Description

API 6A Wellhead Secondary Seal for Casing Spools, Tubing Heads and Wellhead Repair

Product Short Description

SGPE supplies API 6A Wellhead Secondary Seal assemblies for compatible casing heads, casing spools, tubing heads and conventional surface wellhead systems. Installed around the production casing stub, the secondary packoff closes the clearance between the casing OD and internal spool pocket, helping isolate casing annulus pressure from the lower flange connection.

Available configurations include PE, EBS, 4-O, O-O, single and double FS, single and double P, R-Bushing and CANH secondary seals. Depending on the seal family and wellhead interface, working-pressure options range from 5,000 psi to 20,000 psi.

Each casing spool secondary seal and tubing head packoff uses a specific pocket profile, retaining method and energizing arrangement. Therefore, casing size and pressure class alone cannot confirm compatibility. SGPE reviews the actual casing OD, spool nominal bottom, seal-pocket dimensions, pressure direction and service conditions before finalizing the configuration.

Replacement wellhead seals can be matched from an original part number, equipment nameplate, sectional drawing, dimensional report or used sample. Supply options include individual elastomer elements, complete secondary packoffs, bushing assemblies and custom wellhead seal kits for new equipment, workover, shutdown maintenance, field repair, brownfield refurbishment and oilfield MRO projects.

Product Overview

A wellhead secondary seal forms an additional annular barrier around the production casing stub. It normally sits in the lower bowl, bottom preparation or dedicated seal pocket of a casing spool or tubing head.

During installation, the spool moves over the production casing. The secondary packoff contacts the casing OD and internal spool pocket, while compression between these surfaces closes the radial clearance around the casing.

This arrangement helps maintain casing annulus isolation during drilling, completion, production, injection, well testing and workover. It also helps keep well pressure away from the lower flange interface.

Buyers may describe the product as a casing spool secondary seal, tubing head packoff, casing annulus seal or production casing seal. Other common purchasing terms include secondary packoff seal, tubing head secondary seal, wellhead bottom pack-off, casing spool bottom seal and replacement wellhead seal. Although these terms describe a similar function, the product must match the actual casing-to-spool interface.

Main Functions

Main Function	Practical Purpose
Casing annulus isolation	Separates annulus pressure from the lower spool connection
Casing-to-spool sealing	Closes the radial clearance around the production casing stub
Lower flange protection	Helps prevent direct pressure exposure at the flange interface
Pressure-test support	Supports pressure verification after spool installation
Production sealing	Maintains the annular barrier during oil or gas production
Repair and refurbishment	Supports replacement during workover or wellhead overhaul
MRO support	Provides planned and emergency replacement spares

PE, EBS, 4-O, O-O, FS, P, R-Bushing and CANH seals perform the same general task. However, each family uses a different profile, retainer and compression arrangement. One type should not replace another unless the casing interface and spool pocket match.

General Technical Specifications

Parameter	Available Configuration
Product Name	API 6A Wellhead Secondary Seal
Alternative Names	Secondary packoff seal, casing spool seal, tubing head packoff, production casing seal, casing annulus seal and wellhead bottom pack-off
Equipment Application	Casing heads, casing spools, tubing heads and tubing head spools
Main Function	Seals around the production casing stub inside the lower spool bowl
Available Types	PE, EBS, 4-O, O-O, FS, P, R-Bushing and CANH
Listed Casing Range	Common configurations from 4-1/2 in. to 11-3/4 in.
Listed Spool Bottom Range	Configurations from 7 in. to 13-5/8 in.
Working Pressure Range	Available configurations from 5,000 psi to 20,000 psi
PE Rating	Up to 5,000 psi
4-O Rating	Up to 5,000 psi
Single FS Rating	5,000 psi
Double FS Rating	10,000 psi
Single P Rating	5,000 psi
Double P Rating	Up to 15,000 psi
EBS Rating	Up to 10,000 psi for listed configurations
R-Bushing Rating	10,000 psi for listed configurations
CANH Rating	Up to 20,000 psi for listed configurations
Well Service	Oil wells, gas wells, injection wells and project-specific sour service
Replacement Basis	Drawing, part number, nameplate, sample or confirmed dimensions
Supply Scope	Seal element, complete packoff, bushing assembly or full wellhead seal kit
Customization Basis	Confirmed spool pocket, casing OD, pressure and service conditions
Documentation	According to the purchase order and approved quality plan
Quotation Basis	Size, pressure, material, quantity, supply scope and document requirements

The listed working pressure applies only to the approved seal configuration and compatible wellhead interface. Do not apply the rating to another seal family or pocket design without technical confirmation.

API 6A Wellhead Secondary Seal Type Comparison

PE, 4-O, single FS and single P designs cover compatible 5,000 psi wellhead applications.

EBS, double FS and R-Bushing assemblies cover listed 10,000 psi systems. Double P configurations support compatible applications up to 15,000 psi, while CANH assemblies extend to high-pressure surface wellhead systems up to 20,000 psi.

