Overhauling valve assemblies
Overview
This standard identifies the competences you need to carry out a complete overhaul of valve assemblies, in accordance with approved procedures. The valve assembly to be overhauled will have been removed from its operating environment, and the overhauling activities will take place in a maintenance environment or manufacturer's workshop.
In carrying out the overhauling operations, you will be required to follow laid-down procedures and to use specific dismantling and rebuilding techniques. The overhauling activities will involve removing all ancillary components and sub-assemblies, separating the valve housing and removing the valve operating mechanism, bearings, valve seats and seals, and stripping the valve body of all its components. You will be required to inspect the components for damage and wear, and to make decisions on which components can be re-used and which will need replacing.
You will then rebuild the valve assembly, which will involve fitting replacement or overhauled sub-assembly units, such as valve spindle, valve seat, spindle bearings, operating mechanisms and seals and gaskets, and the replacement of all damaged, worn and `lifed' components. The overhauling activities will include making all necessary checks and adjustments to ensure that components are correctly replaced, positioned, aligned, adjusted, torque loaded, locked and fastened, and that the correct sealants are used.
Your responsibilities will require you to comply with organisational policy and procedures for the overhaul of the valve assembly, and to report any problems with the overhauling activities, or with the tools and equipment used that you cannot personally resolve, or that are outside your permitted authority, to the relevant people. You must ensure that all tools, equipment and materials used in the overhauling activities are removed from the work area on completion of the activities, and that all necessary job/task documentation is completed accurately and legibly. You will be expected to work with a minimum of supervision, taking personal responsibility for your actions and for the quality and accuracy of the work that you carry out.
Your underpinning knowledge will provide a good understanding of your work, and will provide an informed approach to applying appropriate overhauling techniques and procedures to valve assemblies. You will understand the dismantling and reassembly methods and procedures used, and their application. You will know how the valve assembly functions, the purpose of the individual components and associated defects, in adequate depth to provide a sound basis for carrying out the overhauling activities to the required specification. In addition, you will have sufficient knowledge of these components to ensure that they are fit for purpose and meet the specifications, thus providing a sound basis for carrying out the reassembly.
You will understand the safety precautions required when carrying out the overhauling activities associated with valve assemblies, especially those for lifting, handling and supporting the equipment being removed and replaced. You will be required to demonstrate safe working practices throughout, and will understand your responsibility for taking the necessary safeguards to protect yourself and others in the workplace.
Performance criteria
You must be able to:
- work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
- follow the relevant overhauling schedules to carry out the required work
- establish the components to be removed and, where appropriate, mark components to aid re-assembly
- ensure that any stored energy or substances are released safely and correctly
- carry out the overhaul to the agreed level, using the correct tools and techniques
- ensure that all removed components are correctly identified and stored in the correct location
- report any instances where the overhauling activities cannot be fully met, or where there are identified defects outside the planned overhauling schedule
- complete the relevant documentation, in accordance with organisational requirements
- dispose of unwanted components, waste materials and substances, in accordance with safe working practices and approved procedures
- deal promptly and effectively with problems within your control and report those that cannot be solved
Knowledge and Understanding
You need to know and understand:
- how to work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
- the hazards associated with overhauling valve and how to minimise them and reduce any risks
- the importance of wearing protective clothing (PPE) and other appropriate safety equipment during the overhaul
- how to obtain and interpret drawings, specifications, manufacturers' manuals, history/maintenance reports, and other documents needed in the overhauling process
- how to carry out currency/issue checks on the specifications you are working with
- the quality control procedures to be followed during the overhauling operations
- the procedure for obtaining replacement parts, materials and other consumables necessary for the overhaul
- company policy on the repair/replacement of components during the overhauling process
- terminology used in valve assemblies
- the basic principles of how the valve assembly functions, its operating sequence, the working purpose of individual units/components and how they interact
- the extent to which the equipment is to be dismantled for overhaul
