4x3"PN260 A105N Carbon Steel Trunnion Mounted Ball Valve

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

The address of this page carries a pressure code that no flange table contains. PN 260 is not one of the codes listed for a ball valve in API 6D, and it is not one of the PN steps in EN 1092-1 either. Class 1500 is written PN 250 in both worlds, and the number 260 sits outside the sequence, which is what a converted bar rating looks like after it has been rounded and then treated as a standard.

That matters more than a typo normally would, because the pressure code is the key an enquiry is looked up by. A buyer who writes PN 260 cannot be quoted a flange facing, a ring gasket or a set of studs from any table, and the shop has to guess which class was meant. So this page does two things in order: it settles the designation, and then it describes the valve that carries it, a four inch body with a three inch bore and a ring joint on each end at the top of the ASME range.

Design and Construction

The 4x3 in the name is a bore statement and not a pair of end sizes. Both flanges are four inch, the passage through the ball is three inch, and the reducer is inside the valve rather than in the pipe. That is why the face to face length follows the four inch valve in ASME B16.10 and not the three inch one, and why a line that was laid out for a three inch valve will not accept this body without a change at the joint. It is also why the valve cannot be pigged: the bore steps down at the ball and a pig has nowhere to go.

The body is forged rather than cast, and it is bolted rather than welded, because at Class 1500 the seats are the parts that wear and a welded body would make a seat change a cut and weld operation on the line. The trim enters through the body joint, and the joint carries the same shell test as the wall. How many joints there are depends on the body style ordered, and the signed drawing is the document that says so; on a four inch valve both the two piece and the three piece versions are built.

The ball runs on upper and lower trunnions. At this class the force on the ball is the full bore area at the line pressure, and a floating ball would put all of it into the seat and the operator, which is why trunnion mounting is the normal construction here rather than an upgrade. The seats are double piston effect or single piston effect depending on the order, and the difference is not cosmetic: one holds pressure from both sides and traps the cavity, the other lets the cavity relieve into the line.

Material Options

The body is A105N, a forged carbon steel supplied in the normalized condition, and the N is the part of the designation that has to appear on the certificate rather than only in the name. It is the ordinary choice for high pressure oil, gas and water service where nothing in the medium attacks carbon steel, and it is the cheapest body that will hold this class at this size. Where the line runs colder than the carbon steel floor, an A350 LF2 forging is the alternative and it is quoted with the order rather than listed as a stock option.

The ball is carbon steel with a surface deposit, either electroless nickel or hard chrome, and the deposit is what the seat actually runs against. On a valve that is cycled often the deposit is the wear item, and a damaged coating exposes the carbon steel underneath to the medium, so the finish is inspected rather than assumed. A tungsten carbide or alloy overlay is available where the medium carries solids.

The stem and the trunnions are 17-4PH as standard, because the torque and the side load at this class go through them and not through the body wall. The seat is PTFE as standard, with reinforced PTFE, PPL, PEEK or a metal seat with graphite as the alternatives, and the choice sets the temperature the valve can be used at far more than the class does.

Technical Specifications

Both ends are ring type joint flanges to ASME B16.5 Class 1500. The ring joint is not a preference at this class, it is what the joint has to be: a raised face with a soft gasket is asked to hold a pressure that would extrude the gasket, and a metal ring in a groove is asked to do the same job with metal on metal. The consequence is that the joint has no tolerance for a damaged groove or a ring of the wrong hardness, and the ring itself is a piping item that is normally ordered with the line rather than with the valve.

Face to face follows ASME B16.10 for a flanged valve of this size and class, and the figure for the build that is ordered is dimensioned on the signed general arrangement drawing. Bore is reduced as the name says, with a full bore version available as a different body rather than as a machining option, because the ball and the seat pocket are sized by the bore.

The operator is a gear as standard at this class, with hydraulic or pneumatic actuation available where the valve is on an emergency shutdown loop or where the torque is beyond a handwheel. Weight is quoted with the drawing for the size and trim, because the figure moves with the body style and the operator and a catalogue number would be wrong for half the builds.

Standards and Compliance

ASME B16.34 gives the pressure temperature rating and the minimum wall for the forging, and Class 1500 is a step inside that table rather than a description of the valve. API 6D adds the pipeline requirements: the pressure code, the marking, the functional tests and the cavity relief. It is API 6D that supplies the number this page is about. Its pressure code table pairs Class 1500 with PN 250, and 250 is the highest PN step in the table, which is the reason there is nothing above it to round up to.

The marking requirement is where the code becomes visible. A valve is marked with its size, its class, its body material and its heat number, and where a PN designation is used it has to be the one that corresponds to the class. That is why a plate reading PN 260 is a plate that cannot be checked against the standard it claims, and why a buyer who receives one is entitled to ask which document it came from.

A class 1500 valve is tested at the same multiples as any other, one and a half times the rating for the shell and one and one tenth for the seat, and the number is large because the rating is. What changes at this class is the joint: a ring joint flange is checked with the ring in place, and a ring that has been used twice is not a ring any more. Fire safe, where it is required, is a separate type test named on the order, and API 607, API 6FA and ISO 10497 are not certificates of one another.

