PACKING :PACKING :

To stop leakage To stop leakage between the stuffing between the stuffing box and the stembox and the stem

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IntroductionThe packed gland is used primarily for sealing process valve shafts (axial movement) and for process pump shafts (rotary movement). The packed gland has provided a low tech. convenient solution throughout the history of engineering. In modern times the packed gland is being replaced by more exotic solutions.

Typical Packed Gland Arrangement

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Applications of Gland Packing:-Gland packing are used for sealing in the following applications:

1. Used for reducing leakage along the stem in Globe valve, Gate valve, and ball valves. 2. Used for reducing leakage of the working fluid in reciprocating pumps. 3. Used for reducing leakage of the working fluid in rotating pumps like centrifugal pumps, screw, and gear pumps.

All the above are entirely different applications and hence the type of gland packing to be used also differs. Also depending on the nature of the fluid to be handled like temperature, pressure, corrosiveness, and suspended solids etc. A correct choice of gland packing has to be made by an engineer.

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Pumps:- The packed gland seal for pump applications is now rarely fitted to new pumps. This is due to it's high maintenance requirements. When fitted it is mostly used in conjunction with long coupled bed plate mounted pumps. Specific operating conditions require distinctly different types of packed gland seals. They require regular checks and maintenance adjustments. Proper lubrication of the gland packing requires a certain leakage rate. Special manufacturers recommendation's are to be observed individually. Service life expectancy is between 1 and 2 years, this can sometimes extend to several years on favorable conditions. Extremely bad fluid conditions (sediments, additives, overheating) can however drastically cut short their service life. Packed glands should preferably be used in conjunction with shaft sleeves in order to avoid damage to the shaft by aggressive fluids or due to improper treatment of the packed gland.

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Valves:- The packed gland is still widely used for stem sealing of various types of valves including gate valves, globe valves, and ball valves. The packed gland provides a low cost option with the capabilities of sealing under a wide range of operating conditions with a wide range of fluids by selecting appropriate packing materials. A packed gland is often used in conjunction with another type of seal or fluid containment e.g. an o-ring seals, bellows containment etc.The gland packing generally creeps over time and therefore needs to be regularly tightened to maintain the seal. The packing can be continuously spring loaded using disc springs or similar to extend the maintenance period.

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General :-The properties of a packing system required for good sealing and trouble free operation include :-

Compatibility with the working fluid at the operating temperatures

Plasticity to conform to the shaft under the influence of the gland force

Lubricant insoluble and immiscible with the sealed fluid

Non-abrasive to minimize shaft erosion

Non-corrosive to avoid damage to the shaft of housing

Wear resistant

Retain properties over time

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Packing Materials:-

Different types of gland packing depending on the type of applications such as for valve stem sealing, centrifugal pump shaft sealing, reciprocating pump shaft sealing, static duties like hatches sealing and pressure vessels manholes sealing etc. Are made from the following basic substances and are a combination of these basic materials and are sometimes reinforced with metal wires for extreme conditions.

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All the gland packing are a combination of the above mentioned basic materials and great research is done by the manufacturers to develop new and more efficient types of packing. The packing made of a combination of graphite, carbon, glass, etc. are used for harsh applications whereas gland packing made of materials like Jute, flax, hemp, and cotton are used for light applications like sea water, potable water etc. The compound PTFE is versatile and can be used for a wide variety of applications.Soft PackingYarn packing can be based on vegetable , animal or synthetic fibres and are based on various typesof fibre. Plaited Braided Twisted Plastic

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THE NON-METALLIC PACKING MATERIALS

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Expanded Graphite Packing Reinforced Graphite Packing

Graphite + PTFE PackingGraphite + Carbon Fiber Packing 10

Temperature Range For Packing Materials:-Table provided for guidance only, final design values must be obtained from suppliers

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Shaft Design:-The shaft/ sleeve surface in contact with the seal should have a surface finish of 0.4 micrometers or better. The clearances above and below the packing should be such to prevent extrusion of the packing material along the shaft. The clearance should not be too small that contact between the static and rotating metal is possible

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MAINTENANCE OF VALVE COMPONENT & PARTS:-

Replacement of Gland Packing:1. Even when valves have no failure such as leakage, the gland packing

should be replaced preferably every 2 to 3 years to reduce valve operating torque and to prevent stem wear.

