POWER EQUIPMENT INSTRUCTOR: ROBERT A. MCLAUGHLIN ZAILI THEO ZHAO

1. POWER EQUIPMENT INSTRUCTOR: ROBERT A. MCLAUGHLIN ZAILI THEO ZHAO PIPING, VALVES & STEAM TRAPS

2. Learning Objectives • Understanding of piping systems, classifications, sizing and grades, including tubing identification.  • Identify the types of valves and their applications and limitations in typical piping system. • Identify the three basic types of steam traps. • Define the functions and limitations of various steam traps. • Discuss leading causes for steam trap malfunctions and how to repair defective units.

3. Piping Systems • Piping is used to connect the various units of machinery and equipment • Includes: • Sections of pipe • Types of fittings to join piping • Valves to control flow • Can also contain other accessories such as: vents, drains, traps, strainers, gages, relief valves, instruments, etc.. • Piping Design Considerations • Type of fluid being transferred • Operating pressures and temperatures • Amount of fluid delivered • Rate of fluid delivered • These conditions determine the type materials, valves, fitting and thickness of pipe or tubing

4. Piping Systems • Governing factors for piping design • Federal and private regulatory agencies • ASME (American Society of Mechanical Engineers) • Concerns all piping connections to power boilers with superheaters. • Boiler external piping is required to conform to the standards. • Most other agencies adopt these standards. • ASTM (American Society of Testing Materials) • Covers minimum standards for piping systems in power plants, pulp and paper mills, and other industrial plants. • ABS- American Bureau of Shipping- • A classification or insurance company for ships. • ABS sets the piping standards for ships, however they used ASME and ASTM as the source of there rules. • USCG- rules defer to the ABS.

5. Piping Systems • These codes cover minimum safety requirements for the : • selection of materials • Dimensions • Design • Fabrication • Construction • Testing of piping systems

6. Piping Connections - Threads • Low pressure applications, steam, water, lube oil, etc. •  Threads are NPT (National Pipe Tread) See sizing chart on the next page • NPT are tapered threads- • ¾˝ per foot • Before threads are engaged, the male threads are covered with a liquid, paste, or tape (Teflon) to : • Lubricate the threads • Help seal the joint

7. THREADS • “male” and “female” threads allow the joint to be engaged by hand a distance shown as F in the drawing below.    • When tightened with a wrench the male threads should extend into the female close to the distance E or the effective thread length. • The last few threads will be imperfect. • USCG prohibits the use of threaded joints in systems which the fluid temperatures are over 925oF.

8. THREADS • Male threads: • Measure the outside diameter of the large portion of the thread at "A"; • Find figure nearest this dimension in column 1 or 2 of chart. • The dimension in column 3 will be your nominal pipe thread size. • Female Threads: • Measure top diameter of thread at "B"; • Find figure nearest this dimension in column 1 or 2 of chart. • The dimension in column 3 will be your nominal pipe thread size.

10. PIPING CONNECTIONS -WELDED • Welding sections of pipe together. • Two methods of attachment: • Butt joint • Socket-welding joint

11. PIPING CONNECTIONS - FLANGED • A flange allows two pipes to be mechanically connected together • Or a pipe to be mechanically connected to a valve, tee, or other piece of equipment. • The principle of a flange is to use a mechanical force to pre-load the gasket sufficiently so that when internal pressure is applied, there is enough contact stress between the flanges and gasket to maintain a seal. • The flange itself needs to be connected to the pipe. • This is usually achieved by welding, though threaded and other weldless connections also exist.

12. FLANGED • Types of flanges include • WELDNECK • SLIP-ON • SOCKET WELD • THREADED • are common types.

13. FLANGED • The joints between flanges have to have gaskets between the faces of the flanges. • Gasket material will depend on the fluid in the system • Most are cut from sheet gasket material, which comes in different thicknesses, 1/32˝, 1/16 ˝, 1/8 ˝ are common thicknesses • Another type of gasket that can be used is the crush type • Also known as Flexitallic gaskets for the company that developed them • Have steel outer ring reinforcing ring and a center portion that is designed to be crushed. 

