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Fluid conveyance · Bronze globe valves

TECHNICAL DATA SHEET

FT-TC-VAL-GLOBO-BRONCE-001

Issue date: August 4, 2026 · Rev. 001

Check the current version

Threaded bronze globe valves, ASTM B62 C83600 — throttling and dual SWP/WOG classes (MSS SP-80)

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Two NPT threaded globe valve references in ASTM B62 C83600 cast bronze (85-5-5-5 alloy) from the TECTUL catalog, with a disc that seats axially on a seat located in the flow path, copper alloy stem and screw, ASTM B16 C36000 brass gland, asbestos-free PTFE packing and ASTM A536 ductile iron handwheel. Six published sizes per reference, 1/2″ to 2″ (DN 15 to DN 50), with the Napoli 330 line has 1 of 6 variants active and the Red White 125, 2 of 6. This sheet develops the one functional advantage that justifies its higher cost and higher pressure drop compared with a gate valve: a globe valve can throttle flow in a stable way.

SKU VT-104977 (Napoli 330 bronze globe valve) · 2 bronze globe references, 6 published sizes each from 1/2″ to 2″ with

1. Technical specifications

Materials by component

C83600 composition per ASTM B62. The seat type per figure (metal-to-metal or PTFE soft seat), the stem alloy grade and the bonnet-to-body joint are manufacturer data: confirmed on quotation or in the PDF sheet attached to the product.

Standards and service framework

Size equivalence

Bronze globe references in the TECTUL catalog

The numbers accompanying the commercial name (330 and 125) are manufacturer figure designations and must not be read as MSS SP-80 classes without confirming against the factory sheet. Face-to-face dimensions, height and weight by size are not standardized by MSS SP-80 for threaded bronze valves and are confirmed on quotation.

2. MSS SP-80 dual classes: how to read the pressure of a bronze globe valve

Like the gate and angle valves, the bronze globe valve is rated under MSS SP-80 (Bronze Gate, Globe, Angle and Check Valves) with dual classes: each class carries an SWP (Saturated Working Pressure, allowable pressure on saturated steam) and a WOG (Water-Oil-Gas, allowable cold non-shock pressure). The two figures are paired and rise together.

¹ Saturation temperature of steam at the stated SWP: it is a thermodynamic property of water, not of the valve. It is the same reference value ASME B16.3-2021 (Table 3-1, note 1) uses for the 186 °C limit of class 150 threaded fittings. WOG/CWP is the maximum cold non-shock pressure (−29 °C to 38 °C); it is not an ASME B16.34 class — the WOG figure is declared by the manufacturer per MSS SP-80.

The two reading rules

Rule 1 — the WOG only applies cold. The 200, 300, 400 or 600 psi in the catalog apply up to 38 °C (100 °F). On steam, the limit is set by the SWP of the same class: a "300 WOG" globe valve is also a "150 SWP" valve and at 186 °C it takes 150 psig of steam, not 300 psi.

Rule 2 — SWP and WOG are paired. The SWP of one class is never combined with the WOG of another. If the supplier only declares the WOG, the class is determined: 200 WOG → Class 125; 300 WOG → Class 150; 400 WOG → Class 200; 600 WOG → Class 300.

The third rule, specific to globe valves: the throttling ΔP is not the rating ΔP

In a gate valve, which works only open or closed, the relevant pressure is the line pressure. In a globe valve that throttles permanently, the critical element is the pressure drop across the seat with the valve partially open. SWP and WOG limit the pressure the body contains, not the differential the seat can sustain continuously without eroding or cavitating. A Class 125 valve installed on a 60 psi line can be perfectly within rating and still destroy its seat if it is left throttling a high ΔP for months. The allowable continuous throttling differential is manufacturer data and is confirmed on quotation.

What the TECTUL catalog publishes. For the two bronze globe references in this sheet (Napoli 330 and Red White 125) the manufacturer does not publish the class number on the product page, and the numbers 330 and 125 in the commercial name are figure designations: they must not be interpreted as classes. The value is confirmed on quotation against the factory certificate or PDF sheet. As a family reference, the stainless globe line in the same catalog does declare 200 WOG (Class 125 → 125 psig SWP at ≈178 °C).

3. A globe valve does throttle: what it gains and what it costs

Globe geometry is exactly the opposite of gate geometry. Instead of a wedge that withdraws from the bore, a globe valve forces the fluid to rise into a chamber, cross a horizontal orifice — the seat — and descend again. A disc rests on that orifice and moves up or down with the stem. The disc motion is parallel to the orifice axis, not perpendicular to the flow.

Why that geometry allows regulation

• The flow area varies progressively and controllably. The effective area is the lateral surface of a cylinder whose height is the disc-to-seat gap: it grows smoothly with stem travel, so there is a wide, stable working band in which the operator can set the flow. In a gate valve, almost all the flow change is concentrated in a short stretch of the travel.
• The disc is guided and backed. Unlike the hanging wedge of a gate valve, the globe disc stays guided by the stem with the fluid thrust along a defined axis: it does not chatter in intermediate positions.
• Wear occurs where it should. The throttling jet strikes guiding surfaces and the disc, not the edge of the sealing surface as in the wire drawing of a gate valve. The valve tolerates working partially open for long periods.
• Travel is short. A displacement on the order of a quarter of the seat diameter is enough to go from closed to fully open, which makes operation quick and precise compared with the full travel of a gate valve.

