20x16 Cryogenic Ball Valve, DN500 X DN400 Reduced Bore, Class 900

The 20x16 cryogenic ball valve is a trunnion mounted, reduced bore isolation valve with a 20 inch inlet flange, a 16 inch outlet flange and a 16 inch bore through the ball, rated ASME Class 900 and manufactured to hold body and seat tightness from -50°C down to -196°C in LNG, air separation and liquid nitrogen service.

It does two jobs normally given to two products. The body reduces 20 inch pipe to 16 inch, and the ball isolates the line, so a project that would have bought a reducer, a spool and a 20 inch valve buys one item. What follows is the engineering behind that trade: velocity, mass on the support steel, torque at temperature, the flange call, test water and freight.

What 20x16 Means and What It Replaces

The first number is the inlet flange, the second the outlet. A 20x16 cryogenic ball valve carries a 20 inch ASME flange at one end, a 16 inch flange at the other, and a 16 inch bore through the ball that matches the smaller line. Both ends are Class 900, so the body is a 20 inch pressure envelope necked down internally to a 16 inch flow path.

The conventional arrangement on a line stepping from 20 inch to 16 inch is a 20x16 reducer, a short spool and a 20 inch valve. The reducing valve deletes all but one: one reducer, one spool, two flanged joints, two ring gaskets, two bolt sets and roughly 1.5 m of pipe length with its insulation.

Each deleted joint is worth more than its bill of materials at -162°C. A ring joint that seals at ambient can weep after the first cool-down, as the studs lose preload while the body contracts and the faces part by hundredths of a millimetre.

The internal step is a cone, not a square shoulder that would trap liquid. The bore stays constant at 406.4 mm. Flow enters at the 20 inch end; reversing the body keeps the face-to-face dimension but contradicts the drawing.

Why a Project Chooses Reduced Bore at DN500

A reduced bore cryogenic ball valve at this size is chosen for mass, torque and cost, and the flow penalty is smaller than most line lists assume.

Twenty inch schedule 10S pipe has an internal diameter near 495 mm, an area of 0.193 m². A 16 inch bore is 406.4 mm, an area of 0.130 m², so the same flow travels 1.48 times faster through the valve.

In liquid service the loss is negligible against a 153 bar rating, and the binding limit is velocity rather than pressure drop. Many LNG specifications cap liquid velocity near 3 m/s for erosion and vibration, so a 20 inch line at 2 m/s already passes 3 m/s through the valve.

Gas duty differs. Thirty metres per second in the bore is high but common in transmission and boil-off service, and the drop stays small because gas density at pressure is low.

Mass follows the bore: a 20 inch ball has roughly 1.95 times the mass of a 16 inch ball, and seat torque scales with the square of the seat mean diameter. The 20x16 keeps the 16 inch operator, often the largest single cost difference on the datasheet.

One case defeats the argument. If the line is pigged, the 16 inch bore is a hard stop, because a gauging or intelligent pig cannot pass and a foam pig stalls at the cone.

Mass, Centre of Gravity and Lifting

A large size cryogenic ball valve of this pattern weighs roughly 900 to 1,500 kg dry. The figure covers body, ball, seats, bonnet, stem and gear operator with flanged ends and an extended bonnet, and excludes actuator, cold insulation and skid.

The spread comes from body pattern, bonnet length and gear ratio, so ask for the calculated mass on the approved drawing, because it drives the crane, the support steel and the freight.

The centre of gravity sits near the ball centre, about 400 to 500 mm above the flange centrelines and offset towards the bonnet. A two-leg sling from body lugs hangs the valve tilted unless it is trimmed.

Two lifting lugs are normally cast or welded to the body either side of the ball section. Rate each lug for the full dry mass, not half, because a two-leg lift with one leg slack puts everything on the other. Keep the included angle at 60 degrees or less.

Never lift from the gear operator, handwheel, bonnet studs or actuator bracket, and do not thread eye bolts into the flange stud holes: those are clearance holes, not rated lifting points. Allow a crane at 1.5 to 2 times the dry mass once rigging and dynamic factor are counted, and check the radius rather than the headline capacity.

Support the valve independently once installed. A 1.2 t body hanging between two flange joints at -162°C puts a bending moment into both. Put a support within 1 m on the 16 inch side. Cold insulation adds 150 to 250 kg and moves the centre of gravity outward, so keep the lugs reachable through it.

Choosing the Operator: Gear, Pneumatic, Electric

The 20x16 cryogenic ball valve is normally supplied with a gear operator sized from a measured torque curve, not a size table.

Cryogenic torque is higher than ambient torque for three reasons that add. The first is contraction. A 406.4 mm CF8M ball loses about 1.2 mm of diameter between 20°C and -162°C, roughly 0.3 per cent. The PCTFE seat ring contracts several times more than the steel around it, so its bore closes onto the ball faster than the ball recedes.

The second is material behaviour: PCTFE at -162°C is stiffer, so the same interference gives higher contact stress and friction. The third is the gland and bearings, where a graphite packed gland tightens as the stem cools and a dry trunnion bearing runs at more than double the friction of a lubricated one. None is large alone; together they account for 30 to 50 per cent.

