08. October 2014 · Comments Off · Categories: Gate valves

How to Order API 600 Gate Valves

NOTE Numbers in brackets are references to clauses or subsections of this International standard.
1) Supplemental requirements of this International standard shall be specifically stated in the purchase order.
2) If no supplemental requirements are to be taken to this International standard, the purchase order just needs to
refer to API 600 and to secify the items in the following list that are marked with an asterisk (*).

cast steel gate valves

The items listed below without an asterisk are options that may also be specified:
a) valve size *;
b) pressure class *;
c) flanged ends, including flange facing finish; or welding ends, including bore *;
d) auxiliary connections and openings;
e) valve orientation;
f) additional hard facing of body and/or wedge guides;
g) bonnet gasket and/or bonnet flange facing;
h) tapped openings;
i) wedge gate or double-disc gate; also type of wedge, if required *;
j) lantern ring;
k) chainwheel and chain;
l) gear operation, including type and arrangement, and the design maximum pressure differential across the
valve;

Large size gate valve

m)power operation, including type of power and power unit, and the design maximum pressure differential
across the valve;
n) bypass—specify either flanged or welded bonnet bypass valve;
o) material of the valve shell *;
p) nominal trim material *;
q) any required exceptions to valve manufacturer’s permissible options (e.g. NACE MR 0103);
r) handwheels;
s) safety shield;
t) chainwheel and safety cables, if furnished as original equipment;
u) alternate stem packing material;
v) bonnet bolting material;
w)inspection by purchaser;
x) high pressure closure test;
y) supplementary examination and testing;
z) export packaging.

04. October 2014 · Comments Off · Categories: Gate valves

Operation Specifications of Cast Steel Gate Valves

5.11 Operation
5.11.1 Unless otherwise specified by the purchaser, the valve shall be supplied with a direct operated handwheel that opens the valve when turned in a counter-clockwise direction.
5.11.2 The handwheel shall be a spoke-rim type with a maximum of six spokes and shall be free from burrs and sharp edges. Unless otherwise specified, the handwheel shall be a one-piece casting or forging or a multi-piece carbon steel fabrication that includes other carbon steel product forms. Fabricated handwheels shall have strength and toughness characteristics comparable to that of handwheels made as one-piece castings (for cast steel gate valve Class 150 etc.) or forgings.

cast steel gate valves
5.11.3 The handwheel shall be marked with the word “OPEN” and an arrow pointing in the direction of opening, except when the handwheel size makes such marking impractical.
5.11.4 The handwheel shall be retained on the stem nut by a threaded handwheel nut.
5.11.5 If operation by a chain wheel, gearbox or power actuator is to be added to the valve, the purchaser shall specify the following, as applicable:
— for chainwheel operation, the dimension from the centerline of the valve stem to the bottom of the chain loop;
— spur or bevel gear and the position of gearing handwheel relative to the pipe axis;
— electric, hydraulic, pneumatic or other actuator type;
— maximum service temperature and pressure differential across the valve disc;
— power supply attributes for power actuators.
5.11.6 Valve-to-gear-box or power actuator flange mating dimensions shall be according to ISO 5210 or shall comply with the purchaser’s specifications.

04. October 2014 · Comments Off · Categories: Gate valves

Bolting Specifications for Cast Steel Gate Valves

5.10 Bolting
5.10.1 Bolting shall be standard inch series bolting, except if the purchaser specifies metric series bolting. Bolting for the bonnet-to-body joint shall be continuously threaded stud bolts with heavy, semi-finished hexagon nuts that are in accordance with ASME B18.2.2 or ASME B18.2.4.6M.
5.10.2 Yoke-to-bonnet bolting shall be either continuously threaded stud bolts or headed bolts with hexagon nuts.
5.10.3 Gland bolts shall be hinged eyebolts, headed bolts, stud bolts or studs. Hexagon nuts shall be used. (suitable for all class ratings, such as cast steel gate valve class 150)

cast steel gate valves
5.10.4 Bolting with diameters 1 in. (25 mm) and smaller shall have coarse (UNC) threads or the most nearly corresponding metric threads. Bolting with diameters larger than 1 in. (25 mm) shall be 8-thread series (8UN) or the most nearly corresponding metric threads. Bolt threads shall be Class 2A and nut threads shall be Class 2B, in accordance with ASME B1.1. Studs used for gland bolting shall use a Class 5 interference fit conforming to ASME B1.12. When metric bolting is used metric bolt threads shall be tolerance Class 6g and nuts tolerance Class 6H in accordance with ASME B1.13M.

