4x3"900LB A105N Three Piece Flanged Ball Valve

Overview of the J-VALVES 4x3 Inch 900LB A105N Three Piece Flanged Ball Valve

A valve called four by three has two sizes and one of them governs. The four is the nominal size: it is the flange, the body, the face to face, the marking and the figure every test is referenced to. The three is the bore, which is the passage the medium actually goes through. Nothing about the pressure boundary follows from the three, and a buyer who looks up a three inch Class 900 table will get a smaller flange, a shorter body and a different test figure.

This is not a nitpick, because the mistake is quiet. The valve arrives with a four inch flange, which is correct, and the buyer measures the bore, finds three inch, and concludes the valve is wrong. Or the reverse: the line is designed against a three inch table, the spool piece is cut short, and the valve does not fit. Both are avoided by treating the two numbers as two separate order lines rather than as a name.

Design and Construction

Three sections with two bolted joints, and both are pressure boundaries that see the same shell test as the wall. The middle section carries the ball and the seats out when the studs are released, which is the reason to take a three piece body at all. The body is a four inch body: its wall, its flanges and its joint faces are sized from the nominal size, and the reduced bore is created by the ball and the seat rings rather than by shrinking the body.

The ball is a three inch ball inside a four inch body, with a bore through it of DN80 and a seat ring sized to that bore. The step between the body bore and the ball bore is where the pressure drop of a reduced port valve comes from, and it is also the feature that makes the valve shorter in the flow direction than a full bore four inch would be. The ball is carried on trunnions because at Class 900 the seat load is beyond what a floating ball could be turned against.

Material Options

The body code is A105N: a forged carbon steel supplied normalized. The letter N is the difference from A105 and it is a heat treatment requirement rather than an alloy change, so what it buys is a refined grain and a heat treatment record behind the certificate. It does not raise the class, and at Class 900 the wall is already set by the nominal size and the rating rather than by the letter.

The seat is PTFE as standard with reinforced PTFE, PPL or a metal seat listed for higher temperature or for dirty service. The stem and the trunnion are named on the order. Where the medium needs a different alloy the body code changes and the whole valve is ordered against it, and where the service is cold enough for a low temperature steel the code changes to a forging suited to that, which is a different order rather than an upgrade to this one.

Technical Specifications

Every figure on this valve is indexed by four inch, because that is what it is: a four inch Class 900 flanged body with a three inch bore through the ball. The flange drilling, the gasket and the stud pattern come from the four inch row of ASME B16.5 at Class 900, in ring joint or raised face. Face to face comes from ASME B16.10 for a four inch Class 900 flanged valve. The bore appears only where flow is discussed, and it appears as a reduced port figure rather than as a size. Class 900 is PN 150 in the API 6D code.

The bore is DN80. That is the only figure on the valve that follows the three, and it is the one that decides the pressure drop and whether the line can be pigged. Everything else, including the mass, the joint torque, the stud size at the body joints and the test figures, follows the four. The drawing should state both, because a drawing that states only one of them invites exactly the confusion this page is describing.

Standards and Compliance

ASME B16.34 supplies the minimum wall for a four inch Class 900 valve and the pressure temperature rating at that class; API 6D supplies the pipeline valve requirements, the marking rules and the documentation. Both of them work from the nominal size, which is the point: the standards do not have a category for a valve that is one size at the flange and another at the bore. To a standard, this is a four inch valve with a reduced port.

API 598 sets the shell test at one and a half times the rating and the seat test at one and one tenth times, and both are referenced to the rating of the class rather than to the bore. That is why the test figure does not change when the bore is reduced: the valve is still a Class 900 four inch valve, and the reduced bore is a flow characteristic rather than a pressure one.

Manufacturing Process

The three sections are machined from a four inch forging, and the seat pockets are cut to take the seat rings that suit the reduced ball rather than the full body bore. That is the operation where a reduced port valve differs from a full port one in the shop: the pocket is deeper relative to the body bore, because the ring has to bridge the step between the two diameters. The joint faces are the datum for the pockets on both sides.

Assembly follows the same order as any three piece valve: ball and seats into one section, the middle section closed over new gaskets, studs brought down in a cross pattern until the faces are parallel, then the stem and operator, then cycling, then test. The step in the bore is checked before assembly, because a step that is not square shows up as a seat that does not sit flat and a valve that leaks in one direction only.

