Table 1: CVS 7970 Specifications
1.750” diameter x 8.0” length
10,000 PSI Maximum (689.5 bar)
125 PSI Maximum (8.62 bar)
Connections
1/2”-14 NPT M and 1/8”-27 NPT F
One particular advantage of the CVS 7970 is its
adjustment range capability. Because of the
complete supplied components, there is no need to
purchase and store additional sets of matching
piston and spring components. The installation or
reorientation of the existing piston components
allows for an adjustment range capability of 2 to
10,000 PSI. This is especially convenient for remote
facilities which require changes to pressure settings
to match changes in process conditions.
The CVS 7970 is available in a High-Low
configuration using two pilots mounted and tubed to
a carbon steel or stainless steel manifold (Figure 8).
Your choice of 2-1/2” NPT process or gauge
connections are available. This design allows for
completely independent setting of the high and low
pilots spanning the range of 2 psi to 10,000 psi. This
configuration is available in Auto Reset (not shown)
or Manual Reset (shown, pg 8).
Piston Arrangement
Changeover Instructions
The information in this manual, including the parts
listings and piston detail drawings, will assist you in
completing the Piston Arrangement Changeover.
Caution: Consult and follow the established
safety procedures of your facility prior to
beginning disassembly of any CVS Controls
product. Ensure that all pressure is
exhausted from the system prior to
performing any service work. Failure to
remove the pressure from the system can
result in serious personal injury.
1. Isolate and depressurize the control system.
2. Disconnect the control circuit instrumentation
tubing from control valve, as well as the
monitored process connection from the
piston housing.
3. Where possible, remove the CVS 7970 from
the service location to perform the
changeover in a clean work environment.
4. Loosen the lock nut and remove from the
adjusting cap. (See figure 2)
5. Gently relieve all spring tension by fully
unscrewing the adjusting cap. This allows
access to the storage tube.
6. Unscrew the piston housing from the valve
body.
7. Turn the piston housing upside down and tap
it gently on a flat, clean surface to remove
the piston arrangement. The pistons should
slide out easily.
8. Thoroughly clean the piston components,
including the piston housing and internal
bores, using warm water and a liquid
detergent. Do not use abrasive tools or
acidic cleansers. Dry all components with a
cloth or paper towel.
9. Lightly lubricate all components and seals,
and assemble the piston arrangement as
desired according to the enclosed detail
drawing.
10. When inserting the new piston arrangement
into the piston housing, apply even pressure.
Press evenly using both thumbs on the
piston’s outer edges for the insertion of the
1-1/8”, 1/2” and 3/16” piston arrangements.
11. For the 1/4” piston insertion, install the 1/4”
piston first, using a needle-nosed pliers.
Then press the other piston components into
place.
12. Lightly lubricate the threads of the piston
housing, body and spring housing. Be sure
to use a grease or medium appropriate for
stainless steel.
13. Reassemble the pressure pilot.
14. Adjust the pressure setting to the required
amount, and function test the pressure pilot.
When the desired setting is achieved, tighten
the lock nut securely against the adjusting
cap.
15. Connect the instrumentation tubing and the
pressure connection to the monitored
process.
16. Introduce pressure to the pressure pilot’s
control circuit and monitored process inlet.
Resume normal operation.