2. Make sure, first of all, that gland packing is suitable for the maximum working pressure and temperature of the process and the kind of the fluid being handled (correct selection of packing materials).

3. Select a proper tool to remove packing so as not to damage the valve stem and valve packing chamber (stuffing box).

4. Clean the valve stem and valve packing chamber carefully.5. Normally. packing should be as thick as half the difference between

the inside diameter of the packing chamber and the valve stem diameter. If no such packing is available, slightly thicker packing will do, but thinner packing is not recommended under any circumstances.

6. Cut the packing with a 30o to 45o incline preferably, with a sharp cutting device or packing cutter. Each piece of packing must be sized properly so that both ends may meet one another with correct dimension.

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Replacement of Gland Packing: cont:-

7. Load packing to half the depth of the packing chamber, and press them down once. then load the remaining packing and tighten them securely. Loading all packing at a time is not recommended. All gland packing should be located so that the seams are 120o apart from each other. This will place the seam of the fourth packing ring in the same vertical position as the first one.

8. Gland packing is usually tightened to a position 3 to 4mm (1/8”) below the top end of the packing chamber. If leakage occurs, tighten the packing further down until leakage stops.

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How to Remove Gland Packing:-

Removing a gland packing can be very tough sometimes, especially if it is old and well set, you need to have specially contoured tools. There are also gland packing extractors available in the market, which look like a cork screw used to open the wine bottles but are flexible. They just have to be twisted to get a grip and then the packing can be pulled out. The problem comes when the old packing have lost their properties and the packing comes outs in fibers.

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PACKING PULLER (HOOK)PACKING PULLER (HOOK)

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ST

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TO REMOVE THE PACKING USING TO REMOVE THE PACKING USING PACKING PULLERPACKING PULLER

1. Remove all old packing using packing puller.

2. Clean the stuffing box and stem thoroughly.

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ST

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A(ID)

B(OD)D

HOW TO DETERMINE THE CORRECT PACKING SIZE & NUMBER OF PACKING RINGS

Packing Size = B – A(Cross Section) 2

Number of = D______Rings Packing Size

or D – Lantern Ring Size Packing Size

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Use inside calipers or if the portion of the gland which enters the stuffing box (the gland follower) is a snug fit, measure its OD. This will be the same as the stuffing box ID.

Use calipers, micrometer or other method.

Subtract the Stem Size from the Stuffing Box Size. (ID − OD)

Divide the difference by 2. ID − OD

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It will be more accurate to use decimal fractions at this point. (0.25” instead of ¼” etc.)

This is the distance the packing’s cross section will fill.

Measure the Outside Diameter (OD) of the Valve Stem.

Measure the Bore of the Stuffing Box. (Stuffing Box ID)

Find the nearest packing size. Using the chart below, convert the decimal fractions to the fractional sizes of packing. If your answer is in between sizes, use the next higher size.

0.0625” - 1/16” - 1.5mm0.1250” - 1/8” - 3.0mm0.1875” - 3/16” - 4.5mm0.2500” - ¼” - 6.5mm0.3125” - 5/16” - 8.0mm

0.3750” - 3/8” - 9.5mm0.4375” - 7/16” - 11.0mm0.5000” - ½” - 12.5mm0.5625” - 9/16” - 14.0mm0.6250” - 5/8” - 16.0mm

0.6875” - 11/16” - 17.5mm0.7500” - 3/4” - 19.0mm0.8125” - 13/16” - 20.5mm0.8750” - 7/8” - 22.0mm0.9375” - 15/16” - 23.5mm

TO DETERMINE THE CORRECT PACKING SIZE

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2 to 3mm (1/8’) size is for the gland follower to press the packing in the stuffing box.

