GAUGE BOARD

Gauge boards are optional on asphalt tanks (Fig. 1). They indicate the asphalt level inside the tank. Gauge boards are simple, reliable devices, but they do require a little maintenance to prevent problems that could adversely affect reliability. The red “bulls eye” should run up and down the scale smoothly as the tank is filled and as asphalt is used. However, there is a problem if it hangs or if you find slack in its running cable. Not only could this result in unreliable level indications, but could cause shutoff problems as explained later.

Problems with gauge boards are usually limited to build-up of asphalt on the cable that supports the bulls eye. Consequently, the cable can’t run freely through the P-trap on top of the tank (Fig. 8). The solution is to manually pull out as much of the cable as you can and clean the asphalt from it.

Figure 8. Support cable for float on gauge board passes through P-trap shown here. Remove plug on side of P-trap to add oil.

Figure 9. Float for gauge board is supported by single cable and is guided by two other cables, one on each side.

Another problem is that the cable may slip off of one or more of the pulleys and wedge to one side of the pulley. This will bind the cable. The remedy is to remove the covers from the P-trap and reset the cable around the pulley.

Another problem that can cause the bulls eye to hang is misalignment at one or more joints of the scale where the segments of the scale are fitted together. The bulls eye can hang on a misaligned edge as it passes over the joint. The remedy is to realign the edges of the joints.

A liquid seal pulley support (better known as the “P-trap”) is on top of the tank. The cable that supports the bulls eye travels through the P-trap and over pulleys inside the P-trap. The P-trap allows the cable to travel through the top of the tank while preventing asphalt fumes from escaping the tank. It contains oil that prevents the fumes from escaping. Oil in the P-trap should be checked monthly. A plug in the side of the P-trap can be removed in order to put oil in the lower section of the P-trap.

The P-trap contains three pulleys that guide the cable through the P-trap. After cleaning the support cable be sure to check that the pulleys are turning freely. You should be able to determine this by pulling down on the bulls eye causing the cable to manually raise the float. You should not encounter any unusual resistance in cable travel except for the effort needed to raise the float inside the tank. Unusual resistance may indicate that one or more of the pulleys is not turning freely. In that case, remove covers from the pulleys and make sure they are not distorted or damaged.