A gear at this size delivers 20,000 to 30,000 Nm at 300:1 to 500:1 with a 400 to 500 mm handwheel. Check rim pull, not ratio. At 250 N a 450 mm wheel gives 56 Nm of input; through 400:1 at 70 per cent efficiency that is about 15,700 Nm, which does not cover an 18,000 Nm cold breakaway. Either the ratio rises, the wheel grows, or the gear gets a hammer blow device.

Pneumatic actuation suits a valve in a control sequence or one that must fail to a position. Size on cold breakaway with a 1.5 safety factor, and check spring end torque separately, because the spring is weakest where the seat has to be pushed home. A double acting scotch yoke actuator of this class uses 30 to 60 litres of air per stroke at 5.5 bar.

Electric actuation suits a valve moving a few times a day on a line without instrument air. Size the motor on running torque with margin and the gearbox on cold breakaway with the same 1.5 factor, because the motor can be stalled at the seat. Whatever the type, its mass loads the bonnet flange: a 300 kg actuator on a 500 mm pad applies a bending moment the studs must carry at ambient and at -162°C.

Flanges, Face-to-Face and the Machining Hold Point

The 20x16 body is flanged to ASME B16.5 Class 900 with ring joint faces at both ends, and the flange call is where most of the commercial risk sits. The flanges are machined onto the body, so a wrong call after machining is a weld repair or a new casting.

At 20 inch, B16.5 covers the size, but project specifications frequently call ASME B16.47 Series A or B. Both are written for sizes from 26 inch upward, and the two series use different bolt circle patterns, so a 20 inch requirement against them usually means the SP-44 dimensions. The profiles differ in outside diameter, bolt circle and bolt count. Get the bolt circle and bolt count in millimetres on the approved drawing, in writing, before the first cut.

Ring grooves are machined octagonal or oval, and the choice must match the gasket the site will buy.

Face-to-face follows ASME B16.10, measured between the 20 inch face and the 16 inch face. Because the body is asymmetric, the dimension is not that of a 20 inch valve and not the average of the two sizes. A Class 900 DN500 by DN400 flanged body typically lands between 1,100 and 1,300 mm overall, but B16.10 lists more than one pattern for some classes, so the drawing governs.

Check the wall at the 16 inch end. The envelope is sized for 20 inch at Class 900, but the metal between the 16 inch seat pocket and the outside diameter is the thinnest section on the body, and it has to satisfy ASME B16.34 after the bore is machined. Ask for the calculated minimum wall there, not only at the neck.

Hydrotest Volume, Drain and Drying

The shell test runs at 1.5 times the 38°C rating, about 230 bar, and the seat test at 1.1 times, about 168 bar, both to API 598. The difficulty is not the pressure. It is the water.

A DN500 by DN400 body with the ball open holds roughly 0.25 to 0.40 m³, so the stand carries 250 to 400 kg of water on top of a valve that already weighs over a tonne. Fill from the lowest point with the highest vent open, at 4 to 6 litres per second through a 25 mm hose, and allow 60 to 100 seconds plus the compression volume. Water compresses about 1 per cent at 230 bar, another 3 to 4 litres, and the hose takes more.

Trapped air is the real hazard. At 230 bar a 5 litre pocket holds over 100 kJ of stored energy. Prove the vent open before the pump starts; on this body the highest point is the bonnet neck, not the flange, so it is tested bonnet up.

Draining takes longer than filling. Put the ball at about 45 degrees so both seat pockets connect to the bore, tilt the body 5 degrees towards the drain, and open the lowest port. Twenty to thirty minutes of gravity drain is normal, and a body that looks empty still holds water in the seat pockets, the stem bore and the ring grooves.

Then dry it. Warm dry air or nitrogen through the body until the dew point at the outlet is -40°C or lower, measured and recorded against the serial number. At -40°C the air holds about 0.1 g/m³ of vapour, low enough that what remains will not form an ice plug.

Moisture has to go because it becomes mechanical. Ice expands about 9 per cent as it forms, and water in a seat pocket jacks the seat off its carrier or locks the ball. Water in a groove freezes and lifts the gasket.

Test water quality matters too. Austenitic stainless pits in chloride, so use demineralised water below 25 mg/L and rinse out any inhibitor before drying, because the residue contaminates LNG and is a hazard in oxygen service.

Packing, Nitrogen Blanketing and Freight Weight

A valve this size ships on a skid, and the packing has one job: deliver a dry, clean, undamaged bore to a site that will install it weeks or months later.

The valve is bolted to a timber skid through the flange bolt holes with sacrificial bolts, or cradled on the barrel with the flange faces clear of the deck. It never rests on a flange face. The skid is sized so a forklift can lift it from either side and the valve cannot roll, and the timber is heat treated to the export wood packaging rules.

The bore and cavity get a barrier bag with about 1 kg of desiccant per cubic metre of enclosed volume, plus a humidity indicator card. The bag is not a substitute for drying, it is a delay: a valve packed at a -40°C dew point stays dry for six months, and a valve packed wet gets wetter.