Seal Type	Listed Pressure Rating	General Arrangement	Main Selection Basis
PE Secondary Seal	Up to 5,000 psi	Bottom-bowl seal retained by snap wire	Casing OD, spool bottom and PE pocket
EBS Secondary Seal	Up to 10,000 psi for listed configurations	Higher-pressure secondary seal arrangement	Casing OD, spool bottom and EBS pocket
4-O Secondary Seal	Up to 5,000 psi	Bushing-style seal for compatible BG lower connection	Casing OD, bushing size and lower preparation
O-O Secondary Seal	Project-specific	Two elastomer sealing elements	Cross-section, groove and spool bore
Single FS Seal	5,000 psi	One FS sealing section	Casing OD and single FS pocket
Double FS Seal	10,000 psi	Two FS sealing sections	Casing OD and double FS pocket
Single P Seal	5,000 psi	One P-profile sealing section	Casing OD, pressure direction and P pocket
Double P Seal	Up to 15,000 psi	Two P-profile sealing sections	Casing OD and double P pocket
R-Bushing Seal	10,000 psi	Bushing body with internal casing seals	Casing size and spool nominal bottom
CANH Seal	Up to 20,000 psi	High-pressure secondary sealing assembly	Complete casing, spool and service review

A matching pressure class does not make two secondary packoff seals interchangeable. The casing OD, seal-pocket geometry, retainer position and pressure direction must also match.

Pressure Rating Selection Guide

Required Working Pressure	Available Options	Important Limitation
5,000 psi	PE, 4-O, Single FS and Single P	Requires the corresponding seal pocket
10,000 psi	EBS, Double FS and R-Bushing	These designs use different interfaces
Up to 15,000 psi	Double P	Requires a compatible double P pocket
Up to 20,000 psi	CANH	Requires complete casing, spool and service review

Before ordering a 5,000 psi, 10,000 psi, 15,000 psi or 20,000 psi replacement wellhead seal, provide the equipment drawing, nameplate or confirmed pocket dimensions.

PE and EBS Secondary Seal Size Chart

PE and EBS secondary packoff seals cover several production casing and spool-bottom combinations.

The following matrix reflects the listed configurations in the current product range. A dash indicates that the standard table does not include the combination.

PE and EBS Selection Matrix

Spool Nominal Bottom	Casing Size	PE Secondary Seal	EBS Secondary Seal
7 in.	4-1/2 in.	5,000 psi	10,000 psi
7 in.	5 in.	5,000 psi	10,000 psi
9 in.	4-1/2 in.	5,000 psi	10,000 psi
9 in.	5 in.	5,000 psi	10,000 psi
9 in.	5-1/2 in.	5,000 psi	10,000 psi
9 in.	6-5/8 in.	5,000 psi	10,000 psi
9 in.	7 in.	5,000 psi	10,000 psi
9 in.	7-5/8 in.	5,000 psi	—
10-3/4 in.	7 in.	5,000 psi	10,000 psi
10-3/4 in.	7-5/8 in.	5,000 psi	10,000 psi
10-3/4 in.	8-5/8 in.	5,000 psi	10,000 psi
10-3/4 in.	9-5/8 in.	5,000 psi	—
11-3/4 in.	9-5/8 in.	—	10,000 psi

The listed 7-inch spool bottom covers 4-1/2-inch and 5-inch production casing combinations.

The 9-inch bottom provides the broadest PE and EBS range, extending from 4-1/2-inch to 7-5/8-inch casing.

For a 10-3/4-inch spool bottom, the listed casing range extends from 7 inches to 9-5/8 inches. The 11-3/4-inch bottom also includes a 9-5/8-inch EBS configuration.

These combinations support new casing spool packages, PE secondary seal replacement, EBS packoff replacement, planned shutdown spares and wellhead MRO inventories.

For a casing size or spool bottom outside the table, send the actual production casing OD and complete wellhead drawing for review.

R-Bushing Secondary Seal Size Chart

An R-Bushing secondary seal combines a metallic bushing body with internal sealing elements around the production casing.

All listed configurations below carry a working pressure of 10,000 psi.

Spool Nominal Bottom	Casing Size	Rated Working Pressure
7 in.	4-1/2 in.	10,000 psi
7 in.	5 in.	10,000 psi
9-5/8 in.	4-1/2 in.	10,000 psi
9-5/8 in.	5 in.	10,000 psi
9-5/8 in.	5-1/2 in.	10,000 psi
9-5/8 in.	6-5/8 in.	10,000 psi
9-5/8 in.	7 in.	10,000 psi
9-5/8 in.	7-5/8 in.	10,000 psi
10-3/4 in.	7 in.	10,000 psi
10-3/4 in.	7-5/8 in.	10,000 psi
10-3/4 in.	8-5/8 in.	10,000 psi
10-3/4 in.	9-5/8 in.	10,000 psi
13-3/8 in.	8-5/8 in.	10,000 psi
13-3/8 in.	9-5/8 in.	10,000 psi
13-3/8 in.	10-3/4 in.	10,000 psi
13-3/8 in.	11-3/4 in.	10,000 psi

The 7-inch configurations cover 4-1/2-inch and 5-inch casing. A 9-5/8-inch spool bottom supports casing sizes from 4-1/2 inches to 7-5/8 inches.

Larger casing programs can use the listed 10-3/4-inch or 13-3/8-inch spool-bottom combinations.

For casing spool overhaul and tubing head repair projects, SGPE can supply a complete R-Bushing assembly with the metallic bushing body and internal sealing components matched as one package.

CANH High-Pressure Secondary Seal up to 20,000 PSI

CANH secondary seals support compatible high-pressure surface wellhead applications up to 20,000 psi.

Because the assembly operates within a high-pressure casing-to-spool interface, final confirmation requires more than the nominal casing size. SGPE also reviews the spool-pocket dimensions, pressure direction, operating temperature, well fluid and expected pressure cycles.

