03. July 2015 · Comments Off · Categories: Gate valves

The installation and maintenance for the gate valves should note the following:
1)The hand wheel, handle and drive mechanism for lifting are not allowed to use, and forbid the collision.
2) Gate Valve should be mounted vertically (ie stem in a vertical position, the hand wheel at the top).
3)With a bypass valve to open the bypass valve opening should be preceded (in order to balance imports and exports and reduce the pressure opening force).
4) with the gate valve drive mechanism, according to the provisions of product installation instructions.
5)If the gate valve switch is used frequently, lubrication at least once a month.
Using media as a cut-off valve, in the full flow through, then the pressure medium to run minimal loss. Valve usually does not require frequent opening and closing, and keeping the shutter fully open or fully closed condition. Not available for use as a regulator or throttling.
For the high-speed flow of medium, open the gate in local conditions can cause vibration of the gate, while the vibration it may damage the gate and seat sealing surface, and the throttling damper will suffer erosion of the medium.
From a structural form, the main difference is that the sealing element is used. According to the form of the sealing element, often divided into several different types of valves, such as: wedge gate valves, parallel gate valve, parallel Gate Valve, Wedge double plate valve.
The most common form of wedge gate and parallel gate valve. The role of this type of valve is only allowed media to flow in one direction, and stop the flow direction. Usually the valve is automatically work in a direction of flow of fluid pressure effect, the valve opens; opposite direction of fluid flow from the fluid pressure and the valve flap from the coincidence of acting on the valve seat, thereby cutting off the flow. Check them belong to this type of valve, which includes swing check valves and lift check valves. Swing Check Valve with ordinary hinge, there is a door on the same disc as the freedom leaning tilt seat surface.

To ensure that the valve position every time to reach the right side of the seat, the valve flap design in the hinge body to valve flap has enough to swing space, and make a real flap valve, comprehensive engagement with the valve seat. Gate valve can all be made of metal can also be embedded in the leather, rubber on metal, or synthetic coverage, depending on performance requirements.
Swing check valves in the fully open position, the fluid pressure virtually unimpeded, so by the pressure drop across the valve is relatively small. Lift check valve located on the valve body sealing surface located seat. Addition to this valve disc is free to lift, the other part as the cut-off valves, fluid pressure from the valve seat sealing surface of valve lift, medium return valve flap led to a seat, and cut off the flow. Depending on conditions, the valve flap can be all metal construction, it can be a mosaic form rubber or rubber ring in the disc rack.

Like gate valves, fluid channels through the lift valve is narrow, so that by elevating the pressure drop valve than the swing check valve a little bigger, and swing check valves for flow restrictions very little. In the production process, in order to make media pressure, flow and other parameters meet the process requirements, the need to install the adjusting mechanism to adjust these parameters. Adjusted operating principle mechanism is by changing the flow area of the gate valve and gate valve seat between the gate valve, to regulate the purpose of the above parameters.

Such gate valves are referred to as control valves, which is divided into relying on power-driven media itself is called self-drive control valve, such as gate valve, regulator valve, all leading up power-driven (such as electricity, compressed air and liquid Power) as he was driving control valve, such as the electric control valve, pneumatic control valve and hydraulic control valve.

Posted by Relia Valve, Professional China valve manufacturer and China wafer valve supplier.

03. July 2015 · Comments Off · Categories: Gate valves

What are the gate valves?

The gate valve opening and closing parts, the direction of movement of the fluid direction perpendicular to the gate, the gate valve can only be fully open and fully closed, can not be adjusted and the throttle. Ram has two sealing surfaces, sealing surfaces the most common mode of gate valve forming wedge, wedge angle with the valve parameters vary, usually 50, the medium temperature is not high when 2 ° 52 ‘. Wedge gate valve can be made into a whole, called the rigid gate; also be made to produce small quantities of deformation gate in order to improve its process of, to make up the sealing surface angle deviations arising during processing, such gate board called valve closed, sealing surface can only rely on referrals made flexible gate.

Quality pressure to seal, which rely on media pressure to ram pressure to the sealing surface of the other side of the seat to ensure the sealing surface of the seal, which is self-sealing. Most of the gate valve is sealed by force, that the valve is closed to rely on external pressure to force the gate valve to ensure that the sealing of the sealing surface.

Gate valves with the valve stem linear movement, called the lift rod valve (also called clear shot valve). Often movements are trapezoidal threaded rod, through the guide slot valve and the valve on top of the nut, and the rotary motion into linear motion, which is the operating torque thrust into action.

