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News Release from: Gardner Energy Management | Subject: GEM venturi steam trap
Edited by the Engineeringtalk Editorial
Team on 14 November 2000
Steam trap offers 19% fuel saving and
much more
A report has found the GEM venturi steam trap offers 19% savings on fuel, 19% reduction in carbon dioxide and nitrogen oxides emissions, low maintenance and no major operational problems.
19% savings on fuel, 19% reduction in carbon dioxide and nitrogen oxides emissions, low maintenance and no major operational problems These are the major findings of the independent Energy Technology Savings Unit (ETSU) study published this week which looks at the performance of the GEM venturi steam trap
Invented by Tim Gardner and manufactured by Gardner Energy Management of Bristol, this revolutionary trap works by releasing a continuous flow of condensate from steam lines through a carefully-sized orifice combined with a venturi.
Unlike mechanical traps, it has no moving parts and so cannot jam open or shut.
The ETSU study covers performance over a year from August 1998 to July 1999 at the laundry of Withington Hospital, Manchester.
ETSU staff logged data before, during and after mechanical steam traps were replaced by 86 GEM venturi traps.
Withington Hospital has an annual throughput of 1.8 million kg of laundered items per year, and the main steam users are two washers, six tumble dryers, three ironing machines, a tunnel dryer and space heating in winter.
Steam traps are used to remove condensate from steam lines and return it to the boiler.
Maintenance of the steam and condensate systems over the years, comments the study, had not received the highest priority.
In an audit carried out before GEM traps were introduced, 11 of 65 mechanical steam traps at the Withington Hospital laundry were found to have failed open and four shut.
The result, says the study, "was an unsightly plume of some 500 kg/hour of steam from the vent pipe on the condensate receiver".
After replacement with GEM traps, the study finds, "The vent steam flow was down to 59 kg/hour, an overall reduction of 89% - and the steam vent plume is no longer a problem." The study calculates a pay-back period in its study at Withington of 2.43 years.
The 86 traps cost £18,370 and installation £5,000, bringing total expenditure to £23,370.
Annual savings totalled £10,350 (£8,570 on energy and £1,780 on treated water make-up) but allowing for maintenance costs of £750 the overall annual savings were £9,600.
Lower gas emissions are a direct consequence of lower fuel usage.
The ETSU study specifically addresses two "concerns" about the GEM trap.
The first concern is that it "may be unable to handle safely and efficiently the range of operating conditions experienced, passing live steam at low loads and backing up condensate at high loads." The Withington system, the study suggests, is an testing one because there is a varying condensate load with constant upstream pressure unregulated by a control valve.
In practice the perfomance of GEM traps in this system recorded by the study also shows that this concern is unfounded.
For instance, the study notes that "The steam supply to the laundry is shut off and restarted on a daily basis, and there is no evidence of water hammer or condensate retention in the steam piping.
The trap replacement project has in no way been detrimental to the operation of the laundry equipment..." The second concern was that the discharge orifice of the GEM trap might become blocked.
Some of those used on space heating lines were found to block but this was assessed as due to the poor condition of the piping or to jointing compound.
It was solved by the routine use of upstream strainers.
The ETSU study concludes: "Installers of new steam systems should seriously consider the use of [GEM venturi steam traps], as should existing steam users where steam trap maintenance or reliability is a problem." Withington Hospital decided to install GEM venturi traps because the low maintenance requirements met local needs.
As John Tucker, then Estates Manager of the South Manchester University Hospitals NHS Trust which manages the Withington laundry, commented elsewhere in the study report, "the Trust is now considering fitting similar traps to other equipment throughout the hospitals.".
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