LONDON BOROUGH OF CAMDEN HIGHGATE NEWTOWN: PIPEWORK CONDITION REVIEW. Revision 002

Transcription

1 LONDON BOROUGH OF CAMDEN HIGHGATE NEWTOWN: PIPEWORK CONDITION REVIEW Revision 002 Prepared by Michael Doyle and Stewart Park, reviewed by Alex Maguire. Issued for comment 10 th January 2013 Updated by Alex Maguire. Issued 14 th January 2013

2 CONTENTS 1.0 INTRODUCTION DESCRIPTION OF EXISTING SSTEMS LIFE EXPECTANC CHEMICAL CLEANING CONCLUDING REMARKS... 9 Highgate Newtown Pipework Condition 7319_RE002_MPD_AM_REV002

3 1.0 INTRODUCTION TGA Consulting Engineers LLP has been engaged by London Borough of Camden M&E Repairs and Improvements department (LBC) to provide an independent opinion on the life expectancy of pipeline installations forming part of the heating distribution system at the Highgate Newtown estate. This study has been prepared in conjunction with another investigation related to the site. TGA has also been engaged to comment on the options for thermal energy generation for the estate. Due to the commonality between these instructions the introduction and general description of existing installations used in the reports is generally common to each. 1.1 Aims and objectives The study will: Undertake a site survey to assess the configuration, age and condition of the existing installations. Provide a general description of those installations Review historic data regarding maintenance, operation and replacement Consider the life expectancy of the installations of an equivalent size and type Consider the process of chemical cleaning and flushing Make recommendations 1.2 Chronology Initial discussions were held with LBC regarding the project 5 th December A briefing meeting following at LBC offices on the 6 th December An initial site survey was undertaken 10 th December 2012 which included a general site walkround and survey of the plantroom. A further site survey was undertaken 17 th December. This included a further site walkround and plantroom survey but also included access to a maisonette in the Northernmost terrace of Lulot Gardens. 1.3 Study limitations TGA has undertaken a visual and non-intrusive survey of the installations relevant to this study only. No functional tests have been undertaken of any systems or system components. In compiling this report TGA Consulting Engineers has relied on information provided by the client and its representatives and existing record information. The output of this document does not provide a proposal that could be adopted without further investigation and detailed design. Any costs provided are budget based upon outline proposals and the information available at the time. 1.4 Disclaimer This document has been prepared in accordance with the scope of TGA Consulting Engineers appointment with its client and is subject to the terms of the appointment. It is addressed to and for the sole use and reliance of TGA Consulting Engineers. TGA Consulting Engineers accepts no liability for any use of this document other than by its client and only for the purposes, stated in the document, for which it was prepared and provided. No person other than the client may copy (in whole or in part) use or rely on the contents of this document, without the prior written permission of TGA Consulting Engineers LLP. Any advice, opinions, or recommendations within this document should be read and relied upon only in the context of the document as a whole. The contents of this document are not to be construed as providing legal, business or tax advice or opinion. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

4 2.0 DESCRIPTION OF EXISTING SSTEMS 2.1 General The Highgate Newtown development was constructed in 1970 s and comprises the following council owned buildings:- BUILDING NAME BUILDING NAME 1-57 LULOT GARDENS 1-14 STONELEIGH TERRACE LULOT GARDENS STONELEIGH TERRACE LULOT GARDENS & 48 STONELEIGH TERRACE 1-11 RETCAR PLACE & 47 STONELEIGH TERRACE RETCAR PLACE STONELEIGH TERRACE 1-20 SANDSTONE PLACE 1-14 RADON STREET SANDSTONE PLACE 2-14 DONTON STREET SANDSTONE PLACE 1-5 COLV WALK SANDSTONE PLACE DARTMOUTH PARK HILL SANDSTONE PLACE In total there are 380 individual dwellings comprising 1, 2, 3, 4 & 5 bedroom flats, maisonettes and terrace houses. 1 and 2 bed dwellings are flats and 3, 4 & 5 bed dwellings are maisonettes or terrace houses. Generally, the existing CH system serving the estate is circa years old. Central boilers have been replaced recently along with pressurisation equipment and circulating pumps. The pipe distribution system is original, has reached the end of its service life and is due for replacement. 2.2 Main Gas Services A single mains gas service enters the boiler house at ground level. A utility gas meter/governor assembly is located in an external gas meter enclosure situated adjacent to Raydon Street. 2.3 Central Boiler Plant Existing CH boiler plant, serving the development, is located in a lower ground floor boiler room located below Sandstone Place. The central boiler installation comprises 3Nr Hoval forced-draught gas-fired boiler units, each rated at 1200kW output. The installed boiler capacity is therefore 3600kW. Individual boilers connect to a common flue header which rises laterally behind the boiler plant within the plantroom. The flue header exits the plantroom and connects to a common chimney which rises through the pedestrian zone deck above the thermal energy plant room. The flues are shown on the cover image of this report. The boiler house also accommodates circulation pumps, pressurisation equipment, controls and a control panel. 2.4 Primary Community Heating Distribution System The existing boilers form part of the overall distribution circuit and heating water is circulated through them constantly. Thermal energy generated by the boilers enters the main flow pipework that runs around the boiler room before connecting to four pumps circuits, viz: Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

