The University of Life teaches us that, ironically, the most important things to do are often the hardest things to do – just try asking any politician about this! Similarly, experience in the field of working on turbine supervisory instrumentation projects, often shows that it is the most important parameters to be measured which are the hardest to get right. Even more strange is that these parameters are at best, given scant consideration, and at worst, they are overlooked altogether until the last moment, just before the turbine is being closed up, or just as it is about to be run, when it is often then too late.
Thrust, Differential Expansion and Case Expansion can have such an impact on the efficient operation and on the general health of the equipment being monitored that it is clearly an anomaly that these parameters are probably the least understood of the TSI parameters. The reasons for this are probably many, not least that the other main parameters of Vibration, Temperature and Valve Position are easier to set up, and are well established and documented. Other historical and anecdotal evidence points to a general scarcity of knowledge and understanding as to the benefits and pitfalls associated with measuring these parameters.
Lack of ownership of the supervisory system is often cited as the reason for this, with no clear responsibility being taken either for the collation of relevant information or for making appropriate allowance in the outage schedule. This is particularly the case for the differential expansion, the setting and checking of which is necessarily time consuming and often requires mechanical and electrical support from outage engineers.
This paper is an attempt to clarify the requirements and to highlight the pitfalls associated with measuring Thrust, Differential Expansion and Case Expansion, which will, it is hoped, lead to a more proactive approach towards them, thereby ensuring that they are adequately provided for in any project schedule.