Flowserve Nordstrom Dynamic Balance Plug Valve and Double DB Plug Valve - Manual (Page 14)

Flow Control
Nordstrom Valves
14 Dynamic Balance ® Plug Valve and Double DB ® Double Isolation Plug Valve FCD NVENIM2005-01
ciples consist of a Body, Plug and Stem, Cover, Adjustment Member,
and Sealant. The function of each of these items is as follows:
1. The Body connects the valve to the pipeline. The Body also
mates with the Plug to form a pressure vessel, capable of opera-
tion under various pressures and temperatures.
2. The Plug, rotated by operation of the Stem, has a tapered sur-
face designed to mate with the Body Taper Bore to provide tight
shutoff.
3. The Cover prevents external leakage and is designed to allow a
finite floating of the Plug.
4. The Adjustment Member is provided so that the position of the
Plug can be set in the proper relation to the Body.
5. Sealant is an integral part of all lubricated Plug Valves and has
three functions:
• Ensures bubble-tight shutoff on hard-to-hold line media by
acting as a secondary seal against seat leakage.
• Provides a flexible and renewable seat, eliminating the need to
force fit or replace sealing parts to obtain a seal.
• Applies Pascal’s Law by providing the hydraulic means neces-
sary to push the Plug from its tapered seat in the Body.
5.11 Sealant System
Nordstrom Valve Sealant functions as an integral part of the lubri-
cated Plug Valve. Sealant is the basic improvement over the dry
plug cock. For sealant to be effective, the valve requires a system of
internal channels: the Nordstrom Sealdport Grooving System.
The Nordstrom Sealdport Grooving System provides complete
shutoff of line media regardless of the flow direction of material
through the valve. Nordstrom valves can be lubricated with the Plug
in any position while the valve is subjected to line pressure. With
the Plug in the closed position, the downstream port is completely
surrounded by a film of Sealant between the Body and Plug seating
surfaces. When rotating the Plug between the open and closed posi-
tions, the grooves exposed to the valve flow passages are discon-
nected from the sealant system.
By maintaining a periodic sealant injection schedule, the Sealdport
grooving system will sustain a pressurized sealant system, regard-
less of whether the valve is in the open, closed, or throttled position.
5.12 Design Features
The principal design features of the Dynamic Balance Plug Valve are
listed below. See illustrations in the Technical Data section.
1. Stem. Stems for wrench-operated valves are made from stain-
less steel for corrosion protection. Wrench-operated Stems have
wrench flats that align the wrench handle with the flow passage
of the Plug, thus becoming an easily visible position indicator.
The Stem is treated with a low-friction PTFE coating to reduce
overall valve torque.
2. Stem Packing. Specially designed by Flowserve Sulphur Springs.
Manufactured from a compound of graphite and PTFE, the stem
packing is pressure-energized (no external adjustments are needed)
and is inert to a wide range of fluids and gases.
3. Plug Balancing Spring. Designed to preload the Plug. This
spring prevents vibration and thermal cycling from wedging the
Plug into the Body Taper, even when the valve is installed upside
down.
4. Bottom Balancing Hole. Integral part of the Dynamic Balance
System. The Balancing Hole of the plug maintains pressure
equalization between the Plug Port and the bottom of the Plug.
5. Balance Hole with Ball Check. (not shown) Ensures that pres-
sure above the Plug is the same as or greater than in the Plug
Port. The Ball Check prevents sealant from entering directly into
the plug port.
6. Sealant Injection Fitting. Provides access for sealant injection
for restoration of damaged seats for drop-tight shutoff.
7. Stem Weather Seal. (wrench operated only) A specially shaped
and constructed seal to protect the stem-to-body joint from
hostile environments that can lead to corrosion.
8. Cover Weather Seals. Consist of individual elastomeric O-rings
around each cover bolt. During assembly of the valve, these
O-rings are compressed between the Body and Cover to protect
the Cover Bolts from the same hostile environments that may
affect the Stem.
9. Tapered Plug. Individually matched to each Body and lapped to
achieve the best possible fit. The Plug’s sealant grooves match
the sealant grooves in the Body to form the Sealdport groove
system. Valves manufactured for corrosive services have Plugs
that are either coated with electroless nickel or made from corro-
sion resistant material.
10. Plug Adjusting Screw. Provides a means of properly position-
ing the Plug into the Body after valve assembly. A hex-head bolt
(or three-bolt cover plate) is provided to reduce the chance of
accidental turning of the Plug Adjusting Screw.