The Dos and Don ts of High Pressure Valves Maintenance and Operation

Transcription

1 The Dos and Don ts of High Pressure Valves Maintenance and Operation UreaKnowHow.com Mark Brouwer V2

2 Content 1. Introduction 2. High Pressure drain and flush valves 3. Stuffing boxes 4. High Pressure butterfly valves 5. High Pressure piping 6. What to do in case of a leak 7. Conclusions

3 1. Introduction UreaKnowHow.com: Largest independent network in the nitrogen fertilizer industry to exchange technical information with the target to improve Safety and Performance of all nitrogen fertilizer plants worldwide. Partnerships E-library > Members representing of all urea plants worldwide Round Tables discussions UreaKnowHow.com catalyzes Safety and Performance Biweekly a Technical paper Now also AmmoniaKnowHow.com is online!

4 1. Introduction Valve Challenges in Urea Plants ü High pressures ü Various kinds of corrosion phenomena and limited choice of materials ü High delta-p s and erosion risks ü Crystallization risks ü Large sizes High Quality valves are crucial for a Safe & Reliable urea plant

5 1. Introduction And Solids are always present (passive corrosion products: iron oxides and chromium oxides) Solid particles in fluid are the most critical parameter for the sealing between stem and seat of a valve

6 2. HP drain and flush valves ü In Urea plants best experiences are with angle and globe type valves ü Use exchangeable seats (easy maintenance) ü Use a controllable stem characteristic ü Optionally gear or pneumatic operated for large sizes

7 2. HP drain and flush valves Back sealing feature Closed position Best practice: Completely open the valve ü stem protects the stuffing box ü increase lifetime and reliability

8 2. HP drain and flush valves Installation advice: Closed position ü Carbamate or High Pressures side against stem ü Behind stem reduces lifetime stuffing box

9 2. HP drain and flush valves Preferred type & position of HP drain valves Horizontal drain lines (angle valve) Vertical drain lines (globe valve) ü Carbamate side against stem side (red arrow) ü In this way solids cannot collect and harm spindle causing leakage

10 2. HP drain and flush valves A regulating stem: ü Enables control of flow ü Reduces erosion damages

11 3. Stuffing boxes Gland bushing Support ring Packing rings Support ring Bottom bushing Coating bushing

12 3. Stuffing boxes Leak along stuffing box Cause: Corroded/damaged spindle

13 3. Stuffing boxes Leak along stuffing box ü Use proper materials (corrosion resistant, also packing rings) ü Check minimum tightening force during pressure test (bubbles from foam) ü Retighten with half turn before feed in (carbamate) ü Apply a flush system

14 4. HP Butterfly Valves Safety Risk due to improper installation Did occur in ammonia plant leading to fire and extensive damage of plant And also in a urea plant And maybe more often but not reported

15 4. HP Butterfly Valves The Causes: ü Big torque from the pipelines ü Bolt forces were not enough ü Lens ring gasket was not in the right position during the assembly

16 4. HP Butterfly Valves Further when the disc is partially open, big forces act on the disc Pay attention to the right installation

17 4. HP Butterfly Valves Solution: BHDT SAFE High Pressure Butterfly Valve Assuring a reliable fixation realizing maximum safety

18 5. High Pressure Piping 316L Urea Grade High Pressure Piping ü Assure proper tracing and insulation ü Assure a proper design and installation ü After years perform regular corrosion inspections ü Replace with higher grade materials

19 6. What to do in case of a leak ü Retightening will not work ü Stop plant ü Assure no scratches on lens ring and flange faces ü Remove solids to see leak and avoid corrosion of carbon steel flanges, bolts and nuts ü Never use furmanite sealing techniques in carbamate lines (crevice corrosion risks!) ü Use right installation procedures and torques

20 6. What to do in case of a leak ü High Pressure valves (should) also have leak detection holes ü Carbamate leaks along a thread is dangerous as it will destroy the thread and threaten the integrity of the valve ü Stop plant in case of a leak ü Never use furmanite sealing to plug the leaking hole ü Use right installation procedures and torques

21 7. Conclusions 1. High Pressure piping and valves are critical for a safe and reliable urea plant 2. The choice and quality of materials is limited and vital 3. The details are very important 4. Choose a reliable and experienced fabricator