California Department of Transportation

Transfer Tank Longitudinal Sealing System

The Transfer Tank Longitudinal Sealer (TTLS)

The Transfer Tank Longitudinal Sealer (TTLS) is the latest development in AHMCT's line of high production, cost effective, longitudinal crack sealing machines (LCSM).

AHMCT researchers have developed this prototype system to further enhance the capabilities of the highly successful LCSM program. This program focuses on the development and field deployment of automated longitudinal pavement crack sealing equipment to Caltrans, using polymer modified hot applied sealants.

Longitudinal crack sealing machines are ideally suited to seal joint cracks between PCC slabs as well as transitions between PCC slabs and AC shoulders. Longitudinal crack sealing equipment will not seal all the cracks on a roadway, but it will seal all types of longitudinal cracks at a continuous speed up to 5 mph. Since longitudinal cracks typically represent the largest share of highway cracks sealed, high production longitudinal sealing can play a significant role in reducing the miles of open pavement cracks which leads to premature pavement deterioration.

The advantages of using a longitudinal crack sealing machine over the standard hand operation become even more remarkable when the operation is conducted without establishing a fixed lane closure. The Transfer Tank Longitudinal Sealer design was specifically tailored to capitalize on the advantage of operation within moving lane closures. The Transfer Tank Longitudinal Sealer was also designed to test an innovative new approach that could potentially provide a virtually continuous hot sealant supply. This could solve the insufficient hot sealant supply problem that has limited the maximum production rate of the Longitudinal Crack Sealing Machine.

The Transfer Tank Longitudinal Sealer Concept

The Transfer Tank Longitudinal Sealer is based on the concept of decoupling the task of melting large quantities of sealant from the highway seal application operation.

TTLS Application Truck

TTLS Sealant Application Truck
TTLS Sealant Application Truck

The seal application truck is the only part of the TTLS system that actually seals longitudinal cracks on the highway. Sealing can be conducted off either side of the truck and the entire operation of the machine can be monitored and controlled from inside the high visibility cab. This eliminates the need for any direct worker exposure to traffic and enhances continuous nature of the moving lane closure operation. The truck carries a 400 gallon propane fired oil jacketed sealant melter kettle which supplies material to the application shoe through a heated line and a variable speed sealant pump. An accurate material level is obtained from load sensing tank mountings.

TTLS Transfer Tank Trailer

TTLS Transfer Tank Trailer
TTLS Transfer Tank Trailer

High production crack sealing requires an equal ability to produce hot sealant at a high production rate. The sealant transfer tank trailer was designed to function as hot sealant re-supply reservoir for the seal application truck. The transfer trailer is oil jacketed, propane fired and has a 600 gallon capacity. The transfer tank also has a load sensing trailer mounting to provide for an accurate material level. A flexible large diameter oil heated transfer hose provides the means to quickly transfer hot sealant to the truck tank. The capacity of the trailer tank was purposely chosen to be far greater than the truck tank, so the remaining hot sealant could accelerate the recovery time. Ideally the transfer tank would recover in time to repeat the process as necessary.

TTLS Sealant Transfer Process

High Speed Sealant Transfer
High Speed Sealant Transfer

TTLS Sealant Transfer Process

The TTLS transfer system was designed to quickly transfer 400 gallons of very hot sealant. To avoid potential dangers a redundant safety system was incorporated into the transfer controller. It senses the transfer hose connection and will stop any sealant flow should the connection become unlocked. This prevents the possibility of leakage. The transfer controller also monitors both tank levels during sealant transfer to mitigate the potential of overfilling the smaller truck tank.

Current Status 

The Transfer Tank Longitudinal Sealer prototype system is operational and is currently progressing through initial field testing. Due to the nature of the machine and the material it dispenses, the bulk of the initial field testing must be preformed on the highway, the only place where miles of longitudinal crack can be found. The seal applicator truck can operate solo and it will be tested first on the highway. The main goals for initial testing are to adopt an operational procedure and to further develop the complexity of the control program. Initial testing and further refinement of the sealant transfer trailer will be fit in with the truck testing as appropriate.

Video of TTLS Highway Test 12/14/05

For Additional Information 

  Arvern Lofton
Caltrans Project Manager
  Steve Velinsky 530-752-4166
  Duane Bennett 30-754-7401