5 Zone 1, twin head pump set, assumed to serve the heating zone south of Raydon Street Zone 2, twin head pump set, assumed to serve the Stoneleigh Terrace zone Zone 3, pump sets not installed, may have been removed following installation Zone 4, twin head pump set, North heating zone, area served unknown Zone 5, single head pump set, North heating zone, area served unknown. The primary distribution system delivers a constant temperature (CT) supply of low temperature hot water (LTHW) to individual dwellings. The primary pipe distribution network is routed to the consumer installations, via pipe risers, horizontal distribution pipelines and buried pipeline. Generally, those sections of the primary pipe distribution system that are accessible for inspection look in reasonable condition. However, there is evidence that the system has leaked in the past with pipe line components having to be replaced. Bearing in mind that the installation is circa years old, this system can be considered to be at the end of its service life. The central boiler installation does not include a boiler house shunt circuit. 2.5 Consumer Installations in Dwellings Central Heating Branch pipelines enter each dwelling and are directly connected to the dwelling radiator circuit. Manually operated service isolating valves have been provided at the point of entry into each dwelling. Heat emitters in dwellings comprise a mix of panel radiators and convectors. Heating appliances have been provided with simple thermostatic radiator valves. Heat emitters and pipework within dwellings are at the end of their service life Domestic Hot Water Domestic hot water is produced by an indirect copper storage cylinder incorporating an LTHW heater Gas Installation A separate gas distribution pipe, owned by the network operating company, has been routed through the building and branch pipe lines have been provided to serve each dwelling. Utility meters are located in the dwellings and tenants/leaseholders are billed directly for the gas consumed. Gas is used for cooking appliances only Electricity Installation Each flat has been provided with a metered electricity service. Tenants/leaseholders are billed directly for the electricity consumed. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

6 2.6 Breakdown Analysis TGA has been furnished with LBC record of repairs to the system for a five year period from January There were 2766 system breakdowns and issues reported to LBI in the period Jan 2008 and Dec Issues that were reported included leaks, control issues, radiator issues, no heat, boiler house issues and miscellaneous. Table 2.1 summarises this data. Table 2.1 Schedule of event or failure data Description Nr of Reported Events Percentage of Total Boiler House/boiler down Controls Leak No Heat Radiator Misc Totals It is evident that the installations serving Highgate Newtown experience numerous operational issues suggesting that the system does not currently function satisfactorily. There is anecdotal evidence that system performance has been a long term issue. Over heating and poor temperature control has been identified as a problem along with the items listed above. A serviceable community heating system should not be experiencing problems to the extent identified above. Unplanned system breakdown will be significantly improved by implementing a modern CH installation incorporating an optimum number of primary distribution circuits; heat interfaces units in each dwelling; and individual pump and controls serving the consumer installation. Primary pumps will need to incorporate variable speed motor controls. 2.7 Plant & Equipment Life Expectancy Life expectancy for individual items of plant, equipment and systems can be taken from CIBSE GUIDE M 2008, APPENDIX 13.A1. In practice, a well maintained item of equipment may well last longer than as stated in CIBSE guide M. See table 2.2 below. Table 2.2 CIBSE Expected serviceable life ITEM 10 RS 15 RS 20 RS 30 RS REMARKS Boilers (commercial) Boiler flues Boiler (combi) Boiler (condensing) Micro CHP HW cylinder Plate HX (domestic Pumps (commercial) Pumps (domestic) Press units Panel radiator Electric panel heater Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

