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Globe Valve BS 1873 and API 602

What is a globe valve? When shall it be used instead of gate and ball valves? In this article, we illustrate the scope of this type of valve (which is, in a word, to regulate the flow), the differences with other types of valve, the alternative designs, and specifications (BS 1873  for the cast steel and API 602/BS 5352 for the forged steel type).

GLOBE VALVE USES

Globe valves are used to regulate the flow of a fluid and to shut-off the fluid (even if for shut-off operations ball valves and gate valves shall always be preferred). Globe valves are bi-directional valves, differently from check valves, meaning that the fluid can flow either way within the valve.

The image illustrates how the valve works and its main components: basically, the flow is managed via a disc that can be lifted (manually or via actuators) from the seat, thus regulating the volume of the allowed flow.

Fluid flow through a globe valve, pressure drop

The key specifications for globe valves used for piping applications in the petrochemical industry are:

  • BS 1873: cast steel valves
  • API 603: stainless steel valves
  • API 602/BS 5352: forged steel valves
  • API 598 and BS EN 12266-1: valves testing
  • ASME B16.10: face to face dimensions for valves
  • ASME B16.5 and ASME B16.47: flanged connections
  • ASME B16.25: butt weld connections design
  • ASME B16.34: pressure and temperature ratings by material grade

GLOBE VALVE ADVANTAGES AND DISADVANTAGESThe advantages are:

  • Good throttling and shut-off capabilities
  • Easy to maintain and resurface the seats
  • Can be used as a stop-check valve in case the disc is not attached to the stem

The main disadvantages are:

  • the valve creates a pressure drop in the piping system (different from gate valves): this is due to the fact that the flow of the fluid is not linear inside the valve, which has an “S-shaped” passageway (see the image below)
  • shut-off requires more torque than gate valves

Globe valve disadvantage: pressure drop

GLOBE VALVE TYPES

The valve is available in three main types, considering the shape of the body:

  • straight or “T” type
  • angle or “90 degrees”
  • Y pattern or “wye globe valve”

 

globe valve designs

 

The globe valve symbol in P&ID diagrams is the following:  Globe valve symbol

 

GLOBE VALVE VS BALL VALVE

The key difference between a globe and a ball valve is that a ball valve is designed, mainly, for shut-off operations, whereas a globe valve is designed, mainly, to throttle fluids. These two valves are industry-standards respectively for shut-off (ball valve) and for regulation (globe valve) applications.

A globe valve does not fit shut-off operations, due to the pressure drop it creates in the piping system (a problem that does not exist for full bore ball valves).

Ball valves have a long service life even in case of continuous on-off operations; globe valves would deteriorate easily under this type of service.

GLOBE VALVE VS GATE VALVE

The main differences between these two valves are:

  • fluid shut off is the main goal of gate valves, whereas flow throttling is the main goal of globe valves
  • gate valves have poor, to none, fluid regulation capacity
  • gate valves do not generate a pressure drop in the pipeline, globe valves do
  • globe valves open faster than gate valves

Concluding on this topic: use a ball valve (or a gate valve) for shut-off operations; use a globe valve for regulation. Do not consider these valves as interchangeable.

Globe valve

GLOBE VALVE DIAGRAM

A general assembly drawing for globe valves is shown in the image:

 

Globe valve drawing

 

Nonetheless, a large number of variations exist, depending on the following factors:

  • body material: cast (BS 1873) and forged (API 602/BS 5352)
  • bonnet design: standard or pressure seal type (for high-pressure applications)
  • bonnet to body connection: bolted or welded
  • valve end connections type: flanged (as shown in the image), buttweld, socket weld/threaded (forged bodies)
  • disc type
  • stem type (rising/non-rising)
  • seal type: conical or flat
  • specification: BS, API, EN
  • type of actuation: manual, with a gearbox, with an actuator

 

