This method statement covers the installation of medical gases system horizontal and vertical piping installations through all the areas in the hospital project.
The medical gas pipes shall run horizontally in the main routing in the corridors. The vertical running will be through the pipes drops to the medical gases outlets, bed head units and other bridge systems.
This procedure defines the method used to ensure the medical gas network installation has been carried out as per contract requirements and best practices.
It gives details of how the work will be carried out and the health and safety issues and controls are involved.
This post covers few sections from the table of content which is for a comprehensive method of statement.
Table of Content
- Scope of Works
- References
- Location of activity
- Abbreviations and Definitions
- Constraints on Operations
- Personnel Responsibilities
- Method Description
- Materials and Products
- Engineering
- Plant, Tools, Equipment and Welfare arrangements
- Access arrangements
- Emergency / Incident Procedures and First Aid / Pollution Control Arrangements
- Communication and Training requirements
- Appendices
References and Standards
Project Contract & Specifications
Inspection and Test Plan ITP
Project Logistics Plan
Related International standards (Health Technical Memorandum)
Medical Gas Piping Materials Requirements
Pipes
Material for pipes should be manufactured from phosphorus deoxidized, non arsenical copper to BS EN 1412:1996 grade CW024A (Cu-DHP) in metric outside diameters to:
BS EN 13348 and:2001 – R250 (half hard) for sizes up to 54 mm; or
BS EN 13348:2001 – R220 (annealed) for larger sizes
Pipe Jointing Fittings
In addition to the above, pipe jointing fittings should be end-feed capillary fittings to BS EN 1254-1:1998.
Other Fittings
Other fittings for connections to copper pipes, for example valve and control panel fittings, may be of copper, brass, gunmetal or bronze to the appropriate standards.
All pipes must be cleaned and degreased for oxygen service and be free of particulate Matter and toxic residues in accordance with BS EN13348:2001. They must be individually capped at both ends and delivered to site identified as medical gas pipes matter and toxic residues.
Although it is not essential to degrease vacuum installations, these are frequently installed by the contractor simultaneously with the medical gas pipelines. Degreased pipe and fittings should, therefore, be used for the vacuum installation to avoid confusion.
Roles & Responsibilities
Project manager shall be responsible overall to complete all Medical Gases works as per specifications, budget, time & quality.
Project Engineer shall be responsible for but not limited to the following important activities:
- Ensure that all the preparation and application works are carried out according to the contract specification and manufacturer’s data sheet(s).
- To ensure that the progressing of works is carried out according to the planned program, and as per the approved Method statement.
- Make sure that all the equipment’s and materials required in executing the works are available according to the planned constriction program.
- Coordinate with the main contractor’s MEP coordinator and safety officer for all safe and proper execution of the work in accordance with the risk assessment.
- To coordinate with the civil team for any area preparation, access, clearance.
Foreman shall be responsible for but not limited to the following important activities:
- To guide and control the tradesmen and charge-hands(s).
- To ensure that work is done as per the approved shop drawing(s).
Method of Medical Gas System Installation
Pipe line installation
Accommodation of pipes
Generally, MOPS should be kept away from areas where they may be subject to any of the following:
- Mechanical damage
- Chemical damage
- Excessive heat
- Splashing, dripping or permanent contact with oil, grease or bituminous compounds, electrical sparks etc.
Service ducts or voids containing medical gas pipelines should have adequate Ventilation to prevent gas concentration in the event of any leakage occurring.
Exposed pipelines should not be installed in the lift shafts, kitchens, laundries, boiler houses, generators rooms, incinerator rooms, storage rooms designed to house combustible materials or in any other fire risk area. Where pipelines in hazardous areas are unavoidable, they should be enclosed in non-combustible materials that will prevent the possibility of the liberation of gases into the room in the event of pipeline failure.
Where pipelines are run in enclosed ducts with other services such as steam mains and water supply systems, they should be inspected regularly as corrosion
can occur as a result of chloride deposits following leakage. They should not be run in enclosed ducts with other services where they cannot be inspected.
Pipelines should be protected from the possibility of lightning strikes.
The route of the pipeline should be identified on the surface and should be clearly shown on site layout drawings. Pipelines concealed within walls and floors should have their route clearly shown on “as fitted” drawings. Pipelines should
not be encapsulated in floors, and any joints should be kept to the minimum practicable. Pipelines in stud or plasterboard walls or partitions are acceptable.
