How To Select Proper Specifications of Stainless Steel Exhaust Flex Pipe ?

Table of Contents

• Why You Should Pay Attention to Exhaust Flex Pipe

• Exhaust Flex Pipe Install Layout

• Exhaust Flex Pipe Material Choice

• Bellows Structure and Flex Adjust Ability

• Choice of Outer Braid and Inner Braid

• Importance of Expansion Joint and Install Suggest

• Role of Exhaust Flex Pipe Nipple

• Choice of cap

• YDCT Production Process and Quality Check

• Summary and Select Suggest

Why You Should Pay Attention to Exhaust Flex Pipe

We always say, exhaust flex pipe is not only exhaust gas channel, it also work as buffer and protect part for whole exhaust system. When engine running, vibration and heat expanding always happen. If no flex pipe to absorb these force, other exhaust parts very easy get damage. System using stainless steel exhaust flex pipe can keep flexible and stable even under high temperature and vibration, and use life become much longer. But before you buy, you maybe need look more than pipe diameter. Structure, material, braid density, install way, bellows layers, wave number, wave height and many parameters, all affect performance. How you choose right exhaust flex pipe, we will talk next.

Exhaust Flex Pipe Install Layout

Before you choose exhaust flex pipe, first you need see install position environment. Many times, install place will face vibration, temperature, dust and space limit. For strong vibration place, adding inner braid and expansion joint upgraded flex pipe can raise absorb vibration ability, so durability also increase a lot. When install space small, we not suggest use double layer or upgraded flex pipe we say earlier, these pipes have high strength and long life but lose some flexibility. If forced bending too big angle, will make stress collect and break early. You also need think install way later (how you replace old pipe). If operate space small, choose welding type flex pipe is big test for welder. If welding skill not enough, light issue is ugly weld, heavy issue is bad weld quality cause leakage, you can feel this clearly when you driving.

Exhaust Flex Pipe Material Choice

Material decide durability directly. We mainly use AISI SS201 and SS304 stainless steel strip. SS201 is for normal light load, cost lower; SS304 anti-corrosion, high temperature resistance, for heavy load or industrial machine, so price higher. If you have more strict condition, like aviation, we also supply nickel alloy and special Ti stainless steel. Many buyers use pipe size ID 1 3/4 inch – 4 inch for vehicle. Default material is 201. If temperature high or vibration big, we suggest SS304 with double layer bellows and inner braid to raise stability and life.

Bellows Structure and Flex Adjust Ability

Bellows is key part. Its strength extremely important. Bellows wave height and quantity decide flexibility and vibration absorb ability. Higher wave can absorb more vibration and cool better. More waves mean pipe bend easier, more flexible, but use more material. Standard bellows wave count fixed with standard length, but if you need add wave, we can do. Standard wave pitch is 12 mm. If you need custom bellows, you can contact us. Our Ω-shape bellows perform better in cooling and vibration absorb than ring shape bellows on market. Wave height, softness, cooling also better. You can test sample to compare.

We also supply high performance single bellows products, including vacuum bellows, precision bellows, valve bellows, bronze bellows and compensator and other bellows parts. If you need, welcome contact.

Choice of Outer Braid and Inner Braid

Outer braid is standard part. It protect bellows, offer mechanical protection and limit, prevent over-stretch. It also resist outside impact wear, so very important. Same as bellows, outer braid commonly SS201. Braid strand quantity based on pipe diameter, usually 80%-85% coverage. Normally 10 strand, we also can make 12 or 14 strands.
Outer braid with thin mesh or flower mesh have better flexibility, coverage lower, flexibility higher. They suitable for small space install. But because coverage low, we usually use SS304 stronger material to make up for lower strength.

Inside bellows is hollow normally. If you want flex pipe more durable, can add inner braid. Inner braid guide gas flow and protect inner wall.

Importance of Expansion Joint

Besides inner braid, can install expansion joint inside bellows. This is longest life flex pipe version because expansion joint help compensate hot expand and vibration. Stress become more average. Under high temperature or frequent start-stop, life become much longer. In bellows we suggest use SS304 expansion joint, because this part touch hot gas directly, SS201 not good enough. But if you buy expansion joint alone, we also provide 201 version or galvanized steel version.

Role of Nipple

You may see some flex pipe have one smooth long section outside. This is transition nipple, important for seal and stability. This smooth section can match vehicle or exhaust pipe connection better, can weld or use U clamp and other clamp. The long section also let user cut and adjust insert depth. This is meaning of universal exhaust flex pipe. We usually use SS409 material for nipple, length 50 mm, thickness 1.5 mm. When your pipe system not fit welding or need match clamp type connection, you maybe need slot cut on nipple, this can increase clamp force and sealing. Normal nipple we not slot, also no need slot.

Choice of Cap

Cap fix braid and bellows. Same like braid, divided inner ring and outer ring. Inner ring usually 201 and used to fix inner braid. Outer ring we have four types: K1, K2, P, 90°. K1 usually SS409, used for flex pipe with inner expansion joint. K2 can be 409 or aluminized steel, used for flex pipe with inner braid. P type used mostly for big diameter pipe. We polish cap to raise brightness and look, also remove burr to avoid scratch wave or braid. If you need laser mark on cap, we also can do.

YDCT Production Process and Quality Check

Our flex pipe process normally:
Cut strip — rolling plate — tube welding — double tube insert (YDCT use double tube) — hold ring open — press ring — tube end expand — bellows forming — cut trumpet — wave press shaping — braid making — install braid — cut edge — ring position — semi-product cut — shaping — install expansion joint — inner support outer buckle — product cut — round shaping — spot weld — install nipple — final check — package.

We check raw material, production have inspector, finished product 100% check, and special lab do destructive and special test. Bellows weld usually laser automatic, but also support manual weld. Our raw material from big factory with standard thickness. Small factories maybe cheaper but material bad, weight obviously lighter. YDCT flex pipe monthly production 350,000 pcs. If you need stable and good factory, YDCT is good choice.

Summary and Select Suggest

In summary, choose exhaust flex pipe not only look diameter. 2.5 inch exhaust flex pipe and 4 inch flex pipe exhaust difference not only number. You need look material, bellows structure, braid, expansion joint, nipple, cap and install environment. Better choose reliable factory. Only strict raw material control, precise production control and strong fatigue and pressure test can ensure you buy solution that can handle hard working condition, not only simple metal pipe.