In this blog post we will not only outline what and why pipe lasers are used but will also provide five key steps to consider and follow when using pipe lasers. The use of pipe lasers is an integral part of any construction site, especially in the underground utilities industry, it can improve worker productivity and provides accurate results. For this reason, it is important that you know how to use them effectively.
What is a Pipe Laser?
Pipe lasers can be used in manhole, above ground and even within the pipe itself. Pipe lasers are used to provide precise control (both horizontal & vertical) when laying sewer pipes. They can be used to provide this linear control to other utilities where apparatus is laid at a set gradient in a straight line.
They can be set up in a manhole excavation, an existing MH (manhole) structure or in the pipe leading out of a MH. The preferred setup location is dictated by other factors, which will become clear later. The inherent accuracy of the laser ensures that the correct position and level of each MH, as designed, is achieved.
Who uses a pipe laser?
Pipe lasers are mostly used by the underground utility industry which includes public service infrastructures installed beneath the ground surface. Additionally, they are also used in the construction and surveying industry. Having a pipe laser is important for construction sites as it increases the productivity of workers and provides accurate results.
Figure 1 is a sketch that outlines the complexity of pipelines on a typical site.
To avoid pipe clashes the design levels and lines must be maintained otherwise pipes will not traverse under or over one another as intended on the design. When this occurs a major redesign of the pipe layout will be required at a considerable expense. Pipes already placed may have to be excavated and re-laid to overcome the problems.
The other sketch also, details the pipework elements such as sewer description, pipe diameter, proposed gradient and MH positions. The MH details (Figure 2) include Diameter, Cover level and Invert level will be presented in tabular form on the drawing.
Setting up and using a pipe laser:
- The starting point for laying a new sewer will normally be from an existing pipe or MH. The position and Invert level of this initial connection must be checked. The start point could also be at a pumping station or ditch outfall. If the design values provided are correct, then take the gradient of the pipeline away from the outfall which is calculated using the invert levels of the existing and the next proposed MH or chamber.
- It is essential to calculate the gradients from these pipe termination values, using both distance and inverts. The quoted gradients should not be relied on as they can be approximate design gradients. Where MHs are moved, the gradients shown are not always revised.
- The pipe laser is usually set in the MH or trench on a stable level base, such as a concrete block. The horizontal alignment of the laser is critical to ensure that the laser line in the excavation is coincident with the excavator trench line at ground level. The Zeta125S has a plumb laser to assist this setup.
- As pipe laying progresses, the laser can be transferred to inside the pipe. This enables pipe air testing to be carried out on each pipe as laid. The laser is not placed in the first pipe as connection of the following pipe will cause disturbance of the laser. The laser can be placed in the pipe if, as shown on the MH details, the construction is complete, and the first pipe is built in and stable.
- When some 10-15 metres of pipe have been laid and backfilled, the laser is transferred to the pipe. This pipe length gives a sufficiently long baseline to maintain the correct alignment.
Some general tips
It is best practice to commence at the outfall, having established the actual 3D position. Many outfalls are on existing roads, where other utilities are present. On shallow drains, a clash with watermains is a possibility, so any redesign can be carried out before most of the pipework is installed.
Extreme variations in temperature between pipes lowered from the ground (exposed to sunshine in summer) and deep excavations(cooler) can cause shimmer and a decrease in accuracy.
The robust and easy to use features of the GeoMax Zeta125 pipe laser allow construction sites and surveyors to accurately measure pipe grades. This makes it an essential asset for all construction workers working on broad spectrum of projects.
Surveytech agrees that the GeoMax Zeta125 pipe lasers is the best product to use when it comes to pipe lasers and as such hires them out for your use. The product and hiring information can be found here: https://survey-tech.co.uk/collections/pipe-lasers.
Please don’t hesitate to contact Surveytech with any questions you have!