Slab lifting with polymers is rapidly replacing old technologies because it’s fast, strong, doesn’t shrink, and has a low impact on the environment. So it’s no surprise that we get a lot of inquiries from contractors interested in adding this service, in addition to individuals wanting to create a startup slab lifting business. So what exactly are we talking about in terms of the essential gear?
A slab lifting rig is a rolling business unto itself. It is a self contained, turnkey, mobile unit that has all of the equipment necessary to perform the work. There are a variety of configurations but all of these setups will contain the following: Trailer or Box Truck, Power Source, Compressed Air System, Fluid Transfer System, Proportioner Pump, Heated Hoses, and Impingement Gun. Let’s look at these in more detail.
Trailers and Box Trucks
This is a matter of preference but since this business is mobile, you need to have one or the other (unless you start out with the ultra-mobile PolyBadger system for small jobs). I prefer trailers because they are easier to load material into if you don’t have a forklift. They are lower and can be equipped with a ramp door for the back of the unit. A trailer can be dropped at the jobsite freeing up the pickup truck for scouting other jobs or for grabbing supplies. Box trucks do have their place too and in some cases may be required for performing slab lifting for DOT work. In both cases we recommend a high ceiling height and at least 16’ of floor space to work with.
Although some slab lifting rigs are designed to work off of shore power, most of them contain a generator to provide power. A rig that is properly built will have a breaker panel allowing the operator to switch on and off the different systems that require power. Depending on the type of proportioner installed in the rig (and the size of the heaters), the generator can be either a gasoline powered unit at approx 18kw, or a diesel powered generator ranging from 22kw to 40+kw power.
Compressed Air System
There are some proportioner pumps such as PMC’s PA-25, where the main pumping action is done through pneumatic power. These units have high CFM requirements and thus need a larger air compressor. Other proportioners like PMC’s PH Series operate off of hydraulic motors and don’t require air at all.
Some air is always needed though, for running the pumps that transfer the polyurethane from drums and totes over to the proportioner. A complete compressed air system will always include an air compressor and air drying system. An air drying system can be either desiccant style or refrigerated.
Fluid Transfer System
Polyurethane lifting foams are two component systems which means there is an “A” side and a “B” side. When these two components meet they react and form structural foam. Because the reaction is so fast, great care is taken to ensure the A and B components are kept separate until the actual point of spraying or injecting. A typical slab lifting rig is going to use either drum transfer pumps (sometimes referred to as stick pumps) or diaphragm pumps to pull material from the drum or tote sets and then transfer that material over to the proportioner. There will be a dedicated “A” side pump and a dedicated “B” side pump.
The proportioner is the heart of the slab lifting rig. Every proportioner should have the power to heat the A side and B side materials to the required temperatures while the materials are actually flowing. Additionally, a proportioner must then also have the pumping power to push the two preheated materials through up to 410’ of heated hoses, maintaining up to 2000 psi the entire way. Because the A material (ISO) is thinner than the B material (Polyol), separate temperatures must be maintained both within the proportioner and through the length of the heated hose. Solid state controls are used to monitor and adjust the temperatures.
The heated hose system is actually a bundle of a few different hoses. There is an individual hose for the A (ISO) material and B (Poly). Each of those hoses has a heating element to keep the materials at their correct temperatures. PMC makes a superior heated hose that has braided heating element s that completely surround the hose for even heat. Heated hoses usually come in 50’ sections and between the second to last and the last section will be a temperature sensing unit (TSU) that relays temperature information back to the proportioner.
This TSU is sending the info through a thermocouple wire which runs the length of the hoses out to the TSU. The temperature information relayed to the proportioner lets it know whether to send more power or to back off the power as necessary.
For example, on a hot day there may be very little hose heat required while on a cold day a constant stream of power will be keeping the materials in the hoses up to temperature. Also within the heated hose bundle will be an air hose for compressed air to power air purge impingement guns. For fluid purge impingement guns designed for slab lifting, a fluid line will also be bundled together to transfer the flush required to blast clean the mix chamber of the gun.
Click the MixMaster gun link to see this type of gun used for slab lifting and resisting back pressure inherent in this line of work. Finally, all of the hoses are contained within a durable scuff jacket to keep the hoses from being damaged while dragged around the job site.
Whether spraying foam or injecting foam for slab lifting, these A and B materials must finally meet. This meeting occurs within an impingement gun. The materials are “impinged” or squeezed through tiny orifices which generates a high pressure stream of A and B (Iso and Polyol). When the preheated, high pressure streams of material meet, the reaction is almost immediate. At this point the mixed materials are ejected through the end of the gun, and beneath a slab.
The ensuing reaction, in addition to the pressure from the pump, generates the force required to lift. This could be either lifting a small sidewalk slab or lifting a railroad track or building foundation. Frankly it is incredible what the entire system working together can do. Because of the incredible back pressure generated from this operation, a gun like the MixMaster Pro is recommended because it is designed specifically for this application. It is not a spray foam gun modified for lifting.
Well this covers all of the main components that make up a slab lifting rig. There are other accessories like fresh air systems, air conditioning, heaters, etc that can be incorporated into a rig but how you customize it is up to you and your wallet. The next blog will include other tools of the trade that will assist you in your success.