Emerson 788 DVC manual Condition Probable Cause Correction

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