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The comprehensive performance comparison of all kinds of thin-walled stainless steel pipes
 
At present , the domestic thin-walled stainless steel connection modes mainly includes single press fitting,double press fitting , Ring compression connection、Socket weld connection The following is a comparison of these connection modes from the production process , performance , construction convenience and other aspects.
 

Connection Mode Performance

Single Press Fittings

Double Press Fittings

Ring compression connection

Socket weld connection
Obtainment of technology

M corporation from Germany

Viega corporation from Germany

From the principle of press fitting technology

Welding Engineering

Production Standard

GB/T19228-2001

GB/T19228-2001

GB/T33926-2017

QB

Technical Application

It has been used abroad for over 60years and for about 20years in China

It has been used abroad for over 50years and for about 20years in China

There is no such product abroad , and it has been used for about 7years in China

It has been used for about 10years in China

Connection Structure

Press pipes and pipe fittings with special tools and the section at pressed interface is hexagonal(below DN50) or round (above DN50).The rigidity of stainless steel plays a connecting role , and the wall thickness of the pipe fittings determines the strength of rigidity.Therefore , the minimum wall thickness required in the GB material shall not be lower than that in GB

Press R cavity in pipe fittings with special tools.The press section is hexagonal(below DN50)or round(above DN50).The rigidity of stainless steel plays a connecting role.

Press pipes and pipe fittings with special tools ,the section at pressed interface is approximately bulging circle, take advantage of stainless steel rigidity to connect.The thickness of the pipe wall determines the strength of rigidity

Welding the outer edge of the pipe with Argon arc welding gun Connecting pipe with the melted stainless steel liquid.

Connection Structure Features

The R cavity of the pipe fitting is finished in the factory and eliminate the hard force concentration by annealing.The interface section is hexagonal . It won’t rotate for installing pipeline accessories.(above DN50 , adopt threaded connection)

The general features are same as single press fitting。There is a socket section outside R cavity which can effectively improve tensile resistance ability , perfectly protect the damage of the shape of R cavity by external force and therefore improving the compression ratio of sealing ring.Effectively protect sealing ring from dust and ultraviolet ray.

There is no R cavity in the pipe fitting .Press  it to form R cavity with a special tool during installation.The deformation of the pipe fitting is large and the stress is concentrated.Since can not remove stress by annealing in construction site,the R cavity has a stress release process which will cause the pipe to loosen and leak in 2 to 5 months and easily cause stress corrosion, especially in the case of high temperature.The section at the connection is approximately circular which may cause leakage by the rotation of the pipe fitting due to the installation of the pipe fittings

The pipe is thin and easy to be welded through(Burn through). Once welded ,it is hard to be repaired. During welding , the high temperature will cause damage to the internal metallography of stainless steel , resulting in low corrosion resistance of the weld, which makes it impossible to complete the annealing and pickling passivation process after welding , make the weld in the weakest state.

Sealing Structure

 

Type sealing ring ,linear longitudinal seal, all points of compression ratio is pretty uniform.  O-type sealing ring has the best elasticity

O -type sealing ring  ,linear longitudinal seal, all points of compression ratio is pretty uniform.  O-type sealing ring has the best elasticity  

Annular pressed broadband cavity seal , rectangular section belongs to the surface seal , because can not guarantee 100% ring compressed.The compression ratio at each point of the sealing circumstance is not uniform , easy to leak.Rectangular section structure , is more suitable for flange connection.

 No sealing ring

Sealing Material

Chlorinated butyl has high permanent compression ratio , accords with GBs. The sealing ring is black , more resistant to ultraviolet radiation aging

EPDM rubber accords with GBs and has excellent permanent compression ability, it has aging resistance . It is a material which is widely used in hygienic requirement  and high sealing requirements of various water accessories .The service life of civil water supply pipeline is higher than that of pipeline verified by Shanghai Polymer Research Institution.The sealing ring is black m more resistant to ultraviolet radiation aging.  

Adopt silicone ,  relatively soft , and the permanent compression ratio ability is not enough, easy to absorb water.There is no relevant GB for this material.Silicone rubber in water supply sealing materials generally in the hose connection in the steel wire seal , belongs to the short life of the sealing materials to be maintained.Generally , the service life in water supply material is 5years.At present silicone rubber is commonly used in short life of the sealing occasions, such as pacifier.Therefore , the compression GB did not include silicone rubber in the GB

No sealing ring

Pipe Fitting Technique

Complicated production process and the technical content is high.The threaded part is precision cast by silica sol .Pipe fittings adopt Cold stamping And they are processed by annealing , pickling and passivation .The sealing ring has been assembled in the R cavity of the pipe fittings.

Same as single press fittings

 

The production process is simple . Pipe fitting and threaded fittings are produced bu extrusion .There is no R cavity for sealing ring in pipe fitting . Pipe fittings and sealing rings are separately sale. The sealing ring that should be assembled during installation in the factory which belongs to semi-finished products of press fittings

Cool Punch Process

Other Accessories(Thread connecting part )

Silica sol precision casting can ensure the physical performance of casting without stress concentration . The dimensions and specification of the Male Hexagon accessories conform to the GB.  Standard wrench can be used for construction which is convenient.

