Threaded and Grooved Pipe

OBj 1- identify types, marks, designations, press ratings on ferrous pipe and fittings.

Pipe Grade/Sched numbers

-Standard (STD)

  • similar to sched 40 from 1/8 to 10”

  • 150 psig rated

  • Most commonly used in residential

-Extra Strong (XS or XH)

  • similar to sched 80 from 1/8 to 8”

  • 200 psig rated

  • Used often in steam and corrosion service

-Double Extra Strong (XXS or XXH)

  • No exact corresponding sched #

  • 1000 psig rated

  • Used often in hydraulic systems

Pipe schedule # is based on 1000 times the pressure/stress ratio. Usually ranges sched 10 to sched 160.

Steel grade A,B,C. A&B is common.

  • A is used for cold bending due to low carbon content it is less brittle.

  • B has more carbon and more tensile strength/

Pipe sizing:

-steel/iron pipe usually comes in 1/8” and upwards

-Size refers to nominal ID at sched 40 up to and including to 12”.

  • If 14” and higher, it’s sized by exact OD.

-Calculate wall thickness → OD - ID / 2

-If wall thickness changes, the ID changes. OD remains the same so standard threading equipment can be used.

-Pipe lengths supplied usually 21’ lengths (+- 1/2”)

-Pipe finishes:

  • black iron : cleaned thoroughly, finished end, protective lacquer for corrosion

  • Pickled and oiled: cleaned thoroughly of rust , grease, paint. Mild acid bath dunk and then oiled

  • Ammonia: cleaned and free of oil

  • Galvanized (standard): bathed in molten zinc. 2oz/ft2. Inside and outside. Zinc deposits only on surface of pipe.

  • Galvanized (bending quality): galvanizing is treated specially to prevent flaking when bending. Zinc has low melting point so do not heat when bending.

  • Painted

  • Bituminized or asphalt

  • Yellow Jacketed: PVC coating to outside

  • Reamed and drifted: Very close tolerance, machine reamed

  • Other: epoxy, concrete, glass lined, plastic

Abbreviations on pipe, valves, fittings:

  1. CWP - cold working (water) pressure

  2. G - gas

  3. O - oil

  4. S - steam

  5. S.P - steam pressure

  6. W.O.G - water, oil, gas

  7. W.S.P - working steam pressure

-When identifying a tee, describe it by the size of the run from largest to smallest size , then identify the branch. Always identify the branch last even if its the largest (called a bull head tee)

-Nipples go in 1/2” increments up to 12”

-Close nipple vs space nipple- a space nipple has actual wall thickness integrity. Cannot use a close nipple on gas.

Union types

  1. Iron to iron

  2. Iron body with bronze seats (Dart)

  3. 1 brass and 1 iron seat (Rex)

  4. Gasket between 2 seating faces (Lip)

Malleable Iron

-cast iron that was heat treated to be less brittle.

-Shaped by hammering

Malleable Iron fittings (black or galvanized):

  1. Class 150 (standard)

    • used extensively

    • 300 psig at 150 F, if steam 150 psig

    • 1/8” to 6” inclusive

  2. Class 300 (Extra Heavy)

    • higher press and temp

    • For steam 300 psig at 550F.

    • Pressure varies based on pipe size

    • 1/4” to 3” inclusive

Pressure Cast Iron Fittings (black or galvanized):

  1. Class 125 (standard)

    • 1/4 “ to 8”

    • Max saturated steam press is 125 psig.

    • Liquid and gases 175 psig at 150F

  2. Class 250 (Extra Heavy)

    1. high temps and pressures

    2. 1/4” to 8”

    3. Max steam pressure 250psig

  3. 400 psig at 150F for liquids and gases

Forged Steel Fittings

  1. Class 2000

    • Used with sched 80 pipe.

    • 2000 psig at 100F, steam is 615 psig.

  2. Class 3000

    • Used with sched 160 pipe

    • 3000 psig at 100F, steam is 925 psig.

  3. Class 6000

    • Use with XXS pipe

    • 6000 psig at 100F, 1855 psig steam psig.

-Max pressure rated decreases as piping system temp increases.

Recessed cast iron- drains and waste

Groove and Shoulder joint:

  • called grooving or vicking, usually victaulic products.

  • Grooved ends butted together, gasket inside that prevents leak.

  • Gasket must be lubricated.

  • Gasket design uses pressure to push it sealed. Higher pressure makes a tigher gasket seal.

  • Joints sometimes might leak during pressurization but will seal up after.

  • Groove types:

    • Roll groove- thinner wall diameter. (min sched is 10). Pressure loss considered insignificant.

    • Cut groove- needs thicker pipe wall (min sched 40)- advantage is no restriction at groove.

Fittings- most common materials used:

  • ductile iron (most common)

  • Malleable iron

  • Galvanized steel

  • Stainless steel

  • Aluminum

  • Copper

Press connect joints:

  • MegaPress for steel. Viega is the only mfg for the fittings.

