Process Engineering Equipment Handbook 2009 Part 4 pdf

Special features include: Proven heavy-duty trunk-piston compressor of high reliability Compact design, good accessibility, easy to maintain Fewer wear parts than in crosshead design

C-90

stroke limiters that are not cast but machined, as well as frictionless guided plateswith low lift and good fatigue properties This OEM has its own compressor valveproduction facility This ensures high reliability and availability of the valves andcompressors The valves fulfill the requirements of ISO 8012, API 618, and theEuropean Standard on compressor safety They are designed to prevent inadvertentwrong assembly into the cylinder See Fig C-73.

Suction valves may be equipped with unloading devices for continuous or steppedcapacity control

Special tools. Together with each compressor, the OEM supplies a set of specialtools to simplify routine service, like the device to conveniently assemble and installvalves for certain sizes of horizontal compressors, or the hydraulic tools, allowingthe proper fastening of vital connections See Fig C-74

Piston rod packing. The packing to seal piston rod and cylinder consists of severalstacked rings, designed as a cartridge for ease of maintenance Packing rings aremade of PTFE or other newly developed compounds as well as sintered metal Theyare subject to stringent quality requirements and feature minimum gas leakage,low friction losses, and minimum wear See Fig C-75

Compressors C-91

FIG C-67 Typical features in an API 618 reciprocating compressor (Source: Sulzer-Burckhardt.)

To provide efficient heat removal, direct or indirect cooling is used, depending onthe application Special designs for high-pressure duties or particular processrequirements are available.

Piston rod packings are generally well suited to meet the increasing demandsimposed by legislation to protect the environment

FIG C-68 Typical crankcase (Source: Sulzer-Burckhardt.)

FIG C-69 Typical bearing (Source: Sulzer-Burckhardt.)

Compressors C-93

FIG C-70 Typical crosshead fastening (Source: Sulzer-Burckhardt.)

C-71 Typical piston nod runout and crosshead design (Source: Sulzer-Burckhardt.)

FIG C-72 Typical piston design (Source: Sulzer-Burckhardt.)

Oil wiper packing. For oil-free compression no trace of oil may be allowed to creepfrom the crankcase along the rod into the cylinder Triple wiper rings—equippedwith garter springs—are well known and also used in labyrinth-type compressorsfor oxygen service Each of the three rings is provided with an oil wiper lip Thecollected oil is led back into the crankcase See Fig C-76

Scraper performance is further improved by providing large communicatingpassages around the crosshead to avoid crosshead pumping effects

Typical application for reciprocating compressors: water-cooled,

lubricated trunk-piston compressor

Typical application processes include: (gases) H2, He, natural gas, CnHm, N2, Ar, CO2,air, and other noncorrosive gases and gas mixtures in the following plant systems:

Compressors C-95

FIG C-73 Typical compressor valve (Source: Sulzer-Burckhardt.)

FIG C-74 Typical cooling for valve installation (Source: Sulzer-Burckhardt.)

Compressors C-97

FIG C-75 Typical piston rod packing (Source: Sulzer-Burckhardt.)

FIG C-76 Typical oil wiper packing (Source: Sulzer-Burckhardt.)

 Helium recovery systems  Petrochemical industry

 Gas production plants

See Figs C-77 through C-87

Special features include:

 Proven heavy-duty trunk-piston compressor of high reliability

 Compact design, good accessibility, easy to maintain

 Fewer wear parts than in crosshead design

 Completely factory-assembled and tested, simple to install without assistance ofmanufacturer

 Modest space requirement, no special foundations needed; therefore especiallysuitable as replacement compressor for revamping of plants and/or “last-minute”delivery

 Modular component concept allows optimal adaptation to users’ operating conditions

 Standard arrangement for 3, 4, and 5 stages allows short delivery times

 Pressure-tight crankcase for elevated suction pressures up to 16 bar abs (220psig), with no gas losses to atmosphere

 Automatic condensate drain with integrated unloaded start system

 Combined concentric suction/discharge valves for high volumetric efficiency, lowvalve temperatures, and fewer valves

 Efficient cooling for continuous duty and low maintenance operation

 Low-pressure ratio per stage provides high-efficiency, low-discharge tures, and less wear

tempera- Consider the multitrunk-piston compressor arrangement The advantages over asingle crosshead machine are:

