D E C 2012

DANIELTM MODEL 788DVC DIGITAL CONTROL VALVES

Table 6-1 provides information for identifying and correcting operational problems you may experience with your control valve. Please keep in mind this information is not exhaustive and that system abnormalities may result from causes other than valve error. This information is provided to assist in general field repairs.

 

Table 6-1. Troubleshooting

Condition

Probable Cause

Correction

Valve will not open

Upstream valve is closed.

Open valve.

 

Pump is not operating.

Start pump and check for cavitation.

 

Downstream valve is closed.

Open valve. (Check coupler on bottom

 

 

loading units and internal valve in

 

 

truck.)

 

Insufficient pressure.

Check pump. Check bypass and strainer

 

 

in line.

 

Clogged strainer.

Clean strainer.

 

Swollen o-rings.

Disassemble valve and replace o-rings.

 

 

Check compatibility of o-rings with

 

 

product.

 

Pilot malfunction.

Consult pilot manual.

Valve opens too slowly

Valve inlet pressure below normal.

Check strainer and pump for

 

 

obstruction.

 

Swollen o-rings.

Disassemble valve and replace o-rings.

 

 

Check compatibility of o-rings with

 

 

product.

 

Pilot malfunction.

Consult pilot manual.

Valve will not close off tightly

Bent indicator stem.

Replace indicator

 

Foreign material lodged in main

Disassemble valve and inspect piston.

 

valve piston seat.

 

 

Swollen o-rings

Disassemble valve and replace o-rings.

 

 

Check compatibility of o-rings with

 

 

product.

Piston or seat o-ring cut or defective.

Disassemble valve and replace, if necessary.

Pilot malfunction.

Consult pilot manual.

6-2

TROUBLESHOOTING

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Emerson 788 DVC manual Condition Probable Cause Correction