The cost: pressure drop

The two 90° turns and the restriction at the seat make the globe valve a significant resistance even when fully open. Using the resistance coefficient model of Crane TP-410, a fully open globe valve is represented by K = 340·fT, against K = 8·fT for an open gate valve of the same size: roughly 42 times more resistance (f_T is the fully turbulent friction factor of pipe of that size).

The two limits of throttling

Cavitation with liquids. When throttling, the local pressure at the vena contracta of the seat falls far below the downstream pressure. If that local pressure drops below the vapour pressure of the liquid at service temperature, bubbles form and implode as pressure recovers: that is cavitation. It sounds like gravel and erodes the seat and disc within weeks. It is avoided by staging the ΔP, raising the downstream pressure, or using a control valve designed for the service.

Erosion with steam and gases. With wet steam or particle-laden gases, the high-velocity jet through a small opening erodes the seat by impact. For permanent steam throttling it is advisable to oversize the valve so it works further open, or to move to a pressure-reducing valve.

The coefficients K = 340·fT (open globe) and K = 8·fT (open gate) are reference values from the Crane Technical Paper No. 410 method for fully open valves; the actual value of each figure depends on the manufacturer's internal design. If pressure drop is critical to the design, it must be verified against the Cv or K published by the manufacturer of the specific reference.

4. Soft or metal-to-metal seat, and flow under the disc

The two seat types

The seat type of each catalog figure (metal-to-metal integral to the body or PTFE soft seat) is manufacturer data: confirmed on quotation or in the factory PDF sheet. The selection rule is simple: if there is steam or medium-high temperature, metal-to-metal seat; if tight shutoff and low torque in cold services are the priority, soft seat.

Flow direction: why a globe valve has one

Unlike a gate valve, a globe valve is not symmetrical: the seat is mounted on an internal web and the disc approaches it from one particular face. The conventional arrangement takes the fluid under the disc, so line pressure pushes the disc in the opening direction (flow-to-open).

Field rule: always respect the manufacturer's marking. If the body carries a flow-direction arrow, follow it without discussion; if it does not, identify the seat arrangement before mounting. Reversing a globe valve designed for flow under the disc subjects the packing to permanent pressure, can cause disc vibration at small openings and, in high-ΔP services, punishes the seat. The flow direction of each figure is confirmed in the factory PDF sheet or on quotation.

Installation and operation

• Thread. NPT seals by tapered metal-to-metal interference (ASME B1.20.1); PTFE tape or paste fills the helices and lubricates the make-up. Apply it on the male thread, never on the female, and without intruding into the bore.
• Tightening. Hold by the body with a wrench on the hexagonal end flats; never by the handwheel or the bonnet.
• Orientation. Preferably with the stem vertical and upward. On steam lines, avoid mounting with the stem downward: condensate collects in the bonnet and punishes the packing.
• Operation. Open and close slowly, particularly on liquids, so as not to generate water hammer by changing the flow abruptly. When closing, tighten only enough to seal; forcing the handwheel onto a metal-to-metal seat deforms the disc.
• Permanent throttling. Avoid operating steadily at very small openings: that is where jet velocity peaks and where cavitation and erosion appear. If the working point always sits near closure, the valve is oversized.
• Maintenance. A drip at the stem is corrected by gradually tightening the gland; that is normal maintenance. A drip through the seat with the valve closed indicates disc or seat wear, not packing wear.

5. Frequently asked questions

What is the real difference between a globe valve and a gate valve?

The gate valve is a full-shutoff device: fully open it leaves an almost full bore and loses very little pressure, but at partial opening the seat erodes and the wedge vibrates. The globe valve does throttle stably, because the disc is guided and the flow area varies smoothly with travel; in exchange, even fully open it loses roughly 42 times more pressure than a gate valve of the same size. Install gate valves at block points and globe valves only where regulation is required.

Is a bronze globe valve suitable for steam?

Yes, up to the SWP of its MSS SP-80 class. A figure that takes 300 WOG cold is Class 150 and carries saturated steam up to 150 psig, whose temperature is ≈186 °C. For steam it must have a metal-to-metal seat, not a PTFE soft seat. The exact class of the catalog's Napoli 330 and Red White 125 references is not published by the manufacturer and is confirmed on quotation.

Are the "330" and "125" in the name the pressure class?

Not necessarily: they are manufacturer figure designations. They must not be read as MSS SP-80 classes without confirming against the factory PDF sheet or on quotation; assuming so can lead to installing a valve below the service pressure.

How much pressure do I lose by installing a globe valve?

Considerably more than usually estimated. Using the Crane TP-410 method, an open globe valve is equivalent to K = 340·fT: on a 1″ line with water at 2.0 m/s that is about 1.60 m of water column (≈0.16 bar) per valve, against 0.038 m for a gate valve of the same size. In systems with several globe valves that loss accumulates and must enter the pump calculation.

Can I leave the globe valve almost closed permanently?

That is the operating mode that punishes it most. At very small openings jet velocity peaks: with liquids cavitation appears — a gravel-like noise and seat erosion within weeks — and with steam or gases, impact erosion. If the working point always sits near closure, the valve is oversized and it is advisable to drop a size or move to a regulating valve.

Which way round is it installed?

A globe valve does have a flow direction. The conventional arrangement takes the fluid under the disc, so that with the valve closed the stem packing is depressurized. If the body carries an arrow, follow it without exception; if it does not, identify the seat arrangement before mounting. The direction of each figure is confirmed in the factory sheet.

6. Application notes

7. Technical notice and limitation of liability