CONSTRUCTION

   Metal flexible corrugated leak proof hoses have been producing by special hydraulic forming from thin-walled butt welded tubes. The corrugation of these hoses can be helical or annular..

   Owing to their corrugated form, metal flexible hoses have high resistance to pressure acting to radial direction and less one to hose axis. To increase pressure resistance, these hoses are single or multiple wire braided. Number of braids, braiding material and hose characteristic, depending on number of braids, are indicated for each type of hoses on the next pages.

   Metal flexible corrugated hoses can be fitted by flanges, threaded connectors, tube weld ends etc. The assembling connectors with the hoses is carried out by protective gas welding, brazing, silver soldering and mechanical jointing.

MATERIAL 

   As flexible conduits they often have to operate elastically under extreme conditions and, because of the thin walls as compared with rigid piping, they must be especially corrosion resistant. Moreover, these hoses have to meet the following requirements:

• good cold forming properties,

• good strength properties,

• optimal thermal stability,

• good corrosion resistance,

• high reliability in operation

   In principle, there is no material which will ideally meet all these demands. The materials, used for our range, cover a large variety of needs occurring in practice. Our standard materials are indicated for each type of hoses. It is possible to make hoses of the other materials but it is conditioned by quantity.

DESCRIPTION

• absorption of movements (movements of one or both end fittings with large amplitude and low movement frequency),

• absorption of vibration (movement with low amplitude and high frequency),

• absorption of thermal expansion of hose assembly,

• compensation of parallel offset in pipelines, 

• absorption of angular movements.

DEFINITIONS AND EXPLANATIONS OF HOSE CHARACTERISTICS

Nominal size (DN)
According to ISO 6708 is represented by numerical indication of size which is common for all components in piping system. Nominal diameter is a convenient rounded off number reference applications and it hasn't to be equal to the actual inside diameter of hose.

Inside diameter (d 1)
An effective section of hose and mostly equal to its nominal size.

Outside diameter

Diameter of cylinder enveloping the straightened out tube.

Braiding
With the aim of improving the pressure resistance and mechanical protecting, hoses can be covered by single or double braiding. The hoses for vacuum applications are not normally braided.

Working pressure (Pr)
Maximum pressure which a hose can withstand during the operation at room temperature ( 20ºC) and at fluid without pressure fluctuations and vibrations. The working pressure is established as a quarter of the bursting pressure:

Pr = bursting pressure/4

If the hoses are exposed to thermal stresses that, is to temperature higher than room one, the working pressure will be decrease. It is established by the following formula:

Pdop=Pr x Kt

Minimal bending radius
Minimal of axis turn of hose permissible in operation. It is determined on the base of measurement and calculating and given in the tables as static for one bending only and dynamic for repeated bending in operation.

The bending radius un active position shall be larger than or equal to the minimal bending radius given in the tables.

The bending radius essentially influences on lifetime of hose. Its increasing will augment lifetime of hose.

Hose mass
Given in the tables, is determined by calculation and measurement. The permissible deviation must be kept in limits ± 10%.

Maximal permissible working temperature
Lowest maximal permissible working temperature of any constituent component:

• hose material,

• attachment method of connecting elements and hoses,

• connecting element material,

• connection method etc.

The working temperatures of hoses without connecting elements are given in the description of the individual hose type.

The quality control is a matter of exceptional importance in consideration of specific quality of flexible hoses as in view of their production so with regard to their exploitation.

Material control

The high quality material is one of the most important factors in high quality flexible corrugated hoses manufacturing. Therefore, we have been purchasing materials from reputable European manufacturers. All materials have to be followed by corresponding certificate such as the one according to DIN 50049-3.1.B. Besides, all purchased materials are submitted to the testing of chemical, mechanical characteristics , resistance on inter crystalline corrosion etc.

Manufacturing process control

The particular care must be taken of the dimension accuracy control and careful material working out. The basic material of hose is exposed to considerable strains during the hydraulic process and it is simultaneously very reliable way of material testing.

Leakproofness of hoses

To check up the leakproofness of hoses, pneumatic or vacuum tests can be done.

The pneumatic test is carried out by air or nitrogen under water. The nitrogen testing is more expensive and it has to be carried out in those hoses which are mainly used in conveying the gaseous or very liquid media During this test hoses are exposed to a pressure equal 10 % of working one or 2 bar minimum.

The vacuum test is applied only in special cases it is considerable y expensive and therefore,it must be apart agreed.

Testing by hydraulic pressure

This testing is carried out in the aim of checking up the hose solidity by hydraulic or pneumatic testing pressure.

A straight sample of hose at room temperature shall be subjected to a testing pressure which shall be 1,5 times the maximal permissible working pressure. Unless otherwise stated, the test medium shall be water. The test pressure shall be applied and maintained for a sufficient length of time to permit a visual examination of all surface joints.

The testing by pneumatic test pressure is carried out under same conditions as hydraulic testing but the medium is gas. Pneumatic testing is potentially a much more dangerous operation than hydraulic testing in that, irrespective of size, any failure during test is likely to be of a highly explosive nature.

Therefore, this testing is applied only exceptional cases by particular agreement.

