Manufacturer Metal Seat Ball Valves

KTN Valves manufactures metal seat ball valves from CL150 to CL2500, in floating and trunnion designs. Every seat is lapped against the ball of its own valve and closes metal against metal, which gives class VI shut-off to ANSI/FCI 70-2. Balls are hardfaced in chrome, stellite or tungsten carbide. Fire-safe API 607 and API 6FA on request.

Category overview

A metal seat ball valve shuts off by metal-to-metal contact between ball and seat, with no polymer in the sealing line. KTN manufactures the range to class 2500, floating and trunnion mounted, in stainless or carbon steel. It answers the services that destroy PTFE: temperature, abrasion, solids and thermal cycling.

Ball and seats are ground and lapped as a matched pair in the plant, which is where class VI shut-off and the higher torque both come from. This is the severe-service end of the KTN ball valve family.

How to choose a metal seated ball valve

Five data points close the selection. The first one decides the category.

• Reason for the metal seat. Temperature above the fluoropolymer limit, abrasion, solids, cycling or a high class. Without one, a soft seat is enough.
• Pressure class. CL150 to CL2500, with the guided ball taking over from CL600.
• Nominal size. It sets the floating-to-trunnion crossover. For drawings in inches, use the DN to inches conversion table.
• Fluid. Clean and hot accepts a chrome plated ball; sand, catalyst or mineral pulp calls for stellite or tungsten carbide.
• Torque. A metal seat raises it and the actuator grows with it: see valve automation.

Applications and sectors

Metal seats belong where shut-off is critical and the service severe. KTN supplies the range to oil & gas, refining and petrochemicals, steam and thermal oil circuits, power generation, mining, cement, pulp and paper, and water treatment.

Steam and thermal oil are governed by cycling: no polymer holds seat geometry through thousands of expansions.

Types and executions we manufacture

KTN manufactures seven live metal seated executions, differing in connection, pressure class and the way the ball is held.

What a metal seated ball valve is and how it works

It is a quarter-turn valve with a drilled ball whose two sealing surfaces are metal. KTN machines, hardfaces and laps that assembly in house.

How a metal seat actually seals

The seat is ground and then lapped against the ball of its own valve until both surfaces are conjugate. Closure comes from metal against metal, with very high contact pressure concentrated in a very narrow band, which flattens the asperities and cuts the flow path.

Three consequences follow. Shut-off reaches class VI of ANSI/FCI 70-2, the tightest grade of the standard and what the market calls a zero leakage ball valve. Torque runs above a soft seat of the same size, since friction rises with contact pressure. And ball and seats form a matched set, replaced together.

Floating versus trunnion ball valve

This choice sets the execution, the torque and the price. In a floating design the ball is not fixed to the body: the seats and the stem drive hold it, and line pressure pushes it against the downstream seat. That thrust produces the seal, with few parts and automatic wear compensation.

The limit is mechanical. The full pressure force over the bore area lands on one seat and grows with the square of the diameter. Torque rises with it and with differential pressure. A metal seat starts from a high contact load, so the curve climbs sooner.

In a trunnion ball valve the ball is fixed by an upper and a lower trunnion running in bearings, so it does not move. The seats move instead, pressed against the ball by springs and by line pressure itself. Torque is much lower and stays nearly constant.

The practical crossover sits around DN150 and class 600. Below it the floating design wins on cost. Above it a metal seated trunnion ball valve is the sensible answer, and from class 900 to 2500 the guided ball is the only viable execution. Actuator sizing follows: a floating valve is sized for the worst-case differential pressure, a trunnion valve stays almost flat.

Fire-safe API 607 and API 6FA

The fire test burns the valve and then measures internal and external leakage. A soft-seated valve relies on a secondary metal seat: once the PTFE burns away, the ball rests against a machined shoulder in the body and shut-off survives. A metal seat holds that geometry from the start, with nothing in the sealing line to lose. KTN supplies the range to API 607 or API 6FA on request.

Materials, balls and seats

KTN manufactures the body in stainless or carbon steel, with a solid ground ball. With no soft insert to absorb wear, the ball finish sets the service life.

Ball hardfacing: chrome, stellite and tungsten carbide

One hard grain in the contact band scores the ball, so the surface is hardened as soon as the fluid carries solids. Chrome plating gives hardness and a fine finish at contained extra cost, for clean fluids where the problem is temperature or the wear of the turn itself. Stellite, a cobalt-based overlay, resists erosion and keeps its hardness hot: steam, thermal oil and fine particles. Tungsten carbide is the hardest of the three and takes outright abrasion from sand, catalyst, slag or mineral pulp.

The extra cost pays when the predicted failure mode is a scored seat. In clean service tungsten carbide buys no tightness; with solids it decides whether the valve lasts one campaign or several years.

When not to use a metal seat

In clean general service PTFE costs less, needs less torque and seals just as well, since class VI of ANSI/FCI 70-2 is reached by both technologies. Specifying metal to metal for water or compressed air raises the price of valve and actuator with no gain in tightness.

