BS 1868: Steel check valves (flanged and butt-welding ends) for the petroleum, petrochemical and allied industries
BS 1868 Standard specifies requirements for cast or forged steel check valves with flanged or butt-welding ends of the following types:
a) swing, for vertical or horizontal flow (see Figure 1);
b) lift:
i) piston type, for angle or horizontal flow (see Figure 2);
ii) ball type, for angle or horizontal flow (see Figure 3);
iii) ball type, for vertical flow (see Figure 4);
iv) disk type, for vertical flow (see Figure 5).
The terms “vertical”, “horizontal” and “angle” relate to the axes of the body ends.
When swing check valves are used in vertical lines the flow must be in an upward direction. For the purposes of this standard any line with a slope (upward or downward) of 5° or less is deemed to be horizontal. In the case of angle pattern valves the inlet should be vertical.
Table 1—Dimensions of check valves a
Inside diameter at flanges (minimum)
| Nominal size | Inside diameter at flanges (minimum) | |||||||
| Class 150 | Class 300 | Class 400 | Class 600 | Class 900 | Class 1500 | Class 2500 | ||
| mm | in | mm | mm | mm | mm | mm | mm | mm |
| 15 | 1/2 | 15 | 15 | — | 15 | — | 13 | 13 |
| 20 | 3/4 | 20 | 20 | — | 20 | — | 19 | 19 |
| 25 | 1 | 25 | 25 | — | 25 | — | 22 | 19 |
| 32 | 1-1/4 | 32 | 32 | — | 32 | — | 29 | 25 |
| 40 | 1-1/2 | 38 | 38 | — | 38 | — | 35 | 29 |
| 50 | 2 | 51 | 51 | — | 51 | — | 48 | 38 |
| 65 | 2-1/2 | 64 | 64 | — | 64 | — | 57 | 48 |
| 80 | 3 | 76 | 76 | — | 76 | 73 | 70 | 57 |
| 100 | 4 | 102 | 102 | 102 | 102 | 98 | 92 | 73 |
| 150 | 6 | 152 | 152 | 152 | 152 | 146 | 137 | 111 |
| 200 | 8 | 203 | 203 | 203 | 200 | 190 | 178 | 146 |
| 250 | 10 | 254 | 254 | 254 | 248 | 238 | 222 | 184 |
| 300 | 12 | 305 | 305 | 305 | 298 | 283 | 264 | 219 |
| 350 | 14 | 337 | 337 | 333 | 327 | 311 | 289 | — |
| 400 | 16 | 387 | 387 | 381 | 375 | 356 | 330 | — |
| 450 | 18 | 438 | 432 | 432 | 419 | 400 | 371 | — |
| 500 | 20 | 489 | 483 | 479 | 464 | 444 | 416 | — |
| 600 | 24 | 591 | 584 | 575 | 559 | 533 | 498 | — |
Body thickness (minimum) C
| Nominal size | Body thickness (minimum) C | |||||||
| Class 150 | Class 300 | Class 400 | Class 600 | Class 900 | Class 1500 | Class 2 500 | ||
| mm | in | mm | mm | mm | mm | mm | mm | mm |
| 15 | 1/2 | 4.8 | 4.8 | 6.4 | 9.5 | 11.1 | ||
| 20 | 3/4 | 4.8 | 4.8 | 7.9 | 11.1 | 13.5 | ||
| 25 | 1 | 6.4 | 6.4 | 7.9 | 12.7 | L5.1 | ||
| 32 | 1-1/4 | 6.4 | 6.4 | 8.6 | 14.2 | 17.5 | ||
| 40 | 1-1/2 | 6.4 | 7.9 | 9.3 | 15.0 | 19.0 | ||
| 50 | 2 | 8.7 | 9.5 | 11.1 | 19.0 | 22.2 | ||
| 65 | 2-1/2 | 9.5 | 11.1 | 11.9 | 22.2 | 25.4 | ||
| 80 | 3 | 10.3 | 11.9 | 12.7 | 19.0 | 23.8 | 30.2 | |
| 100 | 4 | 11.1 | 12.7 | 12.7 | 15.9 | 21.4 | 28.6 | 35.7 |
| 150 | 6 | 11.9 | 15.9 | 16.7 | 19.0 | 26.2 | 38.1 | 48.4 |
| 200 | 8 | 12.7 | 17.5 | 19.0 | 25.4 | 31.8 | 47.5 | 61.9 |
| 250 | 10 | 14.3 | 19.0 | 21.4 | 28.6 | 36.5 | 57.2 | 67.5 |
| 300 | 12 | 15.9 | 20.6 | 23.8 | 31.8 | 42.1 | 66.7 | 86.5 |
| 350 | 14 | 16.7 | 22.2 | 27.0 | 34.9 | 46.0 | 69.8 | |
| 400 | 16 | 17.5 | 23.8 | 28.6 | 38.1 | 52.4 | 79.4 | |
| 450 | 18 | 18.3 | 25.4 | 30.2 | 41.3 | 57.2 | 88.9 | |
| 500 | 20 | 19.0 | 27.0 | 33.3 | 44.4 | 63.5 | 98.4 | |
| 600 | 24 | 20.6 | 30.2 | 36.5 | 50.8 | 73.0 | 114.3 | |
a The range of dimensions for all patterns of check valves is restricted to those covered in BS 2080.