04. October 2014 · Comments Off · Categories: Gate valves

Specifications of Yoke, Packing & Packing Box for Cast Steel Gate Valves

1.7 Yoke
1.7.1 The yoke may be either an integral part of the bonnet or a separate part. The yoke shall retain the stem nutwhich links the handwheel to the stem.
1.7.2 The yoke and stem nut assembly design shall permit stem nut removal while the valve is under pressure and backseated.
1.7.3 Yokes that are separate shall have yoke-to-bonnet mating surfaces machined so as to assure a proper bearing assembly interface.
1.7.4 The yoke-to-stem nut bearing surfaces shall be machined flat and parallel. A lubricating fitting shall be provided for the bearing surfaces.

cast steel gate valves
1.8 Stem and Stem Nut
1.8.1 The minimum stem diameter, ds, shall be as given in Table 5. The minimum stem diameter applies to the stem along the surface area that comes into contact with the packing and to the major diameter of the trapezoidal stem thread. However, the major diameter of the stem thread may be reduced, at the valve manufacturer’s option, by no more then 0.06 in. (1.6 mm). The stem surface area in contact with the packing shall have a surface finish, Ra, of 32 µin. (0.80 µm) or smoother.
1.8.2 Stems shall have a gate attachment means at one end and an external trapezoidal style thread form at the other. Stem nuts shall be used for handwheel attachment and to drive the operating stem thread.
1.8.3 The stem-to-stem nut threads shall be of trapezoidal form as specified in ASME B1.5 or ASME B1.8, with nominal dimensional variations allowed. Stem threads shall be left-handed so that a direct operated handwheel rotated in a clockwise direction closes the valve.
1.8.4 The stem shall be one-piece wrought material. A stem that is a welded fabrication or threaded assembly shall not be provided.

Parallel Single Disc Gate Valves

1.8.5 Out of straightness of the entire length of the stem shall not exceed 0.001 in./in. (0.001 mm/mm).
1.8.6 The stem end that connects to a gate shall be in the form of a “T,” except that for a double-disc gate, the end connection may be threaded.
1.8.7 The stem connection shall be designed to prevent the stem from turning or from becoming disengaged from the gate while the valve is in service.
1.8.8 The stem design shall be such that the strength of the stem to gate connection and the part of the stem within the valve pressure boundary shall, under axial load, exceed the strength of the stem at the root of the operating thread.
1.8.9 The one-piece stem shall include a conical or spherical raised surface that seats against the bonnet backseat when the gate is at its full open position. A stem-bonnet backseat (for all class ratings of cast steel gate valve Class 150, Class 300 etc.) is a requirement of this International standard and, as such, is not meant to imply a manufacturer’s recommendation of its use for the purpose of adding or replacing packing while the valve is under pressure.
1.8.10 The stem nut design shall allow for the removal of the handwheel while keeping the stem (and disc) in a fixed position.
1.8.11 The stem-nut-to-handwheel attachment shall be through a hexagonal interface, a round interface having a keyway or another means of equivalent strength.
1.8.12 When the stem nut is retained in the yoke by means of a threaded bushing, the bushing shall be secured in place using either a lock weld or a positive mechanical lock. Locking by simple metal upsetting such as peening or staking is not permitted.

1.8.13 The closed-position stem thread projection beyond the stem nut on a new valve shall be a distance having a minimum equal to the valve wear travel and a maximum of five times the wear travel for valves NPS ≤ 6 (DN ≤ 150), and three times the wear travel for gate valves NPS > 6 (DN > 150).
1.8.14 Valves NPS ≥ 6 (DN ≥ 150) with pressure class ≥ 600, shall be furnished with stem nuts having ball or roller bearings.
1.9 Packing and Packing Box
1.9.1 The packing may be either square or rectangular or trapezoidal in cross-section. The nominal radial width of the packing, w, shall be in accordance with Table 6.
1.9.2 The nominal depth of the packing box shall accommodate a minimum of five uncompressed rings of packing. Unless otherwise specified by the purchaser, the packing box surface area in contact with the packing material shall have a surface finish, Ra, of 175 µin. (4.5 µm) or smoother.
1.9.3 The nominal bore (inside diameter) of the packing box shall be the sum of the nominal valve stem diameter plus twice the nominal packing width plus a clearance factor, y, i.e. equal to dn + 2w + y. See Table 6 for the required values.
1.9.4 A gland and a separate gland flange shall be provided for packing compression. The gland flange shall have two holes to receive the gland bolting. Slots for gland flange bolts shall not be used. The gland and gland flange shall be self-aligning. The gland shall have a shoulder at its outer edge so as to prevent complete entry of the gland into the packing box.
1.9.5 A lantern ring shall be provided only if so specified by the purchaser. In order to accommodate the lantern ring, the packing box depth shall be at least equivalent to that of a minimum of three uncompressed rings of packing above the lantern ring and three uncompressed rings of packing below the lantern ring plus the length of the lantern ring.
1.9.6 The clearance between the packing box bore (inside diameter) and the outside diameter of the gland (see Figure B.1) shall be nominally less than the diametrical clearance between the inside diameter of the gland and the stem diameter (such as  cast steel gate valve Class 300, .