Spool Nominal Bottom	Casing Size	Rated Working Pressure
9 in.	4-1/2 in.	20,000 psi
9 in.	5 in.	20,000 psi
9 in.	5-1/2 in.	20,000 psi
11 in.	4-1/2 in.	20,000 psi
11 in.	5 in.	20,000 psi
11 in.	5-1/2 in.	20,000 psi
11 in.	6-5/8 in.	20,000 psi
11 in.	7 in.	20,000 psi
11 in.	7-5/8 in.	20,000 psi
11 in.	8-5/8 in.	20,000 psi
13-5/8 in.	7 in.	20,000 psi
13-5/8 in.	7-5/8 in.	20,000 psi
13-5/8 in.	8-5/8 in.	20,000 psi
13-5/8 in.	9-5/8 in.	20,000 psi
13-5/8 in.	10-3/4 in.	20,000 psi

The listed 9-inch configurations cover casing sizes from 4-1/2 inches to 5-1/2 inches.

The 11-inch spool bottom offers the broadest listed CANH range, covering casing from 4-1/2 inches to 8-5/8 inches.

For larger high-pressure wellhead systems, the 13-5/8-inch bottom supports casing sizes from 7 inches to 10-3/4 inches.

Customers requesting a 20,000 psi CANH secondary seal, CANH replacement packoff or high-pressure tubing head secondary seal should provide the complete wellhead drawing and operating-condition data.

Need Help Matching an Existing Seal?

Send SGPE the production casing OD, spool nominal bottom, working pressure, equipment nameplate and available sectional drawing.

Our technical team will review the physical interface and identify any additional information needed for a technical and commercial quotation.

Available Secondary Seal Types

PE Secondary Seal

The PE Secondary Seal fits into the lower bowl of a compatible casing spool or tubing spool. A snap wire holds the assembly inside the spool preparation.

During installation, the spool moves over the prepared production casing stub. Final flange make-up then compresses the secondary seal around the casing OD.

Standard PE configurations support working pressures up to 5,000 psi. This compact casing spool bottom seal suits new equipment, routine replacement and compatible spool refurbishment.

SGPE can supply PE secondary seals as individual elastomer elements or as part of a complete casing spool repair kit.

EBS Secondary Seal

The EBS Secondary Seal supports listed 10,000 psi casing spool and tubing head configurations.

The production casing OD, spool nominal bottom, internal pocket and pressure direction determine the correct assembly. Nominal working pressure alone does not provide enough information for selection.

For old or unidentified equipment, customers may provide the existing part number, sectional drawing or used sample. After confirming the critical dimensions, SGPE can prepare an approval drawing for the replacement EBS packoff.

4-O Secondary Seal

The 4-O Secondary Seal fits casing or tubing head spools with a compatible BG lower internal connection.

Its bushing-style arrangement seals around the production casing inside the spool. Standard configurations support working pressures up to 5,000 psi.

Both the casing OD and BG lower preparation must match the bushing. When the project requires a complete casing spool secondary seal replacement, SGPE can supply the bushing and sealing components as one package.

O-O Secondary Seal

The O-O Secondary Seal, also called an OO secondary seal, uses two elastomer sealing elements inside a compatible casing or tubing head spool.

Although this profile may cover different internal and external dimensions, the groove geometry and seal cross-section must match the existing equipment.

The O-O design can support legacy wellhead repair, obsolete wellhead seal replacement and sample-based manufacturing when the customer provides sufficient dimensional information.

Single and Double FS Secondary Seals

A Single FS Secondary Seal uses one sealing section and carries a listed rating of 5,000 psi. A Double FS Secondary Seal uses two sealing sections and carries a listed rating of 10,000 psi.

FS Configuration	Sealing Sections	Listed Rating	Main Requirement
Single FS	One	5,000 psi	Compatible single FS pocket
Double FS	Two	10,000 psi	Compatible double FS pocket

The double design requires the correct pocket depth and retaining arrangement. It cannot replace a single FS seal in a spool designed for one sealing section.

Single and Double P Secondary Seals

A Single P Secondary Seal uses one P-profile sealing section for compatible 5,000 psi service. A Double P Secondary Seal uses two P-profile sections and supports compatible working pressures up to 15,000 psi.

P Seal Configuration	P-Profiles	Listed Rating	Main Requirement
Single P	One	5,000 psi	Compatible single P pocket
Double P	Two	Up to 15,000 psi	Compatible double P pocket

The casing OD, pocket geometry and pressure direction determine the final P-seal configuration.

R-Bushing Secondary Seal

The R-Bushing design combines a metallic bushing body with internal production casing seals.

The bushing allows a compatible spool bottom to fit a specified casing OD. During wellhead refurbishment or casing-program changes, operators may replace the bushing and secondary sealing elements together.

The listed R-Bushing configurations carry a rated working pressure of 10,000 psi.

CANH Secondary Seal

The CANH Secondary Seal supports compatible high-pressure surface wellhead systems up to 20,000 psi.

The listed range includes 9-inch, 11-inch and 13-5/8-inch spool nominal bottoms.

Each CANH replacement project requires confirmation of the casing dimensions, spool interface, pressure direction, temperature and well-fluid conditions.

How the Secondary Packoff Works

A secondary packoff closes the annular clearance between the production casing stub and the internal spool pocket.

Before installation, the wellhead team cleans and inspects the casing sealing area. The casing spool or tubing head then moves over the casing.