Certificates

Depending on client's request we or specialized agencies carry out the reception control. Therefore, on the basis of carried out testing according to the reception control the corresponding certificates have to be issued. These certificates are issued in accordance with relevant standards ISO 404 or DIN 50049. If the client doesn't denote, we usually issue the certificate in accordance with DIN 50049-3.1 B.

Correct choice of a tube length
The correct choice of hose length is very important . Excessive shortness of hose doesn't give the needed flexibility , in that case it is too rigid. In addition, the hose can be damaged relatively quickly close to the end fittings. Excessive long hose is not only too expensive but it is also quickly damaged in operation. In determining the hose length you should use recommendations, and if you are not sure, consult us.

Permissible bending radius must be observed
Non-observance gives rise to damage of hoses. The instructions, relating to pressures, temperatures etc. must be also followed.

No torsion stress
Our flexible hoses can be only subjected to bandings. Torsion stresses must, therefore , be avoided. This can, in most cases, be realized by suitable installing of the hose. In the case of movements in operation, the hose must be installed in that way that the hoses axis and the direction of movement are in the same plane.

 INSTRUCTION FOR INSTALLATION
Handling and assembly

 The type and form fitting metal tubes, are determined primarily by the direction, magnitude and frequency shifts. Therefore we give here some typical examples of assembly. When installation is especially important to pay attention to put a tube without torsion stress, and also that the axis of connection and movement lie in the same plane.
Be sure to pay attention to:

• mounting without stress (example No. 1)
  

• requires no torsion (example No. 2)
  

 Example 1 Tightened without rotating the tube. By rotating threaded connections, be sure to use a different key to re-raise. If no suitable area frothed key, then use pliers for tube (Rohrzange).

                                                    
                                                   example no. 1                               example no. 2

Example no. 3
Archos 180 degrees long enough length neutral. The distance between the ends of pipe to determine the bending radius R. When choosing the length of the pipe must not incur any displacement connectors. In case of need top reserve the connections we can attach the ends of the protective coil.
When unions use the key counter. When determining the ports to predict that one side of the pipe is installed swivel connector.Should not exceed the permissible bending radius.
Minimum bending radius, depending on the temperature and pressure desired number of cycles. These values are given for all types of flexible tubing.

                                     
                                                                         example no. 3

Example no. 4
 Applying solid tubular port, to prevent the improper folding immediately after the terminal fittings.

                                                     
                                                                         example no. 4

Example no. 5
The direction of movement of the bend lies in the same plane. Harmful torsional stresses thus prevented. 

                                                    
                                                                        primer br. 5

Primjer br. 6
Nije dopušteno nikakvo savijanje neposredno iza priključne armature, što se sprečava primjenom čvrstog cijevnog.
Cijev postaviti u slobodnom visećem luku tako da ne dolazi u dodir s podom ili drugim predmetima.

                                     
                                                                        primer br. 6

Vibracije primjer 7, 8.
Cijevi ugraditi slobodno od zaokretanja. Glavni smjer pomjeranja vibracija i luk cijevi moraju ležati u istoj ravni.
Time se sprečavaju štetna torziona dejstva.

                                            
                                                                          primer br. 7

Vrlo je važno kod vibracija pravilno montirati cijev.

                        
                                                                          primer br. 8

Primjer br. 9
Luk 90 ° izvesti s dopuštenim radijusom savijanja i dovoljnom neutralnom dužinom cijevi.
Presavijanje i rastezanje luka cijevi nije dopušteno.

                                                
                                                                               primer br. 9

Primjer br. 10
Za preuzimanje dvo ili trodimenzionalnih vibracija, cijev treba ovako ugraditi.

                                                  
                                                                                primer br. 10

Primjer br. 11
Cijevi ugraditi normalno na smjer vibracija.

                                                             
                                                                                 primer br. 11

Primjer br. 12
Za preuzimanje ugaonih pomjeranja cijev ugraditi s dovoljnom neutralnom dužinom. Obratiti pažnju na radijus savijanja.

                               
                                                                                 primer br. 12

Primjer br. 13
Ugaono pomjeranje i luk cijevi moraju ležati u jednoj ravnini.
Time se sprečavaju štetna torziona naprezanja.

                                        
                                                                                  primer br. 13

Primjer br. 14
Za preuzimanje toplotnih pomjeranja predvidjeti luk od 90° s dovoljnom ravnom dužinom kraka.
Luk cijevi i smjer moraju ležati u jednoj ravni.

                                                                                   primer br. 14

Primjer br. 15
Lateralna montaža dopuštena je za preuzimanje samo manjih pomaka. Rastezanje ili skupljanje cijevi nije dopušteno.

                                
                                                                                    primer br. 15

Primjer br .16
Za preuzimanje većih pomjeranja cijev ugraditi kao luk od 90 stepeni. Lateralna montaža vise nije dozvoljena.

                                   
                                                                                      primer br. 16

Primjer br. 17
Ukoliko je nemoguće spriječiti mehaničke uslove (vučenje po podu) cijev se može zaštiti sa žičanom zaštitom ili sa zaštitnom cijevi preko postojeće.

                                                                            
                                                                                     primer br. 17

Primjer br. 18
Pri manuelnoj upotrebi cijevi zaštititi od nedopuštenog presavijanja upotrebom čvrstog cijevnog luka.

                                                                      
                                                                                       primer br. 18