b These sizes have been retained only for the purpose of replacing existing valves (see clause 6).
c Minimum body thickness at any point upon inspection.
d For valves of 80 mm nominal size, if intended for use with lapped flanges, the ring number should be R30.
8 Body
8.1 The body design criteria specified in 8.2 to 8.11 shall be observed.
8.2 The body shall be designed to minimize pressure loss as well as corrosive and erosive effects.The body end port shall be circular.
8.3 In the case of swing type and combined horizontal and vertical ball type valves, the full port area shall be maintained without pockets from the inlet port to the valve seat to avoid turbulence.On the outlet side of the valve seat of swing type valves, the body shall be of such proportions that it allows sufficient swing of the disk to give a flow area at least equivalent to full port area.
8.4 The wall thickness of the body shall conform to the thickness as given in Table 1. Drilling of, or pinning to, the wall of a pressure-containing part, e.g.for nameplate fixing, is not permissible where such drilling or pinning would reduce the effective thickness below the minimum permitted value.
8.5 Face-to-face and centre-to-face dimensions for raised face flange end valves and end-to-end and centre-to-end dimensions for butt-welding end and ring-joint flange and valves shall conform to the dimensions specified in BS 2080.
8.6 End flanges shall be cast or forged integral with the body except that flanges may be attached by welding if so specified in the purchase order.The welds of end flanges attached by butt-welding shall comply with the requirements of BS 3351 and shall have any necessary heat treatment as required by BS 3351 to ensure that they are suitable for service temperatures down to-30 °C. Flange attachment by other welding processes shall be the subject of agreement between the manufacturer and the purchaser. All heat treatment after welding on of flanges shall be carried out before machining of the body.
8.7 End flanges shall comply with the requirements of BS 1560-2.End flanges shall be one of the types shown in Figure 1 and Figure 2 of BS 2080:1974.The purchaser shall specify the type of facing required. Valves generally in accordance with this standard but suitable for use in piping systems with flanges complying with the requirements of BS 4504-1 shall comply with the requirements of Appendix A.
8.8 Butt-welding ends shall conform to the details shown in Figure 6.
For butt-welding end valves the minimum inside diameter of the body end port shall comply with the
details given in Figure 6.Pipe schedule number, or pipe wall thickness and outside diameter of the pipe, shall be specified by the purchaser.
When welding butt-welding end valves into piping systems, the welds and any necessary heat treatment shall comply with the requirements of BS 3351.
8.9 For flanged valves the minimum inside diameter of the body end port shall be as specified in Table 1.
8.10 With the exception of ball and angle type valves for vertical/horizontal flow (see Figure 4), valves of sizes 50 mm and above shall have provision for a drain tapping in the body on the bottom centre line.Any other provision for tapping swing or lift pattern check valves shall be as specified by the purchaser and shall comply with Figure 1 as regards location.If the metal thickness of the body is insufficient to provide the effective length of the thread for body tapping, or if the body presents an uneven surface, bosses shall be provided.
8.11 Separate seat rings in the body shall be employed except in the two cases below. a)Austenitic steel valves may have integral seats.
b)Austenitic or hard-facing (body)seat materials may be deposited directly on the valve body;the minimum finished thickness of the deposit shall then be 1.6 mm.
13 %chromium seat material may be directly deposited only on separate steel seat rings;the minimum finished thickness of the deposit shall then be 1.6 mm.
Seat rings may be shoulder seated or bottom seated at the option of the manufacturer and may be screwed in, rolled in, or welded in unless one particular method is specified by the purchaser.Threaded seat rings shall be provided with lugs or slots to facilitate removal.Shoulder-seated rings shall be designed so that any clearance between the back of the ring and the bottom of the ring recess shall not be greater than 1.6 mm for sizes 300 mm(12 in)and smaller, and 3.2 mm for sizes 350 mm(14 in)and larger.
