Titanium flange + bolt + gasket 3-piece set selection: wrong 1 piece will leak, 6-step decision diagram

Published by Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd on 2026-08-07

Titanium Flangeseals are not flanges, bolt, Gaskets can be used to stabilize operation, The complete set of seal three-piece sets needs to be grade matched.Located in Baoji, China Titanium Valley, Shaanxi Province, 100 billion Tuoda, deep cultivationTitanium non-standard equipmentMade for years, Found in a large number of project services, Many projects have flange selection RF convex surface, Pledget Configuration PTFE, Bolts are selected with unreasonable matching of grade 8.8, The equipment is easy to leak after 1-3 years of operation.This article explains everything.Titanium flangeThree-piece selection logic, Covers five types of media adaptation, Five types of pressure matching, Six-step selection process and five practical pit avoidance points, for the chemical, pharmacy, Marine engineering engineering and procurement personnel to provide selection reference.

Core conclusions:Titanium flangeThree key points should be grasped in the selection of three sets, Flange pressure class determines bolt selection, Medium working condition determination Gasket material, flange, bolt, The three-piece gasket set needs to keep the service cycle synchronized.Improper selection of any one component may cause failure of the entire sealing system.

I.Titanium flangeMatching logic between three-piece sets

Flange selection depends on working pressure, dielectric corrosion characteristics, Equipment specifications jointly determined, Improper selection will result in insufficient pressure, Flange deformation occurs after 1-2 years of long-term operationBolt selection needs to be combined with flange pressure class and operating temperature, Mismatched specifications will result in insufficient preload, Initiate seal failureGasket selection key reference medium, temperature and pressure conditions, Corrosion occurs when the selection is wrong, crushing phenomenon, 1-3 Leaks occur during the year.

[Core Question 1]Titanium flangeWhy keep the service cycle synchronized with the three-piece set of bolts and washers? Answer: The service life of the three-piece set needs to be consistent.If the bolt is stable for 10 years, But the gasket only lasts three years., Bolts are prone to rust when replacing washers after 3 years, Eventually the entire seal assembly can only be scrapped.synchronous life design, Unified periodic maintenance can be achieved, Avoid the risk of premature failure of a single component resulting in the scrapping of the entire set of equipment.

Adaptation scheme for working conditions of Class II and V media

conventional water, steam, oil condition, Asbestos pads or flexible graphite gaskets are preferred, Matched with Class 8.8 or A2-70 fasteners, Adapt to general operating conditions, Good cost advantagedilute acid, dilute alkaline environment, PTFE gasket or rubber gasket are recommended, Bolt selection A2-70, A4-70 stainless steel, Can withstand moderately corrosive environmentscontaining chlorine ions, Strong Corrosion Condition of Bromide Ion, PTFE gasket or graphite composite gasket, Matching Hastelloy or Titanium bolts, Achieve three-piece overall corrosion resistanceinflammable and explosive medium scene, Metal wound graphite gasket, With A2-70 bolts, Stable seal structure, Good safety performanceUltra-high pressure conditions with pressure greater than or equal to 6.4MPa, Use metal oval ring or octagonal ring hard seal gasket, Supporting Class 10.9, 12.9 High strength bolts.

Category III and V pressure grade adaptation schemes

PN1.0 Low pressure condition, Flange adopts FF full-plane sealing surface, Bolt selection 8.8 grade, Asbestos mat or flexible graphite gasketPN1.6 to PN2.5 medium pressure working conditions, flange selection RF convex surface, bolts can be selected 8.8 or A2-70, gasket selection flexible graphite, PTFE;PN4.0 medium and high pressure working condition, flange is RF convex surface, bolts are A2-70, A4-70, and metal spiral graphite gasket is matched;PN6.4 high pressure condition, flange adopts MFM concave and convex surface, bolt adopts A4-70 or 10.9 grade, metal spiral gasket or elliptical ring gasket is used;PN10 and above ultra-high pressure conditions, RJ ring flange connection surface, with 10.9 grade, 12.9 grade bolts, metal oval ring, octagonal ring hard seal gasket.

[Core Question 2]Titanium flangeWhy do you need to choose a higher level of matching bolts? Answer:Titanium flangeIts strength is about 30% lower than carbon steel flange, A2-70 and above grade bolts are required for performance compensation.If the bolt grade is low, Pretension force does not meet design requirements, Insufficient sealing surface compression, 1-2 years of operation is prone to medium leakage.

Four, six steps selection operation process

Step 1 Determine the working condition pressure level, PN1.0 selected according to actual working pressure, PN10 and above Pressure SpecificationsThe second step combines the pressure and medium conditions to select the flange sealing surface type, Optional FF, RJ sealing surface typeThe third step depends on the flange class and operating temperature, Determine bolt grade, Optional 8.8Step 4: Combine the medium, Temperature Selected Gasket Material, asbestos, flexible graphite, metal wound, Metal ring pad selected as requiredThe fifth step is to evaluate the service life of the three-piece set and control the service life difference of the three-piece set not to exceed 1 year;Step 6: Implement material acceptance, MTC material certificate shall be provided uniformly for three-piece set, contains material, specification, test data, Easy material traceability.

