Top 10 steam safety and efficiency tips

Steam plant and equipment, although generally very reliable, should not be overlooked when it comes to maintenance. To do so eventually leads to costly breakdowns and repairs, many of which are invariably avoidable. So here are 10 top tips for maintenance technicians. 1 Velocity: Steam should be dry – meaning minimal water content. But water is often present as entrained condensate. This can be damaging to any steam system, leading to early wear – particularly where high steam velocities are involved. "As a rule of thumb, pipe sizes are typically calculated using 25m/sec as the reference speed," says Sutcliffe. "This forms a crucial part of the design, to reduce the impact of water hammer, pitting and wear." 2 Water hammer: Poor condensate management is one of the key reasons for water hammer. As the steam travels over condensate in a steam line, it drags a slug along with it. That is likely to have considerable kinetic energy associated with it that will be dissipated when it hits an obstacle, such as a valve or pipe elbow. 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, again, 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. "It is essential that eccentric, rather than concentric, reducers are used, with the flat side at the bottom," warns Sutcliffe. "Concentric reducers have a funnel-like profile and are sometimes installed by less informed engineers or when costs are being cut. However, these will lead to pooling of condensate and, hence, 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, the velocity of the condensate will allow it to skip over the drain connection. Also, the reduced volume of the drain pipe may cause it to overflow, thereby becoming yet another source of water hammer," explains Sutcliffe. 6 Steam system materials: Particularly in older installations, cast iron (gg25) pipework and equipment is standard. But this exhibits weakness to impact compared to other materials, potentially resulting in catastrophic failure. "We recommend as best practice, SG Iron [spherical graphite iron] or stainless steel [for example 316L] that can be 20-25 times more resistant." 7 Isolation valves: Isolation valves should be installed both sides of steam trap sets to enable safe maintenance. "Recently, industry has migrated to 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," advises Sutcliffe. 8 Pressure gauges: Sometimes neglected, these are crucial for providing information about conditions inside the steam system. "They should be installed before and after a control valve to ensure that it is performing," suggests Sutcliffe. Indeed, fitting them throughout a steam system is an excellent mechanism for getting early indications of process change. 9 Energy efficiency: Producing steam requires large amounts of energy so reducing losses clearly improve the efficiency and reduces operating costs for any steam system. In the worst examples, up to 40% of energy is lost, with failed steam traps accounting for 18%. Sutcliffe's advice: periodic testing and maintenance are key to ensuring that steam traps function correctly. Additionally, pipework and flanges need to be lagged properly, while all unused pipe sections should be isolated and lagged, or, better yet, removed. 10 Respect: "Above all, respect steam," warns Sutcliffe. "As an odourless, invisible, high-temperature 'gas', steam can be extremely dangerous."