Force on restriction plate in pipe

[Spainers87]

Hi All,

We need to test a newly installed distribution main. It is cement lined ductile iron (500mm). There are some issues with the mortar lining coming away from the pipe. The pipe hasnt been commissioned yet but we expect flows of 400-500l/s.

We are worred avout further deterioration and damage to the large PRV downstream.

We need to test a seciton of the pipe to see the effect on the mortar of design flows. We can get flows of 100 l/s for testing so would need to create a blockage of approx 80% to have a flow velocitty boradly equivalent to 500 l/s.

Unsure yet how to create the blockage but to do that I would like to estimate the force experienced by the blockage under the flows indicated.

Any ideas? Thank you in advance.

 

[bimr]

The approach at this time would be to send a section of the pipe back to the manufacturer for evaluation.

It is not possible to achieve a higher velocity using a smaller flowrate, unless you inserted a smaller diameter pipe inside of the larger pipe.

Perhaps you may consider setting up a test rig with a tank, recirculating pump, and section of the pipe.

The force on the pipe would be the pressure (in psi) times the area.

 

[gerhardl]

You have not stated the operational pressure. Anyway, an operational flow of 500l/s corresponds to a flow velocity of about 2.55 m/s. This seems to be well within allowable and normally certified/tested range of high quality pipeline of your description. (Normal requirements seems to be up to 6m/s ?)

As Bimr has described, there is no simple practical way to test 'a length' of pipe if you cannot obtain the full operational velocity.

Ultrasonic measurements might be a possible way to test if lengths already has a loosened lining. Visual inside is also possible by robot. Note: Seek professional advice on test methods 'in situ'. Flow test at suggested level will give no certain answer on durability/lifetime and quality of the pipeline if defects is present.

You state that concrete lining has come away from the pipe. If this actually is the case, it is a serious quality assurance problem, and arises questions on the whole material and manufacturing process, transport, storing and installation procedures.

PRV's of this size and capacity will normally be protected by (for instance) basket sieves, but this will of course give a limited protection. A full pressure reducing station with shutdown valve before and after the PRV, a smaller bypass with on/off valves and a lesser mechanical operated PRV and measurement instrumentation for the bypass line is assumed already installed in case of a breakdown or maintenance of the PRV.

Defect pipes (with loose lining) must be localized and replaced before commissioning. The cost for this and eventual damages later on will be far higher.