FEATURE HVAC
TAKE IT NICE AND SLOW: as you fire-up boilers for winter
Failure to follow the correct boiler or system start-up procedures could lead to dangerous steam pipework problems as winter approaches, warns John Pickering of Spirax Sarco
oiler house operators have been advised that failure to follow the correct boiler or system start-up procedures could lead to dangerous steam pipework problems as the heating season approaches. The advisory notice issued by steam specialist Spirax Sarco specifically pinpoints the threat of water hammer and thermal pipework expansion as key issues when systems become operational again this autumn.
B It is possible for new operators of steam
systems to underestimate the care and time that needs to be given to steam system start-ups following shut down. Both water hammer and thermal expansion are a real threat to steam pipework when systems are fired-up after a long lay-off. Water hammer is much more than an acoustic problem. The entry of steam into a pipe which
already has an accumulation of water can lead to condensation and the forming of a vacuum that in turn can set the water into a violent motion. The momentum of this water can cause extensive mechanical damage to pipework and fittings. Thermal expansion is equally serious. Steam expansion occurs when the steam system is heated too quickly, resulting in
procedure for warming pipework from cold which is outlined by National Industrial Fuel Efficiency Service (NIFES) in the organisation’s handbook. The Boiler Operator’s Handbook sets out
the steam hitting the weakest point in the distribution pipework and literally, buckling the pipework. I have seen pipework bend and expansion bellows become twisted and distorted due to thermal expansion caused by the incorrect procedures being followed. Start-up dangers are a particular threat as the heating season approaches due to many heating systems which use steam as a source of heat being turned off during the summer months. Spirax Sarco recommends an 11-point
Very slow, incremental opening of the steam valve is vitally important
a clear procedure that includes checks to the boiler and valves and crucially, stresses the need for the gradual warming of the system pipework, increasing the pressure and purging it of air and condensate. I cannot stress enough that incremental opening of the steam valve is vitally important. Steam valves should be opened very slowly and if there is any indication of water hammer in the surrounding pipes the steam isolating valve should be shut immediately and not reopened until the pipes have been drained. The start-up procedures for steam pipework are complex and require an experienced operator. If you are in any doubt about the correct procedure call an expert.
John Pickering is an expert in safe procedures for steam distribution systems at Spirax Sarco
Spirax Sarco T: 01242 521361
www.spiraxsarco.com
CHEMICAL SPECIALIST OVERHAULS STEAM DISTRIBUTION NETWORK
Chemical specialist Johnson Matthey has overhauled the steam distribution network at its Billingham plant, saving approximately £60,000 per annum on heat losses alone while significantly reducing maintenance costs. The Billingham site’s processes and office heating was supplied by a
neighbouring facility via an oversized steam line 36 inches in diameter and more than 1000m in length which lacked adequate steam traps. Crucially, the original system was not equipped with isolation valves
which meant Johnson Matthey’s maintenance teams were unable to shut down or isolate the flow of steam. Regular flange leaks were leading to expensive maintenance bills and overall the plant was suffering from heat losses amounting to more than £130,000 per year. Johnson Matthey therefore set out to overhaul its steam distribution
network during the site’s summer shutdown period with support from Spirax Sarco. As part of this pilot scheme designed to explore the potential value of proactive steam system maintenance Spirax Sarco worked alongside Johnson Matthey’s on-site operations and maintenance teams to reduce the length of steam line to approximately 25% of its original length. The old 36-inch steam pipe was then replaced with a pipe of 8-inch and 4-inch sections. This was followed by the introduction of new control and automation devices including steam traps, dirt pockets and pressure indicators to improve the flexibility of use and isolation valves, offering much greater control of the steam supply itself.
8 NOVEMBER 2016 | FACTORY EQUIPMENT
“The lesson we’ve taken from this project is that there are huge rewards to be had by challenging the way things have always been done,” comments gas services and operations team leader Chris McHale. “Replacing a dated and problematic steam line with one much better
suited to our current application may sound basic but the cost, usability and safety benefits have proved second to none.”
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