 Minimal investment risk: You start modestly, then add capacity in reasonablesteps as requirements increase

 Reduced wear and longer life: According to demand, compressors either run atoptimum load or remain idle Simple control system

 High availability: Service your compressors one at a time while the others keep delivering

See Figs C-88 through C-90

Design features

Crank mechanism and lubrication. The two-throw heavy-duty crankshaft with integralbalance weights is supported on roller bearings located in detachable bearingcovers One of these covers also carries the built-in oil pump and filter Theconnecting rods have replaceable trimetal bearing shells at the big end and rollerbearings at the piston pin See Fig C-91

Compressors C-99

FIG C-77 Combined booster and primary compressor for an ethylene plant in Spain Suction pressure 1.7 bar abs,

discharge pressure 286 bar abs Compressor runs at 300 rpm with a power input of 2330 kW (Source: Sulzer-Burckhardt.) FIG C-78 Compressor installation in Germany 2600 m 3 /h of hydrogen at 1 bar abs are compressed to 325 bar abs The five- stage machine operates at 585 rpm with a power requirement of 700 kW (Source: Sulzer-Burckhardt.)

FIG C-79 Skid-mounted hydrocarbon gas compressors for offshore duty in Greece Suction volume 2850 m 3 /h, discharge pressure 19 bar abs, speed 420 rpm, power input 400 kW (Source: Sulzer-Burckhardt.)

FIG C-80 Chlorine compressor installed in a chlorine production plant in Colombia 605 m 3 /h of Cl 2 are compressed to 8.5 bar abs The compressor operates at 480 rpm, the power input is 65 kW (Source: Sulzer-Burckhardt.)

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80

Compressors C-101

FIG C-81 Hydrogen producing and bottling plant in Great Britain with two natural gas and four hydrogen compressors The hydrogen compressors operate at 650 rpm, the discharge pressure is 235 bar abs and the power 80 kW (Source: Sulzer- Burckhardt.)

FIG C-82 Hydrogen sulfide compressor supplied for a chemical plant to compress 1040 m 3 /h H 2 S to 31.4 bar abs The

speed is 495 rpm and the power input 280 kW (Source: Sulzer-Burckhardt.)

FIG C-83 Nonlubricated high-pressure compressor in Finland, compressing 750 Nm 3 /h dry hydrogen from 17 to 230 bar abs

in three stages Shaft power is 100 kW (Source: Sulzer-Burckhardt.)

FIG C-84 Two-stage compressor in the natural gas storage facility of Stadtwerke Bremen, Germany Suction pressure 70 bar, discharge pressure 166 bar, speed 585 rpm, power 420 kW (Source: Sulzer-Burckhardt.)

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FIG C-85 Tube trailer filling station; a typical application for hydrogen compressors (Source: Sulzer-Burckhardt.)

FIG C-86 Compressor in a chemical works for hydrogen bottling in Brazil (Source: Burckhardt.)

Sulzer-The crank pin bearings are forced-feed lubricated, while all other mechanicalcomponents as well as pistons and cylinders are amply lubricated by means ofsplash lubrication The crankcase is sealed and vented to the compressor suctionside.

Cylinders. The cylinders are made of treated high-quality cast iron and jacketed for ample cooling The pistons are manufactured of high-quality cast iron andincorporate specially selected cast-iron piston ring combinations The combined and concentric suction and discharge plate valves are removable as a unit See Fig C-92

Cooling and piping. Water or another liquid coolant provides for all the compressorcooling requirements From a manifolded inlet, the coolant is distributed to allcritical points such as cylinder jackets by means of high-strength flexible hoses SeeFig C-93

The separators located at the outlet of each stage are regularly drained by means

of diaphragm valves actuated by a timer-controlled solenoid The condensate andescaping gas are led from the separators into a condensate receiving tank fromwhere the gas is recycled into the suction line while the condensate can be manuallydrained off to atmosphere

Instrumentation. Each compressor stage is equipped with a pressure gauge andsafety valve The gauges are arranged in a compact panel, which also contains theindicating oil-pressure switch Temperature switches monitor the gas temperature

on selected stages The outlet of the safety valves is piped back to the suction of thecompressor Level gauges for crankcase oil and for condensate receiving tank arealso included See Fig C-94

