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Fluid conveyance · Bronze gate valves

TECHNICAL DATA SHEET

FT-TC-VAL-COMPUERTA-BRONCE-001

Issue date: August 4, 2026 · Rev. 001

Check the current version

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

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Two NPT threaded gate valve references in ASTM B62 C83600 cast bronze (85-5-5-5 alloy) from the TECTUL catalog, with solid wedge, bronze stem and screw, ASTM B16 C36000 brass gland, asbestos-free PTFE packing and ASTM A536 ductile iron handwheel. Nine sizes per reference, 1/2″ to 4″ (DN 15 to DN 100), tapered NPT threaded ends per ASME B1.20.1. This sheet develops the rating system that governs the family — the MSS SP-80 dual SWP/WOG classes — and why a gate valve is a full-shutoff device that must not be operated partially open.

SKU VT-59207 (Napoli bronze gate valve) · 2 bronze gate references, 9 sizes each from 1/2″ to 4″

1. Technical specifications

Materials by component

C83600 composition per ASTM B62. The exact stem alloy grade and the bonnet detail (screwed or bolted to the body) are manufacturer data for each figure: confirmed on quotation or in the PDF sheet attached to each product.

Standards and service framework

Size equivalence

Bronze gate references in the TECTUL catalog

Face-to-face dimensions, height with the stem extended and weight per size are not standardized by MSS SP-80 for threaded bronze valves: each manufacturer sets its own pattern, so they are confirmed on quotation or in the factory PDF sheet attached to each reference.

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

A bronze gate valve is not rated with a single pressure number. MSS SP-80 (Bronze Gate, Globe, Angle and Check Valves) sets dual classes: each class carries two ratings, the SWP (Saturated Working Pressure, allowable pressure on saturated steam — the real thermal limit) and the WOG (Water-Oil-Gas, allowable cold non-shock pressure). The two travel together and rise together.

¹ Saturation temperature of steam at the stated SWP. It is a thermodynamic property of water, not of the valve: at that pressure saturated steam is always at that temperature. 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 and no "class 200 WOG" exists in that standard — the WOG figure is declared by the manufacturer per MSS SP-80.

The two reading rules

Rule 1 — the WOG cast on the body only applies cold. The 200, 300, 400 or 600 psi shown on the casting or in the catalog apply up to 38 °C (100 °F). Above that temperature the allowable pressure drops, and on steam the absolute limit is set by the SWP of the same class. A gate valve marked "300 WOG" is also a "150 SWP" valve: at 186 °C it takes 150 psig of steam, not 300 psi.

Rule 2 — SWP and WOG are paired, class by class. You cannot take the SWP of one class and the WOG of another. When specifying a valve you ask for the class (125, 150, 200 or 300) and that class fixes both numbers at once. 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.

What the TECTUL catalog publishes. For the two bronze gate references in this sheet (Napoli and Red White) the manufacturer does not publish the class number on the product page. No value should be assumed: the MSS SP-80 class is confirmed on quotation against the factory certificate or PDF sheet. Within the same bronze family of the catalog, the bronze angle valve does declare 300 PSI (Class 150 → 150 psig SWP) and the stainless globe line declares 200 WOG (Class 125 → 125 psig SWP), which illustrates the range these lines move in.

3. Why a gate valve shuts off but does not throttle

A gate valve is a solid wedge that descends perpendicular to the flow axis until it seats between two tapered seats machined into the body. Fully open, the wedge retracts completely out of the bore: the fluid crosses a straight passage with almost the same section as the pipe. Fully closed, the wedge seals against both seats. Between those two extremes the valve is not designed to work, and there are three engineering reasons not to do it.

1. Erosion of the seat and of the wedge face. At partial opening the whole flow passes through a narrow slot between the lower edge of the wedge and the seat. As the area shrinks, local velocity spikes and the jet strikes the sealing surfaces directly. The result is the wear known as wire drawing: a progressive groove in the seat and in the wedge edge that permanently ruins tightness. The valve stops sealing properly even after returning to full shutoff duty.

2. Wedge vibration and chatter. In a gate valve the wedge is only restrained when it is seated or fully retracted into the bonnet. In intermediate positions it hangs from the screw inside a turbulent flow zone; the uneven thrust makes it vibrate against the body guides. That vibration wears the guides, misaligns the closure and punishes the stem and gland.

3. The control curve is useless. Even without mechanical damage, a gate valve throttles poorly: the relationship between stem travel and flow is highly non-linear. A large part of the travel barely changes the flow, and then the flow changes abruptly over a short stretch near closure. There is no stable working band in which to set the flow with precision.

