Interesting facts about hoses
The suction and pressure hoses of APD Schlauchtechnik GmbH are designed for the conveying of dry, gaseous and liquid media. The user is obliged to use our products only on the basis of our stated specifications. All our technical data are the result of internal tests and trials in accordance with international standards. They only serve as a guide and refer to a fluid and ambient temperature of +20°C, static pressure and vacuum loads and straight hose lines with a length according to a test standard. The specified values do not apply with deviating temperatures, pulsating pressure and vacuum load, vibration of the hose pipe or the connection sides, heavily curved hoses or improperly attached hoses. In these cases, the suitability for use must be verified by the user. If there there is no experience in using our products, we strongly recommend prior testing or consultation with our technicians. This is especially true at operating conditions with mutual loads (movements), high temperatures, vibration, abrasion, water vapour, chemical loads or S-shaped hose linings. The application examples provided by us are not binding.
Storage of plastic hoses
The storage room must be cool, ventilated and sufficiently dry. High ambient temperatures above +45°C without any airflow can permanently deform plastic hoses. Please note that such temperatures may arise in direct sunlight, even within packaged hose reels. The permanent stack height must be adapted to the respective product and ambient temperature. Hose reels, which are loaded with a higher weight under summer temperatures, may be deformed. It is important to ensure that the hoses are stored free of tension, so without strain, pressure or other stresses, since tension encourages both permanent deformation and cracking. For outdoor storage, plastic hoses must not be exposed to direct sunlight. The packaging may not close hose reel airtight. Depending on the product, plastic hoses must be protected from permanent UV and ozone radiation.
Transport of plastic hoses
Because of the constant movement, transport leads to much greater loads for plastic hoses than those which arise during storage. High summer outdoor temperatures, the heat accumulation on the truck and the constant vibrations during the journey quickly lead to permanent deformation of the hoses. Therefore, at high temperatures, the stack height during transport must be less than it is during storage. During transport, plastic hoses may not be thrown, dragged along the floor, run over or stepped on. This could result in damage to the outer layer and the spiral could become deformed or even completely broken. We assume no liability for this. Therefore, care must be taken to ensure that no damage is caused by improper handling.
Temperature behaviour of plastic hoses
Unlike rubber hoses, the cold and heat have a great influence on plastic hoses. Plastic hoses change their flexibility at low or high temperatures of the medium or the environment. At lower temperatures, they can harden until they become brittle. Pass over at high temperatures close to the plastic-specific melting point in the plastic, i.e. malleable, fluid state. Because of these properties, the pressure and vacuum specifications for plastic tubes are exclusively linked to a temperature of the medium and the environment of around +20°C. If temperatures deviate from the medium or environment, we cannot guarantee compliance with the indicated technical characteristics.
Influence of sunlight on PVC hoses
The UV radiation from the sun can attack PVC hoses and destroy them over time. This happens in connection with the duration and intensity of solar radiation, which is usually less in northern Europe than in southern Europe. Therefore, a precise time period cannot be given. The embrittlement of plastic hoses by UV radiation can be slowed down, but not completely stopped, by adding special UV stabilisers. These stabilisers also wear with continuous UV irradiation. Some of our hose types are fitted with these UV stabilisers as a standard to ensure a long lifetime under direct sunlight. On request, any type of hose can be fitted under certain conditions with UV stabilisers.
Pressure and vacuum behaviour of hoses
Genuine pressure hoses are all types which have a fabric as a pressure carrier. All hose types with plastic or steel spirals are vacuum hoses in the first instance. All hoses can change their length and diameter and become twisted even within the specified pressure and vacuum values. With hoses with fabric as a pressure carrier, changes of up to 5% in length and girth is normal, even under laboratory conditions. Therefore, all operating conditions which deviate from the norm influence the behaviour of these products even more. All hoses which have a spiral but no polyester fabric as reinforcement are only suitable as pressure hoses to a very limited extent, but are mainly intended for vacuum applications. By design, a change in length of these hose types of up to 30% during use, even within the specified pressure and vacuum values, is always possible. All possible length and girth changes, as well as axial twisting of hoses must be considered by the user during use. In use conditions, hoses must not be fixed at short distances as pipes are, but must be able to move freely at all times. In soil, hoses may only be laid in adequately dimensioned conduits. In doing so, all possible changes in the hose geometry are to also be taken into account at all times. We strongly recommend that you determine the hose behaviour in use by means of prior testing and then carry out the installation. With spiral hoses, the elongation and twisting in the case of overpressure leads to a reduction of the inner diameter at the same time. For hoses with steel spirals, the spiral cannot completely follow this reduction of the inner diameter. Thus, the spiral can work through the hose wall to the outside and destroy the hose. With permanent use in the overpressure range, we generally recommend hoses with fabric as the actual pressure carrier. This prevents excessive elongation.
