In appearance, the hoses that serve to supply gas are exactly the same. But professionals have known for a long time that these lead elements differ significantly. Such subtleties must be taken into account both when choosing and during operation.
Features:
Retail chains and specialty stores sell a huge number of construction and repair supplies, including hoses. But external similarities and "the opinion of a neighbor in the entrance" do not allow making the right choice. You can find on the same counter:
- bellows hose;
- PVC product reinforced with polyester threads;
- "Simple" rubber sleeve.
Back in the early 1990s, there was no question of choice. Then any gas appliances were rigidly connected to the supply lines by means of steel pipes. The advent of gas hoses made it possible to make connections more aesthetic and fit into any design. Flexible gas supply takes up less space. Finally, it allows you to select the ideal furniture, and not be completely adjusted to the characteristics of the pipe.
But it is important to understand that the gas hose is a very crucial element. If it is fragile, unreliably connected to pipes, cylinders, stoves or boilers, you will not have to wait long for problems. Connection errors threaten with an explosion, fire. Never use non-specialized hoses for gas supply. And even when using a suitable design, it is advisable to contact professionals.
Design
There are several types of gas bellows. Its simplest type is a banal corrugated sleeve. The improved version uses a protective surface made of corrosion-resistant steel. There is also an option with a polymer coating. The most reliable design includes thermal safety valves that automatically shut off the gas flow if the temperature exceeds a set limit.
The bellows is more expensive than any other option used to supply gas in a domestic environment. There is nothing surprising in this, because such a design is designed for maximum pressure. It is made of stainless steel hose.
Lugs are equipped with fittings made of corrosion-resistant metal. Only special union nuts may be used for fastening to adjacent gas lines.
The most commonly used steel for the hose is AISI 316 . Since the fittings need to be stronger, metal of the AISI 303 or 304 categories is used for them . Some firms, mainly Chinese and Turkish, supply fittings made of carbon alloys. But it is advisable to use components made from one substance. When welding dissimilar metals, electrochemical corrosion is provoked, as a result of which the weld, despite all the skill of the performers, will quickly collapse.
Specifications
Russian GOST provides that the bellows supply of natural gas must work stably at both -55 and +255 degrees Celsius. If this requirement is not met, there is no point in buying a product. Another point is no less important - the permissible pressure. To connect not even a boiler, but “just” a kitchen stove, its level must be at least 6 atm. According to SNiP norms, the highest working pressure in the domestic gas supply system is limited to 0.03 atm.
Such a significant margin of safety (200 times) makes it possible to consider that the bellows hose is absolutely safe. Normal stretch should be 100% over original dimensions. However, no one will check real hoses in this way. Experts have long ago found out that when the length is increased by 50%, it is impossible to guarantee the strength and reliability of the gas supply. The typical connection diameter for most Russian and foreign products is 1/2, 3/4 or 1 inch. If the liner is made to the minimum length, then there are no questions.
Much more controversy arises regarding the limiting length of gas bellows hoses. Gas service representatives very often say that flexible channels longer than two meters cannot be used.
No surprise: they impose expensive services to extend rigid metal pipes. The parameters referred to by gas workers are either invented by them, or, at best, are spelled out in the organization's internal regulatory documents. Until recently, when they were absolute monopolists in the entire serviced territory, it was impossible to refuse such requirements, it was impossible to ignore the instructions. But now the situation is completely different - the power of the gas services ends with a tap installed inside a house or apartment. Further equipment is the property of the homeowners.
Federal standards do not provide for any restrictions on the maximum length of the bellows line. In European countries, according to the EN standard, in fact, flexible hoses cannot be used longer than two meters. But in our country, only the requirements for the following indicators are standardized:
- chemical resistance of the material to the pumped gas;
- permissible heating;
- allowable pressure.
Comparison with rubber hose
Familiarization with specifications and official requirements is certainly a good thing for any consumer. However, one more question must be answered: how much the flexible bellows-type connection actually differs from the usual rubber structure. A pure rubber sleeve sealed with textile threads is very cheap. Its advantages are:
- high flexibility;
- decent functionality;
- a wide selection in a wide variety of retail establishments.