V. Project Application Reference Case

Seawater desalination project, medium seawater 25-40℃, working pressure 0.6MPa.Mismatch in early selection, RF flange with Class 8.8 bolts, asbestos gasket, Bolt corrosion after 6 months operation, Gasket aging leakage, Equipment replacement and shutdown losses are incurred.RF is selected for optimization schemeTitanium flangeA2-70 bolt with flexible graphite gasket, put into use for 5 years stable operation, no leakage problem. PTA unit under strong corrosion condition, medium containing bromoacetic acid 120℃, pressure 2.5MPa.Original RF flange with A2-70 bolts, PTFE pledgets, Bolt corrosion fracture after 1 year operation, PTFE gaskets were attacked by bromine ions at 3 months.Replace RF after optimizationTitanium flangeHastelloy bolts with graphite composite washers, stable working conditions for 4 years of continuous operation. Wet chlorine condition in chlor-alkali plant, Medium 80℃ wet chlorine, Pressure 1.6MPa, The original RF flange with A2 - 70 bolt and asbestos gasket has potential safety hazard, Optimized for TG mortise surfaceTitanium flangeA2-70 bolt with graphite gasket, stable operation for 5 years. ultra-high pressure steam condition, Medium 540℃ high pressure steam, Pressure 10MPa, Initially MFM relief, 10.9 Grade B bolts with metal spiral washers are under pressure, Adjust to RJ ring connection surface titanium flange, 12.9 Grade B bolts with metal oval ring washers, 8 years of continuous operation. Vacuum reactor conditions, medium 100℃, negative pressure- 0.1MPa.RF salient surface was adopted in the initial stage, A2-70 bolt with graphite gasket, Width of sealing surface does not meet vacuum requirement, Optimized for MFM Concave-convex Titanium Flange, A2-70 bolt with metal wound graphite gasket, Vacuum remains stable, Continuous operation for 3 years.

[Core Question 3] What is the most error-prone part of the three-piece selection? Answer: Bolts.Most purchasers focus only on flanges and washers, ignoring bolt grade matching.Titanium flange matching bolts need to reach A2-70 and above grade, Otherwise, the preload is insufficient, The whole set of seals failed.

VI. Selection of five pit avoidance points

Pit avoidance 1: insufficient bolt grade, titanium flange with 8.8 bolts, insufficient preload, easy to leak for 1-2 years, titanium flange priority A2-70 and above fasteners when selecting. Escape Pit 2, Gasket material mismatch, Asbestos pad is selected as strong corrosive medium, Spacer failure 3-6 months, The medium contains chloride ions, PTFE or graphite composite gaskets are preferred for bromide ion. Escape Pit 3, Bolt material confusion, Drawing No. A4-80, Supply replaced by A2-70, Insufficient corrosion resistance, MTC material certificate shall be marked with bolt number and grade during acceptance. Escape Pit 4, The service cycle of the three-piece set is not uniform, Long bolt life, Short gasket life, Difficult to disassemble later, Bolts are easily damaged when replacing gaskets, The service cycle difference of the three-piece set is controlled within 1 year when selecting the type. Escape Pit 5, MTC data incomplete, Missing bolts, Gasket Test Report, Material cannot be traced, Acceptance disputes, Complete MTC documentation needs to include flanges, bolt, Gasket all test data.

VII. Shaanxi Qianyi Tuoda Supporting Technical Services

Located in Baoji, China Titanium Valley, Shaanxi 100 billion Tuoda, Has many years of titanium non-standard manufacturing experience, Three technical support services are available.The first one-to-one selection consultation, provide a medium, temperature, pressure, specification parameter, Technicians quickly issued titanium flange three-piece matching programThe second spot resources support, titanium flange, supporting bolts, washers three sets have sufficient stock reserves, can be shipped in batches on demand;Third MTC Material File Free Review, Customer submits three-piece material certificate, Engineer verifies material grade and authenticity.Contact: 15909236031 / 0917-3557966, official website:http://www.sxqytd.com/

Titanium flange + bolt + gasket three-piece set selection core is still three points, flange rating bolt, medium condition spacer, Three-piece service cycle synchronization.Improper selection and collocation will cause seal leakage and affect the stable operation of equipment. To learn more about Titanium Flanges, you can read the article in the station: 

Titanium flange introduction six steps selectionhttp://www.sxqytd.com/index.php/new/index/id/190.html 

Titanium flange sealing surface type detailed explanationhttp://www.sxqytd.com/index.php/new/index/id/192.html 

"Titanium flange and gasket combination selection points"http://www.sxqytd.com/index.php/new/index/id/194.html

Technical reference standards in this paper: GB/T 9112-2010, HG/T 20592-2009, ASME B16.5-2020, ASME B16.21-2016.Updated: August 7, 2026. disclaimer, This article three-piece set selection, The portfolio is for technical reference only, The actual use of materials will be affected by the medium concentration, temperature, Multiple factors such as field operation and maintenance, Formal project selection is subject to written technical confirmation by both parties.