Top 10 tips about steam safely and efficiently10 January 2014

Steam plant and equipment can be overlooked by maintenance teams, leading to costly breakdowns or repairs that could have been avoided, according to Greg Sutcliffe, global segment manager at Bürkert, who is offering 10 top tips for maintenance technicians.

1. Velocity: steam should be dry, with minimal water content the target, but it is often present as entrained water and condensate, he warns. These phenomena can be damaging and wearing to the steam system – particularly at high velocities. "As a rule of thumb, pipe sizes are typically calculated using 25m/sec as the reference speed. This forms a crucial part of the design, to reduce the impact of water hammer, pitting and wear.

2. Water Hammer: poor condensate management can lead to water hammer – "a condition that should never be tolerated". As the steam travels over condensate in a steam line, it drags a slug of condensate along with it, which can have considerable kinetic energy that is dissipated when it hits an obstacle, such as a valve or pipe elbow, he explains. The results can be mechanically destructive and dangerous.

3. Strainers: Y-type strainers are needed to protect expensive and process-critical equipment from damage and faults due to debris in the steam. However, installed incorrectly they are a potential source of condensate pooling and water hammer. "They should not be installed in the 'belly-down' position, but with the strainer belly in the horizontal plane."

4. Pipe reducers: "It may be necessary to reduce the pipe diameter as part of the steam system design." On steam systems, it is essential that eccentric reducers are used, rather than concentric parts, with the flat side at the bottom," says Sutcliffe. "Concentric reducers have a funnel-like profile and are sometimes installed by less informed engineers or when costs are being cut. However, this will lead to pooling of condensate and can be a prime source of water hammer."

5. Equal Ts: as a rule, when installing a drain pocket, it should be of the same pipe diameter as the steam main – forming 'equal Ts, up to a size of DN100. "If a smaller bore drain pipe is fitted, then the velocity of the condensate will allow it to skip over the drain pipe connection. In addition, the reduced volume of the drain pipe may cause it to overflow, thereby becoming another source of water hammer."

6. Steam system materials: particularly in older installations, cast iron (gg25) pipework and equipment is the standard material, but this has weaknesses to impact (including water hammer), compared to other materials, that can result in catastrophic failure. "We recommend as best practice, spherical graphite iron (SG Iron) or stainless steel (eg 316L), that can be 20—25 times more resistant to impact than standard cast iron."

7. Isolation valves: a crucial part of the safety of the steam installation is the isolation valve, which should be installed both sides of steam trap sets to allow maintenance to be carried out safely. "More recently, industry has migrated to the use of double isolation valves either side of equipment to account for possible leakage past one of the valves and to ensure the absolute safety of maintenance engineers."

8. Pressure gauges: these are crucial for providing information required to understand the conditions inside the steam system. "They should be installed before and after a control valve to ensure that it is performing as required," states Sutcliffe. "In addition, fitting them periodically throughout the steam system will give early indications of process change."

9. Energy efficiency: "Producing steam requires large amounts of energy so reducing losses wherever possible helps to improve the overall efficiency and the operating costs of the system. In poor examples up to 40% of the energy is lost, with failed steam traps accounting for 18% of these losses." Sutcliffe's advice: regular testing and maintenance are crucial to ensure that steam traps function correctly. Additionally, pipework needs to be lagged properly, including pipe flanges, while all unused pipe sections should be isolated and lagged, or, better still, removed.

10. "Above all, respect steam," warns Sutcliffe. "As an odourless, invisible, high-temperature 'gas', steam can be extremely dangerous and, as such, should be treated with great respect."

Brian Tinham

Related Companies
Burkert Contromatic Ltd

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