As the packoff reaches its final position, it contacts the casing OD and internal pocket. Some designs gain additional compression during final spool make-up.

In pressure-assisted profiles, well pressure may increase sealing contact after installation. Once the packoff seats correctly, it separates the casing annulus from the lower flange area.

Operating Stage	What Happens
Casing preparation	The wellhead team cleans and inspects the sealing area
Spool installation	The casing spool or tubing head moves over the casing
Seal engagement	The secondary packoff contacts the casing OD and spool pocket
Mechanical energizing	Final make-up adds compression to the assembly
Pressure support	Pressure may increase contact in compatible profiles
Annulus isolation	The completed interface separates the annulus from the lower flange

Installers should follow the approved installation and pressure-test procedure for the specific casing spool, tubing head or surface wellhead equipment.

Elastomer Materials for Oil and Gas Service

Elastomer selection affects sealing performance, decompression resistance and service life.

SGPE can review NBR, HNBR, FKM and project-specific material requirements. Final compound selection should consider the complete operating environment rather than a single temperature or fluid value.

Elastomer Option	General Service Consideration	Information Required
NBR	May suit conventional oil service, drilling fluids and moderate conditions	Temperature, oil composition and chemical exposure
HNBR	May suit gas service, higher pressure and repeated cycles	Temperature, gas composition, CO₂ and decompression conditions
FKM	May suit higher temperatures and stronger hydrocarbon exposure	Temperature, fluid chemistry and treatment chemicals
Project-Specific Compound	Supports special fluids or operating requirements	Complete pressure, temperature and chemical data

NBR may suit conventional oil service and drilling-fluid exposure, while HNBR may offer improved heat and mechanical resistance in gas service or higher-pressure operations. FKM may suit higher temperatures and stronger hydrocarbon exposure.

The material review should also consider pressure cycles, oil and gas composition, produced-water chemistry, H₂S and CO₂ exposure, methanol, glycol, corrosion inhibitors, aromatic hydrocarbons and rapid gas decompression conditions.

For gas-well, gas-injection and high-pressure production service, include any available rapid gas decompression information in the RFQ.

Oil and Gas Wellhead Applications

Drilling, Casing and Completion

After a casing spool or upper wellhead section enters service, the secondary seal helps isolate the casing annulus.

Surface, intermediate and production casing programs may use different casing ODs, spool bottoms and packoff designs. The actual casing program should therefore guide product selection.

Once the production casing has been run and cemented, the tubing head or upper spool moves over the prepared casing stub. During completion, the tubing head packoff helps isolate the lower annulus before installation of the tubing hanger and Christmas tree.

Onshore and Offshore Production Wellheads

Secondary packoff seals support casing annulus isolation in both land-based and offshore surface wellheads.

Operators may install them with new equipment or replace them during scheduled maintenance, workover and brownfield refurbishment.

Offshore projects often require tighter dimensional control, traceability and document review. SGPE can prepare casing spool secondary seals, tubing head packoffs and coordinated wellhead spare-parts packages for compatible offshore surface systems.

High-Pressure and Gas-Well Service

EBS, R-Bushing, double P and CANH configurations cover different higher-pressure wellhead requirements.

The complete spool design must support the selected pressure rating. Gas wells may also expose the elastomer to repeated pressure cycles and decompression, so compound selection and casing-surface condition require careful review.

Water, Gas and CO₂ Injection

Water injection may expose the seal to treated water, chlorides, oxygen scavengers and corrosion inhibitors.

Gas injection creates repeated pressure cycles, while CO₂ may affect both elastomer and metallic support components.

Buyers should provide fluid or gas composition, water content, pressure and operating temperature before SGPE confirms the seal material.

Sour Service, Well Testing and Workover

H₂S-containing service requires project-specific data, including available H₂S concentration or partial pressure, CO₂ content, working pressure, temperature and produced-fluid composition.

During well testing, the secondary packoff may form part of the pressure-containing interface. The assembly must match the test pressure, test fluid and expected pressure cycle.

During workover or recompletion, operators may replace the casing spool bottom seal after removing or refurbishing the casing spool or tubing head. A change in pressure, well fluid or upper wellhead arrangement may also require a new material review.

Wellhead Repair and Oilfield MRO

Repair workshops and wellhead service companies replace worn secondary seals during overhaul.

Brownfield wells may require a different elastomer compound because operating conditions have changed since the original equipment entered service.

Operators, drilling contractors, rental fleets and distributors may stock PE, EBS, FS and P secondary seals for emergency wellhead repair, planned shutdowns and routine oilfield MRO programs.

API 6A Wellhead Secondary Seal Selection Guide

Selection begins with the existing seal family and installation position.

After identifying the design, confirm the nominal casing size and actual production casing OD. Actual measurements become especially important when the casing shows wear, corrosion, scale or field modification.

Next, verify the spool nominal bottom and seal pocket. The same casing OD may appear in more than one spool size, while different seal families may use different retainers within the same pressure class.

Finally, review the working pressure, temperature, well fluid and pressure direction.