Care is required when selecting pipeline routes to prevent the pipes coming into contact with electric cables and wiring and to minimize the risk of electric shock in the event of fault on adjacent cables.
Pipeline Jointing General Requirements
Except for mechanical joints, copper- to-copper joints only will be permitted on site, made with brazing filler rods which can be used without flux and in the presence of oxygen-free nitrogen, which will be blown through the pipeline during brazing procedure to prevent the formation of oxides.
Carbon Dioxide should not be used as the inert gas shield.
This method eliminates the formation of oxide within the pipe, leaving a clean bore. Some slight burnishing may occasionally be observed on selected joints. Purging is still required to remove the internal shield gas and the other particulate matter not associated with the brazing welding operation.
Copper joints to brass or gunmetal fittings will require the use of flux, with subsequent cleaning to remove the flux residues and oxide deposits.
Heating of the joints for brazing should be carried out with oxygen/acetylene or acetylene, hydrogen, liquid petroleum gas/ ambient air torches. Additional heating may be required for some fittings, for example by means of second torch.
In order to maintain the pipeline cleanliness and prevent formation of verdigrises ‘ after completion, it will be necessary to maintain the completed system charged with medical air until the installation is finally commissioned. On larger projects completed section of pipeline should be similarly protected.
Jointing methods
Mechanical (threaded or flanged) joints may be made where pipelines are connected to items such as valves and control equipment’s. For vacuum pipelines of 76 mm diameter and above, screwed or flanged compression fittings may be used. Mechanical joints should not be used elsewhere for general pipe work installation.
Brazing copper to brass/gunmetal/bronze
Brazed joints should be made using a copper-silver brazing alloy to BS 1845 and an appropriate flux.
The flux residues and copper oxides created by the brazing process should be chemically removed and if necessary the complete assembly must be cleaned and degreased for oxygen service;
No flux should be used for making joints on site. Joints must be carried out under controlled conditions off-site and sub-assemblies delivered to site.
Brazing copper-to-copper joints
brazed joints should be made using a silver-copper – phosphorus brazing alloy to BS 1845. No flux should be used.
brazing should be carried out using oxygen free nitrogen gas as an internal inert gas shield, to prevent the formation of oxides on the inside of the pipe and fittings.
when brazing, ensure adequate protection of adjacent pipe runs to avoid oxidation.
Pipe preparation
Pipe ends should be cut square with the pipe axis, using sharp wheel -cutters and cleaned of any cuttings or loose burs. Only where the cut pipe has either deformation or a burr which is significantly restricts the flow of gas will be deburred if necessary.
Use of Nitrogen internal inert gas shield Application
Oxygen-free nitrogen should be supplied to the inside of the pre-assembled, unbrazed, pipework through a pressure regulator and flow controller or flow regulating device.
If necessary, the purge gas should be fed from two ends of a T-joint. Care should also be taken to ensure that other pipelines in close proximity to the one being brazed do not oxidize due to the heat transfer.
Safety Precautions
If working for prolonged periods in very confined spaces, precautions must be taken to avoid excessive buildup of nitrogen, by ventilating the space or by piping the shield gas safely out of the space.
Control of cylinders
The contractor and the site engineer must keep a record of nitrogen cylinders held on a site. Nitrogen cylinder should be accounted for and removed from the site at the end of the contract, and must not become mixed up with medical gas cylinders.
Other installation processes
Oxygen-free nitrogen should also be used internally on pipework as in paragraph above whenever annealing or hot forming of pipework is carried out.
Inspection of joints
Joints brazed should be inspected in accordance with the following procedure:
- before pressure testing, the site engineer should identify a number of fittings to be cut out for examination in order to establish the quality of the finished joints. The exact number to be cut out will vary with the size of the installation, but as a guide a ratio of one fitting per 200 installations should be cut out. In any event, a minimum of two and not normally more than five fittings be cut out for examination.
- the fittings cut out should be cut open (quartered longitudinally) and examined. If unacceptable joints are found, adjacent fittings should be cut out until the extent of any faulty workmanship has been established. The joints should be assessed in accordance with paragraph 5.7 and 5.8
- the pipeline should be made good;
- the pipe should be fully inserted up to the shoulder of the fittings.
Internal cleanliness
The tube and fitting should be internally clean and free from oxides and particulate matter. Some heat burnishing may be apparent and is acceptable.
