16"300LB WCB Two Piece Flange Trunnion Mounted Ball Valve

Overview of the J-VALVES 16 Inch Class 300 WCB Trunnion Ball Valve

This is a sixteen inch, Class 300, two piece trunnion mounted ball valve with a cast WCB carbon steel body. DN400 is the nominal size, the ends are flanged to ASME B16.5 in raised face or ring joint form, the face to face length is to ASME B16.10, and the standard operator is a worm gear with a handwheel rather than a lever. The ball runs on an upper and a lower trunnion, and the seats are spring loaded and self relieving.

At this size the valve is no longer a component that one person fits; it is a lifted item with a mass, a centre of gravity and a flange joint that has to be pulled up in sequence. Most of what goes wrong with a sixteen inch valve goes wrong in the week it is installed rather than in the years it is operated, and this page is written around that fact: the body, the gear, the support and the bolt tightening all have to be planned before the valve is lifted off the pallet.

Design and Construction

The trunnion is what makes sixteen inch possible. On a floating valve the whole line pressure acts on the ball and pushes it onto the downstream seat, so the seat load and the operating torque both climb with the square of the bore. At DN400 that force is large enough to deform a seat and to require a gearbox that a plant would not want to turn. A trunnion carries the load on bearings at the top and bottom of the ball, so the ball only rotates and the seat load is set by the springs.

The two piece body means one end cap bolts to the main body and the ball goes in from that side. On a sixteen inch valve that end cap is a heavy part on its own, and it is the part that has to be handled with a sling rather than by hand during assembly and during any later seat work. The body is cast WCB, which is the normal choice at this size and class: a forging of DN400 is possible but the cost rises faster than the benefit at Class 300.

Material Options

WCB is the default body for water, oil and gas at moderate temperature, and it is what the photograph and the file name show for this valve. A105 forged carbon steel is offered where a wrought body is preferred, and A350 LF2 is the low temperature grade for service below the point where WCB becomes brittle. CF8 and CF8M are available as cast stainless alternatives where the product is corrosive, and those are different body materials rather than a coating on the carbon steel one.

The trim follows the body. The ball is WCB or A105 with electroless nickel plating as standard, with hard chrome or a stainless overlay where the duty is more abrasive. The stem is 17-4PH or A105 with ENP, the packing is flexible graphite reinforced with a nickel alloy wire or a PTFE V-ring for lower temperature, and the body gasket is a spiral wound type because at DN400 a flat gasket does not have the recovery to follow the flange through a thermal cycle.

Technical Specifications

The declared envelope is sixteen inch, Class 300 which is PN50, two piece cast body, flanged to ASME B16.5, face to face to ASME B16.10, worm gear operated. The size and the class are fixed by the line; the figures that ship are the ones confirmed on the signed general arrangement drawing, including the installed face to face length, because at this size a millimetre of mismatch is not absorbed by the gasket.

Two dimensions deserve attention on a large valve. The first is the face to face length, because ASME B16.10 gives a fixed figure for the size and class and a spool built to a different figure cannot be closed by pulling the flanges. The second is the flange bolt circle, which on a DN400 Class 300 flange has to be checked against the mating flange on site rather than assumed from the nominal size, since a raised face and a ring joint facing use the same bolt circle but do not seal the same way.

Standards and Compliance

The valve follows API 6D where the buyer wants pipeline documentation and API 608 for the ball valve specifics, with ASME B16.34 supplying the wall thickness and the rating. ASME B16.5 governs the flange, ASME B16.10 the face to face length, and API 598 the shell and seat test. Where a ring joint facing is ordered, ASME B16.20 governs the gasket and the groove, and the gasket is supplied with the valve so the groove and the ring are known to match.

Large valves attract more inspection than small ones, not less. A third party inspector will want the wall thickness readings, the flange dimensions, the face to face length, the test record and the material certificate, and on a pipeline order the API 6D documentation package is specified as a deliverable in its own right. A fire safe certificate to API 607 or ISO 10497 is added where the line requires it, and on a soft seated valve it rests on the seat and the graphite packing.

Manufacturing Process

The body and the end cap are cast, then the joint faces are machined so that they stay parallel to each other and square to the bore. On a DN400 body the joint is a large gasketed pressure boundary, and a face that is out of parallel by a small amount will leak no matter how much the studs are pulled, so the faces are checked on a surface plate rather than with a straight edge. The seat pockets and the trunnion bores are machined in the same setting so that the ball axis and the seat axis stay concentric.

The ball is machined and coated, the trunnion bearings are fitted, and the assembly is checked for free rotation before the end cap goes on. The gear is mounted on the pad, the stops are set on the valve, and the assembly is torqued and recorded. Because the gear and the body are shipped as one item, the lifting points on the body are marked and the shipping stays on until the valve is on the flange, which prevents the gear from being used as a lifting lug on site.

