XXII. 2900 Series POSRV Options
A. Backflow Preventer
When the pilot operated safety relief valve is not
vented directly to atmosphere, it is possible to build
up backpressure in the discharge line. This is typical in
situations where several valves manifold into a common
discharge header. Should the discharge line pressure
exceed the valve inlet pressure, it could cause the disc
to lift and allow reverse flow through the main valve.
This situation can be eliminated through the use of the
Backflow Preventer.
Note: Item #23 in Figures 3, 4 and 5 is the same Field
Test Connection shown here in Figure 61. Shuttle
Base (23c) can be square or octagon bar stock.
A.1 Disassembly Instructions
1. Remove Shuttle Plug from Shuttle Base by
unscrewing counterclockwise.
2. Remove Shuttle Ball, Tube Filter, and O-Rings
and discard.
A.2 Cleaning
1. If required, clean parts to remove all rust, burrs,
scale, organic matter, and loose particles. Parts
are to be free of any oil or grease except for
lubrication as specified in this instruction.
2. Cleaning agents used shall be such that effective
cleaning is assured without injuring the surface
finishes or material properties of the part.
3. Acceptable cleaning agents include demineralized
water, nonphosphate detergent, acetone, and
isopropyl alcohol. Parts must be blown dry or wiped
dry after cleaning.
4. If you are using cleaning solvents, take precautions
to protect yourself from potential danger from
breathing fumes, chemical burns, or explosion. See
the solvent’s Material Safety Data Sheet for safe
handling recommendations and equipment.
5. It is not recommended to “sand blast” internal parts
as it can reduce the dimensions of the parts.
A.3 Parts Inspection
1. Shuttle Base: Galling or excessive wear on the
threads. Check for any corrosion or pitting.
2. Shuttle Plug: Galling or excessive wear on the
threads. Check for any corrosion or pitting.
A.4 Reassembly Instructions
Lubricate O-Rings with silicone grease BHGE P/N SP505.
1. Assembly of Field Test Connection / Backflow
Preventer Assembly.
a. Insert one of the Small O-Rings into the Shuttle
Base counter bore.
b. Insert the Tube Filter into the Shuttle Base.
c. Insert Shuttle Ball inside of Tube Filter.
d. Insert the other Small O-Ring into the Shuttle
Plug counter bore. Install Larger O-Ring into
groove located on OD of Shuttle Plug.
e. Thread Shuttle Plug into Shuttle Base, wrench
tighten.
Figure 61: Field Test Connection / Backflow
Preventer Option
23a
23e
23b
23c
23d
23b
Figure 62: Backflow Preventer Option
Ref. No
Part
23a
Shuttle Ball
23b
O-Ring
23c
Shuttle Base
23d
Shuttle Plug
23e
Tube Filter
74 | BHGE
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