The old material gave way to new and modern one

The owners of a typical prefabricated flat in a housing estate in Prague decided to replace the kitchen furniture. When they removed the old one, a very unpleasant surprise awaited them. A leak (gas leak) in one joint was detected on the existing gas pipeline built in 1980s. Repair of such a joint is very complicated and time consuming. Not due to necessary re-sealing of one joint: when you intervene into decades-old threaded piping, the movement of pipes almost surely loosens neighbouring joints that were tight so far. And so you usually have to reseal all joints. It takes much more time than to make a gas pipeline completely new and from modern materials.

The gas connection made of a classic steel pipe, which is connected by threaded elbows and sealed with hemp, was ideal for coal gas. With its moist consistency, it kept proper condition of the sealing hemp in the joints. However, after the transition to dry natural gas, there was a gradual drying of hemp and resulting small gas leaks.

The flat owners therefore immediately invited the gas man, who was asked to reseal the joints. This requirement was clearly rejected by a professional installation company for two reasons.

  1. Laboriousness and time – this particular gas pipeline was about 5 meters long (from the gas meter in the corridor up to the cooker) and contained 24 joints. These should be disassembled and resealed. In addition, some joints were not easily accessible, such as in a shaft with a riser.
  2. Warranty – the installation company should provide an appropriate warranty for such repair of the gas pipeline. It would definitely take a lot of courage to provide a warranty for a complicated repaired piping made of 40-year-old material.

The installation company offered a solution that is fast, safe and ultimately cheaper. Replacement of old steel pipeline with modern pipes made of stainless-steel corrugated tubing MERABELL GAS PROFI. What convinced the flat owner to accept this offer?

  1. Speed of installation – significant savings in installation time decidedly compensate for the slightly more expensive installation material.
  2. Safety – the whole circuit can be realized without a single joint. This eliminates the risk of a joint leak in the future, the cause of the whole problem.
  3. Savings in the future – a significant reduction in the work time of the inspection technician during subsequent inspections. The leak test is only performed at the beginning and end of the line.
  4. 10-year warranty, which is provided by the manufacturer on MERABELL GAS PROFI material

Technical design

The required pipe dimension DN15 was selected using on-line pipe calculator A 10m coil of yellow MERABELL GAS PROFI pipe with a diameter of DN15/3/4” (M00132) was selected. The gas cooker was connected using GAS PROFI hose R1/2"–G1/2", 100 cm long (M0020).

The corrugated piping (DN15) is connected to the outlet fitting of the gas meter G4” through an adapter coupling DN25 – DN15 by means of a system connection (adapter nipple G3/4" – R1/2" for DN15, gasket for DN15 and nut G3/4" for DN15). This pipeline then passes through the core unit and through the passage into the kitchen, where it runs on the surface of the wall up to the future location of the gas appliance. At the end of the DN15/3/4” pipe, there is a system connection (nut G3/4" for DN15, gasket for DN15 and adapter nipple G3/4 "- R1/2" for DN15) with appliance shut-off, namely ball valve DN15, downstream of which a flexible 1-meter-long gas hose MERABELL GAS PROFI is fitted.

The reconstructed pipeline from the gas meter up to the gas hob is altogether 5 meters long, and thanks to the long coils of the MERABELL GAS PROFI sheathed pipe, it was possible to build whole line without a single joint. Necessary shaping of piping is made without heating, by simple manual bending. This significantly speeds up the installation itself of the gas piping and, in addition, it eliminates the risk of leaks in the joints along the route.

Main benefits of GAS PROFI pipes

The MERABELL GAS PROFI pipes are provided with an above-standard 10-year warranty and are equipped with a robust yellow protective jacket made of PE (polyethylene). For pressing purposes, this jacket can be easily removed from the ends with the help of MERABELL cutting knife (M0304). After pressing the nut, it is recommended to re-insulate the exposed pipe ends with self-vulcanizing tape (M0321).

The MERABELL GAS PROFI system is certified according to the ČSN EN 15266 standard (Stainless-steel pliable corrugated tubing kits in buildings for gas with an operating pressure of up to 0.5 bar). This EU standard allows the pipe to be routed in a wall without a protector, underground and through a building structure in a protector, when passing through a peripheral wall in a protective pipe.

Main benefits of GAS PROFI hose

The MERABELL GAS PROFI hose is certified according to the ČSN EN 15266 standard (Stainless-steel pliable corrugated tubing kits in buildings for gas with an operating pressure of up to 0.5 bar) that is already mandatory in the Europe. The hose is protected against mechanical damage on its surface by a clear PVC protective jacket and a stainless-steel braid. The swivel ending on the side of appliance (cooker) prevents the hose from twisting in the thread and possible gas leakage. The warranty period is 25 years, which allows for the use of the hose for a minimum of 8 inspection cycles.

Excerpt from standards and technical regulations

Source TPG 70401:
It is necessary to use stainless-steel pipes according to EN15266 for the construction, repairs and extension of house gas pipelines.

Source EN 1775:
Article 5.2.5 prescribes that joints made of stainless steel-flexible pipes may only be made by persons with special training and reference is made to informative Annex E for instructions on how to join this type of pipes.

Recommended installation procedure

  • measure the length of the piping from the gas meter up to the appliance
  • plan the location of holders used to fix the piping to the wall
  • prepare a protector in which the piping is to be passed through the wall
  • push the protector with piping through the wall and attach piping into respective holders
  • thread a nut on one end of the piping, press the end of the piping, fit the gasket and connect it to the gas meter
  • thread a nut on the second end of the piping, press the end of the piping, fit the gasket and install gas lock
  • instal the gas hose into the gas lock

Project assessment

The installation company uses a stainless-steel corrugated tubing almost daily, so the replacement went smoothly. The complete reconstruction took the two installers a total of 1.5 hours: half an hour for removing the old piping and 1 hour for the installation of the MERABELL GAS PROF piping system. Thus, the assumption of a significant reduction of installation time was unequivocally confirmed. From the point of view of safety, it is important that a gas pipeline without a single joint along the route was built. Strength and leakage tests were performed in compliance with TPG 704 01 standard and inspection technician prepared a report on initial revision.