Why is it that the overspeed testing are required to test?

Why is it that the overspeed testing are required to test?

Turbine overspeed events lead to costly and dangerous catastrophic failures. Therefore the overspeed system has to be periodically tested to ensure the system has the adequate response time to protect the turbines, plants and personnel. Regular, periodic testing is the only way to ensure a protection system is working.

Why is an overspeed trip necessary on a steam turbine?

The overspeed trip system protects personnel and plant systems by preventing missiles that can result when turbines disintegrate at higher than normal rotational speeds. It also protects against financial losses of an extended outage and premature turbine replacement.

How does a turbine overspeed trip work?

When turbine speed reaches an overspeed condition (i.e., 10% above running speed), the centrifugal force on the bolt overcomes the spring force, the bolt moves out and hits a lever which moves the oil dump valve causing depressurization of the oil supply to all steam valves.

What is an overspeed test?

Overspeed testing allows us to run a fan at an increased speed for a given amount of time and prove that it will withstand the customer’s specific application.

What is the purpose of reheating steam in a turbine system?

The main purpose of reheating is to avoid excess moisture in steam at the end of expansion to protect the turbine.

What is the first line of defense against turbine overspeed?

10.2.2.4 Turbine Overspeed Protection System The normal speed control system (EHC) comprises a first line of defense against turbine overspeed.

What happens when a turbine trips?

The turbine trip signal initiates fast closure of all steam inlet valves (e.g., turbine stop valves – TSVs) to block steam flow through the turbine. In a turbine trip event, a malfunction of a turbine or reactor system causes the turbine to trip off the line by abruptly stopping steam flow to the turbine.

What operates the overspeed trip?

Just like any other conventional bolt, the over speed trip bolt is held in place by using a nut and a spring. When the over speed trip operates, the pin holding the steam stop valve in the open position is released, closing the valve and stopping the flow of both, the steam and the fuel.

What are the electronic overspeed trip consist?

Electronic overspeed protection consists of a gear or other measuring surface, speed sensors and a measuring system with trip logic and relay outputs. The speed sensors look at the measuring surface and give a sine or square wave signal, which the measuring system sees as pulses.

What happens if you overspeed?

If the engine overspeeds, the airflow through the intake will rise to an abnormal level. This causes the flap valve to snap shut, starving the engine of air and shutting it down.

Does reheat affect steam quality?

In case of two reheats, steam is super-heated twice at different constant temperatures. A high reheat pressure increases the the moisture content at turbine exhaust which results in scaling and it should be optimised. Thus the work produced is increased ,thereby efficiency increases.