This paper proposes a routing algorithm that enhances throughput and decreases end-to-end delay in industrial cognitive radio sensor networks (ICRSNs) based on ISA100.11a. In ICRSNs, the throughput is downgraded by interference from primary networks. The proposed routing algorithm is targeted at large-scale networks where data are forwarded through different clusters on their way to the sink. By estimating the maximum throughput for each path, the data can be forwarded through the most optimal path. Simulation results show that our scheme can enhance throughput and decrease end-to-end delay.