For swing type valves the body seat shall be inclined at an angle of approximately 5°from the vertical to facilitate closing and to prevent chatter.
Tack welding may be employed to prevent loosening (see BS 3351).
The use of a sealing medium on the threads is not permissible.
9 Cover
9.1 For covers the design criteria specified in 9.2 to 9.5 shall be observed.
9.2 The cover thickness shall conform with the requirements given in Table 1.
9.3 The body-to-cover connection shall be male-and-female, tongue-and-groove, or ring-joint type.Where possible all body/cover connections and gaskets shall be of standard dimensions in accordance with BS 1560-2, except for Class 150, which may be fiat face.
9.4 The cover flange and mating body flange shall be of circular form, except that for valves of all classes below 80 mm they may be square or rectangular.Flanges shall be spot faced or back faced as specified in BS 1560-2.
9.5 The body-to-cover joint shall have at least four through-bolts of the following minimum size, except that for nominal sizes below 40 mm studs may be used.(See also clause 14.)
10 Disk , piston or ball
10.1 Disk (swing or lift type)
10.1.1 The disk shall be of the renewable type with a flat seating face.
10.1.2 Disks may have integral faces or may be fitted with separate facing rings rolled in, directly deposited or welded on.Directly deposited facings shall have a minimum finished thickness of 1.6 mm.In the case of swing type valves the disk shall be secured to the hinge by a nut so as to allow for the self-seating of the disk on the body seat.The nut shall be locked by drilling and pinning.
10.1.3 In the case of lift type valves the disk shall be fitted on, or integral with, the disk spindle so as to guide the disk on to the body seat.
10.1.4 The use of a soft seal ring in the disk seat is dealt with in clause 15.
10.2 Piston. The piston shall be in the form of a cylinder, which may be hollow, the lower end of which is shaped to form a seating disk.The cylindrical part shall fit into a guide so as to make an effective dashpot and for this purpose shall be provided with a bleed hole of proper size near the seating disk.Alternatively, the hole may be provided in the piston guide.The piston and guide shall be of sufficient length to provide effective guidance over the whole length of its travel.The seating face may be weld-deposited, in which case it shall have a minimum finished thickness of 1.6 mm.
10.3 Ball. In horizontal pattern valves the ball shall be constrained in the guide so that a cushioning effect is obtained at the top end of travel.
11 Piston and ball gu ides
11.1 Piston and horizontal pattern ball type check valves shall be provided with a removable guide to guide the piston or ball throughout its entire travel.If the guide is independent of the cover, the upper part of the guide shall be closed and the guide shall be locked in position between the cover flange of the body and the cover;the top of the guide shall be provided with a UNC tapped hole or other means to facilitate removal. The lower part of the guide, whether integral with or independent of the cover, shall be a hollow cylinder or cage to accommodate the piston or ball, permitting it to travel upwards for a sufficient distance to
provide adequate flow under the piston or ball when in the highest position.
11.2 Vertical or horizontal pattern ball type check valves shall be provided with guides that may be integral with the seat, with a grid that limits the travel of the ball but allows adequate flow when the ball is in the fully open position.
12 Hinge and hinge pin (swing type)and spindle support c age (disk type)
12.1 A hinge and hinge pin shall be provided and mounted in the body so as to permit full movement of the disk(see Figure 1).
12.2 A cage shall be provided complete with bearing bush to guide the disk spindle.
12.3 Hinge pin plugs, where fitted, shall be suitably secured to prevent loosening in service.
13 Special fitments
13.1 Outside attachment. If specified in the purchase order and if the design will permit, the hinge pin may be extended through the body of the valve.An outside lever with adjustable weights, damping device, fusible link or locking device etc.to control the movement of the disk may be fitted.
13.2 Loading spring. Consideration should be given to providing a spring to ensure more positive closing of the valve where there is a low differential pressure or when the process fluid is highly viscous.
14 Cover bolting
14.1 The allowable working stress in bolting material for cover flanges at the primary service pressures in clause 4 shall not exceed 62 MPal), assuming that the pressure acts upon an area circumscribed by the outside periphery of the gasket or, for a ring joint, that the pressure acts through the pitch circle of the ring joint.
14.2 Cover flange bolting shall be by stud bolts with a nut at each end of each stud bolt.Stud bolts and nuts shall comply with the requirements of sections 1 and 3 of BS 4882:1973.
14.3 For valves of 40 mm nominal size and below, studs in accordance with BS 2693-1 may be used.
