Target flow rate for a full pipeline 2

[Muud]

I want to modify an existing filter test setup with a 2 inch piping. The usual flow rates are 10 m3/hr and higher. To be able to test a different type of filter for which flow rates are quite low 1 -3 m3/hr on the same system I doubt that the pipes will remain full. The test fluid is water. Is there a way to calc. what is the minimum flow rate for the existing pipes to keep them full at all times?

 

[1503-44]

One other question. Will you need to accurately control the pressure drop across the filter when testing them? It is usually important to understand the relationship between flows and pressure drops when testing filters.

In the above setups, you may not have the ability to accurately control pressure drop across the filter.

 

[Muud]

@ 1503-44 Would cutting off the last bit of the return line and discharging over the tank rim obviate the vacuum breaker or offers any other advantage?

 

[Muud]

I do favor the discharge setup above the tank for the sake of simplicity compared to drilling a new inlet below the water level. However, I have one concern regarding the discharge above the liquid surface. I suppose it may create unnecessary agitation and cause aeration. I think if the discharge point terminate close to the water surface, it will minimize these effects. What do you propose?

 

[Muud]

@ 1503-44, in most of our filter testing, we only maintain a constant flow rate and the pressure drop across the filter is just recorded. However, the other variant of this test, requires a maintaining a constant pressure drop across the filter and the flow rate is varied. So answering to your question, in some cases yes. We do need to control the pressure drop across the filter. What do you suggest to have
control over pressure drop across the filter?

 

[1503-44]

1. Yes, no vacuum breaker required. The fluid in the riser should acquire a final level equal to bottom id elevation of the last bit of horizontal pipe.

2. I also greatly favour no unnecessary holes in any tank, which is part of the reason I proposed my diagrams above.

You may of course get some air entrainment, however that may also be a more realistic approximation of final user conditions. Water devoid of all air is often not reality, but in any case, with a control valve in the discharge pipe holding backpressure on the filter, a vacuum in the discharge pipe downstream of that valve should not be of concern. (see next answer). Neither will siphoning extend through the valve to your test filter, so I see no problem with any configuration you want for the pipe actually going into the tank. You could even go over the tank rim and downturn, going all the way to the tank bottom with that pipe if you want. No stream to air exposure at all.

3. A back-pressure control valve set for your desired discharge pressure, or a differential pressure control valve on the discharge pipe going to the tank with a signl from a differential pressure transmitter across the test filter inlet and outlet thereby directly setting the pressure you want across the test filter.

 

[LittleInch]

ON item 1, if you put a vertical pipe down into the water but just drill holes in it at intervals this will reduce splashing, but also reduce the chance of syphons or other pressure build up / air locks.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Muud]

Thanks all for your feedback