7 3.0 LIFE EXPECTANC 3.1 Pipeline installations It is understood that the distribution pipe work between the central boiler house and the various premises has been installed in black mild steel type pipe work in a mixture of underground service ducts, directly buried, risers and under croft spaces. Heating distribution within each of the premises has been installed in copper type pipe work with pressed steel radiators and convectors in the various rooms. The point at which pipework the steel and copper installations interface is not known. Various problems have been reported by the residents with a recurring instance of a lack of heating temperature and cold radiators. This suggests poor water circulation and a possible build up of debris in the system over a period of time. 3.2 Life Expectancy of Mild Steel Pipe Work CIBSE guide M, 2008 identifies a life expectancy for a closed mild steel central heating system as 25 years. This is based on the system being properly and routinely maintained. In practice, steel pipe lines can last much longer. The determining factors which will affect the life expectancy of a MS pipe system are as follows: 1. The grade of steel used - heavy grade steel will last longer than medium grade steel due to the increased wall thickness of the pipe. 2. Has the system water chemistry been maintained properly more often than not, poor water chemistry control or no control at all, is normal. 3. Is the system pressurised by an open feed and expansion tank the water surface of an F&E tank will allow atmospheric oxygen to diffuse into the water. 4. Are there any dissimilar metals in the system distribution pipe work? This installation includes a mixture of mild steel and copper pipe work which could have resulted in corrosion by electrolytic action over a period of time. 5. Has the water circuit ever been colonised by pseudomonas-like bacteria. 6. Is the pipeline buried in the ground or contained in a dry duct or space. Items 2 to 5 can be a cause of accelerated corrosion of interior surfaces within the system. It can be difficult to detect by inspection of the internal surfaces as effects can be highly localised. Item 6 is significant in respect to the external surfaces of the pipe line. 3.3 Life Expectancy of Copper Pipe Work CIBSE guide M, 2008 identifies a life expectancy for a closed or open copper heating system as 45 years. This is based on the system being properly and routinely maintained. The determining factors which will affect the life expectancy of a copper pipe system are as follows: 1. The quality of copper used and the respective wall thickness, although the age of the system suggests that standard Table X type pipe work would have been used during the installation within each other premises. 2. Has the system water chemistry has been maintained properly more often than not, poor water chemistry control or no control at all, is normal. 3. Is the system pressurised by an open feed and expansion tank the water surface of an F&E tank will allow atmospheric oxygen to diffuse into the water. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

8 4. Are there any dissimilar metals in the system distribution pipe work? This installation includes a mixture of mild steel and copper pipe work which could have resulted in corrosion by electrolytic action. 5. Has the water circuit ever been colonised by pseudomonas-like bacteria. 6. Is the pipeline buried in the ground or contained in a dry duct or space. Items 2 to 5 can be a cause of accelerated corrosion of interior surfaces within the system. It can be difficult to detect by inspection of the internal surfaces as effects can be highly localised. Item 6 is significant in respect to the external surfaces of the pipe line. 3.4 Life Expectancy of Valves and Radiators CIBSE Guide Part M 2008 indicates that copper and cast iron type isolating valves would have an anticipated life expectancy of 30 years, with commissioning valves being 25 years. Pressed steel radiators would have a life expectancy of 20 years with cast iron type anticipated to last for at least 25 years. This is based on the system being properly and routinely maintained. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

