Dense engineering networks and high maintenance requirements are the reality for the gasworks in the two largest cities in the Czech Republic, Prague and Brno, and to improve the security they have installed AVK gate valves with purge points.
The companies who own the gas pipelines – Prazska plynarenska servis distribuce a.s. (Prague) and GridServices - innogy Group (Brno) – have installed AVK steel purge point valves on two steel pipes DN250 and DN300.
Exhausts for bypass and control
AVK steel purge point valves have DN50 exhausts which are used as a bypass to supply a parallel gas pipeline in the event of a malfunction. The exhausts can also be used for control pressure measurements or – in the case of technological interventions in the pipelines – for degassing (gas discharge) and deaeration (air extraction).
The purge point valves are replacing the traditional way of creating purge points which has typically been done by mounting DN25 PE 32 pipes on the pipeline. The normal operating pressure of natural gas in the pipeline is up to 4 bar and the DN25 outlets (purge points) usually used by the customers are inadequate on large gas pipelines. The DN50 exhausts are thus an improvement for the two Czech gas companies, and others indeed, compared to the usual DN25 purge points.
The valves were connected into the existing steel pipes using steel couplings. Some of the old steel pipes were replaced by new PE pipes, and in those cases steel/PE couplings were used for the connections. The assembly went smoothly, and the installations were finalised by adding extension spindles and surface boxes.
AVK gate valves with purge points
Purge points are used for:
- purge residual gas in an isolated pipeline section allowing safe maintenance, repair or extension of the pipe system
- by-pass the isolated section to ensure continuous gas supply
- detect leakages in the pipeline by measuring the pressure by means of pressure gauges
Facts about AVK purge point valves
- Resilient seated valve made of cast steel and with wedge of ductile iron vulcanised with NBR rubber
- Integrated up- and downstream purge points
- Purge pipes are assembled with CE approved ball valves and blind flanges
- Long steel spigot welding ends according to DIN 3239 part 1
- The welding process is performed by certified welders and all welds undergo non-destructive X-ray testing carried out by a certified inspection company
- Valves are as standard with external PUR coating
- Full traceability of every pressure bearing component
- Available with 3.1 certificate