Technically speaking

25 January 2019

Andreas Halvarsson, Ken Grubb and Jerry Westermann outline the important work that ICOLD's Hydromechanical Technical Committee carries out in relation to the design, manufacture and maintenance of hydromechanical equipment.

A hydromechanical technical committee was first mooted by the Morocco Committee on Large Dams and came into being in 2014 via the ICOLD General Assembly.

It has been active in its short life often meeting via coordinated Skype meetings between ICOLD conferences. It is widely geographically represented currently as shown in the table.

The committee’s terms of reference are to consider and analyse current practices as regards the design, manufacture and maintenance of hydromechanical equipment.

Committee members have been collecting statistical data on the equipment used to protect dams and also information on incidents and near misses relating to that machinery. It is hoped that the information will eventually be used as a vehicle for sharing lessons learned and thus allow everybody to learn from the past.

In 2016 the committee ran a Workshop at the ICOLD conference in South Africa on the subject of “Best Practices for Achieving Reliability of Flood Discharge Gates” which was widely attended.

This subject is the basis of a major bulletin being developed by the committee over the last three years. The rationale for this bulletin was summed up by the committee as follows:

Many of the gated spillways built in various parts of the world in the 1800s are still in service due to their durability and substantial replacement cost. The design guidelines used for these older gates varied considerably between Europe, North America, Asia and other parts of the world. In many cases, it can be argued that these guidelines do not reflect the higher standards of safety that presently are in place, nor do they necessarily consider the changes that have taken place in hydrology, regulatory requirements and increases in populations in the flood path downstream. As such, it is vital that international organizations such as ICOLD provide guidance on the operation, maintenance, safety assessment and upgrading of existing hydromechanical equipment. Meanwhile, there are new dams being constructed that could benefit from an international reference document that provides guidance on the fundamental design principles and safety criteria that should be applied while selecting, designing and constructing spillway gate equipment.

There are many excellent publications that have been prepared during recent, and not so recent, times that will be referenced herein. It is not the committee’s intention to prepare a comprehensive document that will provide the same level of detail on the design, selection, operation and maintenance as that which appears in these other publications. Rather, we are focusing on matters that deserve more attention such as consideration of reliability from cradle to grave and the consolidation of best practices that are in use around the globe.

The scope of the current bulletin has been clarified to ensure that it is applied in an appropriate manner. The primary items addressed are as follows:

Hydromechanical equipment includes the gate (barrier), gate guidance (embedded parts) and operating mechanism
Discussed in various parts of the Bulletin, and equally important to the reliable operation of hydromechanical equipment, the electrical equipment including power supplies, control systems and sensors are not covered to the same level of detail as the mechanical equipment
The scope generally excludes the civil works beyond the guidance system, determination of the discharge capacity and operational aspects addressed by other committees.
It also excludes static and non-restoring structures such as Labyrinth weirs and fuse gates.

The purpose of the Bulletin is to provide a concise reference for designers, manufacturers, developers, owners and operators on the various aspects of flood discharge gates that have the potential to impact public safety. The bulletin applies to both new and existing systems.

Perhaps the most critical aspect of gate safety is the overall reliability of the flood discharge gate operating system and its ability to fulfill its functional requirements; primarily to release flood waters upon demand. Fundamental to the achievement of high system reliability are the following factors:

Each and every component of the gate operating system, including the gate itself, the lifting gear, power supply, control system, the water level sensing system and so on, must have an appropriate level of reliability
The assessment of system reliability follows a rigorous process, considering component reliabilities, their interactions and their individual contributions to the system reliability
Suitable acceptance criteria for the system reliability be established.

It is important to note, modern health and safety legislation requires that, when an engineering structure could put lives at risk, comprehensive evaluations of the risk be carried out and, if deemed necessary, steps be taken to reduce the risk to an acceptable level. It is no longer sufficient to abide by obsolete regulations that, for instance, state that a spillway is deemed to be safe if it can pass the maximum flood with one gate out of service.

As such, the main objective of the Committee’s Bulletin is to encourage owners to undertake comprehensive reliability assessments of their spillway gate overall system. Additionally, the Bulletin provides practical advice on:

the primary features of some of the more common types of flood discharge (spillway) gate equipment
reliability principles and presentation of methods commonly used for evaluation of reliability
procedures on accepted operation and maintenance
potential improvements that could yield gains in overall system reliability.

Every effort has been taken to ensure that the bulletin contains practicable guidance that can be applied to improve reliability. A working draft is currently being reviewed and edited within the committee team and has a document structure as follows:

Chapter 1 - Introduction
Chapter 2 – Incidents and Failures
Chapter 3 – Fundamental Principles
Chapter 4 – Gate and Hoist Types
Chapter 5 – Duty, Specifications and Standards
Chapter 6 – Risk Assessment
Chapter 7 – Commissioning
Chapter 8 – Inspection, Testing and Exercising
Chapter 9 – Operation and Maintenance

It is hoped that the forthcoming bulletin will make a major contribution towards dam safety from a hydromechanical viewpoint.

Authors

Andreas Halvarsson, M.Sc.Eng. - Andreas has been working exclusively with hydropower plants both nationally and internationally for 20 years. He works for WSP in Sweden and is eam leader for a group in Stockholm and are Swedish (SwedCOLD's) representative and vice chairman of ICOLD's Committee [V] Hydromechanical equipment. Most of this time he has been working on hydromechanical equipment such as intake and outlet gates. The focus has been on design and the preparation of tender/working documents for both new production and renovation. Surveys, inspections, construction management, project management and investigations are also included as part of his duties.

Ken Grubb – Consultant Technical Director - Ken is a Consultant Technical Director at KGAL Consulting Engineers with over 40 years of experience designing, constructing, installing and commissioning water control systems. His main specialism is in the design of hydraulic steel structures, particularly for use in dams, docks, ports, marinas and locks. He has a vast amount of experience across a wide range of types of hydraulic steel structures and industries, including commercial ports and harbours, marinas, navigable waterways, flood defence and hydropower installations. Ken plays an active role in the consideration of risk and safety in relation to machinery design and has run independent courses, lecturing on the European Union’s Machinery’s Directives and their practical implementation.

Jerry Westermann, M.Eng, P.Eng - Jerry is a Hydro-mechanical Consultant located in Hatch’s Niagara Falls, ON Office and has more than 30 years of continuous service working with Hatch on hydroelectric projects. As chairman of ICOLD’s recently-formed Hydromechanical Technical Committee, Jerry works with other gate experts around the globe with the objective of establishing guidelines for dam safety, irrigation and hydro power. Jerry has managed numerous large and small hydro projects encompassing feasibility studies, detailed design of new developments, refurbishments and support of operations. He has expertise in the assessment and design of gate equipment, penstocks and hydro turbines with a particular focus on innovation. Additionally, he has played the leading role in Hatch’s turbine field testing assignments and has executed more than 50 such tests.