Dry nitrogen goes into the body at 0.3 to 0.5 bar, with a gauge on a flange cap so the pressure can be checked at receipt. A reading of zero means the packing has been breached or the valve opened, and the valve should be re-dried rather than assumed good.

Flange protection is a bolted plywood or plastic cap with a ring shaped blank filling the joint groove, so the sealing surface touches nothing. The caps stay on until make-up.

Shipping weight is dry mass plus skid and packing, normally 1,100 to 1,800 kg, and that number drives the freight quote more than the valve does. Sea freight charges on weight or volume, whichever is greater. A crate here measures about 2.6 by 1.4 by 1.9 m, roughly 6.9 m³, and air freight values volume at about 167 kg per cubic metre, so the crate prices at around 1,150 kg.

Documentation travels in a pocket outside the crate and again in a sealed envelope inside: EN 10204 3.1 material certificate, pressure and seat test records by serial number, dimensional report, torque record and drying record. NACE MR0175 documentation is available on request.

Where a Large Size Reduced Bore Valve Is Used

LNG send-out and loading lines

A 20 inch line stepping to 16 inch at a valve station is common on send-out headers and on loading lines of smaller terminals, where line size is set by surge and valve size by flow. The duty is -162°C at boiling point, so any pressure drop causes flash, and a fraction of a bar is acceptable where one bar is not. The bonnet is sized from the insulation, usually 250 to 350 mm of PIR with cladding, so the gland stays above 0°C while the body sits at LNG temperature.

Air separation cold box and oxygen service

In an air separation unit the same body appears on liquid oxygen and liquid nitrogen headers at -183°C and -196°C, often at lower class with the same geometry. Oxygen adds cleanliness: bore, seat pockets and cavity must be degreased and free of hydrocarbon before packing, and drying becomes a safety step. These valves ship with a cleaning certificate and a nitrogen charge.

Ethylene and refrigerated petrochemical service

Refrigerated ethylene sits near -104°C, cold enough for PCTFE seats and an extended bonnet but not cold enough for the full LNG test programme. A large size reduced bore valve suits ethylene letdown and storage lines, where a 20 inch header feeds a 16 inch branch and the isolation point is the branch.

Values to Confirm Before the Drawing Is Released

Most of the cost of getting the DN500x400 cryogenic ball valve wrong is incurred before metal is cut, in the numbers below.

Frequently Asked Questions

Six questions come up on every enquiry for this size.

20x16 Cryogenic Ball Valve FAQ

What does 20x16 mean on a cryogenic ball valve?

The first number is the inlet flange size and the second is the outlet flange size, both in inches. So a 20x16 valve has a 20 inch flange at one end, a 16 inch flange at the other, and a 16 inch bore through the ball that matches the smaller line. Both ends are Class 900, and the body does the reduction internally, replacing a separate reducer and a 20 inch valve.

Why use a reduced bore valve instead of a separate reducer?

It removes one pressure body, two flanged joints, two gaskets, two bolt sets and about 1.5 m of pipe, and cuts dry mass from roughly 2,500 kg to between 900 and 1,500 kg. That shrinks the support steel, the crane and the operator. Each deleted joint is also a leak path at -162°C. The exception is a pigged line, where the 16 inch bore blocks the pig.

How much does a 20x16 Class 900 cryogenic valve weigh?

Roughly 900 to 1,500 kg dry, for a trunnion mounted CF8M body with extended bonnet and gear operator, without actuator or insulation. The range reflects body pattern, bonnet length and gear ratio. Add 150 to 250 kg for cold insulation, 150 to 350 kg for an actuator, and 150 to 300 kg for skid and packing. Lift plans should use the calculated mass on the approved drawing.

Which operator is recommended for a 20 inch cryogenic ball valve?

A gear operator of 20,000 to 30,000 Nm suits a valve turned a few times a year, provided rim pull stays at or below about 250 N at cold breakaway; otherwise specify a higher ratio or a hammer blow device. Use pneumatic or electric actuation where the valve cycles often or must fail to a position, sized on cold breakaway with a 1.5 factor and the spring end torque checked separately.

Is Class 900 the same as PN150?

Only as a nominal pressure equivalence. Class 900 is rated about 153 bar at 38°C in CF8M to ASME B16.34 group 2.2, and PN150 is the PN figure conventionally quoted for it. The flange dimensions differ, and EN standards list PN100 and PN160 rather than PN150, so a Class 900 flange and a PN150 flange do not bolt together. Treat the equivalence as a rating comparison, never a dimensional one.

How is a large cryogenic valve packed and shipped?

Bolted to a heat treated timber skid, never resting on a flange face, with a barrier bag, about 1 kg of desiccant per cubic metre, a humidity indicator, and a 0.3 to 0.5 bar dry nitrogen charge with a gauge. Both ring grooves are blanked and capped with bolted plywood. Shipping weight runs 1,100 to 1,800 kg, and a crate volume near 6.9 m³ decides whether freight is charged on weight or volume.