Neal Manufacturing
The leather seals in a hydraulically powered sealcoating machine…
Three power options
The pump system has the greatest influence on what materials the machine can apply and how quickly. The three pump options are:
Bowie pumps, the oldest design, feature a gear that spins inside a cylinder. The gear creates suction that pulls liquid into the intake side of the pump and pushes it out the discharge side. They create enough pressure to move five or six pounds of sand per gallon, which covers most, but not all, mixes.
They also don’t require daily maintenance. However, abrasive high-sand mixes and asphalt emulsions wear down the rotary gear and cause a gap in the seal, which causes the pump to lose pressure. The pump must be disassembled to replace the gaskets and steel wear plates around the seal. These components can cost $1,200 to repair and $2,000 or more to replace.
Air-powered diaphragm pumps use an air compressor to pull liquid in as a rubber diaphragm contracts and push it out as it expands.
They handle many types of materials, including water and non-abrasive oils. Most produce enough pressure to pump mixes with as much as two pounds of sand per gallon.
However, they use rubber seals rather than leather seals, like hydraulic-powered piston pumps, or steel plates, like Bowie pumps. Rubber is less expensive than steel, but must be replaced regularly.
Hydraulic-powered piston pumps use pistons to continuously pull liquid in and push it out. Because pistons are more powerful than the compressed air that powers diaphragm pumps, the design is ideal for thick material such as asphalt emulsions and modified sealers.
The design handles mixes with 10 or more pounds of sand per gallon, a definite bonus when applying high-sand mixes to heavily trafficked streets and roads. It also moves the most material in the least amount of time and requires the least maintenance.
The piston design uses leather seals that require no daily upkeep and pump about 150,000 gallons before replacement is required. While it’s a good idea to check the pump once a week to ensure the seals stay lubricated, you’ll usually only have to rinse out the pump before long-term storage, such as for winterization.
They’re the most expensive option, but may be worth the investment.
Next page: Three application methods
