Facing reference
Flat Face (FF) Flanges
A flat face has no raised gasket seating step. Confirm the gasket coverage, mating flange material and joint loading rather than identifying it only by appearance.
A face form, not a manufacturing route
Flat face describes the mating surface. It does not mean the flange is necessarily made from plate or identify its material. Specify the flange type and construction separately from the FF designation and verify the governing dimensions.
Gasket coverage and material
Full-face gaskets are associated with many flat-face arrangements, but the required gasket must come from the approved joint specification. Gasket material, thickness, bolt holes and seating load need to suit the actual flange pair. The diagram is not a universal gasket selection rule.
Avoid unreviewed mixed-face joints
Do not mate a flat-face component to a raised-face flange without approval of the resulting load path. Flange material, thickness and stiffness influence the response to bolt tightening. Confirm compatibility with the equipment manufacturer or responsible designer for the complete assembly.
Selection reference only. Offered scope, technical compliance and availability are confirmed against the complete project enquiry.
Mating face and gasket requirements
For Flat Face (FF) Flanges, face geometry, gasket selection and assembly loading must be reviewed together. Confirm the complete mating pair before ordering.
| Parameter / designation | Technical information | Selection requirement |
|---|---|---|
| Mating flange | A flat gasket-contact face with the specified bolt pattern and seating area. | Do not pull a flat-face flange against a raised face without an approved joint design. |
| Gasket coverage | Full-face gaskets are commonly considered; the approved joint determines actual coverage and hole layout. | Match gasket inside/outside diameters and bolt holes where present. |
| Flange material | Identify both mating flange materials, including any cast iron or other brittle component. | Material stiffness and allowable assembly loads affect gasket and bolting selection. |
| Surface condition | Specify flatness, surface finish and the permitted condition of the sealing area. | Scratches, corrosion or uneven seating can impair gasket compression. |
| Assembly loading | Use the approved gasket, fasteners, lubricant and tightening procedure. | Do not prescribe a universal torque from flange size alone. |
Compare related options
Compare Flat Face (FF) Flanges with the related forms or references below. A related product is not necessarily a permissible substitute.
| Related product / reference | Distinction | Check before selection |
|---|---|---|
| Raised Face (RF) Flanges | A raised face provides a gasket seating surface inside the bolt circle. Specify the face dimensions, finish and gasket as a coordinated joint requirement. | RF dimensions under the exact flange standard and designation |
| Ring Type Joint (RTJ) Flanges | An RTJ face uses a machined groove and a matching metal ring gasket. Ring and groove designations must be specified as a system, not chosen by nominal pipe size alone. | Flange standard, connection designation and groove details |
| Tongue and Groove Flanges | A tongue-and-groove joint pairs a projecting tongue with a matching groove. The two faces and the confined gasket dimensions must be specified together. | Tongue side, groove side or complete mating set |
| Male and Female Flanges | A projecting male face mates with a recessed female face. Specify the full seating geometry and gasket requirements rather than substituting tongue-and-groove terminology. | Male, female or matched pair |
| Lap Joint Assembly | In a lap-joint assembly, the stub end provides the gasket seating surface. The separate backing flange transfers bolt load and can rotate for alignment before tightening. | Backing flange and stub-end designations separately |
Inspection, documents and delivery
Define acceptance requirements for Flat Face (FF) Flanges in the purchase order. Required examinations and documents depend on the material, design and project specification.
| Review stage | Information to confirm | Order requirement |
|---|---|---|
| Material identity and traceability | Specification, grade, heat/lot identification and the required material certificate. | Agree documentation and marking before manufacture; visual appearance cannot verify alloy identity. |
| Dimensional verification | Seating diameter, face profile, recess/projection and mating clearances. | Identify inspection points, tolerances, units and drawing revision. |
| Surface and end condition | Gasket-contact surface, attachment end, edges and any coating exclusions. | State finish and visual acceptance criteria; agree protection of machined surfaces. |
| Supplementary examinations | Any specified PMI, NDE, hardness, impact, corrosion or other tests. | Define the method, sampling and acceptance criteria; tests are not automatically included. |
| Assembly compatibility | Gasket dimensions/material, mating flange and bolting procedure. | Design approval and correct assembly remain separate from a dimensional inspection report. |
| Packing and order release | Quantity, identification, surface protection, documents and delivery destination. | Agree preservation, packaging and release requirements with the order. |
Enquiry checklist
Details for Flat Face (FF)
Specify the complete joint and design conditions. This checklist is not a dimensional table or an engineering approval.
| Item | Requirement |
|---|---|
| Flange | Type, construction, material and applicable standard |
| Face | Flat-face dimensions and required finish |
| Gasket | Approved coverage, material, thickness and bolt-hole pattern |
| Joint | Mating face and permitted assembly loading |
Continue the specification