Comparing plug valves with other isolation valves, including gate valves, knife-gate valves, butterfly valves, and pinch valves.

1. Plug Valves and Other
Flow-Stoppers
Brian Gongol, M.Ed.
DJ Gongol & Associates, Inc.
August 24, 2022
Iowa Section AWWA Fall Short Course
Ankeny, Iowa

2. Why do we use isolation valves?
• Mostly for protection during maintenance and service
• Sometimes for throttling service

3. Overview of valve types

4. Plug valves
(rectangular port)

5. Plug valves
(round port)

6. Pinch valves

7. Gate valves

8. Cast knife-gate
valves

9. Two-piece
knife-gate
valves

10. Butterfly valves

11. Installation characteristics
A valve isn’t installed in a vacuum;
it matters how it fits into the system

12. Valve weight contributes to pipe stress
Valve weight

13. Heavier valves are harder to maintain or repair
Valve weight

14. Designs should account for workforce availability
(a two-person lift is less desirable than a one-person)
Valve weight

15. Pipe stress is real

16. Valve weight (4”)
Light Medium Heavy
Rectangular-port plug valves 72 lbs.
Round-port plug valves 115 lbs.
Pinch valves 66 lbs.
Gate valves 103 lbs.
Cast knife-gate valves 75 lbs.
Two-piece knife-gate valves 27 lbs.
Butterfly valves 15 lbs.

17. Valve weight (10”)
Light Medium Heavy
Rectangular-port plug valves 264 lbs.
Round-port plug valves 394 lbs.
Pinch valves 309 lbs.
Gate valves 392 lbs.
Cast knife-gate valves 251 lbs.
Two-piece knife-gate valves 88 lbs.
Butterfly valves 66 lbs.

18. Valve length
• Longer valves are bulkier

19. Valve length
• Shorter valves may fit into tight locations

20. Valve length
• Switching from long to short may require
expansion joints or fabricated pipes
• Switching from short to long may require
field modifications

21. Valve length (4”)
Short Medium Long
Rectangular-port plug valves 9.00”
Round-port plug valves 9.00”
Pinch valves 12.00”
Gate valves 9.00”
Cast knife-gate valves 2.00”
Two-piece knife-gate valves 2.00”
Butterfly valves 2.00”

22. Valve length (10”)
Short Medium Long
Rectangular-port plug valves 13.00”
Round-port plug valves 13.00”
Pinch valves 25.00”
Gate valves 13.00”
Cast knife-gate valves 2.75”
Two-piece knife-gate valves 2.75”
Butterfly valves 2.50”

23. Seating
Does the valve seat itself? Or
does it need a pressure
differential?

24. Seating Does the valve seat in only
one direction of flow?

25. Seating If flow is reversed, does the
valve still close?

26. Seating Are multiple pieces of
equipment sharing a header?

27. Seating
Bidirectional One way only Never really tight
Rectangular-port plug valves ⛔⛔
Round-port plug valves ⛔⛔
Pinch valves ⛔
Gate valves ⛔⛔⛔
Cast knife-gate valves ⛔⛔
Two-piece knife-gate valves ⛔
Butterfly valves ⛔⛔

28. Where can solids build up inside the valve?
Solids

29. Where can solids catch on surfaces inside the valve?
Solids

30. What’s the worst that can happen if solids get stuck?
Solids

31. Solids resistance
Highly resistant Can clog Likely to clog
Rectangular-port plug valves
Round-port plug valves
Pinch valves
Gate valves
Cast knife-gate valves
Two-piece knife-gate valves
Butterfly valves

32. Leakage
Look at paths to allow water out

33. Leakage
What parts can wear out
and cause leakage?

34. Leakage
Can parts be repaired with the valve
still in service?

35. Bonnets are there to
capture leaks

36. Leakage
Almost none If things wear out Likely to leak
Rectangular-port plug valves
Round-port plug valves
Pinch valves
Gate valves
Cast knife-gate valves
Two-piece knife-gate valves
Butterfly valves

37. Serviceability
• How many moving parts
does the valve contain?

38. Serviceability
• How many parts are subject to abrasion?

39. Serviceability
• Can any parts be accessed externally?
• Seals
• Operators
• Packing
• Working mechanisms

40. Serviceability
• How heavy are the parts?

41. Who climbs the ladder
and does the lifting?

42. Serviceability
Easy to service Medium effort Hard to service
Rectangular-port plug valves
Round-port plug valves
Pinch valves
Gate valves
Cast knife-gate valves
Two-piece knife-gate valves
Butterfly valves

43. Friction
losses
(Cv)
Friction losses are
standardized around Cv

44. Friction
losses
(Cv)
Cv is the flow (in GPM) that a
valve can pass at a 1 psi
pressure drop

45. Friction
losses
(Cv)
A high Cv is good
A higher Cv means more flow
without excess friction loss

46. Friction
losses
(Cv)
Different valve styles have
higher or lower friction at
different sizes

47. Friction
losses
(Cv)
Friction losses translate to
energy use, which is a huge
contributor to life-cycle cost

48. Friction losses (Cv) (4”)
Low Medium High
Rectangular-port plug valves 1,160
Round-port plug valves 982
Pinch valves 817
Gate valves 1,500
Cast knife-gate valves 1,200
Two-piece knife-gate valves 915
Butterfly valves 1,282

49. Friction losses (Cv) (10”)
Low Medium High
Rectangular-port plug valves 4,540
Round-port plug valves 4,870
Pinch valves 4,552
Gate valves 10,500
Cast knife-gate valves 7,500
Two-piece knife-gate valves 12,903
Butterfly valves 8,238

50. Throttling
service
How does the flow change if the
valve is throttled?

51. Throttling
service
Does constricting the flow make
clogging more likely?

52. Throttling
service
Will solids build up in bad places if
the valve is throttled?

53. Throttling
service
Is the degree of closure proportionate
to the throttling obtained?

54. Throttling service
Great for throttling OK to throttle Hard to throttle
Rectangular-port plug valves ⛘⛘
Round-port plug valves ⛘⛘
Pinch valves ⛘
Gate valves ⛘⛘
Cast knife-gate valves ⛘⛘
Two-piece knife-gate valves ⛘⛘
Butterfly valves ⛘⛘⛘

55. Closely related to leakage (they’re two sides of the same coin)
Suction service

56. Pinhole leaks can be enough to defeat a vacuum
Suction service

57. Friction losses are more hazardous on suction (their impact is magnified)
Suction service

58. When valves take turns

59. Suction service
Keeps air out Needs a close eye Likely to let air in
Rectangular-port plug valves
Round-port plug valves
Pinch valves
Gate valves
Cast knife-gate valves
Two-piece knife-gate valves
Butterfly valves

60. Operational requirements
• Exercise
• Cleaning/unclogging
• Seats, seals, packing

61. Price: Up-front? Life-cycle?
Low Medium High
Rectangular-port plug valves
Round-port plug valves
Pinch valves
Gate valves
Cast knife-gate valves
Two-piece knife-gate valves
Butterfly valves

62. Questions?
• Thanks for your time and
attention!
• This presentation can be
found at
gongol.net/presentations
• Brian Gongol
DJ Gongol & Associates
• 515-223-4144
• brian@gongol.net
• @djgongol on LinkedIn,
Twitter, and Facebook

63. Credits
• A limited number of stock images and icons were
automatically inserted by PowerPoint
• All other images (including all product-specific and project
site photos) are the original work of the author
• Copyright 2022 by Brian Gongol, all rights reserved