ASME TDP-1-2006 pdf free download.Recommended Practices for the Prevention of Water Damage to
Steam Turbines Used for Electric Power Generation.
ASME TDP-1 includes recommended practices concerned primarily with the prevention of water damage to steam turbines used for fossil-fuel-fired electric power generation. The practices address damage due to water, wet steam, and steam hackflow into a steam turbine. The practices are applicable to conventional steam cycle, combined cycle, and cogeneration plants. The practices cover design, operation, inspection, testing, and maintenance of those aspects of the following power plant systems and equipment concerned with preventing the induction of water into steam turbines:
(a) motive steam systems
(b) steam attemperation systems
(c) turbine extraction/admission systems
(d) feedwater heaters
(e) turbine drain system
(f) turbine steam seal system
(g) start-up systems
(h) condenser steam and water dumps
(i) steam generator sources
Any connection to the turbine is a potential source of water either by induction from external equipment or by accumulation of condensed steam. The sources treated herein specifically are those found to be most frequently involved in causing damage to turbines. Although water induction into the high and intermediate pressure turbines has historically been recognized as the most damaging, experience has shown that water induction in low pressure turbines can cause significant damage and should also be taken seriously.
2 CRITERIA
2.1 Basis
2.1.1 The recommended normal practice to prevent turbine water induction is to
(a) identify systems that have a potential to allow water to enter the turbine
(b) design, control, maintain, test, and operate these systems in a manner that prevents accumulation of water
2.1.2 However, since malfunctions do occur, one or more of the following steps are recommended to prevent turbine damage due to water induction:
(a) detect the presence of water either in the turbine or, preferably, external to the turbine before the water has caused damage
(b) isolate the water by manual or, preferably, automatic means after it has been detected
(c) dispose of the water by either manual or, preferably, automatic means after it has been detected
2.1.3 No single failure of equipment, device, or signal, or loss of electrical power, should result in water or cold steam entering the turbine.
2.1.4 Steam lines connecting to the steam turbine directly or indirectly should be designed to ensure that any saturated steam or condensate that may have collected while the line or portion of the line was out of service is drained and warmed adequately prior to being returned to service.
2.1.5 Any automatic control system used to control steam line drain valves identified in these guidelines should be designed so that the system has a means of initiating automatic valve actuation and a separate means of verifying the appropriateness of the automatic action. For example, if a drain valve is closed automatically based on a timer, something other than the timer, such as a level switch that would alarm if water were still present in the steam line, should be used to verify that the timer initiation was appropriate. If an inappropriate action is taken, an alarm should he provided.
2.1.6 An integrated control system (ICS) such as a distributed control system (DCS) can, by its inherent design, provide additional control and monitoring capability for power plant systems and equipment. Use of an ICS has been considered as an option for control and monitoring potential sources that might allow water to enter the turbine. If an ICS is available, the additional redundancy and availability of that system should be used as indicated in this Standard. However, if no ICS is provided, following the non-ICS specific recommendations is intended to still represent a conservative design for protection from water induction.
2.2 Definitions
2.2.1 General
cold steam: as a general rule, defined as steam inducted into the steam turbine with the steam temperature more than 100°F lower than the temperature expected for the operating condition of the turbine, or loss of measurable superheat. Temperature mismatches of more than 100°F may be permissible on a case-by-case basis, if this has already been considered in the design of the turbine.