Steam Turbine Inspections: A Comprehensive Guide

What Is a Steam Turbine Inspection?

A steam turbine inspection is a regular assessment of steam turbines as part of their maintenance and loss prevention. The inspection is conducted by a loss prevention inspector who reviews, records, and witnesses different operations and tests to determine if the machine is working at its optimum. It is also used to determine whether the turbines are properly and regularly maintained. These inspections are necessary to ensure the service life of a turbine is maximized and also to ensure the safety of the people working around them.

During an inspection, the inspector will search for a few things, including:

• Necessary certifications and documentations
• Unusual sounds using a borescope, a tool that enables inspectors to determine the condition of the turbine without dismantling the machine.
• Damages, cleanliness, and strength of welded connections
• The integrity and strength of turbine parts, such as emergency stop valves and steam chest
• Safety and alarm systems of the turbine

In this article you will learn:

1. Why and how often Steam Turbines need to be inspected

2. How Steam Turbines should be maintained

3. Why a digital checklist complements Steam Turbine Inspections perfectly

How Often Should Steam Turbines Be Inspected?

Steam turbines are an important element in providing electricity all around the country. Thus, proper and regular maintenance plays a critical role to ensure their optimal performance. A properly maintained turbine can last up to 50 years on average.

An effective steam turbine maintenance starts with regular preventive maintenance conducted on a daily, weekly, monthly, and annual basis. Maintenance personnel and operators can do most of these routine tasks. On the other hand, repairs, overhauls, and necessary maintenance should be done by experts and experienced service engineers.

Some of the inspections and maintenance that take place include:

• Monthly and semi-annual inspections
  These are less frequent preventive maintenance tasks performed on-site.
• Annual inspections
  These types of checkups include assessing machine performance and operating problems. The inspector will also review parts inventory and discuss the necessary training operators need to undergo.
• Minor overhauls
  These happen every two to three years where bearings and seals are physically inspected. During this type of maintenance, bearing housings are opened, seals and bearings are removed and inspected, and components are replaced when necessary.
• Major overhauls
  They are more detailed than minor overhauls and done every five years. During this time, the entire turbine including the rotors, casing, gear lubrication system and controls, and couplings are inspected and overhauled.

Aside from these inspections, a routine inspection is also conducted by steam turbine operators. All important activities and periodic observations are documented in a log during routine checkups. Some of the tasks included on the steam turbine inspection checklist are:

• Monitoring changes in steam consumption
• Calculating the efficiency of unit and casing using outlet and inlet temperatures and pressures
• Scanning casing temperatures to identify leaks and other damages
• Measuring stage pressures
• Conducting vibration analyses to monitor machine condition
• Measuring the differential movement of the turbine’s shaft and casing.

How to Maintain a Steam Turbine?

To achieve optimum and efficient performance, steam turbines should have the right steam pressure at the turbine inlet. Furthermore, the steam should have no condensate entrapment. The following are the four best practices to achieve optimum turbine operation and maintenance:

1. Steam Quality

If there’s condensate entrapment in the steam supply, the turbine steam rates increase while its efficiency decreases. It also causes erosion of the equipment’s components. To prevent this from happening, the steam supply lines and components should be insulated.

Furthermore, steam supply lines should be equipped with condensate removal components which include steam trap stations and steam line trap stations.

2. Pipe Contraction and Expansion

Turbine flanges are prone to absorb excessive forces from thermal expansion, pipe dead weight, spring rate, and thrust. Thus, they need to be analyzed, reviewed, and installed properly to prevent these excess forces.

The steam piping design should leave room for expansion and contraction. The steam lines should contain the correct number of right-sized hanger supports.

Guides should make sure that the force on the turbine must not go beyond the values stated by the manufacturer.

3. Supply and Exhaust Line Size

The steam piping should be able to handle the full-line steam pressure. The size of the supply line should be calculated for the load and the pressure drops. Pressure loss in the supply line significantly affects turbine performance.

4. Steam Piping Support

Steam pipings need support for pipe dead weight. There are two types of support for this — spring and rigid designs.

Rigid support restricts pipe movement in conjunction with an expansion joint. A typical installation uses supports, anchors, and guides. Although these components have different functions, they all support steam piping. Conducting a detailed analysis will ensure that proper weights are supported.

How a Digital Checklist Helps You Perform Steam Turbine Inspections

With Lumiform’s audit app you can easily perform a multitude of safety and quality inspections on the go from your smartphone or tablet - be it online or offline. Easily create checklists for Steam Turbine Inspections of any kind and easily collect data in the field to reduce machine errors and threats to employees.

• Lumiform offers more than 10,000 ready-made templates to choose from, so that you can quickly and safely go digital.
• If you prefer to create your own checklists, why not try Lumiform’s flexible form builder? It helps you convert any paper-based Steam Turbine Inspection sheets into a digital format within minutes.
• With the intuitive and easy-to-use mobile app you and your inspectors can perform audits with ease and save time.
• All inspection results are automatically summarised in a report and can be sent to responsible personnel on-the-fly.
• Comprehensive and automated analyses help you uncover threats and errors fast and effectively and thus allow you to concentrate on improving processes continuously.