Relief Valve Slurry Application

[stanier]

I am looking for a relief valve DN200 for a mine dewatering application. I need it to relieve at 115m head (163psi). Fluid will be bearing solids. Discharge is to atnosphere.

A spring loaded pinch valve would do but Red Valve limit their pressure to 150psi.

The rigs that these will be mounted on do not have compressed air.

Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[JimCasey]

Not having air make it more complicated.

Some Ideas:
(1) You could use the Red valve if you find a place 10M higher to mount it. Thereby subtracting enough head to get the internal pressure to less than 150 psi.

(2) An electrically controlled system: Pressure switch to monitor system pressure, solenoid valve, and a rack-and pinion actuator on a ball valve. Drive the system with process water pressure. Filter and regulate the water after the pressure switch. If the water contains corrosives, the actuator and solenoid could be stainless steel. Make the pressure switch normally closed, open to alarm. Make the actuator on the ball valve "fail open" so on any loss of electrical supply, the relief opens and dumps pressure.

I did not suggest a pure electrically operated valve because electric actuators are so slow a damaging pressure spike may not be adressed. A fast electric actuator on a small valve takes at least 6 seconds to stroke. By then, the damage is probably done.

 

[Ashereng]

A common alternative to pneumatic actuation is hydraulic actuation.

Many valve suppliers are able to provide both. Maybe try talking to your preferred valve vendor first.



"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[Ashereng]

Oh, almost forgot.

Another solution is bottled gas, such as nitrogen, for the motive medium instead of instrument air.

The downside of course is cost, and they also tend to leak a bit more.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[JimCasey]

Ashereng:
Good points.
My general attitude toward overpressure/safety devices is that they sould be passive: i.e., if you take away the energy source or if a component fails, they perform their safety function.

A bottled nitrogen system >could< do this, but when you run out of N2, you're down until somebody schlepps a tank of N2 to the process.

Hydraulics is a good idea. Something like a Rexa or a Worcester 72 electrohydraulic ball valve actuator can be quite failsafe and operate without much operator intervention.

 

[stanier]

Thanks for the thoughts

Hydraulics on a trailing pump set in a mine environment is a concern because of dirt/maintenance/vibration.

I am not too worried about the surge as the interconnecting pipelines are PE. The modulus is low so the celerity will also be low. The valve wsnt for surge purposes in any event just to protect from overpressure. I will do the surge analysis when I have selected the pumps. Power is reliable in this mine and they would rather repair the PE than have fancy protection devices that they dont maintain.

I have suggested bottled gas and they are still thinking about it.

Process water containing fines tends to be difficult to keep clean. Filters clog and are not maintained.

Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[waross]

How about a bottled liquid instead of bottled gas. You can get a lot more pounds of liquid CO2 in a bottle than pounds of nitrogen. I have also found CO2 to be much more readily available than nitrogen.
With either one, there is a safety issue in the event that a failure dumps the bottle contents, in that either gas will displace the oxygen in the vicinity. With nitrogen you estimate the remaining contents by pressure, with CO2 or other liquified gas you estimate the remaining contents by weight. There are valves for liquid propane bottles that connect to two bottles. The gas is drawn from one bottle. When the pressure fails, (the bottle is empty) the valve shuttles to the other bottle and raises a flag. You may be able to adapt this to CO2 to indicate that a bottle is empty.
respectfully

 

[Ashereng]

waross,

Where have you used liquid CO2 as motive gas?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[JimCasey]

Both the Worcester and the Rexa Hydraulic actuators I mentioned are fully self-contained. Both are designed to be mounted in remote areas and to operate with little attention after you hook up the wires.