Valves and Valve Equipment

Three-Piece Stainless Steel Ball Valve: In-Line Maintenance and Technical Data

Learn about the design, technical data and typical applications of three-piece stainless steel ball valves that can be serviced while the end connections stay in the line.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

Three-piece threaded stainless steel ball valve

In industrial lines that need frequent maintenance, removing the valve from the pipe every time costs time and labour. A three-piece stainless steel ball valve consists of two end connections and a centre body clamped between them with bolts. This design allows the centre body to be removed while the end connections stay in the pipe, so the ball and seats can be renewed without dismantling the line.

This article covers the advantages of the three-piece design, typical technical data, applications and installation points.

How Does the Three-Piece Design Work?

As with all ball valves, the ball with its central bore is turned 90° by the handle to the fully open or fully closed position. In a three-piece valve the ball and PTFE seats sit inside the centre body, which is joined to the end pieces with long bolts.

In-line maintenance: After depressurising and draining the line, the bolts are loosened and the centre body is taken out. Seats, seals and ball are replaced and the body is refitted. The threaded pipe joints are not disturbed.
Two-stage sealing: The ball is sealed by PTFE seats, the stem by separate stem seals.
Flexible installation: The valve can be installed in any position.

Technical Data

Values are given for the Ayvaz V-3T / V-3TP series supplied by ORFA and may vary by model:

Feature	Value
Body and ball	AISI 304 or AISI 316 stainless steel
Seats	PTFE
Connection	Threaded (BSP or NPT, depending on model)
Nominal size	DN15 (1/2″) – DN100 (4″); smaller sizes also available
Maximum pressure	63 bar (PN63)
Operating temperature	-25 °C / +180 °C
Testing	Every valve 100% leak-tested with 10 bar air under water

63 bar is the ambient-temperature rating; in PTFE-seated valves the allowable pressure decreases as the temperature rises. V-3TP models are full port with AISI 316 bodies.

Advantages

Easy maintenance: Internals can be renewed by removing the centre body from the line.
Low pressure drop: When fully open the ball bore offers very little resistance.
Quick operation: Quarter-turn opening and closing; the handle shows the valve position.
Tight shut-off and corrosion resistance: PTFE seats and stainless construction ensure long life.
Automation-ready: The same product family includes actuator-compatible three-piece models with ISO 5211 mounting pads.

Tip: Ball valves are on/off valves. Using them half-open for throttling erodes the PTFE seats. Use a globe valve or balancing valve where flow control is needed.

Applications

Heating and cooling lines
Process and utility lines in food and chemical plants
Shipbuilding
Paper mills
Hot and cold water lines
Lines with frequent maintenance where downtime must be short

Frequently Asked Questions

What is the main advantage of a three-piece ball valve?

The centre body can be removed while the end connections stay in the pipe. Maintenance such as seat and seal replacement can therefore be done quickly without disturbing the pipe joints.

Does the line need to be drained for maintenance?

Yes. Before removing the centre body, the line must be depressurised, drained and properly isolated.

When should I choose a three-piece instead of a two-piece valve?

A three-piece valve is advantageous where the valve needs frequent maintenance, where abrasive or dirty fluids are carried, or where an actuator may be fitted later. For general lines with low maintenance needs a two-piece valve is more economical.

Conclusion

With in-line serviceability, high pressure rating and corrosion resistance, three-piece stainless steel ball valves are a strong choice for industrial lines where easy maintenance matters. See all models on our Ball Valves page.

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