Manufacturing Process

The body starts as a forging, is normalized, and is then machined from the flange faces inwards. The flange face and the ring groove are cut in the same setup so that the groove stays concentric with the bolt circle, because a groove that is off centre loads the ring on one side and that is the joint that weeps at pressure. The bore is machined through, the seat pocket is cut square to the joint face, and the body joint face is finished as the datum for the pocket.

Assembly puts the ball, the seats and the stem in through the body joint, sets the seat preload, and closes the joint on a new gasket with the faces checked for parallel before any stud is torqued. The ring grooves are blanked and taped for painting and transport, because a painted or bruised groove is a joint that has to be re-cut on site, and no one wants to re-cut a Class 1500 flange in a plant.

Quality Control and Testing

The forging certificate is the first record, and it is issued against the heat number that is later stamped on the plate. Where the order calls for a positive material identification report or an ultrasonic examination of the forging, that is quoted with the order and written against the same heat; neither is claimed here as a standing practice, because a forging that has not been tested is a normal commercial forging and the difference is a line on the purchase order.

The shell test is run with the body assembled, at one and a half times the Class 1500 rating, and the body joint is watched along with the wall. The seat test follows in both directions at one and one tenth times the rating with the cavity open, and on a double piston effect seat the cavity test is run separately because the seat is designed not to relieve into the line. The valve is then stroked, the gear is felt by hand, and the plate is read against the certificate before packing.

Applications and Industry Service

This valve belongs on high pressure oil and gas lines, on wellsite and metering piping, on hydraulic power lines and on any service where the class is set by the system rather than by the pipe size. The reduced bore is the normal choice where the line is four inch but the flow does not need a four inch passage, and it buys a smaller ball, a lower torque and a lighter valve for the same pressure boundary.

It is the wrong valve for a line that is pigged, for a line where the pressure drop across the valve has been calculated on a full bore, and for a service where the medium carries solids that settle in the cavity between the seats. It is also the wrong choice where the joint will be opened often, because a ring joint at this class is a joint that is made once and left alone.

Installation, Operation and Maintenance

The ring gasket is fitted dry and clean, the groove is checked for damage before the ring goes in, and the flanges are brought parallel before any stud is tightened, because a ring joint cannot pull itself square and a misaligned joint will load the ring on one edge. Studs are torqued in a cross pattern to the values in the flange standard for the size and class, and the joint is not re-torqued after the line is hot unless the procedure says so.

The valve is stored with the grooves protected and the bore dry, and it is not left standing on a flange face. In service the maintenance items are the seat, the stem packing and the deposit on the ball; the body joint is opened only for a seat change, and after it is remade the shell test is repeated, because a body that has been opened is a new pressure boundary and at this class that is worth proving.

How to Specify and Order

The order line needs size, class, pressure code, body style, body material, bore, seat, end connection, operator and test standard. Write the class as Class 1500 and, if a PN designation is wanted for a European reader, write PN 250 beside it. Do not write PN 260 on the order, because no flange table, no gasket list and no bolting schedule in either system will accept it, and the shop will have to ask.

The second line to get right is the seat, because at this class the seat material decides the temperature and the leakage rate more than the body does. State the medium, the design temperature and the design pressure, say whether the cavity has to relieve into the line or be held, and take the answer as one class with one code. Everything else on the valve follows from those two lines.

FAQ

Q: Is PN 260 the same as Class 1500?

A: No, and 260 is not a designation that exists. API 6D pairs Class 1500 with PN 250 in its pressure code table, and EN 1092-1 also stops at PN 250. A 260 looks like a bar rating that was converted and rounded, then written into a name as if it were a standard code. The valve is a Class 1500 valve, and that is what the order and the nameplate should say.

Q: Does the wrong code change the valve?

A: It does not change the metal, but it changes everything downstream of the enquiry. Flange facing, ring gasket, stud size and joint torque are all looked up by class, and a code that cannot be found in a table leaves the buyer and the shop to guess which class was meant. On a Class 1500 joint a guess is expensive, because the wrong ring or the wrong stud grade shows up at the hydro test rather than in the office.

Q: Why is the bore reduced on a four inch valve?

A: Because the line is four inch but the flow does not need a four inch passage. A three inch bore through a four inch body gives a smaller ball, a lower operating torque and a lighter valve for the same pressure boundary. What it does not give is a pigging passage, and the pressure drop has to be calculated on the three inch bore rather than on the pipe size.

Q: Why ring type joint rather than a raised face?

A: Because at Class 1500 a soft gasket on a raised face is being asked to hold a pressure that would extrude it. A metal ring in a machined groove seals metal to metal and does not creep, which is why the joint is standard at this class. The cost is that the joint has no tolerance for a damaged groove, and it is not a joint to open on a routine basis.

Q: What decides the temperature this valve can be used at?

A: The seat, not the class. The body covers the carbon steel range, but a PTFE seat sits well below the top of it, and the alternatives step up one at a time. The design temperature has to be stated on the enquiry so that the seat is chosen against it, because a valve with the right body and the wrong seat is a valve that has to come out of the line.

Q: Which of the three addresses for this valve should be used?

A: The one that carries the class as Class 1500. The other two addresses describe the same valve with the correct designation, and this page exists because the code in its address has to be corrected rather than repeated. One address should be kept live and the others should point at it, so that a search for either spelling lands on the same drawing.