Centralizer

No.	Type	Code	English Description	Casing Size Range (OD)	Key Construction / Feature	Standard Materials
1	Bow-Spring Centralizer (Single-Bow)	BS-S	Forged / stamped bow-spring casing centralizer, single-layer bow springs. Non-welded hinged or slip-on one-piece design. Low starting force, high restoring force for vertical & moderate deviated wells, meets API-10D restoring force requirements.	4-1/2" ~ 20" (114.3 mm – 508 mm)	Hinged type / Slip-on integral type; single bow stack	Spring steel 65Mn, SAE-1070, alloy spring steel; end collars: carbon steel A106/A283
2	Bow-Spring Centralizer (Double-Bow)	BS-D	Double-layer bow-spring centralizer. Higher restoring force than single-bow, for high-angle deviated & horizontal wells, improves casing stand-off ratio.	4-1/2" ~ 20" (114.3 mm – 508 mm)	Hinged non-welded preferred; double bow stacks	Spring steel 65Mn, SAE-1070; end collar carbon steel
3	One-Piece Integral Bow-Spring Centralizer	BS-OP	Slip-on one-piece stamped centralizer, no hinge pins, no welding. Heat-treated monolithic structure, anti-fatigue, easy to slip over casing coupling-free pipe.	2-7/8" ~ 20" (73.0 mm – 508 mm)	Integral stamped body, slip-on installation	Spring steel 65Mn, alloy spring steel
4	Semi-Rigid Centralizer	SR	Semi-rigid compressible vane-type centralizer. Combines partial spring deflection & high structural strength; allows slight compression when passing tight hole sections, suitable for rotating casing operations during cementing.	4-1/2" ~ 13-3/8" (114.3 mm – 339.7 mm)	Cast / stamped vanes, limited elastic deformation	Cast carbon steel, low-alloy cast steel
5	Solid Rigid Centralizer (Straight-Vane)	RG-ST	Rigid non-spring integral centralizer with straight vanes. Fixed outer diameter, no spring deflection; positioned by stop collars / set screws, high impact resistance for heavy-load deviated wells.	4-1/2" ~ 20" (114.3 mm – 508 mm)	Solid cast / forged body, straight vanes	Cast carbon steel, cast aluminum alloy, A694 series
6	Solid Rigid Centralizer (Spiral-Vane)	RG-SP	Rigid spiral-vane centralizer. Helical vanes improve mud circulation & cement displacement; widely used for deviated / horizontal wells, reduce hole wall scraping.	4-1/2" ~ 20" (114.3 mm – 508 mm)	Spiral helical vanes, solid monolithic body	Cast carbon steel, cast aluminum alloy, A694 F42-F70
7	Roller Centralizer (Low-Torque)	RL	Rigid-body centralizer fitted with heat-treated rollers. Convert sliding friction to rolling friction, drastically reduce drag & torque; permit casing rotation & reciprocation in horizontal / high-angle wells.	4-1/2" ~ 13-3/8" (114.3 mm – 339.7 mm)	Spiral / straight vanes with alloy rollers; roller pins & bearings	Body: cast/alloy steel; Rollers: heat-treated alloy steel; NACE MR0175 optional for sour-service wells
8	Hinged Non-Welded Bow-Spring Centralizer	BS-HN	Hinged segmented bow-spring centralizer, zero welding on bow-to-collar joints, assembled by hinge pins & locking tabs. Convenient field mounting around casing couplings without sliding over casing end.	4-1/2" ~ 20" (114.3 mm – 508 mm)	Hinge pin construction, can clamp onto casing at any position	Bow: spring steel 65Mn / SAE-1070; Collar: carbon steel

Centralizers are commonly manufactured from carbon steel or other suitable steel materials selected according to the operating environment and mechanical requirements.
Typical material considerations include:

Material Group	Grade Description	Application
Spring Steel	65Mn, SAE-1070	Bow-spring centralizer bows, heat-treated for high restoring force
Carbon Cast / Forged Steel	Cast carbon steel, A106, A283, A694 F42-F70	Rigid body, semi-rigid body, end collars
Cast Aluminum Alloy	Al-Si cast alloy	Light-weight rigid spiral-vane centralizers, low-impact wells
Alloy Steel for Rollers	Heat-treated low-alloy steel	Roller components for roller centralizer
Sour-Service Grade	NACE MR0175 compliant steel	H2S corrosive downhole environment

Note: Custom special sizes available upon request for liner, tubing and non-standard casing.

1. Primary Cementing
Centralizers are widely used during primary cementing. They help maintain a more uniform annular space between the casing and wellbore wall, allowing cement slurry to flow more evenly around the casing.

2. Surface Casing
Centralizers can be installed on surface casing to help maintain casing position while running the casing string and placing cement around it.

3. Intermediate Casing
For intermediate casing, centralizers help maintain casing standoff through different wellbore sections and support more consistent cement placement.

4. Production Casing
Production casing often requires effective centralization to support cementing and zonal isolation. Centralizers are positioned according to the casing and cementing program.

5. Deviated Wells
In deviated wells, gravity can cause the casing to move toward the low side of the wellbore. Centralizers help reduce this eccentricity and maintain the required casing standoff.

6. Horizontal Wells
Horizontal wells typically require careful casing centralization because the casing can rest along the lower side of the wellbore. Properly selected centralizers can help maintain an adequate flow path for cement.

7. Deep Wells
Deep wells may involve long casing strings and complex wellbore conditions. Centralizers help maintain casing position during casing running and cementing operations.

8. Liner Installation

Centralizers can also be used with liners to help position the liner within the open hole or previous casing and support more uniform cement placement.

Casing × Hole Size (inch)	Bow Quantity	Outside Diameter (mm)	Inner Diameter (mm)	Overall Length (mm)
4-1/2" × 6"	4	160	116	450 / 575
4-1/2" × 6-1/4"	4	167	116	450 / 575
4-1/2" × 7-7/8"	4	210	116	450 / 575
4-1/2" × 8-1/2"	4	230	116	450 / 575
5" × 6"	4	160	128	450 / 540
5" × 7-7/8"	4	210	128	450 / 575
6" × 6-3/4"	4	180	128	450 / 575
5-1/2" × 7-7/8"	5	210	140	450 / 575
5-1/2" × 8-1/2"	5	216 / 245	140	450 / 575
5-1/2" × 8-3/4"	5	222 / 250	140	450 / 575
5-1/2" × 9-1/2"	5	242 / 264	140	450 / 575
5-1/2" × 9-7/8"	5	251 / 264	140	450 / 575
7" × 8-1/2"	6	216 / 230	179	450 / 575
7" × 8-3/4"	6	222 / 233	179	450 / 575
7" × 9-1/2"	6	242 / 264	179	450 / 575
7" × 9-7/8"	6	251 / 264	179	550 / 650
9-5/8" × 12-1/4"	8	346	245	550 / 650
9-5/8" × 12-13/16"	8	378	245	550 / 650
9-5/8" × 13-3/8"	8	346 / 352	245	550 / 650
10-3/4" × 14-3/4"	9	405	275	550 / 650
10-3/4" × 15-1/2"	9	374	275	550 / 650
13-3/8" × 17-1/2"	10	440 / 466	342	550 / 650
13-5/8" × 17-1/2"	12	440 / 466	342	550 / 650
20" × 26"	12	696	510	550 / 610 / 650