04. October 2014 · Comments Off · Categories: Gate valves

Types and Features of Gates for Gate Valves

5.6.1 Gate configurations are categorized as illustrated in Figure 2.

Solid one piece wedge
Flexible one piece wedge
Split wedge
Paralle one piece wedge

5.6.1.1 A one-piece wedge gate—as either a solid or flexible wedge design—shall be furnished, unless otherwise specified by the purchaser.

5.6.1.2 A two-piece split wedge gate or parallel seat double-disc gate may be furnished when specified by the purchaser. A split wedge gate consists of two independent seating parts that conform to the body seats when closed.
A double-disc gate has a spreading mechanism that forces the two parallel discs to the body seats when closed.

cast steel gate valves

5.6.2 Except for a double-disc gate, in the open position, the gate shall completely clear the valve seat openings.
5.6.3 The body shall have guide surfaces to minimize wear of the seats during operation of the valve, to accurately position the gate throughout the travel distance to its seat, and to ensure the alignment of the gate and stem in all orientations without gate binding or galling. Wedge guides and/or body guides need not be hardfaced unless specified in the purchase order, or when required to allow for proper operation in any orientation, including affects of wear or galling.

5.6.4 Gate seating surfaces shall be integral or faced with weld metal. Unless specified, hardfaced seating surfaces are not required. Finished thickness of any facing material shall be not less than 0.06 in. (1.6 mm).
5.6.5 Wedge gates (used for cast steel gate valves)shall be designed to account for seat wear. The dimensions that fix the position of the gate seats relative to the body seats shall be such that the gate, starting from the time of manufacture, can, as a result of seat wear, move into the seats by a distance, h, defined as wear travel. Wear travel is in a direction that is parallel with the valve stem. The required minimum wear travel varies with valve size in accordance with Table 4.

Table 4—Minimum Wear Travel

 

Valve Size Range

NPS (DN)

Wear Travel

h

in. (mm)

≤ NPS ≤ 2 (25 ≤ DN ≤ 50) 0.09 (2.3)
2 1/2 ≤ NPS ≤ 6 (65 ≤ DN ≤ 150) 0.13 (3.3)
≤ NPS ≤ 12 (200 ≤ DN ≤ 300) 0.25 (6.4)
14 ≤ NPS ≤ 18 (350 ≤ DN ≤ 450) 0.38 (9.7)
20 ≤ NPS ≤ 24 (500 ≤ DN ≤ 600) 0.50 (12.7)
03. October 2014 · Comments Off · Categories: Uncategorized

Flange face finish

The ASME B16.5 code requires that the flange face (raised face and flat face) has a specific roughness to ensure that this surface be compatible with the gasket and provide a high quality seal.
A serrated finish, either concentric or spiral, is required with 30 to 55 grooves per inch and a resultant roughness between 125 and 500 micro inches. This allows for various grades of surface finish to be made available by flange manufactures (and valve manufacturer) for the gasket contact surface of metal flanges.
The picture on the right shows a serrated finish on a Raised Face.

Cast steel globe valves

The most used Surfaces
Stock Finish
The most widely used of any flange surface finish, because practically, is suitable for all ordinary service conditions. Under compression, the soft face from a gasket will embed into this finish, which helps create a seal, and a high level of friction is generated between the mating surfaces.
The finish for these flanges is generated by a 1.6 mm radius round-nosed tool at a feed rate of 0.8 mm per revolution up to 12 inch. For sizes 14 inch and larger, the finish is made with 3.2 mm round-nosed tool at a feed of 1.2 mm per revolution.
Spiral Serrated (commonly used for valves, such as ball valves)
This is also a continuous or phonographic spiral groove, but it differs from the stock finish in that the groove typically is generated using a 90-deg tool which creates a “V” geometry with 45° angled serration.
Concentric Serrated
As the name suggests, this finish is comprised of concentric grooves. A 90° tool is used and the serrations are spaced evenly across the face.
Smooth Finish
This finish shows no visually apparent tool markings. These finishes are typically utilized for gaskets with metal facings such as double jacketed, flat steel and corrugated metal. The smooth surfaces mate to create a seal and depend on the flatness of the opposing faces to effect a seal. This is typically achieved by having the gasket contact surface formed by a continuous (sometimes called phonographic) spiral groove generated by a 0.8 mm radius round-nosed tool at a feed rate of 0.3 mm per revolution with a depth of 0.05 mm. This will result in a roughness between Ra 3.2 and 6.3 micrometers (125 – 250 micro inch).