The positive side of rubber is deservedly considered resistance to mains, wandering and static electricity. And it's easiest to mount the eyeliner from a rubber hose. However, such a connection is more dangerous. The fact is that gradually the rubber cracks, which at first cannot be noticed visually. And the tightness may already be broken!
In practice, ordinary rubber hoses are only used to connect the stove to a gas cylinder. Even in this case, the operating time does not exceed two years. Only a more expensive type of product containing special elastic additives can be used without replacement for up to 5 years. The vast majority of people and even organizations prefer rubber sleeves with internal polymer reinforcement.
The legislation of a number of industrialized countries categorically prohibits the use of accessible steel braided hoses. The fact is that plastic is no better than rubber in terms of resistance to operational load and in terms of use. It should also be borne in mind that the gas supply line can only be connected with dielectric gaskets. The bellows lasts much longer and is much more stable than rubber analogs. As for the increased price, compared to the cost of gas equipment and connection services, it will in any case be almost imperceptible.
As practice shows, bellows liners:
- do not cause complaints from government agencies;
- work great even after a strong blow or in an aggressive environment;
- best of all resist prolonged static load;
- protected from static electricity.
Selection recommendations
It is best to start choosing a gas line by studying the accompanying documents. Normally, there must be a certificate drawn up according to the standard state model. Of course, you should go strictly to specialized stores, and not to markets or spontaneous points of sale. The easiest way is to find hoses with a length of 1 or 2 m. To determine the appropriate value, add 20% to the required distance. In this case, the installed liner will not be taut, like a string ready to burst.
Polymer-coated bellows are definitely better than metal products. Modern products of this kind allow the supply of both natural and liquefied gas. The outer coating increases the resistance of the metal layer to mechanical stress, corrosive agents and the ingress of electrical discharges in contact with conductive structures.
The same type of hoses can be used for both the stove and the cylinder. The main thing is that their internal clearance is not too small, so that there is enough bandwidth.
Chinese products are best avoided. Yes, in this country the quality of goods has improved markedly. But all the same, the risk in such a responsible business as the gas household is unacceptable. The hoses should be carefully checked for possible tampering. Nuts and fittings are selected only exactly fit in size. If the stove is equipped with an electric ignition, you should use only fire-safe flexible pipes - they are even more reliable than the white insulating inserts in conventional products.
How to connect?
Connecting bellows-type hoses to columns, gas boilers and other similar equipment is quite simple. First, the “exit” is found on the desired device. They immediately look whether it is made in a straight or angular pattern. If you make a mistake at this stage, the eyeliner will be very curved. As a result, it will lose its valuable practical characteristics, and safety will be in question.
The hose is connected to the direct outlet through a threaded steel elbow. A 1/2 "adapter is placed on a ¾ or 3/8" thread. The steel tube is connected to a ball valve placed on a riser or to the external circuit of the cylinder. A union nut is screwed on one end. Important: be sure to use a paronite gasket, on which a steel mesh is additionally placed.
It is strictly forbidden by safety rules to lay sleeves inside walls or under the floor, hide them behind decorative boxes. The radius of each bend should be at least three times larger than the tube diameter. Many old houses use flap taps, but it is better to replace them immediately with more modern ball counterparts.
Plumbing tape or special tape can be used as seals. Of course, the quality control of the work is done only with soap foam, and not with an open flame!
Life time
Sooner or later it is time to replace the bellows gas hose. It usually serves for about 25 years. But to postpone this moment, it is enough to follow simple recommendations:
- do not cover the hose;
- do not mount it with interference;
- do not stain;
- carefully avoid twisting and bending;
- exclude the ingress of condensate and liquid water;
- immediately put the hose with such a margin that it will suffice for cleaning, moving furniture or major repairs.
In the next video, you will find a review and comparison of PVC, rubber and bellows hoses.