4x3 Inch 1500LB A105N Trunnion Ball Valve

Overview of the J-VALVES 4x3 Inch 1500LB A105N Trunnion Ball Valve

This is a four inch class 1500 forged A105N trunnion mounted ball valve with a three inch bore and a ring type joint flange. The marking 4x3 describes a DN100 flange around a DN80 bore, and the reduction is in the body rather than in the ball: the ball itself is a full port ball machined to DN80, so the flow path through the ball is a clean cylinder and the step is at the seat pockets.

That distinction matters when a buyer reads a photograph caption that says full bore. The valve is a reduced bore valve relative to the four inch line, and it is a full port ball relative to its own DN80 bore. Both statements are true and they describe different things, which is why the size on this page is written as two numbers with the flange and the bore named separately.

Design and Construction

The body is forged in two pieces and joined at one ring type joint flange. At Class 1500 that joint is the critical feature: the internal pressure tries to open it, the studs hold it closed, and the ring is confined in a groove so it cannot be extruded. A flat gasket at this class is pushed outward faster than the bolts can hold it, which is why the facing changes from raised face to ring joint at Class 900 and above.

The ball is carried on a trunnion at the bottom and driven by the stem at the top, with the seats spring loaded onto it from both sides. That means the valve seals in both directions, the seat load does not rise with line pressure, and the torque stays low enough for a lever at four inch Class 1500. The seats relieve if cavity pressure rises above line pressure, so no external cavity vent is fitted.

Material Options

A105N is a forged carbon steel with a controlled nitrogen addition for grain size, and it is the default body at this class because a forging carries the Class 1500 wall without the porosity risk of a casting. It is ultrasonic tested where ordered, on the billet rather than the finished body, because that is where a shrinkage defect would sit.

Where the medium is corrosive, the body moves to A182 F316 or F44, and the choice follows the chloride content and the temperature rather than the pressure. The trim moves with it: a hard chrome or ENP ball for clean service, stainless or duplex for abrasive or corrosive service, and a seat that runs from PTFE to a hardfaced metal seat depending on how hot the line actually gets.

Technical Specifications

The two size numbers are the ones to read carefully. DN100 is the flange and DN80 is the bore, and a buyer who orders by the first number alone gets a valve that bolts up correctly and restricts the line. The pressure class fixes the wall, the flange, the shell test pressure and the ring joint facing together, and the face to face length follows ASME B16.10 on the drawing rather than a catalogue.

The extension length is the fourth number and it is a site dimension. It is measured from the body flange face to the top of the extension, set by the operating level or the insulation thickness, and it is not interchangeable between projects. A valve ordered without it arrives with a standard extension that fits nothing in particular.

Standards and Compliance

The risk on a reduced bore valve at this class is not a missing standard, it is applying the right standard to the wrong number. API 6D and ASME B16.34 both key off the class and not off the bore, so a 4x3 valve is treated as a Class 1500 valve throughout: the wall, the flange, the shell test pressure and the ring groove all follow Class 1500 even though the flow path is DN80. Reading the standards off the bore instead of the class is how a body ends up under walled.

At Class 1500 the ring joint is a separate item with its own standard and its own material choice, and that is a compliance point rather than a detail. A soft iron ring in a corrosive medium is the wrong ring whatever the flange is made of, and the ring material belongs on the purchase order next to the body material.

Manufacturing Process

The forging is normalised, then machined as a pair so the joint faces and the seat pockets come from the same setting. The ring groove is cut after the joint faces and checked with a profile gauge against ASME B16.20, because a groove a few hundredths deep will leak with a perfect ring and the error is invisible without a gauge.

The trunnion bore at the bottom of the body is cut in the same setting as the seat pockets, since a trunnion off centre by a few hundredths loads the bearing on one side and shows up as a heavy lever rather than as a leak. The extension is welded at its base and that weld is penetrant tested before the assembly is pressure tested.

Quality Control and Testing

The shell test is run with the joint torqued to the drawing figure, so that the test reflects the joint as it will be in service. At Class 1500 a joint that is going to weep does it on the bench, and a joint that is retorqued rather than reopened and refitted with a new ring is a leak waiting for the first thermal cycle.

The cavity relief check is specific to the trunnion design and runs before painting. Torque is measured at the rated pressure and issued with the drawing, because the difference between a comfortable lever and a two handed one at four inch Class 1500 is small and the actuator selection depends on the measured figure rather than a catalogue one.

Applications and Industry Service

The valve is used on high pressure gas lines, wellhead and injection skids, oil transfer at high pressure, and process isolation where a four inch flange is the pipe size and the flow does not need the full bore. The reduced bore is deliberate on most of those duties: the line is sized for a flow a DN80 bore can pass, and a full bore valve at Class 1500 would cost more and weigh more for no gain.

It is the wrong valve where the line will be pigged, because the bore step is a ledge a pig cannot pass. It is wrong where the medium carries chlorides at temperature, and it is wrong where the flow is already near the line capacity, since the reduction behaves like a short orifice rather than like a length of pipe.

Installation, Operation and Maintenance

The valve goes in with the end cap downstream and the ring correctly seated in its groove, studs lubricated, and the cross pattern done in three stages with a torque wrench. At Class 1500 the stud preload is high and an uneven pull distorts the joint face, and the leak appears at the first thermal cycle rather than at commissioning.

A seat change is a joint job: isolate, vent, drain, take the studs out, lift the end cap, and the downstream seat and ball are accessible. The ring and the seat O rings are replaced every time, and the groove is inspected for a dent before the new ring goes in. On an extended stem valve the extension is supported where it passes through the insulation rather than being held by it.

How to Specify and Order

An order needs the two size numbers stated separately, the class, the body and trim, the ring material, and the extension length if one is required. For this valve that is DN100 flange, DN80 bore, Class 1500, A105N, PTFE seat, ring type joint, and the extension dimension from the drawing.

Ask for the material certificate to EN 10204 3.1, the pressure test record, the ring groove inspection, the cavity relief check and the measured torque. Spares worth holding are a ring joint, a seat and O ring kit and a set of packing rings, and on a Class 1500 valve the ring is the cheapest item on that list and the one that stops a reassembly.

FAQ

Q: What does 4x3 mean on this valve?

A: The first number is the flange and the second is the bore. This valve bolts to a four inch line and passes a three inch bore, so it is a reduced bore design. The ball itself is a full port ball at DN80, which is why a caption can say full bore and still describe a reduced bore valve.

Q: Is Class 1500 the same as PN250?

A: Yes. API 6D clause 7.2 lists PN250 against Class 1500. The valve is marked with the class and flanged to ASME B16.5 Class 1500, which uses a ring type joint facing rather than a raised face.

Q: Why a ring type joint at this class?

A: Because a flat gasket is pushed outward by the internal pressure faster than the bolts can hold it at Class 1500. The ring is confined in a machined groove so it has nowhere to extrude to, and the seal is metal to metal rather than a compressed sheet.

Q: Can the ring joint be reused?

A: No. The ring takes a set when it is compressed, so a reused ring leaks. It is a consumable and belongs on the spares list, and the groove is inspected for damage every time the joint is opened because a dented groove will leak with a new ring as well.

Q: Why is the stem extended?

A: To put the operator at a reachable level, or outside an insulation jacket. The packing stays in the body, so the extension moves the operator rather than the seal, and a weeping gland remains a body job rather than something adjusted at the top of the extension.

Q: Does this valve need a cavity relief vent?

A: No. The seats are self relieving, so pressure trapped in the body cavity lifts a seat and escapes to the low pressure side. That is how the API 6D cavity relief requirement is met on this design and the relief direction is marked on the body.