API 6D valves

SMOOTH FINISH
Is it suitable for spiral gasket and non metallic gasket?
For what kind of application is this type?
The above questions are often asked. I try to answer.
Smooth finish flanges are more common for low pressure and/or large diameter pipelines and primarily intended for use with solid metal or spiral wound gaskets.
Smooth finishes are usually found on machinery or flanged joints other than pipe flanges. When working with a smooth finish, it is important to consider using a thinner gasket to lessen the effects of creep and cold flow. It should be noted, however, that both a thinner gasket and the smooth finish, in and of themselves, require a higher compressive force (i.e. bolt torque) to achieve the seal.
You may have probably seen this comment:
Machining of gasket faces of flanges (end flanges of valves, such as gate valves) to a smooth finish of Ra = 3.2 – 6.3 micrometer
(= 125 – 250 microinches AARH)
AARH stands for Arithmetic Average Roughness Height. It is used to measure the roughness (rather smoothness) of surfaces. 125 AARH means 125 micro inches will be the average height of the ups and downs of the surface.
63 AARH is specified for Ring Type Joints.
125-250 AARH (it is called smooth finish) is specified for Spiral Wound Gaskets.
250-500 AARH (it is called stock finish) is specified for soft gaskets such as NON Asbestos, Graphite sheets, Elastomers etc. If we use smooth finish for soft gaskets enough “biting effect” will not occur and hence the joint may develop leak.
Sometimes AARH is referred also as Ra which stands for Roughness Average and means the same.

01. October 2014 · Comments Off · Categories: Gate valves

Bonnet Dimensions & Bonnet-to-body Joint of Cast Steel Gate Valves

1.4 Bonnet Dimensions
1.4.1 When designing the stem, gland, lantern ring (if supplied) and backseat the manufacturer shall take into account stem guiding and the prevention of packing extrusion.
1.4.2 The bonnet shall include a conical stem backseat in one of the following forms:
— a bushing positively secured against coming loose, i.e. not relying on friction;
— an integral surface in the case of an austenitic stainless steel valve;
— an austenitic stainless steel or hardfaced weld deposit that is a minimum of 0.06 in. (1.6 mm) thick.
1.4.3 Bonnets shall be one-piece castings or forgings. However, bonnets may be attached by welding when approved by the purchaser and are subject to the same exceptions and requirements as specified in 5.3.1.2.1.
1.4.4 The gland bolting shall not be anchored to the bonnet or yoke through a fillet welded attachment or stud welded pins. The anchor design shall not include slotted holes or brackets which do not retain gland bolting during repacking.
1.5 Bonnet-to-body Joint
1.5.1 The bonnet-to-body joint shall be a flange and gasket type.
1.5.2 For Class 150 gate valves, the bonnet-to-body joint shall be one of the following types illustrated in ASME B16.5.
— flat face,
— raised face,
— tongue and groove,
— spigot and recess,
— ring joint.
1.5.3 For valves having pressure class designation Class > 150, the bonnet-to-body joint shall be as in 5.5.2, except that the flat face joint is not permitted.

gate valve
1.5.4 The bonnet flange gasket shall be suitable for the temperature range –20 °F (–29 °C) to 1000 °F (538 °C) and be one of the following:
— solid metal, corrugated or flat;
— filled metal jacketed, corrugated or flat;
— metal ring joint;
— spiral wound metal gasket with filler and a centering/compression ring;
— spiral wound metal gasket with filler, to be used only in a body-to-bonnet joint design that provides gasket compression control.
API STANDARD 600 For Class 150, the following are also acceptable:
— corrugated metal insert with graphite facings;
— when approved by the purchaser, flexible graphite sheet, reinforced with a stainless steel flat, perforated, tanged, or corrugated insert equipped with annular containment rings;
1.5.5 Except for Class 150 and PN 16 valves and valves in sizes NPS 2.5 (DN 65) and smaller, bonnet-to-body flanges shall be circular.
1.5.6 Bonnet and body flange nut bearing surfaces shall be parallel to the flange face within ±1°. Spot facing or back-facing required to meet the parallelism requirement shall be in accordance with ASME B16.5. (Adopted by China gate valve manufacturer)

cast steel gate valves
1.5.7 The bonnet-to-body joint shall be secured by a minimum of four through type stud bolts. The minimum stud bolt size for each valve size shall be as follows:
— either 3/8 or M10 when 1 ≤ NPS ≤ 2 1/2 (25 ≤ DN ≤ 65);
— either 1/2 or M12 when 3 ≤ NPS ≤ 8 (80 ≤ DN ≤ 200);
— either 5/8 or M16 when 10 ≤ NPS (250 ≤ DN).
1.5.8 The total cross-sectional area of the bolts in valve bonnet bolting shall be in accordance with the requirements of ASME B16.34, Paragraph 6.4.
1.5.9 At assembly, gasket contact surfaces shall be free of sealing compounds. A light coating of a lubricant, no heavier than kerosene, may be applied if needed to assist in proper gasket assembly.