Penetration
- Penetration of brazing alloy
- due to tolerances of the capillary space on these pipes and fittings, full penetration of the brazing alloy may not occur and is not necessary.
- the minimum penetration at any point on the joint must be three times the wall thickness of the tube or 3 mm, whichever is greater.
Capping
Sections of pipeline should be capped as soon as they are completed to prevent the ingress of air.
Removal of flux residues and oxides
The residue of flux and oxide resulting from the brazing of copper-to brass / Gunmetal / bronze fittings must be removed before components are delivered to Site. The following procedure should be used, or alternatively, one which is no less Effective may be substituted.
Allow joints to cool naturally to room temperature or at least to a temperature at which they can be handled. This is specifically for gunmetal fittings which, if cooled (or quenched) from the brazing temperature by dipping in cold water, could crack.
The flux residues should be removed by immersion in hot water and brushing with Stainless steel type wire brushes.
The oxides formed should be removed by immersing in a 5-10% sulfuric acid at
65 degrees Celsius (nominal) to which 25-50 g / liter of potassium dichromate has been added. The component should then be thoroughly rinsed in hot water at 80 degrees Celsius (nominal), this should result in a bright, clean component.
The fitting should be degreased if necessary and bagged.
Purging with the working gas
Purging should be carried out strictly accordance with the procedure given in ‘Validation and verification‘.
Pipe supports
The pipeline should be adequately supported at sufficient intervals in accordance with schedule given below to prevent sagging or distortion. Supports for surface mounted pipework should provide clearance to permit painting of the surface. Where it is essential for pipes to cross electric cables or conduit, they should be supported at intervals on either side of the crossing to prevent them from touching the cables or conduit. Supports should be of suitable material or suitably treated to minimize corrosion and prevent electrolytic reaction between pipes and supports.
|
Outside Dia (mm) |
Maximum interval for vertical runs (meters) |
Maximum Interval for horizontal runs (meters) |
|
12 |
1.2 | 1.0 |
|
15 |
1.8 |
1.2 |
|
22 |
2.4 |
1.8 |
|
28 |
2.4 |
1.8 |
|
35 |
3.0 |
2.4 |
|
42 |
3.0 |
2.4 |
|
54 |
3.0 |
2.7 |
| 76 | 3.6 |
3.0 |
Pipelines need not be laid with falls. In the case of vacuum, the sub\ atmospheric pressure will result in the evaporation of any moisture entering the system. It is possible, however, for vacuum jars to overflow and thus for system to require flushing through.
The connection from individual vacuum terminal unit into the main unit should be taken from the top of the pipeline to avoid flooding other vertical pipe drops during flushing. Each vacuum main riser should be provided with a double valve arrangement to permit drainage when the system is under vacuum: one of the valves should be lockable in the closed position. No other sloping or drainage arrangement are required.
Pipelines need further protection in certain circumstances as follows:
- where pipes pass through walls, partitions or floors they should be fitted with sleeves of copper pipes which conform to BS 2871 and be provided with appropriate wall or ceiling plates;
- in radio diagnostic procedure rooms etc., radio frequency (RF) screening by means of extended sleeves will be necessary. The advice of the equipment manufacturer should be sought.
- Corrosion of pipes can occur where they are in contact with timber treated with Fire-resistant or flame-retardant compounds; for example, some timber used for roof trusses and floor joists.
This contact should be avoided by the use of impermeable non-metallic materials in the area where contact may occur. PVC spacers or adhesive PVC tape may be used for this purpose. If spacers are used, they should not be liable to drop out due to shrinkage or subsequent movement of the pipe or timber.
Such precautions are not required where untreated timber is used or where the treated timber is effectively sealed with paint or varnish before the pipes are fixed to it.
Identification of Medical Gas pipelines
Pipelines should be identified in accordance with BS 1710 and color banding for the pipelines should be used outside of the plant room. Color band identification should be applied near to valves, junctions, wall etc. Each gas should be identified in 6 mm letters. Self-adhesive plastic labels of approved manufacturer may be used for this purpose. A band 150 mm wide is usually adequate. All color – coded tapes applied by the pipe manufacturer should be removed before the systems are identified, in accordance with this paragraph.
Care should be taken to maintain pipeline identification when periodical re-painting is undertaken. The direction of flow should be indicated.
Appendices
Inspection & Testing Plan ITP
Inspection & Test Checklists
Job Safety Analysis JSEA
Logistic Plan
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