Quality Control and Testing

The shell test is at one and a half times the Class 900 rating with the body under observation at the wall and at both joints, and the seat test follows at one and one tenth times in both directions with the cavity open. Both figures come from the class and the nominal size, and neither changes because the bore is three inch. A test sheet that quotes a three inch figure for this valve is a test sheet for a different valve.

The marking is where the two numbers have to be handled deliberately. The plate carries the nominal size, the class, the body code and the heat number, and the bore is stated separately rather than folded into the size. That way a reader who needs the flange reads four, a reader who needs the flow area reads three, and neither has to guess which convention the maker used.

Applications and Industry Service

This valve is for a four inch line where the flow does not need the full area but the pressure does need Class 900, which in practice means high pressure process, injection, and the discharge side of equipment where the line was sized on velocity rather than on pressure drop. The reduced port saves mass and cost against a full bore valve of the same class, and the price of that saving is a permanent pressure drop at the step.

It is the wrong choice where the line will be pigged, because the pig meets the step; where the pressure drop budget is already tight, because the step sits there for the life of the line; and where the flow is two phase, because a step is a place where the phases separate. In those three cases the answer is a full bore four inch valve, which is a heavier and more expensive product rather than a better version of this one.

Installation, Operation and Maintenance

The flanges are four inch Class 900 and the mating flanges have to be the same pattern, which is worth stating because a line built for a three inch valve will not accept this one at either end. The valve is supported under the body where the mass makes it necessary, the flanges are brought parallel before any stud is torqued, and the ring joint where fitted is a new ring at every break rather than a reused one.

Maintenance is the middle section out, which brings the ball and both seat rings with it, and the step in the bore is the part to inspect at the same time: a step that has been eroded changes the pressure drop and is the first sign that the medium is carrying solids. After reassembly the shell test is repeated, because the valve has been opened and its pressure boundaries are new again.

How to Specify and Order

The order should carry the nominal size and the bore as two separate items rather than as a name, so that the flange, the face to face and the test figures are unambiguous. The rest of the line is class, body style, body code, seat material, end facing, operator and test standard. Where the project has a pressure drop budget, the bore belongs in the order as well, because the difference between a full port and a reduced port of the same size is that budget.

The documents to read before acceptance are the plate, the certificate and the drawing. The plate carries the nominal size and the class with the bore stated separately; the certificate carries the heat and the normalizing record behind the N; the drawing carries the face to face, the flange pattern and both joint torques. On this valve the drawing is also the place where a buyer can see that the body is four inch and the ball is three.

FAQ

Q: Is a 4x3 valve a three inch valve or a four inch one?

A: It is a four inch valve with a three inch bore, and that is not a technicality. The flange, the face to face, the wall, the test figures and the marking all follow the four. Only the passage through the ball follows the three. Treating it as a three inch valve at the ordering or testing stage produces a valve with the wrong flanges or a test sheet quoted against the wrong table.

Q: What test pressure applies?

A: The shell and seat figures for a four inch Class 900 valve, which is what API 598 derives from the class rating and the nominal size. The reduced bore does not lower or raise them, because the pressure boundary is the four inch body and the seat is tested at the same one and one tenth times the rating as any other Class 900 valve of that size. A three inch figure does not apply to this valve.

Q: Does the reduced bore change the flange?

A: No. The flange is the Class 900 four inch pattern, and the reduced bore is created inside the body by the ball and the seat rings. This is why a line built for a three inch valve cannot accept this one: the pipe flanges would be the wrong size even though the bore matches. The bore and the flange are two independent decisions and both belong on the order.

Q: Why choose a reduced bore at all?

A: Because it saves mass and cost against a full bore valve of the same class while keeping the same pressure boundary. The price is a permanent pressure drop at the step in the bore, and a passage that cannot be pigged. On a high pressure line where the flow was sized on velocity rather than on pressure drop, that trade is usually worth taking, and where it is not, the answer is a full bore valve.

Q: How is the valve marked?

A: The plate carries the nominal size, the class, the body code and the heat number, with the bore stated separately rather than folded into the size. That convention is deliberate: a reader who needs the flange reads the nominal size, a reader who needs the flow area reads the bore, and neither has to guess which convention the maker used. API 6D sets what has to be on the plate.

Q: Can this valve be installed where the line is pigged?

A: No, not with a pig that needs a clear passage. The step between the four inch body bore and the three inch ball bore is a hard obstruction, and a pig will either stop at it or damage itself. Where the line is pigged, the valve has to be full bore, which means a different product: a four inch full port Class 900 valve rather than this one.