14. FLANGED • The flange faces must be aligned properly • The bolts must be tightened in the proper sequence • The proper bolt diameter is 1/8 ˝ smaller than the flange bolt hole dia. • The proper bolt length is with 2-3 threads of the bolt extending through the nut • Compression Fittings- Seamless alloy tubing like for hydraulic lines and lube oil lines • Flared fittings- Tubing, copper, Air lines • Soldered- low pressure, copper and brass water lines, refrigerant • Cemented- PVC, low pressure, drain lines

15. Piping Measurements • To accurately describe pipe, you need the following information: • OD- Outside Diameter • ID- Inside Diameter • OD-ID= Wall Thickness or Schedule • Schedule is identified by • standard schedule 40 • Extra Strong Schedule 80 • Double Extra Strong Schedule 160 • Other schedules Schedule 20, Schedule 120 • The higher the number, the thicker the pipe

16. Piping Measurements • Pipe is measured by nominal dimension • Called iron pipe size (IPS) and wall thickness • Nominal means close to but may not indicate actual dimension • Sizing from 1/8˝ to 12 ˝ are known by their nominal inside diameter. • The nominal outside diameter is standard regardless of schedule or wall thickness. • An increase in the schedule results in a decrease of the inside diameter. • 12 ˝ and over is designated by the actual OD, the wall thickness, and the weight per foot. • Pipe can also be described by its class of use: • Class 1 pipe- good on systems of 150 psi and above, and 150oF and above • Class 2 pipe- good on systems below 150 psi and 150oF.

17. Piping Measurements • Tubing is measured by OD and wall thickness. • For example: • Copper tubing wall thickness designated by letters • Type K • Type L • Type M • Type K copper tubing is the thickest, L is medium, and M is the thinnest.

18. Piping Fittings • Fittings are used in piping systems to: • Redirect the flow of fluid- 45o Elbows, 90o Elbows, • Extend a straight line of flow- Couplings • Split flow- Tees, Y connectors • Allow for easy access to parts of the system- Unions • Fittings may be installed by threading, welding, brazing, or the fittings may be flanged. • It really depends on the types of fluid, the system pressure, and the system temperature as to what connection method will be used. • Unions by design can be installed two ways; however there is only one correct way (cover in class).

20. Pipe Systems • All piping systems need to have support. • The can be from the top, sides or underneath piping system. • The will be installed is such a way as to allow for support of the piping in the system, plus the weight of the fluid contained within. • Must allow for expansion of the system piping • Types of supports: • Spring • Solid clamp • Roller

21. Valves • Purpose: to control system fluid flow for • Maintenance • Operation • Casualty Control • Proper procedure for opening • Open fully then back off ¼ turn. • Valve won’t jam • The next person won’t try to open it further

22. Valves • Major components • Disk attached to stem. • Disk seats against a seating surface in the body • Seat- • The seat and disc of valves used for high temperature service are often surfaced with a hardened material • Valve Body- • Bonnet • Stuffing Box • Packing gland or packing nut • Valve wheel (Hand wheel)

23. Types of valves - Globe • Disc attached to stem • Disc seats against a seating surface • May be fully open & closed, or partially open • Good for throttling. • Large pressure drops across globe valves, especially when throttling. • Should be installed so that the flow comes from under the seat. • System pressure will assist in opening the valve • If the packing needs attention, there will be no system pressure in the bonnet of the valve.

24. Gate Valve • Flat (parallel) or tapered gate interposed perpendicular to axis of flow. • Allows for straight through flow with little restriction or pressure drop. • Not practical for throttling applications (the disc will vibration & chatter) • Operate fully open or closed. • Come in a wide variety of sizes and types • Rising Stem • Non Rising Stem

25. Needle Point Valves • For fine adjustment of flow. • Tapered point at the inside end of the valve stem. • Used for throttling, especially when small quantities of gas or liquid are to be flowing.

26. Butterfly Valve • Lightweight, less space required than a gate or globe. • Quick acting (requires only ¼ turn.) • Can be used to throttle. • Low pressure application • Smaller place.