Open the gate valve, when the gate valve lift height equal to diameter of 1: 1 times, the fluid channel is completely smooth, but at run time, this position can not be monitored. Actual use, is the apex of stem as a sign that the fixed position, as its fully open position. Temperature appears to consider locking phenomenon, usually open to the vertex position, and then rewind 1 / 2-1 circle, as the location of a fully open valve. Therefore, the fully open position of the gate valve, according to damper position (ie, travel)to determine.

Some gate valve, the stem nut is located at the gate, handwheel drive stem rotation, leaving the gate to upgrade, this valve is called the rotating rod valve or valve called the dark bar.

Gate valves have the following advantages:
1)The fluid resistance, sealing surface by erosion distressed medium and small brush.
2)Open and close more effort.
3)The medium flows unrestricted, non-spoiler, without reducing pressure.
4)A simple shape, structure, length short, good manufacturing processes, a wide range.

Gate valve defects are as follows:
1) Between the sealing surface can lead to erosion and abrasion, maintenance more difficult.
2)Overall large size, open requires a certain amount of space, opening and closing a long time.
3) The structure is more complex.

Gate valve types, according to the sealing surface configuration can be divided into wedge gate-type valve and parallel gate-type valve, wedge gate-type valve can be divided into: single-gate type, gate-type double plate and elastic; parallel gate-type valve can be divided into single-gate type and double plate. Divided by the threaded stem position can be divided into two clear shot valve gate and dark bar.

Gate valve installation and maintenance should note the following:
1)The hand wheel, handle and drive mechanism for lifting are not allowed to use, and forbid the collision.
2)Gate Valve should be mounted vertically (ie stem in a vertical position, the hand wheel at the top).
3)With a bypass valve to open the bypass valve opening should be preceded (in order to balance imports and exports and reduce the pressure opening force).
4)Belt drive mechanism, according to the provisions of product installation instructions.
5) If you frequently switch the valve to use, lubrication at least once a month.

Posted by Relia Valve, Professional China valve manufacturer and China wafer valve supplier.

02. November 2014 · Comments Off · Categories: Gate valves

Gate Valves

gate valve, also known as a sluice valve, is a valve that opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restric­tion is desired.

Gate valves are primarily designed to start or stop flow, and when a straight-line flow of fluid and minimum flow restriction are needed. In service, these valves generally are either fully open or fully closed.

The disc of a Gate valve is completely removed when the valve is fully open; the disk is fully drawn up into the valve Bonnet. This leaves an opening for flow through the valve at the same inside diameter as the pipesystem in which the valve is installed. A Gate valve can be used for a wide range of liquids and provides a tight seal when closed.

On opening the gate valve, the flow path is enlarged in a highly nonlinear manner with respect to percent of opening. This means that flow rate does not change evenly with stem travel. Also, a partially open gate disc tends to vibrate from the fluid flow. Most of the flow change occurs near shutoff with a relatively high fluid velocity causing disk and seat wear and eventual leakage if used to regulate flow. Typical gate valves are designed to be fully opened or closed.When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low friction loss.

Construction of a Gate valve

Gate valves consists of three main parts: body, bonnet, and trim. The body is generally connected to other equipment by means of flanged, screwed or welded connections. The bonnet, which containing the moving parts, is attached to the body, usually with bolts, to permit maintenance. The valve trim consists of the stem, the gate, the disc or wedge and the seat rings.

Types of a Gate valve

The gate valves are normally classified as wedge gate valves (generally called cast steel gate valves), knife gate valves and slab gate valves and forged steel gate valves.

The gate valves can be classified as  API 6D gate valves, API 600 gate valves and  API 602 gate valves.

Discs of a Gate valve

Gate valves are available with different discs or wedges. Ranging of the Gate valves (made by China gate valve supplier) is usually made by the type of wedge used. The gate faces can form a wedge shape or they can be parallel.

The most common were:

  • Solid wedge is the most commonly used disk by its simplicity and strength.
    A valve with this type of wedge can be installed in each position and it is suitable for almost all liquids. The solid wedge is a single-piece solid construction, and is practically for turbulent flow.
  • Flexible wedge is a one-piece disc with a cut around the perimeter to improve the ability to correct mistakes or changes in the angle between the seats.
    The reduction will vary in size, shape and depth. A shallow, narrow cut gives little flexibility but retains strength.
    A deeper and wider cut, or cast-in recess, leaves little material in the middle, which allows more flexibility, but compromises strength.
  • Split wedge is self-adjusting and selfaligning to both seats sides. This wedge type consists of two-piece construction which seats between the tapered seats in the valve body. This type of wedge is suitable for the treatment of non-condensing gases and liquids at normal temperatures, particularly corrosive liquids.
  • Most common wedges in Gate valves

    Most common wedges for Gate valves

Stem of a Gate valve

The stem, which connects the handwheel and disk with each other, is responsible for the proper positioning of the disc. Stems are usually forged, and connected to the disc by threaded or other techniques. To prevent leakage, in the area of the seal, a fine surface finish of the stem is necessary.

