Catalyst Durability

Nett^® catalysts are designed and manufactured to maintain high activity for the entire life-span of the engine. There are, however, circumstances under which the catalyst life might be shortened. There are two major causes of catalyst deactivation:

• high temperature
• poisoning.

Nett^® catalyst may suffer thermal degradation and loss of activity when exposed to temperatures above 650°C (1200°F) for prolonged periods of time. LPG engines have high exhaust temperatures, much higher than diesel and usually higher than gasoline, and may be close to the above limit. Catalytic combustion of carbon monoxide and hydrocarbons further increases the temperature in the catalyst. Good engine maintenance is very important to avoid catalyst overheating. Many engine problems might result in higher than usual exhaust temperatures. Engine misfire is extremely dangerous; unburned fuel is oxidized in the catalyst with a tremendous release of heat. The catalyst shell changes its color to a spectacular cherry-red but the life span of the catalyst could be shortened to a few hundred hours. A pyrometer to monitor exhaust temperature at the outlet from the catalyst may be supplied with Nett^® catalytic mufflers. The pyrometer gauge installs in the operator's dashboard to enable action in case of overheating. High exhaust temperatures could be a sign of either a poor engine tune-up with excessive emissions or a more serious engine problem.

Several chemical elements have the ability to selectively poison or mask the catalyst surface. Some of the substances to be avoided, e.g. phosphorus, may be present in the engine lubricating oil. Catalyst poisoning is usually not a serious problem on LPG engines but may occur as a result of excessive lube oil consumption.