Selection Step	Information to Confirm	Why It Matters
Identify the seal family	PE, EBS, 4-O, O-O, FS, P, R-Bushing or CANH	Each family uses a different interface
Confirm casing size	Nominal size and actual OD	The casing OD controls sealing contact
Confirm spool bottom	Applicable nominal bottom size	One casing size may fit several spools
Confirm pressure	5,000, 10,000, 15,000 or 20,000 psi	Pressure narrows the available configurations
Review the pocket	Bowl, groove, BG connection or bushing shoulder	Pocket geometry determines compatibility
Confirm the retainer	Snap wire, bushing, ring or other arrangement	The retainer controls the installed position
Review service data	Temperature, pressure and well fluid	Service conditions affect material selection
Inspect the interfaces	Casing surface and spool pocket	Damage or debris may create a leak path
Confirm the supply scope	Element, complete packoff, bushing or full kit	Prevents an incomplete order
Confirm documentation	Drawings, reports and certificates	Defines the required delivery package

Dimensions Required for Replacement Seal Matching

For a replacement casing spool secondary seal, tubing head packoff or wellhead bottom pack-off, SGPE may request the following measurements.

Measurement	Description
Production casing OD	Actual outside diameter at the sealing area
Seal ID	Inside diameter of the existing seal
Seal OD	Outside diameter of the seal or assembly
Overall height	Total axial height
Seal-pocket diameter	Internal diameter of the spool pocket
Seal-pocket depth	Axial depth of the pocket
Retaining groove diameter	Diameter of the retaining feature
Snap-wire groove dimensions	Width, depth and axial position
Bushing ID and OD	Internal and external bushing diameters
Shoulder position	Location of the seal or bushing shoulder
Flange-face distance	Distance from the pocket to the bottom flange face
Groove width and depth	Cross-sectional groove dimensions
Seal cross-section	Profile and section dimensions
Pressure direction	Direction from which pressure reaches the seal
Element arrangement	Single, double or multi-element design

A used elastomer may swell, shrink or deform after service. Whenever possible, compare the sample with the actual casing OD and spool-pocket dimensions.

Replacement Casing Spool Seal and Tubing Head Packoff Matching

Two replacement wellhead seals may look similar while using different profiles, groove depths, retainers or pressure directions.

The replacement review normally starts with the equipment nameplate, which may identify the original manufacturer, model, pressure class and serial number.

An original part number also helps, although one equipment family may include several design revisions.

A sectional drawing gives the clearest view of the pocket, casing interface and retaining arrangement. A used sample can help identify the seal profile and assembly sequence, but it should not serve as the only dimensional reference.

Review Stage	Technical Review Focus
Nameplate review	Manufacturer, model, pressure class and serial number
Part-number review	Original reference and possible design revision
Drawing review	Pocket, casing interface and retaining arrangement
Sample inspection	Profile, assembly sequence and visible condition
Dimensional confirmation	Casing OD, pocket, groove and shoulder dimensions
Service review	Pressure, temperature, H₂S, CO₂ and well fluid
Scope confirmation	Element, complete packoff, bushing or full kit
Approval drawing	Customer confirmation before custom production

SGPE does not claim universal interchangeability across different wellhead brands or equipment generations.

Final compatibility depends on the confirmed physical interface rather than the original product name, nominal casing size or pressure rating alone.

Custom Secondary Seal and Seal Kit Supply

A custom review may be necessary when the standard listed configurations do not match the existing wellhead.

Typical projects include nonstandard production casing ODs, legacy casing heads and casing spools, discontinued seal part numbers, modified spool pockets, obsolete tubing head packoffs, brownfield upgrades, complete bushing-and-seal replacement and custom wellhead seal kits for oilfield MRO programs.

SGPE can also review sample-based manufacturing when the original drawing is unavailable. However, actual equipment dimensions remain essential because a used elastomer may no longer retain its original shape.

Customers should provide a sectional drawing or complete dimensional report whenever possible.

After reviewing the available information, SGPE can prepare an approval drawing before manufacturing the custom secondary packoff, casing spool seal or replacement wellhead seal kit.

API 6A Wellhead Secondary Seal Price Factors

The price of an API 6A Wellhead Secondary Seal depends on the complete technical configuration.

Price Factor	Effect on the Quotation
Seal type	PE, EBS, FS, P, R-Bushing and CANH use different structures
Pressure rating	Higher-pressure assemblies may use more complex components
Casing size	Larger sizes require more material and larger tooling
Spool bottom	The spool interface controls seal and bushing dimensions
Supply scope	Element-only supply differs from a complete secondary packoff or kit
Elastomer	NBR, HNBR, FKM and special compounds have different costs
Metallic parts	Bushings, support rings and retainers affect total price
Quantity	Project quantities and spare packages affect unit pricing
Custom engineering	Nonstandard dimensions may require drawing or tooling review
Documentation	Inspection records and third-party inspection affect project cost
Packing and delivery	Export packing, destination and Incoterm affect the final offer

For an accurate price or quotation, provide the seal family, actual casing OD, spool nominal bottom, pressure class, material requirement, quantity and required supply scope.

Quality Control and Project Documentation

SGPE controls the secondary seal assembly from material preparation through final packing.

The inspection team compares available elastomer and metallic-component records with the approved production documents. The team then checks critical dimensions such as seal ID, seal OD, overall height, groove size and bushing dimensions.

Inspectors examine elastomer surfaces for cuts, cracks, contamination and visible molding defects. They also check metallic support components for machining quality and dimensional conformity.

Before packing, the team verifies the component sequence, seal direction, retainer position and assembly fit.