Use calipers, depth gauge or other method.

Subtract Lantern ring size from L2.

- L3 = (L2 - L ring)

Use calipers, micrometer or other method to measure the thickness of lantern ring.

Will determined the number / layer of packing required.

Measure the Depth of Stuffing Box. (L1)

Subtract 2 or 3 mm (1/8”) for the gland follower to insert. (L2)

- (L1 - 1/8”)

TO DETERMINE THE CORRECT NUMBER /LAYER OF PACKING

Divide L2 by the packing size to get the number of packing

required. (L2 ÷ packing size)

Measure the Depth of Stuffing Box. (L 1)

Subtract 2 or 3 mm (1/8”) for the gland follower to insert. (L2)

- (L1 - 1/8”)

Measure the thickness of Lantern Ring (L ring)

PACKING WITHOUT LANTERN RING

PACKING WITH LANTERN RING

Divide L3 by the packing size to get the number of packing

required. (L3 ÷ packing size)

Will determined the number / layer of packing required but have to remember how many packing above and below lantern ring.

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How to Cut Gland Packing:- The gland packing should be cut with a sharp knife to avoid fraying of the edges. Do not use scissors or hack saw blade etc. A heavy duty engineer’s knife or a sharpened ordinary knife would do. There are two methods of cutting the gland packing:-

straight or at 90 degrees i.e. Butt joint 45 degrees i.e. Skive joint.

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PACKING CUTTERPACKING CUTTER

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PACKING CUTTERPACKING CUTTER

FIXED SCALEFIXED SCALE- Shaft (stem) Diameter- Shaft (stem) Diameter

SLIDDING SCALESLIDDING SCALE- Packing Size- Packing Size

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TO CUT A PACKINGTO CUT A PACKING

PACKINGPACKING

1. Coincide Sliding Scale to Fixed Scale

2. Tighten the Nut on Sliding Scale

3. Push the packing in & clamp

4. Cut the packing using sharp knife

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INSTALL ONE INSTALL ONE RING RING AT A TIMEAT A TIME

How to Install Gland Packing:-

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Install one ring at a time. Make sure that it is clean and has not picked up any dirt in handling. If clean oil is available, lubricate the shaft and the inside of the stuffing box.Joints of successive rings should be staggered and kept at 90° apart. Recommendable stagger is:- 90° apart for 4 rings and more, 120° apart for 3 rings and 180° apart for 2 rings. Each individual ring should be firmly seated with a tampering tool.

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1/8”(3 – 4mm)

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The Lantern Ring and its Purpose:- A lantern ring is an annular ring with channels for the passage of lubricant, cooling or flushing fluid that is inserted between the two sets of gland packing. Fluid is fed from an external pipe to the lantern ring for lubrication and the cooling of the packing. It is used in applications where a number of packing are there and it would be difficult of the intermediate packing to get fluid for lubrication. It is also used where the fluid to be sealed is contaminated with abrasives or is corrosive and a clean fluid is required for lubrication. While installation it is crucial that the holes in the lantern ring meet or are aligned with the holes in the pipes. It is very important to inspect and align the lantern ring during each overhaul of the pumps.

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LANTERN RINGLANTERN RING

LANTERN RING TAPLANTERN RING TAP(Lubricant Port)(Lubricant Port)

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ASSEMBLE TOOLS AND EQUIPMENT

Necessary: •Wrench for gland nuts.•Wrench for any gland flushing.•Flashing and inspection mirror.•Cleaning materials (rags, cleaning fluid compatible with product).•Packing pullers. •Packing lubricant.•Tamping tool.•Safety equipment.•Replacement packing.•Sharp knife.Optional:•Preformed packing set.•Hook, scraper and probes for removing difficult packing.•Lantern ring pullers.•Etc.

