In OUR Gas Processing plants, steam is used as a heating medium in process reboilers and utilities. Condensate carryover induces water hammer in the distribution-piping network, causes pipe/structure dislocations, and creates serious risk to plant operations, safety and integrity.
This paper presents the techniques to identify the root causes and mitigation measures to minimize such incidents and enhance energy saving opportunities in steam network.
The existing steam generation and distribution network is huge with multiple plant interfaces due to brownfield expansions. A comprehensive analysis of integrated network for design, operation, maintenance and monitoring along-with detailed survey was performed.
Gap analysis of steam system components was conducted to identify the improvements considering current standards and best practices. Detailed dripleg/trap adequacy checks, condensate load calculation, trap survey and steam quality check was performed. RCA reports were reviewed for causes of incidents and recommendations incorporated.
Study revealed that optimized driplegs, steam trap types, insulation and monitoring program, reduces steam blow-off and enhances energy savings and plant performance.
Analysis showed that existing network operates just above saturation temperature and lacks provisions to remove condensate and trap management needs improvement. For uninterrupted plant operation, bypass valves of failed traps were opened to atmosphere resulting in steam/condensate losses.
Key findings are;
Piping/structure not designed for hammering and should be avoided by minimizing condensate from source and removal during distribution
Steam dryness is nearly 93% indicating >7% is condensate to be drained from steam system.
Valve/flange insulation removed during maintenance not reinstated, accelerates condensate formation and energy loss.
Reverse and bidirectional flow occurs; however, piping is designed for unidirectional flow.
Slope not provided; however, modification to existing piping is not feasible.
Dripleg/Steam trap interval >100m at many locations does not comply max.50m requirement and existing driplegs are undersized.
Flanged connections are susceptible for steam leaks, should be minimized.
Survey indicated that >50% steam traps are either blocked or blowing steam (passing).
Thermodynamic traps predominantly provided in saturated steam systems are ineffective for actual condensate loads and blocked by corrosion particles
Blocked traps create water hammering. Steam leaks cause energy loss and damages supports, concrete paving and foundations
Major recommendations are;
For interconnected networks, maintain uniform temperature across all desuperheaters and provide driplegs / traps either side of expansion loops.
Use float drain traps at desuperheater downstream and inverted bucket traps in distribution piping.
For maintenance ease, utilize universal connector/compact trap valve stations.
Replace failed traps immediately.
Evaluate using cyclone separators to improve steam dryness. Develop trap database and conduct surveys through specialists
Study recommendations being implemented in phases.