The trade-off: minimal pressure drop when open

The trade-off of not throttling is also its greatest virtue. With the wedge retracted, a gate valve is practically a length of pipe. Using the resistance coefficient model of Crane TP-410, a fully open gate valve is represented by K = 8·fT, while a globe valve of the same size is represented by K = 340·fT — roughly 42 times more resistance for the same size and the same flow (f_T is the fully turbulent friction factor of pipe of that size).

The coefficients K = 8·fT (open gate) and K = 340·fT (open globe) are reference values from the Crane Technical Paper No. 410 method for fully open, full-bore 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. Construction: rising vs. non-rising stem, and installation

The two stem schemes

In threaded bronze valves from 1/2″ to 4″ the prevailing design is the rising stem with inside screw: the screw threads inside the bonnet and rises with the wedge. The OS&Y scheme (outside screw and yoke), where the thread stays entirely out of the fluid, belongs to larger flanged valves and fire protection lines, not to this threaded family. The exact scheme of each figure is confirmed on quotation or in the factory PDF sheet.

Installation

• Thread. The NPT seal is metal-to-metal taper interference (ASME B1.20.1); the sealant — PTFE tape or paste — fills the helices and lubricates the make-up, but it is not the sealing element. Apply it on the male thread, never on the female, and without intruding into the bore.
• Tightening. Always hold by the body, with a wrench on the hexagonal end flats. Never use the handwheel or the bonnet as a tightening point: the bonnet can loosen and the handwheel can deform.
• Position. A gate valve accepts any orientation and has no flow direction, but the preferred position is stem vertical and upward: it keeps the packing out of the sediment zone and eases operation and gland maintenance.
• Clearance. Leave the stem travel height plus the handwheel above the valve, and lateral room to turn the handwheel a full revolution.
• Commissioning. Open and close slowly. On new lines, flush construction debris before seating the wedge: a burr trapped in the seat produces a leak that is later wrongly blamed on the valve.
• Maintenance. A drip at the stem is corrected by gradually tightening the gland; that is normal maintenance, not a failure. If the drip persists with the gland tightened, replace the PTFE packing.
• Operation. Always leave the valve fully open or fully closed. If the line needs throttling, install a globe valve downstream (it has its own data sheet) and keep the gate valve as the block valve.

5. Frequently asked questions

Is a bronze gate valve suitable for steam?

Yes, up to its SWP. Under the MSS SP-80 dual system, a gate valve that takes 300 WOG cold is a Class 150 and carries saturated steam up to 150 psig, whose saturation temperature is ≈186 °C. That SWP is the real limit on steam, not the 300 psi of the cold label. The exact class of the Napoli and Red White references in the catalog is not published by the manufacturer: it is confirmed on quotation.

Can I leave the gate valve half open to reduce the flow?

No. At partial opening the jet erodes the seat and the wedge edge (wire drawing) and the wedge vibrates against its guides; within weeks the valve stops sealing tight and the damage is irreversible. Besides, the travel-versus-flow relationship of a gate valve is highly non-linear, so it does not even throttle well. Use a globe valve to throttle.

What does the "200 WOG" cast on the body mean?

WOG (Water-Oil-Gas) is the maximum cold non-shock pressure, between −29 °C and 38 °C, per MSS SP-80. In the dual system, 200 WOG corresponds to Class 125, whose limit on saturated steam is 125 psig at ≈178 °C. Above 38 °C the WOG figure no longer applies.

What is the difference between rising and non-rising stem?

On the rising stem the screw travels up as the valve opens and the visible travel indicates valve position, but it demands clear height above. On the non-rising stem the screw turns in place, overall height does not change and it fits pits and confined spaces, but the thread stays permanently submerged in the fluid and there is no visual position indication. In threaded bronze from 1/2″ to 4″ the rising inside-screw type prevails.

Does the bronze in these valves dezincify in potable water?

ASTM B62 C83600 bronze contains only 4–6 % zinc, far below the threshold (~15 % Zn) at which dezincification — the selective loss of zinc that embrittles the part — becomes significant in copper-zinc alloys. That is why valve bronze, unlike some yellow brasses used in plumbing fittings, does not usually require a DZR grade. The project's sanitary and potable-water contact requirements are confirmed separately against the manufacturer's certificate.

What sizes does TECTUL carry in bronze gate valves?

Two references with nine sizes each, 1/2″ to 4″ (DN 15 to DN 100): Napoli and Red White.

6. Application notes

7. Technical notice and limitation of liability