Sealing Systems Energy Efficiency.pdf

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Sealing SystemsSealing SystemsEnergy Efficiency

Fluid Sealing Association

Friction is OnlyFriction is OnlyThe Beginning

Fluid Sealing Association

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Sealing Systems Impact Efficiency

Friction losses are only the beginning– There is lost productp– There are cooling requirements– There are heating requirements

Some sealing systems use more energy than the pump driverM k t h h t thMarket research shows greater than 50% of the time inefficient sealing systems are used

Seals Contain Process and Energy

ProcessEnergy Can bewastedinto theinto the

atmosphere

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Basic Pumping System

P di hPump discharge

Valves

Mechanical SealBearing Housing

Flanges

Expansion Joint

Pump Suction

Pump

Motor

Bearing lubricant seals

Where are the Seals?

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Basic Pumping System

Pipes are joined with flanges– The flanges are sealed with gaskets

Valves are used to isolate parts of the system– The valve stem is sealed with compression packing. It

is a dynamic seal that accommodates linear and rotary motion

– The valve is joined to the pipe with flangesThe pump shaft goes through the pump housing and

d lneeds a seal– A mechanical seal or compression packing are

dynamic seals that accommodate rotary motion

Sealing Systems Impact Efficiency Directly

Leaks from static and dynamic seals waste product and contaminate thewaste product and contaminate the environmentDynamic seals consume energy from the friction between the static and moving partsg p– Contact pressure between parts in relative

motion is high due to the need to contain system pressure

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Sealing Systems Impact Efficiency Indirectly

Suction leaks can reduce pump efficiencyyFriction from packing on valve stems can affect control valves and prevent maintaining the desired outputSeal replacement can result in product loss and require entire systems to beloss and require entire systems to be de-pressurized and then re-pressurized

Sealing Systems Impact Efficiency Indirectly

Shaft sealing can require temperature control for operation– Re-circulating lines reduce pump efficiency– External cooling reduce the thermal efficiency of

the system– External injection has to be later removed

requiring evaporation – External injection has to be separated from the

product and treated before it can be disposed ofproduct and treated before it can be disposed of– External circulating systems for single or dual

seals require additional pumps

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An Example of a Sealing System That Wastes Energy

In a power plant the steam condensate circuit is a closed loopcondensate circuit is a closed loop systemWater is added to make up what is lost through the system leaksSome is lost as feed-waterSome is lost as feed waterSome is lost as steamSome is lost as condensate


Feed-water, steam and condensate are at a higher energycondensate are at a higher energy state than make-up waterEnergy required to elevate make-up water energy level to:

Condensate: 212 BTU/lb– Condensate: 212 BTU/lb– Feed-water: 370 BTU/lb– Steam: 1400 BTU/lb

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With a system where leakage is approximately due to

Feed-water 25%Steam 25 %Condensate 50%

– The energy required for 1 lb of leakage is:212 x .5 + 370 x .25 + 1400 x .25 = 548.5212 x .5 370 x .25 1400 x .25 548.5 BTU/lbOr 4577 BTU/Gal.


With a water make-up rate 50 GPM, the energy required to be added to thethe energy required to be added to the system is:– 4577 BTU/Gal x 50 GPM x 60 min x 24 hr x

365 days = 120,283,560,000 BTU/Year– Or 35,251,635 kilowatt hour

This is just the energy loss from leaksThis is just the energy loss from leaks. It does not include reheating by the system of the cooling of seal areas

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Energy Waste in Perspective

The average annual electricity consumption for a U.S. residential putility customer is about 11,000 kWh 50 GPM make up water that needs to be added in a Power Plant is the equivalent of the consumption of b t 3200 habout 3200 homes

We need to seal energy in a system, not just liquids.

Sealing Systems Impact Efficiency

Sealing systems contain energy as well as fluidsSome sealing systems use more energy than the pump driverMarket research shows greater than 50% of the time inefficient sealing systems are usedsystems are usedSealed equipment can be 10%-20% more efficient than sealless pumps

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Driver Power ConsumptionDepending on selection of the packing or

Frictional Power Consumption of Compression Packing @ 1750RPM @ 100 psig

20

3020

packing or mechanical seal type, sealing systems have a potentially significant influence on the

Frictional Power Consumption of Mechanical Seals@ 1750 RPM @ 100psig

4 3

0

10

20

1.000 2.000 3.000 4.000

Shaft Size (inches)

HP

0

10 kW

Packing 5 rings (1.000 x .312, 2.000 x .375, 3.000 x .500, 4.000 x .500)

power consumed by the pump driver.