Quality Stage	Inspection or Document
Material verification	Review of available elastomer and metallic component records
Dimensional inspection	ID, OD, height, groove and bushing measurements
Elastomer inspection	Review for cuts, cracks, contamination and visible defects
Metallic-part inspection	Machining quality and dimensional conformity
Assembly inspection	Seal direction, retainer position and component fit
Product identification	Part number, type, casing size, pressure rating and batch reference
Drawing package	Product or approval drawing when required
Inspection report	Dimensional and visual inspection results
Certificate package	Certificate of Conformity and agreed material records
Packing documents	Packing list and product photographs
Additional inspection	Third-party inspection support when specified

The final document package depends on the purchase order and approved quality plan.

State all required reports, certificates and third-party inspection requirements in the RFQ.

Installation and Leakage Prevention

Only trained wellhead personnel should install or replace a secondary seal.

Before installation, remove cement, rust, scale, drilling debris and sharp edges from the production casing stub. Inspect the sealing area for scratches, corrosion and excessive ovality.

Clean the spool pocket, then verify the seal type, casing OD, spool nominal bottom and pressure rating.

Some designs have a defined top, bottom or pressure direction. Confirm the orientation before lowering the spool.

Use suitable tools and compatible lubricant to protect the elastomer.

For PE configurations, make sure the snap wire sits fully inside its groove. For R-Bushing and other bushing-based designs, confirm the final bushing and retainer positions.

Installation Step	Key Check
Inspect casing stub	Remove cement, rust, scale and sharp edges
Inspect sealing area	Check scratches, corrosion and ovality
Clean spool pocket	Remove debris and old sealing material
Verify the product	Confirm type, casing OD, spool bottom and rating
Check orientation	Follow the correct top, bottom and pressure direction
Protect the elastomer	Use suitable tools and compatible lubricant
Install the retainer	Fully seat the snap wire, bushing or retaining parts
Lower the spool evenly	Avoid tilting, impact and excessive force
Complete make-up	Follow the approved wellhead procedure
Conduct pressure testing	Increase pressure gradually and monitor stability

Common Causes of Secondary Seal Leakage

An incorrect seal family, wrong casing OD, unsuitable spool bottom or damaged casing surface may cause leakage.

Debris inside the pocket, incorrect orientation, incomplete retainer installation and mismatched bushing dimensions may also prevent proper seal energizing.

An unsuitable elastomer may swell, harden, soften or crack. Excessive pressure, excessive temperature, rapid gas decompression and reuse of a permanently deformed seal may further reduce performance.

Leakage Cause	Recommended Check
Incorrect seal family	Confirm the original profile and spool pocket
Wrong casing OD	Measure the actual casing outside diameter
Wrong spool bottom	Confirm the nominal bottom and drawing
Damaged casing surface	Inspect and prepare the sealing area
Contaminated pocket	Remove debris and old sealing material
Incorrect material	Review fluid, temperature and gas exposure
Incorrect orientation	Verify the pressure direction
Incomplete retainer	Check the snap wire or bushing position
Incorrect bushing size	Confirm bushing ID, OD and shoulder position
Excessive service conditions	Verify pressure and temperature requirements
Rapid gas decompression	Review the gas-service compound requirement
Reused seal	Install a new element unless an approved procedure permits reuse

API 6A Secondary Seal Versus Other Wellhead Packoffs

A primary wellhead seal and a secondary seal may both seal around casing, but they normally occupy different positions.

The primary sealing system often forms part of the casing hanger or primary packoff. In contrast, the secondary seal sits lower in the casing spool or tubing head and seals around the production casing stub.

Seal Category	Typical Position	Main Function
Primary wellhead seal	Part of the casing hanger or primary packoff	Provides the primary casing suspension barrier
Wellhead secondary seal	Lower bowl or bottom preparation of the spool	Seals around the production casing stub
Casing hanger packoff	Around or above the casing hanger	Seals the hanger-to-body annulus
Tubing hanger packoff	Around the tubing hanger	Seals the hanger-to-tubing head interface

Because “wellhead packoff” and “wellhead seal” are broad purchasing terms, buyers should identify the exact installation position when preparing an RFQ.

Why Choose SGPE for API 6A Wellhead Secondary Seals?

SGPE supplies PE, EBS, 4-O, O-O, FS, P, R-Bushing and CANH secondary seals for compatible surface wellhead equipment.

Available pressure classes cover conventional and high-pressure wellhead systems from 5,000 psi to 20,000 psi.

Rather than relying only on the seal name, nominal casing size or pressure class, our technical team reviews the actual casing OD, spool bottom, pocket geometry and retaining structure.

SGPE can evaluate casing spool secondary seal replacement and tubing head packoff projects from an original part number, equipment nameplate, used sample, sectional drawing or dimensional report.

Depending on the design, the supply package may include the elastomer seal element, metallic bushing, snap wire, support ring, retaining components and other matching parts. SGPE can also supply a complete secondary packoff assembly or custom replacement wellhead seal kit when the project requires a coordinated package.

Customers may combine secondary seals with casing hangers, tubing hangers, lock-screw packing, RTJ gaskets, studs, nuts and other API 6A wellhead replacement parts.

According to the purchase order, SGPE can provide agreed drawings, dimensional reports, Certificates of Conformity, inspection records and packing documents.

SGPE supports oil and gas operators, drilling contractors, wellhead service companies, repair workshops, distributors, rental fleets and EPC contractors with technical review and export supply.

Related API 6A Wellhead Products

SGPE also supplies casing heads, casing head spools, casing spools, tubing heads and tubing head spools.