Arrangement and drive. The basic gas compression system consists of a packagedunit with a sturdy steel skid (see Fig C-95) on which the complete compressor,

Compressors C-103

FIG C-87 Mobile high-pressure nitrogen plant with low-pressure air feed module, PSA module, and diesel-driven nitrogen compressor module for oil-well servicing (Source: Sulzer-Burckhardt.)

flywheel, V-belt drive, coolers, separators, condensate receiving tank, and piping(see also Fig C-94) are installed An integral universal motor base is also provided.The skid, designed on the basis of field measurement data and of finite elementcalculations, is supplied with six vibration dampening elements.

The air compression system has a similar arrangement as above, but with openrelief valves and with an automotive-type suction filter instead of the flexible inlet header See also Figs C-96 through C-98

FIG C-88 Compressor selection, dimensions, coding, and materials (Source: Sulzer-Burckhardt.)

Compressors C-105

FIG C-89 Main compressor operating data (air and similar gases) (Source: Sulzer-Burckhardt.)

FIG C-90 Main compressor operating date (gases) (Source: Sulzer-Burckhardt.)

Compressors C-107

FIG C-91 In pressure-tight execution (optional) the crankcase is equipped with oil-cooled double mechanical seals (Source: Sulzer-Burckhardt.)

FIG C-92 Typical valve (CT compressor type) (Source: Sulzer-Burckhardt.)

FIG C-93 Typical pressure gauge and safety valve on each compressor stage (Source: Burckhardt.)

Sulzer-Standard supply scope. This may differ according to customers’ specifications.

Compressor crank mechanism

 Crankcase with crankshaft seal for suction pressures up to 1.1 bar abs and ventline to suction or crankcase with mechanical seals for suction pressures from 1.2

to 16 bar abs (see Figs C-96 through C-98)

 Two crankcase purging gas valves (gas compression only)

 Oil pump (crankshaft-driven), filter, pressure gauge, and level sight glass

Gas stream

 Flexible hose on suction or automatic-type air filter

 Interconnecting gas piping from first stage to outlet separator on last stage

 Shell and tube gas cooler and separator after each stage

 Automatic condensate drain consisting of:

 diaphragm valve on each separator

 condensate receiving tank with level sight glasses

 manual drain valve on the condensate tank

 return line condensate tank-suction line

 Pressure gauge and relief valve after each stage

 Flexible hose on discharge with nonreturn valve and compression fitting

FIG C-94 Standard panel, including optional contamination indicator for oil filter and gauge with pressure limit switch for sequential condensate drain system (Source: Sulzer-Burckhardt.)

FIG C-95 Typical compressor skid (Source: Sulzer-Burckhardt.)

Water system

 Interconnecting water piping between inlet manifold, jackets, coolers, and outletmanifold, by means of high-strength flexible hoses

 Control, vent, and drain valves

 Flow sight glasses

 Temperature gauges

Compressors C-109

FIG C-96 Standard condensate receiving tank (Source: Sulzer-Burckhardt.)

FIG C-97 Filter system (Source: Sulzer-Burckhardt.)

FIG C-98 Remote control (Source: Sulzer-Burckhardt.)

Electrical equipment

 Solenoid valve for condensate drain control with separate time relay

 Temperature switches on second and last stages

 Oil pressure switch

 Oil refill system to permit oil refill during operation

 Noise-retaining weatherproof housing

 Suction filter 10m

 Coalescence and activated carbon filter to remove oil downstream of compressor,

to get oil aerosol content down to 0.2 ppm (weight) approximately

 Pressure-maintaining valve

 Additional instrumentation

 Automatic condensate tank drain (level controlled)

 Sequential condensate drain system to ensure that each separator drains individually

 Crankcase heater (at or below +5°C ambient temperature)

 Additional manual condensate drain valves for each separator

 Closed execution for diaphragm valves for condensate drain (included for H2service)

 Terminal box on or beside compressor skid

 Remote control box on or beside compressor skid

 Control cabinet (including motor starter) (Fig C-99)

Nonlubricated sealing system in “LABY ® ” compressors

Significant inventions often depend on simple principles that seem self-evident inhindsight This is true of the labyrinth sealing technique An extremely largenumber of throttling points provides the sealing effect around pistons and pistonrods No contact seals are used See Figs C-100 and C-101

Whereas plastic sealing rings depend on permanent mechanical friction forefficient performance, the labyrinth principle embodies an extremely small

clearance between sealing element and counterpart This is the key to thedurability, reliability, and availability of this compressor type and, therefore, to itseconomic operation.