Quality Control and Testing

Every valve is shell tested at one and a half times the rating and seat tested at one point one times in both directions to API 598. At this size the test is a slow operation because the body has to be filled and the air purged before the pressure is applied, and the hold time is observed rather than shortened. The torque is measured after the test on the assembled valve and recorded, and that figure is what the gear was selected against.

The dimensional record is longer than on a small valve. Wall thickness is read at defined points on the body and the end cap, the flange is gauged for outside diameter, bolt circle, bolt hole diameter and facing, the face to face length is measured end to end, and the gear is checked for full travel against the ball position. All of it is recorded on an inspection sheet and goes out with the valve, because a site that has to lift a DN400 valve into a spool wants the numbers before it rigs, not after.

Applications and Industry Service

The duty is large bore isolation on water transmission, oil and gas gathering and transmission lines, pump station suction and discharge, tank farm headers, and plant cooling water. In those positions the valve is usually either fully open or fully closed for long periods, and it is operated during a planned sequence rather than modulated, which is what a trunnion ball valve is good at.

It is not a control valve and should not be used to throttle. A partly open ball valve at DN400 puts the seat and the ball edge into the flow at high velocity, and the erosion that follows is fast and local. Where the line needs throttling, a separate control valve is fitted and this valve stays as the isolation block either side of it, which is also what lets the control valve be serviced without draining the whole system.

Installation, Operation and Maintenance

Plan the lift before the valve arrives. Use the lifting points on the body rather than the gear or the handwheel, keep the valve in its shipping position until it is on the flange, and support the pipe either side of the valve because a DN400 assembly with a gear will load the flange joint if the pipe is allowed to hang on it. Align the flanges before pulling any studs up, never use the studs to pull a misaligned joint together, and tighten in a cross pattern in stages to the torque the gasket maker specifies.

Operate the gear through the full quarter turn at commissioning and record the torque, then compare it against the figure on the drawing. A valve that takes noticeably more torque than the record is either misaligned, or has a seat problem, or has been left in a position where the cavity is pressurised. On a large valve, do not leave it part open for long periods and do not use the handwheel to force a valve that has jammed, because the gear will deliver far more torque than the stem was designed to take.

How to Specify and Order

State size, class, body grade, ball and seat trim, flange facing, face to face standard, operator and any accessory. For this valve a typical line reads: sixteen inch, Class 300, WCB body, ball WCB with ENP, PTFE seat, raised face to ASME B16.5, face to face to ASME B16.10, worm gear with handwheel. If a ring joint facing is required, say so at enquiry stage because the groove and the gasket are supplied together and cannot be added later without opening the valve.

Send the line fluid, the design pressure and temperature, the installed face to face length if the valve is a replacement, and the mating flange standard. Tell us whether the valve will be motorised later, because a pad drilled for a gear and a pad drilled for an actuator are not always the same and changing it after the valve is on site means lifting it out again. Those details at enquiry stage are what keeps a large valve order on schedule.

FAQ

Q: Why is a lever not offered at sixteen inch?

A: Because the breakaway torque of a DN400 trunnion valve after a long closed period is beyond what a lever should be asked to deliver by hand. A worm gear multiplies the input and holds the valve where it is set, which a lever does not. The gear is the standard operator on this size, and it is selected against the measured torque of the assembled valve rather than a catalogue figure.

Q: Will this valve fit an existing ASME B16.10 spool?

A: It is built to ASME B16.10, so it should, but measure the installed face to face length on site before ordering a replacement. The standard gives a fixed figure for the size and class and a spool built to a rounded figure cannot be closed by pulling the flanges. On a DN400 joint the gasket will not absorb the difference.

Q: Should I order raised face or ring joint?

A: Ring joint is the usual choice on high pressure and hot hydrocarbon lines where a raised face gasket is not considered reliable enough; raised face is the norm for water and general service. Both use the same bolt circle but they do not seal the same way, and the groove and the ring have to be a matched pair, so the facing has to be decided at enquiry stage rather than on site.

Q: How is a sixteen inch valve lifted and installed?

A: On the lifting points cast or marked on the body, never on the gear or the handwheel, and the valve stays in its shipping position until it is on the flange. The pipe is supported either side so that the valve does not carry the line load, the flanges are aligned before any stud is pulled up, and the studs are tightened in a cross pattern in stages to the gasket maker torque.

Q: Is WCB suitable for low temperature service?

A: Not below the point where carbon steel becomes brittle. The low temperature option in this family is A350 LF2, which is a different body material and is ordered as such. WCB is the right answer for water, oil and gas at moderate temperature and is the grade shown on this page.

Q: Can this valve be motorised later?

A: Usually, but the mounting pad has to be right. A pad drilled for a worm gear and a pad drilled for an actuator are not always the same, and changing it after the valve is installed means lifting it out again. If there is any chance the valve will be actuated, say so at enquiry stage and the pad is machined for it from the start.