The wellhead spare-parts range includes casing hangers, tubing hangers, primary packoffs, casing hanger seals, tubing hanger seals, lock screws, lock-screw packing, elastomer seal kits and metal-to-metal seals.

Customers may combine these components with API 6A gate valves, gate valve spare parts and complete wellhead repair kits.

Additional supply options include ring type joint gaskets, adapter spools, spacer spools, double studded adapters, wellhead flanges, studs, nuts and selected Christmas tree components.

SGPE can coordinate these products into drilling wellhead, production wellhead, workover, shutdown or oilfield MRO spare-parts packages.

Frequently Asked Questions About API 6A Wellhead Secondary Seals

1. What is an API 6A Wellhead Secondary Seal?

An API 6A Wellhead Secondary Seal is a packoff assembly that seals around the production casing stub inside the lower section of a compatible casing spool or tubing head. It closes the radial clearance between the casing OD and internal wellhead pocket, helping isolate casing annulus pressure from the lower flange connection.

Buyers may also call it a casing spool secondary seal, tubing head packoff, production casing seal, casing annulus seal, secondary packoff seal or wellhead bottom pack-off. Although these terms describe a similar function, the replacement must match the actual casing-to-spool interface.

Operators use these seals during drilling, completion, production, injection, well testing, workover and wellhead repair. They may support new equipment, scheduled maintenance, emergency field replacement or oilfield MRO inventories.

2. Where is a wellhead secondary seal installed?

A wellhead secondary seal normally sits around the production casing stub in the lower bowl, bottom preparation or dedicated seal pocket of a casing spool or tubing head spool.

During installation, the spool moves over the prepared casing. The secondary packoff contacts the production casing OD and internal wellhead pocket. Mechanical compression, together with pressure assistance in certain profiles, then creates the annular barrier.

The exact installation position varies between PE, EBS, 4-O, O-O, FS, P, R-Bushing and CANH designs. Review a sectional drawing or spool-pocket detail before ordering a replacement casing spool seal or tubing head packoff.

3. Which wellhead secondary seal types does SGPE supply?

SGPE supplies PE, EBS, 4-O, O-O, single and double FS, single and double P, R-Bushing and CANH secondary seals for compatible surface wellhead equipment.

Listed PE, 4-O, single FS and single P configurations cover compatible 5,000 psi applications. EBS, double FS and R-Bushing assemblies cover listed 10,000 psi systems. Double P configurations support compatible service up to 15,000 psi, while CANH designs cover listed high-pressure interfaces up to 20,000 psi.

Supply options include individual elastomer elements, complete secondary packoffs, bushing-and-seal assemblies and coordinated wellhead seal kits. SGPE can also review custom or legacy replacement requirements from drawings, nameplates, dimensions or used samples.

4. What is the difference between PE and EBS secondary seals?

A PE Secondary Seal normally uses a bottom-bowl arrangement with a snap-wire retainer and supports working pressures up to 5,000 psi in compatible configurations. It suits casing spool and tubing spool applications that contain the corresponding PE pocket and retaining groove.

An EBS Secondary Seal supports listed 10,000 psi configurations and uses a different pocket or retaining interface. It suits higher-pressure casing spool or tubing head arrangements designed for the EBS profile.

PE and EBS seals may share some nominal casing and spool-bottom combinations, but they are not automatically interchangeable. Confirm the production casing OD, spool nominal bottom, pocket geometry, retainer position and pressure direction before ordering.

5. What is the difference between single and double FS or P secondary seals?

A single FS secondary seal uses one FS sealing section and carries a listed rating of 5,000 psi. A double FS seal uses two sections and carries a listed rating of 10,000 psi.

A single P secondary seal uses one P-profile sealing section for compatible 5,000 psi service. A double P configuration uses two P-profile sections and supports compatible working pressures up to 15,000 psi.

Single and double versions require different pocket depths, profiles and retaining arrangements. Do not install a double FS or double P assembly in a single-seal pocket unless the casing spool or tubing head was designed for that configuration.

6. Which secondary seal supports 20,000 psi service?

CANH secondary seals support compatible high-pressure surface wellhead applications up to 20,000 psi.

The listed CANH range includes 9-inch, 11-inch and 13-5/8-inch spool nominal bottoms. Depending on the spool size, available production casing combinations extend from 4-1/2 inches to 10-3/4 inches.

CANH selection requires more than pressure class or nominal casing size. SGPE also reviews the spool-pocket dimensions, actual casing OD, pressure direction, operating temperature, well fluid, gas composition and expected pressure cycles.

CANH replacement packoffs may support high-pressure oil wells, gas wells, well-testing systems and selected production or injection wellheads, subject to complete technical confirmation.

7. Can SGPE supply casing spool seal replacements and tubing head packoffs?

Yes. SGPE can review and supply replacement casing spool seals, tubing head packoffs, casing annulus seals and complete secondary sealing assemblies for compatible equipment.

For an accurate review, provide the original manufacturer, equipment model, part number, pressure class, production casing size, actual casing OD and spool nominal bottom. A sectional drawing, equipment nameplate, seal-pocket dimensions or photograph can further improve identification.

Depending on the project, SGPE can supply only the elastomer element or prepare a complete packoff with the required bushing, snap wire, support rings and retaining components. These packages support workover operations, planned shutdowns, brownfield refurbishment and emergency oilfield repairs.

