Nor-Cal N-Series Op Lit - Manual (Page 10)

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N-Series Isolation Poppet Valves
6.2 Valve Will Not Open All The Way or At All
Observe the pneumatic connection on top of the valve to watch the valve stem rise and fall. A completely open valve should show the valve stem / push-to-fit-
connector interface about 0.4” (10mm) above the top cap of the valve. If the valve does not appear to be opening completely, possible causes include:
• Inadequate air supply pressure. (Minimum pressure is 60 psig [414 kPa])
• A kink or blockage in the pneumatic supply line or inlet fitting.
• A faulty solenoid valve, whereby the pressurized air is not routed to the pneumatic cylinder
• Pneumatic air cylinder piston O-ring leak. (Listen for hissing and feel for air escaping between the stem and the top cap near the air inlet fitting.)
• Piston stem seal leak causing compressed air to enter inside of bellows. (Listen for hissing and feel for air escaping between the stem and the top cap
near the air inlet fitting.) This failure mode can also lead to overpressure and failure of the bellows, in which case compressed air would enter the
vacuum system.
6.3 Valve Does Not Seal Adequately As Measured Between Inlet and Outlet Ports
This failure is most often related to the poppet O-ring seal. Consider the following possibilities:
• Poppet seal O-ring is defective, such as being cracked, chipped, process hardened, etc.
• Poppet seal O-ring is contaminated with process debris.
• Poppet valve seat is contaminated with process debris.
• Valve is not closing fully (refer to Section 6.1)
6.4 Vacuum System Will Not Pump Down To Base Pressure
This usually indicates a leak in the vacuum system or a problem with the vacuum pump. There are naturally many different possible causes for this problem, and
some may have nothing to do with the N-Series valve at all. A basic pump operation and vacuum line integrity check should be performed first to narrow the
problem down. If, by process of elimination, it is suspected that a system leak is stemming from the N-Series valve please check the following:
• If available, use a He-leak detector to determine the exact location of the leak. Verify leak integrity at the inlet and outlet flanges as well as in and
around the top cap of the valve.
• Flange leaks can occur if the flanges or O-rings were damaged during installation.
• A valve body leak could occur if the valve was subjected to severe bending moments during installation. Look for signs of deformed port protrusions
and subsequent cracking.
• If the static top cap O-ring is compromised, then ambient air will leak in to the valve body cavity and on in to the vacuum system.
• If the valve bellows is cracked or broken, then ambient air will leak in to the vacuum system through the annulus between the stem and the top cap
near the air inlet fitting.
Seal and bellows kits are available to repair a defective valve in the field. Please refer to Section 7 for spare parts ordering details.
6.5 Position Indicators Are Not Sending Open / Close Signals
The position indicators are designed to provide remote indication when the N-Series valve is either fully open or fully closed. There is a reflective ring on the valve
stem that is used to trigger the optical detection circuit used in the position sensing. If open / close signals are not received by the customer, please consider
these causes:
• The valve is not closing fully, thereby not triggering the closed indicator. (see Section 6.1)
• The valve is not opening fully, thereby not triggering the open indicator. (see Section 6.2)
• The sensor cable is not connected properly or the connector pin-out is wrong. (Refer to Section 5.5 for proper position indicator connection.)
• The position indicator is broken and needs replacement.
The N-Series valve position indicators are mounted on a printed circuit board which, in turn, is located in a preformed slot in the valve actuator cap. It is held in
place by the label on top of the valve. This label must be removed in order to access the position indicator circuit board.