HUMAN FACTOR ENGINEERING - VALVES:- Ergonomics and Anthropometry in Engineering Design

HUMAN FACTOR ENGINEERING - VALVES

VALVE CRITICALITY ANALYSIS - IMPORTANCE TO HUMAN FACTOR ENGINEERING

Valves are critically rated with the aim of minimizing risks to health and safety, balancing ease of access for operations as well as ensuring that risk or probability of human error is kept as low as reasonably practicable.

Fig 1 - Typical Ball Valve dimension and weight

For this reason, valves are carefully categorized based on functionality, with a view to affecting and determining its best orientation and position. They include:-

Category-1 (C-1) Valves:-

These are valves essential to normal or emergency operations where rapid or unimpeded access is essential. They are valves that are:-

1.  Essential to production

2.  Essential to process safety or asset integrity

3.  Particularly large valves

4.  Used in operating conditions where failure rates are unknown or unreliable

5.  So important, where consequence of failure to obtain quick access would be serious

Since unencumbered access to this category of valves is important, permanent accessibility shall be provided at deck or ground level via a permanent elevated surface. Valve identification and status shall be clearly visible to an approachable operator position.

Fig 2 - Safe acceptable distances for a "standard man"

Category-2 (C-2) Valves:-

These are valves that are not critical for normal or emergency operations, but are used during routine inspection or maintenance activities.

These valves meet the following criteria:-

1.  Valves associated with equipment for which rapid intervention is unlikely to be needed.

2.  Valves with a low operating or inspection frequency

Height and reach distances and visibility should be same as category 1 valves. They may be located within acceptable area depending on their size and the force needed to operate them.

The use of auxiliary equipment such as mobile platform, man-lift, and scaffolding to gain access is generally acceptable.

Fig 3 - Safe and acceptable distances for access between valves

Category -3 (C-3) Valves:-

These are normally non-operating valves that are used or inspected on an infrequent or rare basis. e.g. Hydro-static test vent valve, high point vent or low point drain etc.

Permanent accessibility to these category of valves is not essential with no specific location requirements are imposed.

Fig 4 - Preferred and Acceptable distances for suitable to the operator

Fig 5 - Operable Valve distance from deck/grade level

Requirement For Gear Operators For Valves

A guideline for determining whether or not a valve will require gear operator based on the type of valve, its size and pound ratings are highlighted below

Fig 6 - Guideline for valves requiring Gear operators

It should be noted that many manufacturers provide gear operators with their standard offers, based on their respective unique specification.

Ergonomics & Human Factor In Engineering Design

Human Factors and ergonomics also known as comfort design, functional design or user friendly systems, is the practice of designing products systems or processes to take proper account of the interaction between them and the people who use them.

Fig 7 - Valve position and location and its suitability to the operator

Ergonomics on the other hand is the scientific discipline concerned with the understanding of interactions among human and other elements of a system in order to optimize human well-being and overall performance.

Put simply, it is concerned with the fit between the user, equipment and their environment. it takes into the account the users capabilities and limitations in seeking to ensure that tasks functions, information and the environment suit each user.

Human factor and ergonomics is also employed to fulfill the goals of occupational health, safety and productivity.

Proper ergonomic design is necessary to prevent repetitive strain injuries and other musculoskeletal disorders which can develop over time and lead to long term disability.

Fig 8 - Including Ergonomically factor in design 

 Opening or closing of valves can be completed either by manual input or automated devices driven by various energy sources.

Manual operators are simple, inexpensive and require little peripheral -planning beyond the installation and orientation of operators in the process line.

Two concerns considered during selection of manual operators are the efforts required to operate the valve and the number of turns some valves require. a lot of effort and a high number of turns can result in personnel fatigue, safety concerns, excessive time for operation and the need for multiple personnel.

Fig 9 - Automation Operated valves

 Also under consideration when selecting manual operators, are the valves expected frequency of operation and the physical location, such as whether it might be high in superstructure or situates=d in an inhospitable environment. Both also present challenges to humans.

Two basic aspects that primarily define operator selection are:-

1. Human factor

2. Economic factors

Human Factors:-

This is simply the human capability to cycle the valves in a safe, timely and economically sound manner. This will require considerations such as:-

         i.      1.  Work needed to be done to operate the valve,

       ii.       2. The environment in which the valve is located

      iii.       3. The time required to complete the task

     iv.         4. The health and safety of the personnel involved

Fig 10 - Proper spacing provided at design stage for operator's access

Economic Factors:-

They revolve around cost and monetary implications. Some major considerations includes:-

         i.  1.  Cost of the actuators

       ii.   2.  Cost of the infrastructure

      iii.   3.  Maintenance to support automated solutions 




References - DEP 30.00.60.13-Gen



TimmsVille Engineering offers affordable courses for interested candidates requiring these knowledge. We offer both practical, in-depth theoretical training as well as software competence.........See more