Gate valves are classified as either:

  • Rising Stem
  • Non Rising Stem

For a valve of the Rising Stem type, the stem will rise above the handwheel if the valve is opened. This happens, because the stem is threaded and mated with the bushing threads of a Yoke. A Yoke is an integral part from a Rising Stem valve and is mounted to the Bonnet.

For a valve of the non Rising Stem type, there is no upward stem movement if the valve is opened. The stem is threaded into the disk. As the handwheel on the stem is rotated, the disk travels up or down the stem on the threads while the stem remains vertically stationary.

In the main Menu “Valves” you will find links to detailed (large) drawings of both stem types.

Seats of a Gate valve

Seats for Gate valves are either provided integral with the valve body or in a seat ring type of construction. Seat ring construction provides seats which are either threaded into position or are pressed into position and seal welded to the valve body. The latter form of construction is recommended for higher temperature service.

Integral seats provide a seat of the same material of construction as the valve body while the pressed-in or threaded-in seats permit variation. Rings with hard facings may be supplied for the application where they are required.

Advantages and disadvantages of Gate valves

Advantages:

  • Good shutoff features
  • Gate valves are bidirectional and therefore they can be used in two directions
  • Pressure loss through the valve is minimal

Diaadvantages:

  • They can not be quickly opened or closed
  • Gate valves are not suitable for regulate or throttle flow
  • They are sensitive to vibration in the open state

By Kevein from Zhejiang Relia Valve Co., Ltd. professional China valve supplier, China wafer check valve and China metal seated ball valve supplier

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)
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.

30. September 2014 · Comments Off · Categories: Gate valves

Body Dimensions of  Cast Steel Gate Valves

1.3.1 Flanged Ends
1.3.1.1 Body end flanges shall comply with the dimensional requirements of ASME B16.5. Unless otherwise
specified, raised face end flanges shall be provided.
1.3.1.2 Face-to-face dimensions shall be in accordance with ASME B16.10 or ISO 5752. Body end flanges and
bonnet flanges shall be cast or forged integral with the body. However, flanges may be attached by welding when
approved by the purchaser.

cast steel gate valves
1.3.1.2.1 Welding a flange to a valve body shall be by full penetration butt-welding. Unless otherwise specified,
attachment weld shall conform to ASME B31.3 or ISO 15649 for normal fluid service, including weld quality
acceptance criteria and qualifications for the weld procedure and welder or welding operator. Heat treatment shall be
performed in accordance with Table 3.
1.3.1.2.2 Integral or other alignment rings (centering backing rings) used to facilitate welding shall be removed after
the weld is completed.
1.3.2 Butt-welding Ends
1.3.2.1 Butt-welding ends for valve sizes greater than NPS 2 shall conform to the requirements of ASME B16.25 for
the bore specified for use without backing rings. Conversion of a flanged end gate valve to a butt-welding valve is not
permitted except by agreement between the purchaser and manufacturer.
1.3.2.2 End-to-end dimensions for butt-welding end class designated valves shall be in accordance with ASME
B16.10, unless otherwise specified by the purchaser.
1.3.3 Body Seats

cast steel gate valves
1.3.3.1 The inside diameter of the seat opening shall not be less than that specified in Annex A of ASME B16.34 for
the nominal pipe size and pressure class.
1.3.3.2 Integral body seats are permitted in austenitic stainless steel gate valves. When an austenitic stainless steel or a
hardfacing material is used for the body seat, this material may be weld-deposited directly on the valve body.
15.3.3.3 Where separate seat rings are provided, they shall be shoulder or bottom seated, and either threaded or
welded in place, except that for NPS < 2 (DN ≤ 50) rolled or pressed in seat rings may be used. Threaded seat rings
in ASME Class 600 or higher pressure class valves shall be seal welded.
1.3.3.4 Body seat rings shall have adequate seating area surface and shall have edges equipped with a radius or
chamfer as necessary, to prevent galling or any other damage to the disc when the valve is operated against pressure.
1.3.3.5 Sealing compounds or greases shall not be used when assembling seat rings; however, a light lubricant
having a viscosity no greater than kerosene may be used to prevent galling of mating threaded surfaces.