Above all, the unique labyrinth sealing technique is employed for applicationswhere no lubricants are allowed in the cylinder and where no abrasion particlesare accepted in the process gas This is particularly true for oxygen compression,where safety is the most important aspect At the other extreme it is also employed

Compressors C-111

FIG C-99 Control cabinet (Source: Sulzer-Burckhardt.)

FIG C-100 How a labyrinth seal works (Source: Sulzer-Burckhardt.)

for applications where the process gas is heavily contaminated with impurities,such as polymerization products or other very small and hard particles They haveeffectively no influence on the labyrinth seal performance, compressor reliability,wear rate, and maintenance intervals.

Piston and piston rod are guided by the crosshead and the guide bearing, whichare located in the oil-lubricated crankcase Both guiding elements are made of metaland are oil lubricated, thus ensuring a precisely linear operation of the labyrinthpiston as well as an extremely long life of the piston/piston rod guiding system.The distance piece separates the gas compressing section from the oil-lubricatedcrankcase

LABY ® design options and features

A large variety of standard labyrinth-piston compressors, with many additionalcylinder blocks, is available with suction volumes up to 11, 000 m3

/h and dischargepressures exceeding 300 bar See Figs C-102 through C-104 for various types.Design features of the totally closed “K”-type compressor with gas- and pressure-tight crankcase are illustrated in Fig C-103C and D See these figures and Fig C-105

Common features The labyrinth piston (see Fig C-106)

 May be double- or single-acting (depending on application)

 Seals by repeated gas throttling

FIG C-101 Typical section showing oil-lubricated and oil-free zones (Source: Sulzer-Burckhardt.)

for applications where the process gas is heavily contaminated with impurities,such as polymerization products or other very small and hard particles They haveeffectively no influence on the labyrinth seal performance, compressor reliability,wear rate, and maintenance intervals.

Piston and piston rod are guided by the crosshead and the guide bearing, whichare located in the oil-lubricated crankcase Both guiding elements are made of metaland are oil lubricated, thus ensuring a precisely linear operation of the labyrinthpiston as well as an extremely long life of the piston/piston rod guiding system.The distance piece separates the gas compressing section from the oil-lubricatedcrankcase

LABY ® design options and features

A large variety of standard labyrinth-piston compressors, with many additionalcylinder blocks, is available with suction volumes up to 11, 000 m3

/h and dischargepressures exceeding 300 bar See Figs C-102 through C-104 for various types.Design features of the totally closed “K”-type compressor with gas- and pressure-tight crankcase are illustrated in Fig C-103C and D See these figures and Fig C-105

Common features The labyrinth piston (see Fig C-106)

 May be double- or single-acting (depending on application)

 Seals by repeated gas throttling

C-112 Compressors

FIG C-101 Typical section showing oil-lubricated and oil-free zones (Source: Sulzer-Burckhardt.)

FIG C-102A With open distance piece: This standard compressor is equipped with an open distance piece and a nonpressurized crankcase It is used for compression of gases, where a strict separation between cylinder and crankcase is essential and where process gas is permitted in the open distance piece (e.g., for O 2 , N 2 , CO 2 , process air, etc., generally in the industrial gas industry) (Source: Sulzer-Burckhardt.)