GLOBE VALVES DIMENSIONS

The tables show the dimensions and weights of BS 1873 valves, bolted bonnet type.
Globe valves dimensions

CLASS 150

Dimensions in inches (millimeters)

SizesL / L1H (Open)W
2″8 (203)13-3/8 (340)8-7/8 (225)
2-1/2″8-1/2 (216)14-1/2 (368)8-7/8 (225)
3″9-1/2 (241)16-1/2 (419)11-7/8 (302)
4″11-1/2 (292)17-3/8 (441)12-3/4 (325)
5″14 (356)24 (610)12-3/4 (325)
6″16 (406)24 (610)17-3/4 (451)
8″19-1/2 (495)26-3/4 (679)21-5/8 (549)
10″24-1/2 (622)30 (762)30 (762)
12″27-1/2 (699)33-7/8 (860)30 (762)
14″31 (787)56 (1422)31-1/2 (800)
16″36 (914)64 (1626)35-1/2 (902)
GEAR OPERATOR RECOMMENDED FOR SIZE 10″ AND ABOVE

CLASS 300

Dimensions in inches (millimeters)

SizesL / L1H (Open)W
2″10-1/2 (267)13-3/8 (340)9 (229)
2-1/2″11-1/2 (292)15-3/8 (390)9 (229)
3″12-1/2 (318)16-1/2 (419)13 (330)
4″14 (356)19-3/8 (492)14 (356)
5″15-3/4 (400)21-1/2 (546)15-3/4 (400)
6″17-1/2 (445)24-3/8 (619)17-3/4 (451)
8″22 (559)31-1/4 (794)22 (559)
10″24-1/2 (622)45 (1143)34 (864)
12″28 (711)49 (1245)34 (864)
GEAR OPERATOR RECOMMENDED FOR SIZE 8″ AND ABOVE

CLASS 600

Dimensions in inches (millimeters)

SizesL / L1H (Open)W
2″11-1/2 (292)15-1/2 (394)9-1/2 (241)
2-1/2″13 (330)17 (432)11 (279)
3″14 (356)19 (483)13 (330)
4″17 (432)21 (533)14 (356)
5″20 (508)25 (635)15-3/4 (400)
6″22 (559)26-7/8 (683)18 (457)
8″26 (660)35 (889)20 (508)
10″31 (787)49 (1245)24 (610)
12″33 (838)58 (1473)30 (762)
GEAR OPERATOR RECOMMENDED FOR SIZE 8″ AND ABOVE

CLASS 900

Dimensions in inches (millimeters)

SizesL / L1H (Open)W
2″14-1/2 (368)20-1/2 (521)12 (305)
3″15 (381)22-3/4 (578)14 (356)
4″18 (457)26-1/2 (673)21-1/2 (546)
6″24 (610)36 (914)20 (508)
8″29 (737)37 (940)24 (610)
GEAR OPERATOR RECOMMENDED FOR SIZE 6″ AND ABOVE

GLOBE VALVE DIMENSION CLASS 1500

Dimensions in inches (millimeters)

SizesL / L1H (Open)W
2″14-1/2 (368)24 (610)14 (356)
3″18-1/2 (470)26 (660)16 (406)
4″21-1/2 (546)28 (711)18 (457)
6″27-3/4 (705)37-1/2 (952)24 (610)
8″32-3/4 (832)45 (1143)24 (610)
GEAR OPERATOR RECOMMENDED FOR SIZE 6″ AND ABOVE

GLOBE VALVE DIMENSION CLASS 2500

Dimensions in inches (millimeters)

SizesL / L1H (Open)W
2″17-3/4 (451)25-1/2 (648)16 (406)
3″22-3/4 (578)32-1/2 (825)20 (508)
4″26-1/2 (673)47 (1194)24 (610)
6″36 (914)70-1/2 (1790)28 (711)
8″40-1/4 (1022)//
GEAR OPERATOR RECOMMENDED FOR SIZE 6″ AND ABOVE

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