Pipe renewal in a dairy
The "DMK Deutsches Milchkontor GmbH" with its 26 locations in ten German federal states and approximately 7,500 employees is Germany's greatest dairy company; the primary product milk is delivered by more than 8,300 active producers. One of the 26 DMK locations is the Saxon community of Edewecht near Oldenburg. Sections of the existing vitrified clay pipe were severely damaged in several places, due to many long years in service; their technical failure demanded renewal of the line. Affected was a mains, 55 m in length, and a 25 m long mains which approaches the first mains at a right angle. These two sections showed the typical damage symptoms: lengthwise and transverse fractures were spread along these two; some spots featured shard formation and even structural collapse.
The "DMK Deutsches Milchkontor GmbH" with its 26 locations in ten German federal states and approximately 7,500 employees is Germany's greatest dairy company; the primary product milk is delivered by more than 8,300 active producers. The co-operatively organised enterprise with its headquarters in the town of Zeven in Lower Saxony processes approximately 6.7 billion kilograms of milk annually. Making internationally accredited quality products, it belongs to the leading pan-European companies for dairy produce.
One of the 26 DMK locations is the Saxon community of Edewecht near Oldenburg. Here, round about 590 employees contribute to the supply of the international markets with milk products "Made in Germany". The corporate facilities of this DMK location with its grand silos, numerous elongated production halls and outhouses form a square block of formidable circumference - surrounded by pastures green in the middle of the countryside. Beneath the roofs of these production halls, high-tech state-of-the-art plants process thousands of litres of fresh milk, making butter, cheese, powdered whey and the like.
In one of these large halls in Edewecht, short and long conveyor belts and roads perform their jobs, wide and narrow pipes of supply and discharge systems course through, pumps, containers, tanks, cooling units and others are scattered everywhere - most of them made of high-quality stainless steel. Everything stands on a wall-to-wall tiled floor in hygienic and well-tended surroundings; of course, industrial hygiene and diligence are the alpha and omega in a milk processing business.
When looking at this extensive equipment, one thing is certain: for the production processes, huge amounts of fresh water are required and similar amounts of waste water have to be discharged again after use. The last item is our keyword: the waste water discharge system. Discharge takes place through lines made of vitrified clay pipes ND 200 which are installed directly beneath the tiled floor at a depth between 1.50 and 2.00 m. At times, the waste water has temperatures of 80 °C (flushing water) and contains chemicals such as nitric acid, caustic soda and phosphoric acid (in very low concentration of 1 to 2 %, however) as well as Javelle water and alkaline foam cleaners. These chemicals, which are applied in all sectors of food production, accrue with the frequent cleaning and disinfection of the milk production facilities and machinery as well as within the area of supply and discharge pipes. Also, a 20 percent brine solution which is required for making certain products is discharged through the waste water system. Further waste waters flow into the line via installed floor inlets in the hall; these stem from occasional spillovers from a variety of different process phases.
Sections of the existing vitrified clay pipe were severely damaged in several places, due to many long years in service; their technical failure demanded renewal of the line. Affected was a mains, 55 m in length, and a 25 m long mains which approaches the first mains at a right angle. These two sections showed the typical damage symptoms: lengthwise and transverse fractures were spread along these two; some spots featured shard formation and even structural collapse. Swift and reflected action was asked for in view of the sensitive location and the associated acuteness of a renewal. The following points had to be considered:
- intrusion into a (running) food producing business
- compliance with/requirements of the hygiene regulations
- confinement of the working space due to the production plant
- skirting the erected scaffolding for the current job of repairing the ceiling
- the course of the waste water line directly beneath the floor of the hall
- the demands on the pipe material to be selected.
The situation quickly became clear and the professionals on site made their decision: for the renewal of the badly damaged mains, static pipe bursting was the solution; it offers the trenchless renewal in the same bore path, replacing the old pipe by a new pipe with the same diameter or even larger. The GRUNDOBURST400G produced by TRACTO-TECHNIK was definitely the optimal choice for this venture with its very specific demands. Following the expertise of the manufacturer, the responsible party chose Concept-HL thrust pipes made of PP-HM for their new pipes (ND/OD 225, installation length 1.00 m), which are approved by DIBT (German institute for building technology).
With these, all requirements could be satisfied and adequate solutions were found for all constraints:
- only small hand excavations were needed (the sensitive hygiene regulations would not allow large machine application)
- the existing openings in the floor were easily enlarged for manholes/pits to accommodate the pipe bursting rig
- the compact dimensions of the pipe bursting rig made an unrestricted application in the confined working spaces possible - it also helped to by-pass the working scaffolds in the hall
- the light-weight pipe burster was easily transported without additional machinery
- rapid installation and a quick new start-up of the plant hardly interfered with the day-to-day production business
- rapid work cycles and high performance made sure of = minimal work restrictions of the production process = high daily output with rapid installation progress (cost-saving)
- the long service life of the new pipes is economically attractive
- the PP-HM thrust pipes are resistant to cleaning agents and disinfectants
- the PP-HM thrust pipes are equipped with smooth spigot and socket joints inside and out, with two fixedly inserted lip seals.
The starting signal for the pipe renewal works was cued by extending two existing, normally tightly sealed floor openings by means of a diamond cutter and two further hand excavations for positioning the GRUNDOBURST400G. The utilised 54 mm QuickLock bursting rods with guiding mandrel were easily pushed through the two mains with lengths of 55 m and 25 m. When the roller blades where pulled back, the old pipes made of vitrified clay and the shards, which were the only remainders of the defective pipe in some parts, were broken up by the bursting head and the broken pieces displaced into the surrounding soil (sand) just as easily, while the new MV thrust pipes made of PP-HM were pulled in at the same time. It became obvious that the tensile load, monitored by a GRUNDOLOG measuring instrument, never came close to exceeding the permissible threshold value of 150 kN.
The actual pipe renewal works were polished off quickly and smoothly with erecting, setting up and conversion of the equipment in two short days, to the utter satisfaction of all. In the meantime, the dairy continued to produce all the many goods made of luscious milk, unhampered and without hindrance.
Further 80 m of the damaged old pipe at the DMK GmbH location Edewecht are still waiting for repair, this job will also be managed in no time at all.