0

1

2

3

1.000 2.000 3.000 4.000

Shaft Size (inches)

HP

0

1

2

kW

Single Unbalanced Dual Balanced Single Balanced Dual Dry Gas Seal

However …Driver power consumption is the tip of the iceberg.gThe potential for wasted thermal energy from a poorly selected Sealing System can be staggering, often exceeding the total power consumed b th d iby the driver.The following Case Studies illustrate this point.

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Case Studies Data

Most of the data was generated by HIMost of the data was generated by HI Associate Members and are part of theMechanical Seals Guidebook for pumps:

Applications Guidelines

FSA Members added parallel cases for the packing sealing solutions

An upcoming joint HI/FSA webinar is planned for “Fundamentals of

Case Studies Data

pMechanical seals”.– The course is based on the handbook – It does include the information presented

here in one of its sectionsCase studies illustrate the variations in– Case studies illustrate the variations in power consumption from various sealing systems as well as their relative operating costs

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Case Study 1 – Heat Transfer Oil

Several different sealing systems can be compared using a typical hot oil pumping application

Application specifics:Application specifics:– Single stage, end suction centrifugal pump (API 610 compliant)

providing heat to several areas of a plant– Pumped fluid: Hydrocarbon @ 315°C (600°F)

Specific Gravity 0.8Specific Heat 1.67 kJ/kg-°C (0.4 Btu/lb-°F)

– System pressure: 345 kPag (50 psig) in seal chamber– Pump shaft: 3600 RPM, 50mm (2.0”) diameter in the seal area

Pump driver: 50HP (typical)– Pump driver: 50HP (typical)– Sealing Devices:

Compression PackingMechanical Seals

– Heat lost at the pump must be replaced at the system boiler / heat exchanger

Case 1A – Least Energy Efficient

Low Temperature Seal with API Plan 32 – Cool External Flush

47 kW (160,000 BTU/hr) power required to

7.6 lpm (2 gpm) kerosene flush @ 38°C (100°F)

replace heat lost through dilution of the pumped fluid

frictional power consumed by seal

Sealing System Power Consumption = 47.4 kW

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Case 1B – Poor Energy Efficiency

Power required to replace heat lost through cooling 4.7 lpm

Low Temperature Seal with API Plan 21 – Cooled By-pass Flush

g g p(1.25 gpm) pumped fluid from 315°C (600°F) to 115°C(240°F) by the water-cooled heat exchanger

Power losses also include 38 lpm (10 gpm) of cooling water used by the heat

h


exchanger


Case 1C – Improved Energy Efficiency

1.52 lpm (.4 gpm)

Low Temperature Packing (0.1 ff) Flow Through Flush

p ( gp )kerosene flush @ 38°C (100°F)

9.4kW (32,100 BTU/hr): Power required to replace heat lost to product & flush outlet (30% of Flush going into product)


2509 W (8,569 BTU/hr): frictional power consumed by packing

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Case 1D – Greatly Improved Energy Efficiency

A portion of the sealed fluid is

Low Temperature Seal with API Plan 23 – Cooled Closed-loop Flush

pisolated from the hot process so that the total cooling load is significantly reduced and the change in temperature across the heat exchanger is reduced (as compared to the Plan 21 in Case 1C)



Case 1E – Significantly Improved Energy Efficiency

(A properly installed steam flush uses very little steam, and has almost no effect on the process temperature)

High Temperature Packing (0.12 ff) with Steam Injection

the process temperature)

Q2 = 440W (1,500 BTU/hr)heat radiated from seal chamber area

Q1 = 3.0kW (10,236 BTU/hr)frictional power consumed by packing


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Case 1F – Significantly Improved Energy Efficiency

Q = 440W (1 500 BTU/hr)

High Temp Packing(0.1 ff, 2 x Carbon Fiber, (1,500 BTU/hr)

heat radiated from seal chamber area

4 x Graphite) No Flush

3.0 kW (10,236 BTU/hr) frictional power consumed by packing

Sealing System Power Consumption = 3.4 kWSources: FSA Life Cycle Cost Estimator tool, www.fluidsealing.com .

Case 1G – Optimal Energy Efficiency (Liquid Lubricated Seal)

High Temp Seal with API Plan 02/62 – Dead Ended / Steam Quench

(A properly installed steam quench uses very little steam, and has almost no effect on the process temperature)

heat radiatedfrom seal

chamber area



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Case 1H – Optimal Energy Efficiency (Dry Gas Seal)

High Temp Dual Seals with API Plan 74 Pressurized Gas BarrierO-ring Reliability?

