Globe Control Valve Bore ID: ASME B16.34 Sizing Reference

Overview: Why Bore ID Is Not Standardized

For globe control valves, the wetted bore (internal diameter) of the inlet and outlet flow passages is not a published, standardized dimension in the way that pipe OD, flange OD, or flange bolt circle are. ASME B16.5 (Pipe Flanges and Flanged Fittings) calls out flange dimensions — bolt circle, number of bolts, flange OD, raised face diameter, and bore — but per B16.5 Table 20 and II-20 notes, the wetted bore for slip-on and lapped flanges is "determined by purchaser". For control valves specifically, ASME B16.34 §6.2.2 simply requires that flanged ends conform to B16.5 geometry; it does not assign a nominal bore value to the valve body itself.

The reason is practical: a globe valve body is a cast or forged part whose internal geometry — seat bore, cage bore, plug/stem guide bore, and inlet/outlet transition — varies by trim size, flow characteristic, and pressure class. The controlling restriction in a throttling globe valve is the seat–plug interface, not the end connection. As a result, the inlet/outlet bore is sized to (a) not be the controlling element relative to the seat, and (b) provide enough cross-section to seat a gasket on raised-face (RF) or ring-type joint (RTJ) flanges without the gasket intruding into the flow path.

ASME B16.34 Mandatory Appendix E — The Hidden Reference

Although B16.34 §6.2.2 does not publish valve end bores, the standard's Mandatory Appendix E, Table E-4 (page 219 in the 2017 edition) does provide end dimensions for flanged valves for use in piping layout. This is the table the original question's author eventually located. The table is not a manufacturing spec for valve body bores — it is a piping interface reference that lets the designer assume a minimum bore when the valve detail is not yet released. Always confirm with the vendor's certified drawing before fabrication.

Related references that touch bore geometry but do not standardize it:

• ASME B16.34 — Valves: Flanged, Threaded, and Welding End
• ASME B16.5 — Pipe Flanges and Flanged Fittings (NPS ½ through 24)
• Emerson Fisher Globe Control Valves catalog (C011 / X1412)

Question 1 — How a Manufacturer Sizes Inlet/Outlet Bore

If you are designing the valve (manufacturer side), the bore ID is the result of internal hydraulic and mechanical constraints, not a standard lookup:

1. Start with seat bore (the controlling Cv element). For an equal-percentage or linear trim, the rated Cv dictates the seat diameter from Fisher's Cv tables or ISA 75.01.01Cv equations.
2. Step the body bore larger than the seat by an empirical margin (typically 25–60 % area, depending on whether the design uses a contoured or a cage-guided plug). A larger inlet prevents the end connection from becoming the second restriction and avoids vena-contracta recovery losses at the inlet.
3. Verify gasket seating geometry for the chosen RF or RTJ flange. For RTJ (ring-type joint) flanges, the body bore must be at least the RTJ groove's minor diameter plus a small radial clearance; otherwise the ring can bottom out in the flange. For CL1500 RTJ, this typically means the body bore must clear the BX or RX ring's effective sealing diameter plus approximately 0.06 in radial clearance per side.
4. Match downstream piping to avoid an expansion/contraction > 3:1 area ratio where practical, since step changes in the valve body can re-introduce turbulence and shift the installed Cv below the rated value.
5. Cast/forging feasibility — high-pressure CL1500 and CL2500 globe bodies (e.g., Fisher HP, Fisher EH, Type E) are commonly cast in WC9 (1.25Cr-0.5Mo) or CF8M, and the wall thickness between the bore and the OD must clear ASME B16.34 §6 minimum wall requirements for the pressure class.

Question 2 — How a Buyer/Engineer Determines the Bore

From the user side, the working order to find a real bore number is:

1. Request the certified outline drawing (GA / assembly drawing) from the manufacturer. For Fisher HP-series CL1500 RTJ, the drawing lists flange size, flange class, face finish, raised-face diameter, and a "body bore" or "waterway" dimension on the body detail view.
2. Ask the vendor's inside sales / application engineering for the waterway cross-section in the data sheet (Fisher call this the "body port diameter" or "inlet port ID" depending on product line). Expect an answer in inches for US-built valves.
3. Use B16.34 Table E-4 as a fallback when no drawing is yet available. Treat the value as a piping-layout assumption, not a fabrication spec.
4. Measure it on a physical sample with a bore gauge or via CT scanning. This is the only way to get a true value when the documentation is missing.

Specifications — Fisher HP CL1500 RTJ Reference Data

The following table summarizes what is typically published in Fisher HP series data sheets for NPS 1 through NPS 6, Class 1500 RTJ end connections. Bore values are nominal and must be confirmed against the specific valve serial number and certified drawing.

Practical Engineering Notes

• Equal-percentage trim almost always benefits from a body port ID ≥ 1.3 × seat bore to keep the inlet from distorting the flow profile at low travel.
• RTJ gasket interference is the most common reason a field engineer cares about body bore on a CL1500 valve. If the body bore is too small, the BX ring will not seat and the joint will leak at low bolt preload.
• High-pressure-drop gas / liquid flashing service can move the vena contracta upstream of the seat. The body port then becomes a relevant surface for erosion; specify a minimum bore-to-seat ratio in these services.
• Cavitation in CL1500 service is most often controlled at the trim, not the body. Refer to Fisher's anti-cavitation trim (e.g., Cavitrol) rather than reaming the body bore.
• Replacement valves must match the original face-to-face length per ISA 75.08 / IEC 60534-3-1, even if the body bore is slightly different from the original.

Related Components and References

For the broader system, the body bore interacts with the following elements. The linked Emerson globe control valve catalog covers the full product family; the Functions of All Parts (Body, Bonnet, Plug, Actuator) walkthrough on YouTube is a useful visual reference for the geometry described above. Additional Emerson literature relevant to bore sizing includes Fisher product bulletins on the HP, EH, and EZ trim families, and the Fisher Catalog 12 for general control valve sizing.