 Consists of a very small number of parts

 Is made of solid metal without any plastic material

 Avoids permanent mechanical friction

 Avoids contamination or fouling of the process gas

 Guarantees extremely long sealing element life and assures low maintenance cost

 Accepts a wide range of operating temperatures (-160 to +270°C and higher)

 Is insensitive to impurities in the gas

 Ensures unexceeded reliability in oxygen service

The compressor valve (see Fig C-107)

 Helps to achieve ideal combinations of cylinder design, valve size, and compressorplant components

 Ensures high reliability and availability of the compressor

 Embodies frictionless guided plates with very low lift and extremely good fatigueproperties

 Consists of identical parts for suction and discharge side, but special designfeatures prevent inadvertent wrong assembly of valves into the cylinder

 Comprises stationary parts, such as valve seat and stroke limiter not being cast,but machined out of special stainless steel

 Incorporates dynamically moving parts, such as valve plates and damper plates,manufactured according to most modern techniques and made of special stainlesssteel

 Includes aerodynamically optimal shapes with low pressure drop

The piston rod gland (see Fig C-108)

 Features radially floating and self-centering labyrinth sealing rings made ofgraphite

 Comprises stainless-steel gland chambers for the sealing rings

 Incorporates a leak-gas collecting chamber at the lower end for feeding the leakgas, where possible, back to the suction-side first stage

 Allows, if necessary, for specially designed applications with several connections

The piston rod guide bearing (see Fig C-109)

 Is available in cooled or uncooled application

 Is available with a replaceable bush and is splash-lubricated

 Is combined with the oil scrapers and designed to exclude oil from the distancepiece, the piston rod gland area, or the cylinder section It eliminates the necessityfor additional oil-vapor removal equipment

The crankshaft seal for open-type compressors (see Fig C-110)

 Is equipped with an oil slinger ring and, except on the smaller compressors, with

an additional packing ring

 Is designed to exclude dust and dirt from the crankcase and to provide an tight crankshaft passage through the crankcase wall

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The crankshaft seal for compressors with gas-tight crankcase (see Fig C-111)

 Is equipped with a mechanical sealing system completely immersed in lubricating oil

 Prevents oil from draining into the crankcase during standstill periods

 Incorporates an additional sealing ring to exclude dust and dirt from the shaftseal area

 Provides and ensures a gas- and oil-tight crankshaft passage through thecrankcase wall

LABY ® research and development projects The compressor valves. Valves installed in a reciprocating compressor have a tough life They have to open and close automatically once every crankshaftrevolution, quickly and reliably under severe temperature and pressure conditions.Troubles and excessive wear or losses are avoidable if valve quality as well as the match of valve, compressor, and operating conditions are optimal See Fig C-112

Painstaking design and years of feedback from operations have raised compressorvalves to a very high standard in terms of material, manufacturing technology, andaerodynamic shape Nevertheless, to retain an OEM’s lead in valve technology,continue to invest in valve research There are further possibilities to reduce stresspeaks in dynamically loaded parts, to optimize the aerodynamic characteristics, toinfluence the movement of the dynamic parts, to introduce improved materials andmanufacturing techniques

Compressors C-115

FIG C-102C With gas-tight crankcase and mechanical crankshaft seal: The distance piece of the standard open-type compressor is closed, and the crankshaft bears a mechanical gas-tight seal where it passes through the crankcase wall This design is used for compression of gases which are compatible with the lubricating oil (e.g., for hydrocarbon gases, CO, He, H 2 , Ar, etc.) and where

no process gas may leak to the surroundings The suction pressure is limited by the design pressure of the crankcase (Source: Sulzer-Burckhardt.)

The sealing labyrinth. This component is the subject of ongoing research.Considerable time and effort is invested in exploring the flow behavior of gases inoscillating sealing labyrinths and comparing the results with simulated computercalculations Better understanding of the influence of piston speed, labyrinth shape,labyrinth clearance, and other factors on compressor performance emerges SeeFigs C-111 through C-113.

Dynamic crank throw behavior. This remains a subject of investigation Compressorparts are not entirely rigid, but rather flexible, and may oscillate or vibrate duringoperation It is important to have fundamental and detailed knowledge of means

to eliminate or suppress undesired movements See Figs C-114 and C-115

Acoustic calculations. Nowadays these are important With computer technologyone can choose between both digital and analog studies according to API 618

New design materials. For cylinders, pistons, piston rods, and other parts, newdesign materials are under consideration to meet new requirements from customers

or to employ labyrinth-piston compressor in new applications

Quality control (QC) for reciprocating compressors. QC is regularly adapted to possiblenew requirements of the market as well as to new measuring and monitoringmethods to obtain optimal quality