8. Can SGPE manufacture a replacement wellhead seal from a used sample?

A used sample can help identify the seal profile, component arrangement, pressure direction and retaining method. However, it should not serve as the only dimensional reference.

Pressure, temperature, hydrocarbons, produced water, H₂S, CO₂ and treatment chemicals may cause an elastomer to swell, shrink, harden or deform. Measurements from an old packoff may therefore differ from its original manufactured dimensions.

For sample-based replacement, compare the used part with the actual production casing OD, spool-pocket diameter, groove width, pocket depth, shoulder position and retaining arrangement. When sufficient information is available, SGPE can prepare an approval drawing before manufacturing the custom replacement seal.

9. Can one wellhead secondary seal fit several wellhead brands?

A secondary seal should not be treated as universally interchangeable across different wellhead brands, models or equipment generations.

Two casing spool seals may look similar while using different cross-sections, pocket depths, groove dimensions, retainers or pressure directions. Design revisions may also change the internal interface even when the nominal casing size and pressure class remain the same.

Confirm compatibility from the original part number, equipment nameplate, sectional drawing, used sample and actual casing-to-spool dimensions. The physical interface, rather than the product name alone, must guide final selection.

This review is particularly important for legacy wellhead repair, discontinued seal replacement and mixed-equipment MRO projects.

10. Which elastomer material should I select?

The correct elastomer depends on the complete service environment, including working pressure, operating temperature, pressure cycling, well fluid and chemical exposure.

NBR may suit conventional oil service, drilling fluids and moderate operating conditions. HNBR may suit gas service, higher-pressure applications and repeated pressure cycles. FKM may suit higher temperatures or stronger hydrocarbon and chemical exposure.

The material review should also consider produced-water chemistry, H₂S concentration or partial pressure, CO₂ content, methanol, glycol, corrosion inhibitors, aromatic hydrocarbons and rapid gas decompression.

For gas wells, CO₂ injection wells, sour-service wellheads and gas-injection projects, provide the most complete fluid-composition and operating data available before SGPE confirms the compound.

11. What affects the price of an API 6A Wellhead Secondary Seal?

The price depends on the seal family, production casing size, spool nominal bottom, pressure class, elastomer material and required supply scope.

An individual PE, EBS, FS or P elastomer element has a different cost structure from a complete R-Bushing assembly, CANH packoff or custom wellhead seal kit with metallic support and retaining components.

Project quantity, nonstandard dimensions, approval-drawing requirements, tooling review, material documentation, dimensional inspection, third-party inspection, export packing and delivery terms may also affect the quotation.

For accurate pricing, provide the actual casing OD, spool details, working pressure, material requirements, quantity, document requirements and required supply scope.

12. What information is required for a quotation?

To prepare an API 6A Wellhead Secondary Seal quotation, SGPE normally requires the secondary seal type, nominal casing size, actual production casing OD, spool nominal bottom and working pressure.

Identify the wellhead component, such as a casing head, casing spool, tubing head or tubing head spool. When known, include the original manufacturer, equipment model, part number and serial number.

Operating data should include the minimum, normal and maximum temperature, along with the well fluid and available H₂S, CO₂, produced-water or chemical-treatment information. Gas-service enquiries should also include any rapid gas decompression requirements.

Drawings, data sheets, nameplate photographs, dimensional reports and used-sample images help SGPE identify the replacement. The RFQ should also confirm the quantity, spare requirement, delivery location, Incoterm, inspection documents and whether the scope includes an individual seal element, complete secondary packoff, bushing assembly or full wellhead seal kit.

Information Required for a Quotation

Required Information	Customer Data
Secondary Seal Type	PE, EBS, 4-O, O-O, FS, P, R-Bushing, CANH or unknown
Well Type	Oil well, gas well, injection well or other
Production Casing Size	Nominal size and actual OD
Spool Nominal Bottom	Applicable spool bottom size
Working Pressure	5,000, 10,000, 15,000 or 20,000 psi
Wellhead Component	Casing head, casing spool, tubing head or tubing spool
Original Manufacturer	Provide when known
Model or Part Number	Provide when available
Operating Temperature	Minimum, normal and maximum
Well Fluid	Oil, gas, water, H₂S, CO₂, drilling fluid or completion fluid
Quantity	Order quantity and required spare quantity
Supply Scope	Seal element, complete packoff, bushing assembly or full kit
Reference Documents	Drawing, data sheet, nameplate, photograph or sample
Inspection Documents	Required certificates and reports
Delivery Term	Delivery location or requested Incoterm
Quotation Requirement	Unit price, total price, lead time and document scope

Request an API 6A Wellhead Secondary Seal Quotation

SGPE supplies PE, EBS, 4-O, O-O, FS, P, R-Bushing and CANH secondary seals for compatible API 6A casing heads, casing spools and tubing heads, with working-pressure configurations from 5,000 psi to 20,000 psi.

For replacement matching, provide the seal type or part number, production casing size, actual casing OD, spool nominal bottom and working pressure. Drawings, equipment nameplates, dimensional reports, photographs or used samples can help confirm the correct configuration.

For gas, injection or sour-service applications, also include the operating temperature, well-fluid composition and available H₂S or CO₂ data.

Send your technical information to SGPE for configuration review, price confirmation and quotation. Individual seal elements, complete secondary packoffs, R-Bushing assemblies and custom wellhead seal kits are available for new equipment, workover, shutdown, refurbishment and oilfield MRO projects.

E-Mail:
info@sgpe.com