9 4.0 CHEMICAL CLEANING Pipe lines can be periodically chemically cleaned during its life cycle. This process will remove oils and greases, scale, loose magnetite, rust and bacterial contamination. Typically, new pipe systems are chemically cleaned, flushed and dosed with appropriate chemical additives. The process can involve pickling the pipe line with mild acids to remove scale and rust, leaving a bright metal internal surface. The system is then flushed and re-filled with water which is pacified to prevent the corrosion and colonisation with bacteria. It is of the utmost importance that the water chemistry in new systems is maintained properly. This will involve regular sampling of the water, topping up with chemicals as required, and keeping a proper record. Failure to maintain good water chemistry can result in rapid deterioration of the pipeline. BSRIA Guide BG29/2011 deals with pre-commissioning cleaning of pipe work systems. 4.1 Chemically Cleaning an Ageing Pipe System In theory, any pipe line system can be chemically cleaned and conditioned. Pipe line conditioning can involve lining pipelines with epoxy coatings or simply re-instituting a suitable water chemistry regime. The process of cleaning would include a desk top exercise to determine size the system and flow rate because the flow velocity required for flushing would need to be considerably higher than the design heating service flow rate in order to remove the debris. The initial cleaning works would involve flushing with water at a suitable velocity up to three times higher than the design water flow rate and then following that with a chemical flush, again at high velocity and elevated temperature, using a citric acid based chemical polymer suitable for use with both copper and mild steel pipe work. This would be monitored by periodic sampling and chemical analysis to determine the cleanliness of the pipe work. When this is completed the chemical would be fully drained down and disposed of safely. The system would then be required to fully flushed again using water at high velocity to remove all chemical residue, this is because the chemicals used can change state after a time period and become more aggressive and potentially dangerous. The procedure would then involve the introduction of a passivating chemical solution to encourage formation of a magnetite layer on the surface of the pipe work. Finally the chemical solution would be fully drained down and the system filled with softened treated water containing an oxygen scavenger and ph corrected to the appropriate value for the particular heating system served. In ageing systems, where the condition of the pipeline is unknown and where no proper control of water chemistry has been applied, there is a significant risk that the chemical cleaning process will open pin-holes that have been hitherto remained closed by scale and rust, thus resulting in water leaks in unpredictable locations and causing damage and loss of heating service. Pipeline components, particularly those containing dissimilar metals, non metallic seals and gland packings can be adversely affected as can sites within the system where the material microstructure has been changed, such as at the site of a butt or seam weld. Chemical cleaning and flushing of an older system could result in water leaks from valves and joints in various unpredictable locations, possibly in concealed service ducts, risers and under floors. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

10 4.2 Pipe work Condition Some sections of badly corroded pipe work have been replaced recently. The following photographic record clearly identifies the extent and scale of the corrosion occurring with the installations. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002

11 5.0 CONCLUDING REMARKS The pipeline installation serving Highgate Newtown district heating system is approximately 35 years old. Materials used in the system include both copper and medium or heavy grade steel. CIBSE suggests that if properly maintained and treated throughout their life, installations of this type could have a life expectancy of 25 and 45 years respectively. However, there is no documentary evidence to suggest that appropriate cleansing of all installations has taken place. Conversely, there is significant evidence from both physical inspection and records of failure and repair that the system is failing. Even given the life expectancy of pipelines, when aggressive cleaning agents are used, the receiving pipeline is aged further as material layers are stripped away. Poor circulation in the system indicates a build up of deposits within it. These deposits will contain elements of the pipelines that have been worn away over time and whilst detrimental to circulation, they have the effect of sealing minor defects in the pipelines. Cleaning of the pipelines will remove these deposits and most likely result in a greater frequency of leaks. If the planned plant replacement project goes ahead, the system will operate at a higher temperature and most likely pressure than it currently does. This will result in increased stresses on the installations as pipework expands and contracts more readily and sees greater pressure on internal joints. It is highly likely that failure of any retained pipelines would increase as a result. There is no guarantee that pipeline treatment would yield measureable improvement in this case. It is considered that any treatment would be to the detriment of the installation and would actually result in a higher frequency of pipeline failure. The practicalities of treating this system, in which primary water is circulation through dwellings, are also significant, with no guarantee that the correct dosage would reach the system extremities. Risks to the operation of the system and to health and safety when the chemical is in use would also require detailed consideration. It is recommended that the system is not treated but that pipelines are replaced as part of a wider replacement project. Highgate Newtown Pipework Condition _RE002_MPD_AM_REV002