply to Codey.

Thanks again,

Scot

Hello HydroScot

Not quite sure what you're doing, but to answer Also that the 7m/sec velocity is necessary for turbulent flow? - Not on water it isn't. As you say Reynolds number is high (~ 700000 with viscosity 1cP = 0.001 Pa.sec). If the hydraulic flushing fluids etc have viscosity 100 cP, Reynolds number is still ~ 2x high enough for turbulence. Car engine oil has viscosity ~ 30 cP according to my data.

Your calculated flow 3500 ltre/min is about right for 7 m/s in 4" pipe.

Cheers...Codey

Hi Codey,

I appreciate your response, thanks.

What I am trying to do is to size the most efficient pumps (flow) to ensure a turbulent flow in a range of pipe diameters up to and including 4" dia. The specn is quite vague but the 7m/sec has been supplied by the customer (via an agent, so I am unable to get any more clarification!)

I myself do have experience of flushing much smaller pipes and size the pump system output based on a Reynolds number of approx 4,000 for turbulent flow, so I question why the velocity (and pump delivery) needs to be so high. I suppose I am asking if you (or any other reader) have experience of flushing ships pipe lines (which I am assuming are hydraulic) but the specn meantions acid and alkaline cleaning chemicals for which I have no further detail.

I have attached the specn FYI (Abbreviated to suit) as follows:

The flushing station to be of modular type, it will be used onboard vessels (boats, tug,boats, etc..)
- No. of pumps: 2-4 electric pumps with suitable characteristies, compact with the circulating tank (pumps can be run as one, two or three parallel connection in order to increase the flow rate).
- Pumps capacity : enough to have flushing speed not less than 7m/sec.
- Pumps' output pressure 5 bar (or higher if needed to cover our requirements).
- Each pump can run independently to allow flushing small pipe diameters.
- The required velocity 7m/sec. will be at the end of the flushing loop (length of pipes are variable).
- Type of motors: AC induction motor, 3 phase, 380V, 50Hz, IP67, 3 wire without neutral, marine. explosion proof type of motor to be offered as an option with separate price.
- Pipes' diameters to be flushed up to 4"
- Pipes materials are carbon steel, stainless steel.
- Circulating tank capacity to be about 3m3 equipped with heater and cooler.
- The flushing station will be used outdoor (30 - 50 C, 95% humidity).
- The flushing station made of stainless steel material to resist corrosive atmosphere.
- Complete set of pressure line and return line hoses to be supplied equipped with quick closing coupling ( 4 hoses 30m long each).
- Return line with filtration unit ( 3, 5 & 10 micron), filters of standard type to be supplied.
-- Fluids to be used for flushing will include cleaning chemicals (acids & alkaline), hydraulic flushing oils, etc....
- All types of contaminated solids can be removed.
- The flushing station to be equipped by mean of nitrogen injection to improve the cleaning ability.
- Flooded suction is accepted.
- All gauges, indicators & accessories to be supplied and to be stated in your offer.
- The flushing station equipped with the suitable lifting eyes for transportation & hoisting purposes.

............end of specn.

Of course, the customer may have good reasons for such a high flow rate (the oil reservoir size indicates a high flow rate doesn't it?), so maybe I should just go with the flow (pun intended) and quote for high flow pumps. Next problem then is to get high flow filters to suit !

What do you think?

regards. Scot

Hello Scot

I've no direct experience of what you're doing, but a few comments, if it's any use.

Spec says 7 m/s, presumably based on experience, so I think I'd go along with it. As discussed, it's turbulent by a big margin.

The required velocity 7m/sec. will be at the end of the flushing loop (length of pipes are variable) - comment that velocity and turbulence don't depend on pipe length.

With ref to the 5bar minimum - I don't know what pipe runs are involved, but losses are fairly high at 7 m/s, estimated ~ 80m of 4" pipe or 40m of 2" to give 5 bar ΔP on water. I think you need details of the fluids, as hydraulic flushing oil sounds like it could have signicant viscosity. This means higher headloss and could affect pump selection and perhaps pump type. I assume centrifugal if it's like water, but maybe not if it's much more viscous.

For the filter, I used one from Boll a year or two back, link below. Flow was ~ 4600 litre/min, but it wasn't at 10 micron, 1mm if I remember right. There are plenty (pun intended!) (if they're still called that) of suppliers around.

www.bollfilteruk.co.uk

Cheers....Codey

Hi Codey,

I take your point regarding pressure drop allowance, but not knowing the pipe run lengths it will involve some quesswork.

I downloaded some info on flushing oils and it appears that they are available in a variety of grades e.g. 15, 32 etc as per standard oils, but I am not party as to what grade the customer will use, so will qualify "low viscosities" in my quote.

I do not know of Boll but have used Plenty in the past (contradiction intended). Pall have just confirmed that they can supply filters with the expected flow rates and micron ratings so I will probably stick with them as we already use them for our standard filtration systems. I will check out Boll though.

Thanks again.

Scot.

Hello. 1.) Acid and alkaline solutions. This refer to the chemical cleaning (pickling). In this phase you don't need a minimun speed or reynolds number. 2.) Flushing: hot oil flush. when the temperature is high, the viscosity is low. For example, VG46 oil (viscosity grade 46) to 40 C is 46 mm2 / s. A 80 C is 20 mm2 / s.