  • Fittings use a sealing element and grip ring with bidirectional teeth that grip the pipe. Compression fitting.

  • ½ to 4”

  • -14 to 200 psig, -40 to 284F

obj 2 - identify application of codes, regulations, mfg specs.

-briefly touches on B31, B149.1, and Plumbing code.

-B31 is for pressure over 15 psig, or hot water generated at pressures >160 psig and >250F.

obj 3 - ferrous, alloyed, non ferrous pipe

  • non ferrous is usually more resistant to corrosion and magnetism.

  • Ferrous is the most used metal, rusts in moist air

  • Pig iron was the first known purified iron. (very high in carbon)

  • As iron is purified, carbon is reduced, making it less brittle and more ductile. But leas hard wearing

Obj 4 - fabrication of steel pipe

  • NPS - nominal pipe size

  • NPT - nominal pipe thread

  • Mild steel usually 0.1 or 0.2% carbon to mfg pipe

  • Ferrous (Iron) pipe

    • mild carbon steel

    • Wrought iron

    • Cast iron

    • Alloys with iron

  • Alloy (contains iron and other metals):

    • Copper alloy

    • Stainless alloy

    • Chrome alloy

  • Non-Ferrous ( little to no iron) pipe

    • aluminum

    • Copper

    • Brass

    • Lead

    • Plastic

    • Concrete

    • Wood

  • NPT defined as a taper that enlarges at 3/4” per foot of thread.

  • ASPT and NPT are the same thing.

  • Joint compounds primarily act as lubricants not sealants

  • Teflon tape applied same direction, approx 1.5 wraps, ensure first 2 threads left bare.

  • Oxygen lines to be cleaned with carbon tetrachloride after install before the oxygen is introduced into pipe

  • Pitch on pipe thread is the spacing between the crest on the thread (or center to center of the peaks)

  • Joint tightening- hand turns must be more than turns with wrench.

  • Threads are cut at 60 degrees angle. ¾” per foot of thread measured across diameter.

    Obj 5 - calc cut length for threaded and grooved

  • 4 common dimensions:

    • center to center

    • Center to end

    • End to end

    • End to end overall

  • 5 less common dimensions:

    • center to back of pipe

    • Center to front of pipe

    • Center to face of fitting

    • Face to face of fittings

    • Center to back of fitting

  • Throw vs thread engagement vs fitting allowance:

    • throw: reference line to face if fitting. Reference line usually the centerline of fitting.

    • Thread engagement: how much of the pipe enters into fitting.

    • Fitting allowance: subtracting thread engagement from the throw is the fitting allowance. Essentially the dead space where the pipe does not go.

  • Grooved piping has no thread engagement so it’s treated similar to butt weld joints. Mfg provides throw and pipe end separation.

    obj 6- hand tools to thread

  • Hand threading:

    • Use “pumping” action. Use your body weight above the handle, do not raise handle above waist.

    • Remove “swarf”- oily shavings

    • Use proper cutting oil not vehicle oil

    • Stop threading when outer faces of dies are flush with 1 end of pipe or when sizing plate reaches dropout point on tool housing. Going beyond will make a straight (aka running) thread.

    • Threading CW, once done, turn CCW to remove threader

obj 7 - power tools for threading

  • start rotating machine before touching material. Pulls alot of amperage if u start turning when already on material

  • Pre-oil if no auto oiler, oil as you cut. If threading non ferrous, the cutting oil used is different. Oil continuously as you cut.

  • Thread complete when thread goes at the end of die tooth (usually go pat 1 or 2 turns tho)

  • Nipple chuck used for holding short or close nipples for threading

  • Cutting fluid uses:

    • keeps tool and material cool

    • Lubricates cut

    • Good finish on work

    • Helps clear swarf

      Better use more than not enough

  • If using oxygen service, ensure no cutting oil inside pipe. This can cause fire.

  • cutting oil types:

    • Mineral fatty oil blend

      • Most common

      • Mainly for Non ferrous metals, some light mild steel

      • Non corrosive, non staining, high precision, transparent

      • Not good for extreme pressure (EP)

    • EP oils (extreme pressure)

      • added sulphur and chlorine compounds

      • More viscous with high active sulphur . Less viscosity does decrease the cooling power though

    • Specialty

      • non corrosive types, suplhured fatty types

    • Soluble cutting fluid

      • used if cooling is highly important.

      • Oil capable with emulsion

      • Cast iron, malleable iron, brass, copper, aluminum

    Selecting fluid:

  • Steel, wrought iron- thread cutting oil

  • Stainless steel- special high sulphur

  • Copper- mineral lard oil

  • Brass pipe- soapy water

  • Plastic- lubricant for no oil cutting

  • Do not allow cutting fluid temps to exceed 43 C.