- the sequence to be adopted for the dismantling/reassembling of the valve assembly
- the techniques used to dismantle the valve assembly, without damage to the components or surrounding structure
- the need to protect the system integrity by ensuring that exposed components are correctly covered/protected
- how to lift and move large components and assemblies; the methods and equipment used to transport, handle and lift the components during the overhauling activities
- the need to ensure that lifting and handling equipment is within its current certification dates
- methods of checking that components are fit for purpose, how to identify defects and wear characteristics, and the need to replace `lifed' and consumable items
- the uses of measuring equipment
- methods of reassembling the valve, using new or previously overhauled components
- how to make adjustments to replaced components/assemblies to ensure that they function correctly
- the various mechanical fasteners that are used, and their method of removal and replacement
- the tools and equipment used in the overhauling activities, and how to check that they are in a safe/usable condition
- the importance of ensuring that all tools are used correctly and within their permitted operating range
- the importance of ensuring that all tools, equipment and components are accounted for and returned to their correct location on completion of the overhauling activities
- the procedure for the safe disposal of waste materials
- the need to complete the overhaul documentation and/or reports following the overhauling activity
- the problems that can occur during the overhauling activity, and how they can be overcome
- the extent of your own authority and to whom you should report if you have a problem that you cannot resolve
Scope/range
Scope Performance
- Carry out all of the following during the overhaul of the valve assembly:
- obtain and use the appropriate documentation for the overhauling activities
- adhere to procedures or systems in place for risk assessment, personal protective equipment and other relevant safety regulations and procedures to realise a safe system of work
- provide and maintain safe access and working arrangements for the work area
- ensure that the valve assembly is suitably supported, and that appropriate lifting and handling equipment is available
- carry out the overhauling activities, following good practice/approved procedures
- ensure that components and surrounding structures are maintained free from damage and foreign objects
- return all tools and equipment to the correct location on completion of the activities
- leave the work area in a clean and safe condition on completion of the activities
- Overhaul both of the following types of valve:
- rotary action valves
- linear action valves
- Overhaul valve assemblies operating on two of the following methods:
- globe (single or double seat )
- gate
- plug
- wedge gate
- pinch
- rotating shoe
- parallel slide
- ball
- needle
- piston
- butterfly
- diaphragm
- other specific method
- Carry out all of the following activities on the valve equipment being overhauled:
- cleaning/decontaminating valves prior to dismantling
- pre-disassembly checks and tests
- releasing stored energy (where applicable)
- proof-marking/labelling of components to aid reassembly
- dismantling equipment to unit/sub-assembly level
- dismantling units to component level
- checking components for wear and serviceability (such as visual, measurement, use of probes/scopes)
- replacing all damaged or defective sub- assemblies and components
- removing and replacing components having interference fits (such as by expansion, contraction, pressure)
- lapping in components (where applicable)
- replacing all `lifed' and consumable items (such as seals, bearings, gaskets)
- reassembling the valve unit
- making mechanical connections
- setting and adjusting replaced components
- applying correct lubrication during assembly
- applying gaskets and sealant/adhesives
- securing components using mechanical fasteners and threaded devices (such as nuts, bolts, circlips, pins)
- tightening fastenings to the required torque
- applying locking and retaining devices (such as circlips, pins, wire locking, lock nuts, stiff nuts, swage nuts)
- applying protection to openings to prevent entry of contaminating debris
- Replace/refit a range of valve assembly components, to include ten of the following:
- valve body
- locks and stops
- bonnet
- valve springs
- valve spindle/shaft
- shims and packing
- diaphragms
- levers and linkages
- valve plug
- locking devices
- piston
- wire thread inserts
- valve seat
- pipes and unions
- valve disc or slide
- mechanical controls (such as plungers, springs, rollers)
- static seals/gaskets
- electrical controls (such as solenoids, motors, switches)
- stem seals/gland packing
- bearings
- other specific valve components
- Carry out checks and tests on the overhauled valve assembly, to include all of the following:
- visual inspection for completeness of all operations
- visual inspection for freedom from damage or foreign objects
- applying protection to openings to prevent entry of contaminating debris
- carrying out any `special-to-type' checks
- Overhaul valve assemblies, in compliance with one of the following:
- BS, ISO or BSEN standards and procedures
- customer standards and requirements
- company standards and procedures
- valve manufacturer's requirements