Pushrod and crawler inspection cameras are the two most common types of cameras used for surveying underground pipes, sewers, etc. How, though, do they differ and under what circumstances would you need one rather than the other?
Crawler systems have a camera attached to the front of a wheeled unit known as a ‘crawler’ whereas pushrod systems have a camera attached directly to the end of a reel. Pushrods are therefore pushed through pipes, whilst crawler units are driven through them.
Generally, pushrod systems (like this Minicam SoloPro+) are more portable, are suitable for use in small-diameter pipes and have lower maximum inspection lengths. Crawler systems (like Minicam’s Proteus Lite) usually have more features, are larger and, thanks to their longer reels, can be used to inspect longer stretches of
pipe before the operative needs to stop surveying and find an alternative entry point.
Logically, you’d probably assume that you’ll always be better off choosing a crawler system, but this isn’t necessarily the case. Firstly, crawler systems cost more to purchase or hire. Secondly, depending on what you’re surveying and your overall objectives, there are times where a pushrod system is not just more economical but also better suited to the task at hand.
Pushrods are better suited to DN100 and smaller pipes
Crawlers vary in size and the smallest can be used to inspect DN100 pipes. If the pipe that needs to be surveyed is smaller, a crawler simply will not fit. Even if the pipe’s diameter happens to be DN100, a pushrod is still likely to be a better option if you’re surveying a section of pipe less than 120 metres in length or where you’re likely to encounter obstructions or debris. This is because the largest pushrod has a maximum inspection length of 120 metres and specialist crawlers designed for smaller pipes have low ground clearance meaning that they’re more likely to get caught on foreign objects in the pipe.
But crawlers aren’t always better for larger pipes
Yes, a crawler system will be the only option when surveying large pipes, but there are accessories that make using a pushrod system in pipes of up to DN225 diameter practicable. A simple skid will secure the camera head in DN150 pipes, whilst a roller skid (a skid featuring pivoting arms with wheels) can be used to inspect pipes between DN150 and DN225.
If the pipe in question is over DN225, however, a crawler system will be needed.
Pushrods are easier to transport
A Minicam SoloPro+ with a 60 metre reel weighs approximately 25KGs whereas the company’s starter crawler system, the Proteus Lite, weighs close to 50KGs. The SoloPro+ also has wheels built onto its frame. The Proteus Lite, on the other hand, requires a separate wheeled trolley, adding both additional weight and cost.
A drainage van can make it much easier to move systems from one location to another, as well as provide a reliable way to power systems. These benefits, though, disappear if the survey entry point cannot be accessed by a vehicle.
Crawlers can survey larger stretches of pipe in one go
The SoloPro+ has a maximum reel length of 120 metres whilst Proteus crawler systems are available with reels of up to 500m. As a result, provided more than 120 metres of pipe can be surveyed at once, crawler systems are more efficient as there’s no need for operatives to remove the systems and find new entry points following their pushrod having run out of reel.
Conclusion
Pushrod systems are more affordable than crawler systems and provided you’re surveying short lengths of pipe less than DN225, are likely to be a better option for this reason. They’re also easier to transport making them a better solution where specialist vehicles cannot park near an entry point.
Crawlers, on the other hand, can survey significantly larger lengths of pipe in a single go making them more efficient. They’re also the only real option when surveying pipes larger than DN225. Finally, whilst pushrod systems are easier to move closer to inspection points (when a van or other vehicle cannot be used), this can be offset by adding a trolley unit that’ll make it easier for operatives to move a crawler system from one place to another, though this results in further outlay on an already more expensive system.
Determining which system is better suited to your company will require you to consider the nature of the work you regularly undertake, the frequency with which you receive requests for certain types of surveying work and your plans for expansion. In the event that you’re regularly asked to perform certain types of work but are unable to undertake it due to a lack of equipment but these requests still aren’t frequent enough to justify the cost of a crawler inspection system, hiring an underground inspection system is certainly going to be more cost effective in the immediate term.
If you’re unsure of which type of system you need, please don’t hesitate to contact DCR. We’ll be happy to talk you through not just whether you’d be better served by a pushrod or crawler system, but variations of these systems and even alternative products where possible too.