Based on DIN EN ISO 1402.-7.3, the values given for the burst pressure with compressed air and pneumatic hoses were determined at about 20°C and water as a pressure medium.
Using hose couplings
In suction applications, plastic spiral hoses can be integrated with a variety of commercially available fittings. In the application, the hose sucks firmly onto the fitting and seals itself off. In pressure applications, spiral hoses are much more complex and are to be permanently sealed due to the strain and change in diameter. Our fittings from product group 989, which are customised to the particular type of hose, are ideally suited to this. When using standard fittings, please ask for our respective procedures recommendations. With PVC fabric hoses, make sure that the material has a significantly lower notch toughness compared to rubber. Therefore, fittings may not have any sharp edges that can rip when assembling the inner layer. If the plastic fabric hoses are fixed to a hose connector by means of press sleeve or hose clamps, make sure that the pressure is applied with the least possible force. Otherwise, the hose layers can become nicked up to the fabric by the fitting or the hose clamp, whereby the hose becomes immediately unusable. For safety reasons, we recommend hose connectors with lower gearing than the thickness of the hose inner layer. Basically, it should be ensured that, when using fittings, all kinds of hoses are not bent sharply right behind the fitting.
Discharge capability of hoses
To derive electrostatic charges in the transport of powdery or granular media, all plastic hoses can be used with copper wire or steel spirals. Through the grounding at both ends of the braid or spiral, these hoses are considered to be conductive. For use in potentially explosive areas, the TRBS 2153 must be followed. The usefulness of hoses and compliance with all mentioned in the TRBS 2153 rules are in each case, to consider by the user and to ensure.
Food grade quality of hoses
By definition, plastic hoses belong to the commodities that may be intended for contact with food. The European Regulation EU 10/2011 makes a difference in Appendix 3 on page 75 between the 6 different categories A, B, C, D1, D2 and E, according to which a foodstuff commodity (hose) can be tested. The test for a particular category is carried out using a simulant, and must be run on the finished component (hose). The continued common practice of many manufacturers to merely confirm that the hose basis suitable for foodstuffs is not permitted. In the Regulation, all food is mostly assigned to a single simulant (category). The food categories for which our products are approved are designated by printing on the hose. We publish specific information on the contact time and possible exclusions in our Declarations of Conformity, which are available at all times. When choosing one of our products, it is the responsibility of the user or the customer to check that it is approved for the intended food and the contact time. Regulation 10/2011 can be viewed on the internet at eur-lex.europa.eu/LexUriServ/LexUriServ.do at any time. Of course, we are also happy to advise you.
With hoses, reference is generally made to the inner diameter, while pipes (e.g. sizes 910, 920 and 925) are differentiated according to the outer diameter. With almost all products, we also indicate the wall thickness for the sake of completeness.
The burst pressure is the pressure under which a hose will become destroyed due to the pressure. The test is always run in line with the international standard DIN EN ISO 1402. The burst pressure is used to define the operating pressure taking account of the general safety factors.
The operating pressure is always determined in line with the international standard DIN EN ISO 7751.
Pressure that is maintained during non-destructive testing and for a specified duration in order to verify the integrity of the hose assembly. Depending on the hose construction, the test pressure is up to 50% above the operating pressure. At test pressure, the hose must not show any leakage or permanent deformation.
Negative pressure (vacuum)
This is the set negative pressure that a hose can withstand without resulting in flattening or detachment of the lining or layer separation. The determination is always based on the international standard DIN EN ISO 7233.
The bending radius of a hose is defined as the radius of the smallest drum around which the hose can be laid without the cross-section becoming significantly changed compared to the original shape. In each case, the test is performed in accordance with the standard which determines the product. To achieve a long service life, the following should be noted when using the hoses: Selection according to the maximum operating pressure given in the catalogue. The hose should never be deformed by force (e.g. kinking, crushing, running over with vehicles, twisting, etc.). Dragging hose pipes over rough floors and sharp edges is to be avoided. The hose should not be permanently bent at the couplings or subjected to excessive tensile stress. Contact of unprotected hose ends with the flow medium should be avoided. Emptying and careful cleaning may significantly extend the life of a hose pipe.
Almost all types of hoses can be optimised to customer requirements for the particular application. Wall thicknesses, dimensions, pressure or vacuum support, colours, lengths and shapes can be already be changed during production. We are happy to answer your questions at any time.