Silica sol precision casting can ensure the physical performance of casting without stress concentration . The dimensions and specification of the Male Hexagon accessories conform to the GB.  Standard wrench can be used for construction which is convenient

Seamless stainless steel pipe is produced by Cold extrusion (Cold Hobbing) which is easy to form stress concentration .The outer hexagon dimension specification of threaded fittings are out of standard that can not match standard wrench ,and only pipe wrench can be used ,which is very inconvenient.  

Seamless stainless steel pipe is produced by Cold extrusion (Cold Hobbing) which is easy to form stress concentration .The outer hexagon dimension specification of threaded fittings are out of standard that can not match standard wrench ,and only pipe wrench can be used ,which is very inconvenient.

Working Pressure

Working pressure 1.6MPA that accords with GB

Working pressure 1.6MPA that accords with GB

Working pressure 1.6MPA that accords with GB

Working pressure 1.6MPA that accords with GB

Specification of Pipe

Accord with GB/T19228,take DN25 for instance , the actual inner diameter is 26.58mm

Same as single press fitting

Accord with GB/T33926,take DN25 for instance , the actual inner diameter is 23.8mm

Take DN25 for instance , the actual inner diameter is 23.8mm,low water flow.

Wall Thickness of Pipe

Accord with GB

Accord with GB

Wall thickness is lower than GB,generally is 70-80% wall thinner than GB

Same as ring pressure type

Material Cost

Because of pipe’s wall thickness , pipe and pipe fittings’ cost are reasonable

pipe and pipe fittings’ cost are reasonable

Due to the outer diameter and wall thick are lower than GB, each product weight is 70-80% lighter than press fitting, thus the total price is pretty low. Pipe fittings’ price isn’t contain sealing ring . The cost of pipe fitting is close to press fitting

Due to the outer diameter and wall thick are lower than GB, each product weight is 70-80% lighter than press fitting, thus the total price is pretty low.

Construction Cost

One time press form?,short time of installation and the procedure is simple.Just insert the pipe into pipe fitting for pipe fitting has already assembled with sealing ring , saving installation time

  Same as single press fitting

Long time of installation , need secondary or third time press to make long working hours.Complicated procedure , installing the sealing ring into pipe then press it . If the sealing ring isn’t in place , unplug pipe and reinstall in .That results in nearly 15% more time for installation than press fittings

Argon are workers are paid more than ordinary workers. Need welding wire , argon and other auxiliary materials dynamic electricity.These auxiliary materials make up about 9% of materials. Long time installation is around1.6 times as long as press fitting installation.The preparation time of argon gas protection is basically the same as that of press fittings

Service Life

Stainless Steel has service life for 70years,due to the wall thickness conforms to GB , the corrosion resistance is strong.The sealing ring is chlorinated butyl rubber up to 50years

Same as single press fitting. Sealing ring adopt EDPM rubber, the service life is longer than that of pipeline

The service life of stainless steel is 70years.However the wall thickness is thinner that press fitting and there is no corrosion allowance thus it exists a risk of corrosion by other environmental factors.Sealing ring ,silicone rubber’s performance decline after 5years

The service life of stainless steel is 70years.However the wall thickness is thinner that press fitting and there is no corrosion allowance thus it exists a risk of corrosion by other environmental factors. Welding process is not proper will cause problem in quality.

Fire Protection Requirement

No open flame , no fire hazard

No open flame , no fire hazard

No open flame , no fire hazard

There is open flame during installation , fire hazard

Transmission Energy Consumption

Save energy

Free maintenance

Maintain after2 years because of leakage Change sealing ring after 10years

  Welding process is not proper will cause short time maintenance

 

Analyze:
1.From material purchased cost , the Socket weld connection is pretty low and  Ring compression connection is second
2.From product security , double press fitting is better than single press fitting ,single press fitting is better than Ring compression connection or Socket weld connection
3.From installation cost , double press fitting and single press fitting is pretty lower, Ring compression connection And welded pipe fitting is high
4.From the analysis of fire requirement , the risk of Socket weld connection is top especially when the interior decoration construction at the same time , it’s easy to cause fire. 
5.From the sealing performance , Ring compression connection is the worst.
6.From the daily maintenance and energy consumption, Ring compression connection is the worst.
Conclusion:
From the comprehensive cost material cost and installation cost of stainless steel , the four connection mode are similar,but if consider the service life, maintenance costs and daily energy consumption, double press fitting and single press fitting is excellent and economical.It is because people do not obtain an understanding of stainless steel,and consumers are misled of the low purchased cost and then chose Ring compression connection or Socket weld connection From the dialectical point of view , things are both opposite and unified.Reducing the amount of product materials can low down cost but the installation costs and daily maintenance costs will be increased and the service life will be reduced either.Although the raw material consumption of double press fitting and single press fitting are slightly higher than that of Ring compression connection and Socket weld connection. It greatly improves service life and reduce daily maintenance cost as well as energy consumption.Therefore,double press fitting and single press fitting are the most scientific connection modes of thin-walled stainless steel.
 

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