6x4"300LB WCB Two Piece Flanged Trunnion Mounted Ball Valve

Overview of the J-VALVES 6x4 Inch 300LB WCB Two Piece Flanged Trunnion Mounted Ball Valve

Two numbers in one designation is a shorthand that carries real information, and it gets read wrong in both directions. A buyer who calls this a six inch valve expects a six inch bore and finds a four inch one; a buyer who calls it a four inch valve orders four inch gaskets and cannot bolt them to the flange. The valve is both, at different places, and the order should say 6x4 so that neither reading is left to the supplier.

The second half of the shorthand is where the number comes from. Reduced bore is not a free choice: API 6D tabulates the bore for each size, and the value behind 6x4 is one of those rows. That matters at acceptance, because it gives the inspector a table to measure against instead of a supplier drawing, and it matters at replacement, because a different maker valve with the same 6x4 designation has to meet the same row.

Design and Construction

The ball is carried on an upper and a lower trunnion rather than floating. At a four inch bore with a three hundred pound rating a floating ball would still work, but the body around it is a six inch casting, and a trunnion keeps the operating torque low enough for a worm gear instead of a long lever. The trunnions run in bearings in the body, and the side load from line pressure goes there instead of into the seats.

The body is in two pieces with one bolted joint. On this size the joint is at one end, so the end cover comes off towards the pipe and the ball and seats come out with it; the other end stays on the line. That is a different maintenance route from a three piece body, where the middle section lifts out, and it decides how much pipe has to be supported when the valve is opened.

Material Options

The body is cast carbon steel, and the nameplate carries the casting code rather than a standard designation. What that buys is the ordinary range: water, oil, gas, steam and light process duty where a carbon steel shell is adequate. What it does not buy is chloride resistance or resistance to dilute acid. The code on the plate is what the mill certificate is written against, and the composition behind it belongs on the 3.1 documentation, not in a catalogue line.

Trim is a separate decision. The ball is carbon steel with hard chrome plating, or a stainless grade where the medium asks for it. The stem is precipitation hardening stainless or a stainless grade. Seats are PTFE, reinforced PTFE, PPL or nylon, with a metal seat available where temperature or abrasion rules the soft compounds out. Each of those changes the leakage class as well as the temperature ceiling.

Technical Specifications

The flange is a six inch Class 300 pattern to ASME B16.5, with raised face standard and ring joint available. Face to face follows ASME B16.10 for a flanged valve at that size and class, which means the body is as long as a six inch valve and not as short as a four inch one; that is the dimension that decides whether the valve drops into an existing gap in the line. Neither number is printed here, because both belong to tables and printing them would make them look measured.

Inside the body, everything that touches the medium is four inch. The ball, both seat rings, the bore through the body and the flow path are DN100 parts. The gaskets, the studs and the pipe connection are six inch parts. This split is the practical core of the 6x4 designation: a spare parts list written by size alone will be wrong on one side or the other, whichever size was written down.

Standards and Compliance

ASME B16.34 fixes the minimum wall for the size and class and publishes the rating for the material group. API 6D is the pipeline valve document, and it is the one that defines the reduced bore table as well as the design, test and marking rules. API 608, the quarter turn product standard, is named on the page as well; where it and API 6D differ, the pipeline document is the stricter one for a valve that goes into a process line.

Testing follows API 598. The shell test is applied to the whole valve at one and a half times the Class 300 rating, which is a statement about the valve and not about the bore. A common mistake is to expect a 6x4 valve to be tested like a four inch one because the bore is four inch; the pressure boundary is the six inch body, and it is tested as such.

Manufacturing Process

The body is a casting, and the machining is where a reduced bore body earns or loses its concentricity. The bore, the two seat pockets and the flange faces are machined from as few setups as the casting allows, because the seat pockets have to be coaxial with each other and square to the flange face. A casting with an offset core shows up here as an uneven wall on one side of the bore, which is a scrap decision rather than a machining one.

Assembly follows the same sequence as any trunnion valve: ball in, trunnions into their bearings, seats in, end cover on. On this size the cover joint is the only gasketed pressure boundary, so its face condition and stud torque get the attention that a three piece body would split between two joints. The cover is marked so that it goes back the same way up, and the valve is cycled and tested before the nameplate goes on.

Quality Control and Testing

The shell test comes first, at one and a half times the rating, with the valve closed and the body cavity vented so that a leak in either seat pocket has somewhere to show. Then the seat test at one and one tenth times, in both directions, with the acceptance criterion being no visible leakage. Both numbers come from API 598 and both are quoted here as standard values rather than as factory settings.