SHUT DOWN THE UNIT OR PUMP

PREPARE THE UNIT OR PUMP FOR PACKING REMOVAL

Notify people who will be affected by shutdown. If necessary, obtain permission. Please SAFETY tag on the power switch.

PROCEDURAL STEPS TOOLS, TECHNIQUES, METHODS etc

Shut off pump suction or discharge lines if there is any pressure or head when the pump is off.Secure any external flushing or lubrication system.Bleed off any system pressure.Observe any safety precautions if the product is dangerous or if the temperature is high.

REPACKING PROCEDURE:

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PREPARATION PHASE 33

SLIDE GLAND CLEAR OF OLD PACKING

Remove or swing adjusting nuts out of the way to allow gland to slide clear.

REMOVE OLD PACKING TO THE LANTERN

PREPARE THE UNIT OR PUMP FOR PACKING REMOVAL

Use packing pullers, hook, scraper or other means to get all the old packing out.If using a puller with a corkscrew or metallic end, the end should be inserted between the packing and the stuffing box.DO NOT PUT ANY HARD or METALLIC removal devices in contact with the shaft.

Determine number of rings below lantern.Insure that bottom rings have been removed.

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DETERMINE CORRECT LANTERN DEPTH

Measure or count rings to the lantern.

REMOVE ANY LANTERN

Use lantern pullers.Pull out square to avoid shaft or stuffing box damage.

Use rags and compatible cleaning fluid.The cleaner the area, the better the repacking.If the shaft has high or rough spots, they can be cleaned or burnished with a stone.

REMOVE PACKING BELOW LANTERN

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PACKING REMOVAL PHASE 34

INSPECT BOX FOR OLD PACKING SIGNS OR SHAFT WEAR SIGNS OF DAMAGE, GROOVES, SCORE MARKS etc.

If possible, feel stuffing box.If box is too small or too deep, a mirror and light should be used.You MUST make sure that it has ALL BEEN REMOVED.A small lump of packing will destroy the efficiency of a new packing.

PLACE NEW RINGS ON THE SHAFT

INSERT REMAINING RINGS

If you are using a packing set, make sure that the arrangement is in the right sequence.If a stiffer packing is used, place them on the shaft with a twist NOT A HINGE-LIKE OPENING.If you have not cut the packing rings – Do it now.Ensure the proper placement of rings in relation to any lantern.

The lantern must be aligned with the stuffing box lantern connection. The depth of the lantern must be known to you.

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INSERT AND SEAT THE BOTTOM RING

The bottom ring should be seated with the split on top.A tamping tool is used for the proper fit.

INSERT RINGS TO THE LANTERN

Each ring must be inserted, tamped and seated individually.The splits should be spaced 900 from the ones preceding.

The last rings can be tamped in with the gland itself.

INSERT AND SEAT LANTERN

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REPACKING PHASE

REPLACE GLAND AND HAND-TIGHTEN GLAND NUTS

Ensure packing will receive lubrication.Prepare area for heavy leakage.Obtain permission or notify affected people.Open any suction or discharge lines that were secured.Observe safety precautions for the product if any.

RECONNECT ANY GLAND ARRANGEMENT

PERIODICALLY RECHECK AND READJUST PACKING

Remove SAFETY TAG on POWER switch.

Where any tightening causes a heat built-up (Usually reached within an hour).

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PREPARE FOR PUMP START-UP AND LEAKAGE

This will greatly increase the packing life.

START-UP PUMP

Tighten the gland nuts EQUALLY ½ “Flat” at a time.Do not increase heat.Adjust at 15 minute intervals.

Check for signs of excess leakage or heat build-up.Readjust to the minimum leak-rate for that pump. (5 – 20 drops per minute is a typical range)

ALLOW GENEROUS LEAKAGE FOR 15 MINUTES

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START UP AND BREAK IN PHASE

GRADUALLY CUT DOWN LEAKAGE

DETERMINE MINIMUM LEAK RATE

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