The right execution then sits in the soft-seated siblings: threaded BSP, NPT and socket weld, DIN flanged to EN 1092-1, ANSI flanged cast steel, sanitary clamp end and wafer type between flanges.

Connections, standards and actuation

Every execution carries an ISO 5211 top flange, so lever, gearbox or actuator mounts without adaptors. Shut-off is rated class VI to ANSI/FCI 70-2, with the fire-safe option to API 607 or API 6FA.

In wafer and lug bodies the pipe flange face matters as much as the drilling: see the guide to flange faces. Levers and mounting kits come with the valve accessories range.

Actuation is where specifications fail most often. Size the actuator on breakaway torque at maximum line pressure, with margin for a valve left in one position for months.

Buying metal seat ball valves direct from the manufacturer

Quotations come from the plant that machines the ball. Seven lines close a price:

• Size in DN or inches.
• Connection: wafer, lug, threaded with integral pads or flanged.
• Pressure class or PN, from CL150 to CL2500.
• Body and ball material, plus hardfacing: chrome, stellite or tungsten carbide.
• Ball support: floating or trunnion mounted.
• Fluid, temperature, differential pressure and solids content.
• Actuation, and whether API 607 or API 6FA fire-safe applies.

Buyers comparing metal seated ball valve suppliers usually find a distribution chain in between. Going direct removes that margin and opens the made-to-drawing route: special bore, special body material or an actuated assembly. To replace another brand, send the previous reference and drawing and KTN builds the equivalent. Every order leaves with its certificate of origin, and EN 10204 3.1 material certificates are issued on request.

Wholesale volumes, project lots and the full catalogue are quoted the same way, with stock on the standard range. State the duty on the contact page to request a quotation, or call +34 937 818 219, 8:00 to 19:00.

Why choose KTN as your manufacturer

Grinding, hardfacing and lapping each ball and seat set in house is what makes a matched metal seat possible. That work happens at KTN Valves (Kara Technology News, S.L.), a Spanish manufacturer at Ctra. Rubí-Sabadell km 13, nave 7, 08191 Rubí, Barcelona.

Quality runs under ISO 9001 with Bureau Veritas inspection. The same plant supplies the wider industrial valve range and actuators sized on the real torque of each valve.

Related categories

• Industrial ball valves. The parent category, six executions side by side.
• Wafer type ball valves. For any wafer requirement in AISI 316 between DIN EN 1092 or ANSI B16.5 flanges, soft or metal seated.
• ANSI flanged ball valves. For API 608 cast steel bodies in class 150 and 300 up to 8″.
• DIN flanged ball valves. For EN 1092-1 drilling in PN16 to PN40, or a PFA lined body.
• Threaded ball valves BSP, NPT and socket weld. Below 2″ (DN50), where a thread replaces the flange.
• Sanitary clamp end ball valves. For hygienic duty in 316L with an Ra 0.8 µm finish and CIP cleaning.

Frequently asked questions

What is a metal seat ball valve and when do I need one?

It is a ball valve whose seats are metal, lapped against the ball, with no PTFE in the sealing line. KTN manufactures metal to metal ball valves for services that destroy a soft seat: high temperature, steam, thermal oil, abrasive slurries, solids in suspension and pressure classes above CL600. In clean general service a soft seat is cheaper and seals equally well.

Do metal seated valves really give zero leakage?

KTN metal seated ball valves are rated class VI to ANSI/FCI 70-2, the tightest grade of that standard and what the market calls zero leakage. The tightness comes from lapping each seat against the ball of its own valve. Because they are a matched set, ball and seats are always replaced together, never separately.

Floating or metal seated trunnion ball valve?

The practical crossover is around DN150 and class 600. Below it, line pressure pushing the ball onto the downstream seat works well and the floating design costs less. Above it, a trunnion ball valve fixes the ball on upper and lower trunnions and lets the seats move, which keeps operating torque low and nearly constant. From CL900 to CL2500 the guided ball is the only viable execution.

How much torque does a metal seat add, and how is the actuator sized?

A metal seat runs above the torque of the same size with PTFE, because the sealing band carries far higher contact pressure. In a floating valve the figure grows with differential pressure; in a trunnion valve it stays almost flat. Size the actuator on breakaway torque at maximum line pressure, with margin, using the ISO 5211 flange of the valve.

Are you a metal seated ball valve manufacturer or a supplier?

KTN Valves manufactures in Rubí, Barcelona, and sells direct, so there is no distributor margin between the drawing and the finished valve. Standard executions of the catalogue are held in stock, wholesale and project quantities are quoted from the plant, and non-standard valves are made to drawing. Send the previous supplier reference to obtain an equivalent.

Do you supply graphite seated ball valves?

The KTN seat catalogue covers PTFE, reinforced PTFE, pentafite and lapped metal to metal. Enquiries for graphite seated ball valves are usually driven by temperature, and the metal to metal execution covers that range with class VI shut-off. Specific packing and gasket materials for a given temperature are confirmed per project, together with the fire-safe requirement.