Casting quality is checked before any of that. Wall thickness, core position and the soundness of the seat pocket area are the three things that matter on a reduced bore body, because that pocket is where the casting is thinnest and where a shrinkage cavity turns into a leak path. If the order asks for radiography or dye penetrant on the body, that is written as a requirement, not assumed from the fact that the valve is cast.

Applications and Industry Service

This valve sits where the line is six inch and the flow does not need the full bore. Typical duty is a block valve on a process branch, a pump discharge isolation, or a section isolation on a line that was sized for a future flow it never reached. The reduced bore costs pressure drop and buys a smaller ball, a lower torque and a shorter gearbox, which is why it is common on lines that are not pressure critical.

It is the wrong valve where the line has to be pigged, because the bore step blocks a pig, and where the pressure drop across the valve has been counted at full bore in the hydraulic model. It is also wrong where the medium carries solids that will settle in the step between the six inch flange and the four inch bore. Those three are design mismatches, not defects.

Installation, Operation and Maintenance

Install with the gearbox accessible and the stem vertical or horizontal. The body is heavy for a four inch bore, so support the pipe on both sides before the flange studs are tightened; a valve used as a pipe support will leak at the flanges long before it leaks at the seat. Bring the mating faces parallel, fit new gaskets, and tighten in a cross pattern. On a gear operated valve the handwheel is the only position indication, so open and shut are marked on the quadrant before the line is filled.

Maintenance on a two piece body means taking the end cover off, and the ball and seats come with it. That requires the line to be depressurised and the downstream side drained, because the cover is the only pressure boundary that opens. The alternative, lifting the whole valve out, is often faster on this size and avoids disturbing the cover joint at all. Either way the gasket is new and the studs go down in a cross pattern from the centre outwards.

How to Specify and Order

Write 6x4, then write the flange standard and facing, the body code as it will be stamped, the seat compound, the operator and the test standard. Writing six inch alone leaves the bore open; writing four inch alone leaves the flange open; writing 6x4 with no facing leaves the joint to the supplier. Those are the three ways this valve arrives wrong, and all three are cured by one line on the enquiry.

Ask for the size data sheet and the drawing with the quotation. The data sheet gives the bore row and the flange pattern, the drawing gives the face to face and the cover joint torque. On a reduced bore valve the bore row is the one to compare between suppliers, because two valves with the same size and class can differ there if one of them is quoting to a different edition of the table, and that difference shows up as a step in the line nobody modelled.

FAQ

Q: What does 6x4 mean on a ball valve?

A: It means a six inch flanged body with a four inch bore. The six inch part sets the flange pattern and the face to face length, so the valve fits a six inch line. The four inch part sets the ball, the seats and the flow path. Both numbers are needed: write only one and the other is left to the supplier, which is how the wrong bore or the wrong gasket arrives.

Q: Is the bore a chosen dimension or a standard one?

A: It is standard. API 6D tabulates the bore for each size, and the reduced bore figure for this size is one row of that table. That gives an inspector something to measure against that is independent of the maker, and it means two 6x4 valves from different suppliers should have the same bore, if both are quoting to the same edition of the standard.

Q: Is a 6x4 valve tested like a four inch valve?

A: No. The shell test is applied to the pressure boundary, which is the six inch body, at one and a half times the Class 300 rating. The bore does not reduce the test pressure, and it does not make the body a four inch body. A 6x4 valve that is tested like a four inch valve has been tested to the wrong document.

Q: Why is this valve gear operated rather than lever operated?

A: Because the body is six inch even though the bore is four inch. The gearbox is there for the torque and for the reach, not because the bore needs it. A lever would work hydraulically at four inch, but the operator would be reaching across a six inch flange pair and the lever swing would be long. Gear operation is the practical answer at this body size.

Q: Can a pig pass through this valve?

A: No. The step between the six inch flange and the four inch bore blocks a pig, which is why reduced bore valves are not used on pipelines that are pigged. If the line has to be pigged, the valve has to be full bore, and that is a different body with a different torque and a different price.

Q: Are there other listings for this size on the site?

A: Yes, several, including two piece and three piece descriptions and one with a different seat compound in the title. They describe the same body size and class under different names, so one URL should be kept as the indexed page for the 6x4 300LB query and the others redirected to it rather than left to compete.