27. Check Valves • Some are automatically operated with no hand wheels or stems and some have the capability of being shut off. • Used to prevent return or back flow • Several Types • Lift Check • Swing Check • Ball • Stop Check Valves (can be positively shut off)

28. Ball valves • Quick opening (1/4 Turn) • Excellent for full flow applications • Can also be used for throttling • The fluid flow acting on the partially exposed ball can cause erosion. • High pressure •  plug valve

29. Strainers • Prevents the passage of grit, scale, marine life, and other foreign matter that could obstruct pump suction valves, throttle valves etc • Baskets can be removed for easy cleaning. • Simplex — only one basket, flow must be stopped to clean • Duplex — two baskets — flow may be diverted to allow cleaning of off-line strainer • Y-Strainers

30. Steam Traps • Steam traps are used is systems to • Drain condensate from heat exchangers • They hold steam in heat exchangers until it has completely collapsed to condensate. • Allows latent heat available in steam to be exchanged • They are used in low points of steam piping systems help avoid water hammer • Three main functions of steam traps are • Allow condensate which was steam to collect and flow back to the condensate system. • Vent air and other gases • Prevent the escape of steam- loss of available latent heat.

31. Steam Traps and Pipes • A steam trap is an automatic valve • it senses the difference between steam and condensate. • The trap discharges the condensate • with little or no loss of steam, • which contributes to high operating efficiency. • Steam traps are divided into three main groups: • thermostatic • mechanical • thermodynamic

32. Thermostatic Traps • It measure temperature • The balanced-pressure thermostatic trap has a liquid-filled bellows that expands and contracts. • When steam is in contact with the bellows • causes the bellows to expand • closes the valve • If condensate or air is in contact with the bellows, • bellows contracts and condensate is discharged • Steam pressure does not affect the operation of this trap,

33. Thermostatic Traps

34. Thermostatic Traps • The bimetallic trap also works according to the thermostatic principle. • Two strips of suitably different metal bonded together • The top strip expands more than the bottom one when heated • allowing cool air and condensate to pass through • As steam enters the traps and heats up the bimetallic strip, the strip bends and closes off the valve.

35. Thermostatic Traps • The liquid expansion thermostatic trap is operated by the expansion and contraction of a liquid-filled thermostat • When the steam is turned on, air and condensate pass through the open trap. • As the condensate temperature increases, the oil in the thermostatic element expands and closes off the valve. • An adjusting nut positions the valve relative to its seat, which allows the trap to be set at a given temperature, usually 212℉, or lower. • Some liquid expansion traps are used for freeze protection. When the temperature drops to 40℉, the trap opens, creating enough flow to prevent freeze-up.

36. Mechanical Traps • Mechanical traps distinguish between steam and condensate by their different densities. • Various floats are used to operate the discharge valve. • a ball floats on the surface of the condensate • as the condensate level drops, • ball covers the discharge passage • prevents the loss of steam • Air must be removed for the trap • can be vented automatically form the float trap

37. Mechanical Traps • Figure shows a float-and-thermostatic trap • Float rises when condensate enters, opening the valve • The valve closes if there is no condensate in the trap • If there is a temperature drop caused by air, the valve opens. • Element expands and closes when steam enters the trap.

38. Mechanical Traps • The inverted bucket trap • When system condensate enters • bucket is at the bottom and valve open • Air vented through a small hole on top of the inverted bucket • water level rises on both the inside and outside of the bucket • As steam fills the inverted bucket and makes it float, close valve. • Steam slowly escapes out of the bucket through the vent hole. • If the escaping steam is replaced by condensate, • bucket sinks • opens the valve

40. Thermodynamic Traps • Or disk traps, • identify steam and condensate by the difference in their kinetic energy or velocity as they flow through the trap • Low pressure flash steam • pushing down on the large surface on top of the disk • overcomes the force of the live steam pushing up in the smaller, exposed disk area.

41. THERMODYNAMIC TRAPS

42. Thermodynamic Traps • After startup, cool condensate lift the disk off its seat • As the temperature of the condensate increases, • Some of it flashes into steam • The mixture of steam and condensate flows outward across the underside of the disk. • Because flash steam has a larger volume • the flow increases as more flash steam is formed • high velocity causes a low-pressure area • to be formed under the disk and • the expanding flash steam exerts pressure on top of the disk, • forcing the disk downward and stopping all flow

43. Thermodynamic Traps • although the flash steam pressure is much lower • but the large exposed area • As the flash steam above loses heat, some of it condenses, reducing the pressure above the disk. • The disk is again lifted off its seat, and the cycle repeats itself.

44. THANK YOU