Q1 = 35 W (120 BTU/hr) frictional power consumed by seals

Q2 = 440 W (1500 BTU/hr) heat radiated from seal chamber area

O-ring Reliability?

by seals


Case 1 Populations Found in Industry TodayFSA member companies have assembled data on 28,000 seal applications where the pumping Plan 2

Plan 32

Plan 23

pp p p gtemperature exceeds 200°C (400°F), similar to Case Study 1.

– Chart 1 represents the frequency of the API piping plans used in these 28,000 high temperature applications

– Chart 2 shows the comparative power consumption values for

0% 5% 10% 15% 20% 25%

Plan 74

Plan 21

Selection Frequency

Plan 21

Driver (Case 1)

Plan 32

p peach sealing system in Case 1.

– We estimate around 20% of these applications use compression packing, but we have no reliable data on packing type or piping arrangements.

0 10 20 30 40 50

Plan 74

Plan 2

Plan 23

Power Consumption (kW)

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Case Study 2 – Water Based Slurry

Water based slurry applications are ubiquitous in general industry markets (e g Pulp & Paper Watergeneral industry markets (e.g. Pulp & Paper, Water & Waste Water , Mining & Minerals, Power Generation)

An estimated 50% of these pumps use compression packing with cool external flush.

When using seals, Plan 32 - Cool External Flush is g ,also typically the default seal support system selected in these industries.

Case Study 2 – Water Based SlurryApplication Specifics

End suction centrifugal pump (ANSI B-73 compliant)

Pumped fluid: Water with entrained solids @ 75°C (170°F)

Example: Green or Black liquor

System pressure: 345 kPag (50 psig) in seal chamber

Pump shaft: 3600 RPM, 50mm (2.0”) diameter in the lseal area

Flush water introduced at the pump must be removed downstream to restore the integrity of the pumped fluid

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Case 2A – Least Energy Efficient

6.6 lpm (1.75 gpm) clean

Low Temperature Seal with API Plan 32 – Cool External Flush

Q3 = 249 kW (849,000 BTU/hr) power required to remove flush water from the pumped product to restore process integrity

water flush @ 10°C (50°F)



Case 2B – Poor Energy Efficiency

Packing (0.12 ff) with water injection Carbon bushing from Lantern ring

Q3= 59.5kW (204,085 BTU/hr): Power required to remove 1.9 lpm (.5 gpm)


Q1 = 1800 W (6,141 BTU/hr): frictional power consumed by packing

clean water flush from the pumped product to restore process integrity

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Case 2C – Improved Energy efficiency

.4 lpm (.1 gpm) clean water

Packing (0.1 ff) with Cool External Flush

Q3 = 9 kW (30,870 BTU/hr) power required to remove flush water (60 % to process) from the pumped product to restore process integrity

p ( gp )flush @ 10°C (50°F)

4250 Wfrictional power consumed by packing


Case 2D – Improved Energy Efficiency

Dual Seals with API Plan 54Circulated Barrier from External Source

power required by the motor of the auxiliary pump to circulate the barrier fluid

frictional power consumed by seals


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Case 2E – Optimal EnergyEfficiency (Dry Gas Seal) Dual Seals with API Plan 74 – Pressurized Gas BarrierReliability with solids inside inboard seal?

Q1 = 35 W (120 BTU/hr) frictional power consumed

Reliability with solids inside inboard seal?

pby seals


Conclusions

Potential sealing system savings can exceed the energy savings obtained from switching to variable f d i t i i i ll i ifrequency drives, trimming impellors, or re-sizing pumps in many applications.Selection of inappropriate sealing systems can place significant additional thermal energy requirements on plant utilities.Sealing systems found in many industrial applications (even when functioning as intended) are extremely wasteful of energy, and their thermal power consumption can exceed the power output of the driver itself.

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Conclusions

Improved technology sealing systems available today can eliminate the need for energy-wasting systems that result in cooling/dilution of the process and thethat result in cooling/dilution of the process and the need for downstream separation/evaporation, re-heating, and/or effluent treatment. Data available from FSA members for 28,000 high temperature pumps show frequent use of energy-wasting seal support systems.A significant initiative will be needed to educateA significant initiative will be needed to educate industry on the potential for energy savings through the adoption of improved sealing system designs.Publicize the Handbook and Webinar

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Sealing Systems Energy Efficiency.pdf