Quality inspection is performed during the manufacturing process after eachimportant step All pressure-stressed parts, such as cylinders, cylinder covers,

C-116 Compressors

FIG C-102D With gas- and pressure-tight crankcase and mechanical crankshaft seal: This standard compressor is equipped with a closed single-piece crankcase designed for a gas pressure of 15 bar or higher All openings are closed and sealed with o-rings The crankshaft bears a mechanical gas-tight seal where it passes through the crankcase wall Since the crankcase is filled with process gas, this machine is used to compress gases that are compatible with the lubricating oil and where no process gas may leak to the surroundings Suction pressure may range between subatmospheric and crankcase design pressure This machine finds its applications in closed cycles, for hydrocarbon gases, refrigerants, VCM, CO, N 2 , CO 2 , He, H 2 , Ar, etc (Source: Sulzer-Burckhardt.)

FIG C-103A, B Design features of D- and E-type compressors with open distance piece (Source: Sulzer-Burckhardt.)

(B)

C-117

FIG C-103C, D Design features of the totally closed K-type compressor with gas- and tight crankcase (Source: Sulzer-Burckhardt.)

pressure-(C)

(D)

C-118

C-119

C-120 Compressors

FIG C-105 Dimensions and performance parameters for K-type compressor (Source: Sulzer-Burckhardt.)

crankcases, oil-pump casings, and others, are hydraulically tested, and leakagetests are made on the assembled gas- and pressure-tight compressors Duringassembly, all bearing and piston clearances are measured and recorded on request,and the alignment is checked.

Smaller compressor units are subject to a mechanical running test as well as

to running-in of the pistons A barring-over test is made on larger, completelyassembled machines

Test and material certificates are provided on request

“LABY’S” for liquefied natural gas service (low gas temperature application)

See Fig C-116A, which shows the complete diagramatic assembly of compressorand accessories in liquefied natural gas (LNG) service Figure C-117A is aphotograph of the plant Figure C-116B depicts the operating temperatures involved in a specific application An LNG boil-off compressor has to cope with

a variety of basic physical problems for which a product designed to normalstandards would be inadequate Two application aspects are of special interest inthis context

Exposure to cryogenic temperatures. LNG at barometric pressure boils off at -160°C.This temperature is well below the limit where some of the common engineering

FIG C-106 The labyrinth piston (Source: Sulzer-Burckhardt.)

C-122 Compressors

FIG C-107 The compressor valve (Source: Sulzer-Burckhardt.)

FIG C-108 The piston rod gland (Source: Sulzer-Burckhardt.)

FIG C-109 The piston rod guide bearing (Source: Sulzer-Burckhardt.)

C-110 The crankshaft seal for open-type compressors (Source: Sulzer-Burckhardt.)

FIG C-113 Sealing labyrinth R&D rig (Source: Sulzer-Burckhardt.)

C-126 Compressors

FIG C-114 Stress map taken during R&D on the dynamic crank (Source: Sulzer-Burckhardt.)

materials alter their properties As an example, note the loss of ductility of mostunalloyed carbon steels within a temperature span from 0°C to about -50°C FigureC-117B shows the modes of impact transitions of C-steels and of Ni-alloyed nodulariron

Bone dry gas. Natural gas in the form of boil-off is virtually free from water vapor

as the dew point is as low as -160°C Experience dictates to what extent moisture

in a tribological system is an important parameter Together with a number of otherfactors, it has a distinct bearing on wear rates under nonlubricated conditions.Those who decide to employ dry-running self-lubricating materials for piston ringsmust accept their mechanical and thermal constraints under bone dry runningconditions The operator must consequently set the stroke and speed of his machine

in accordance with the gas conditions, so that the wear rate of the sealing andguiding elements can be held within acceptable limits Already the initial choice ofthe dry-running material is itself subject to error because the designer is faced with

a multitude of available material selections

The operator is more free to optimize the design of individual parts of the compressor when the labyrinth principle is employed with the following main features:

 Avoidance of permanent mechanical friction

 Ability to use materials with known, easily certifiable qualities

 Simple design of the elements exposed to the process gas

Design and material selection of pistons and cylinders (application case study). Oneend-user installed a labyrinth piston compressor for handling LNG boil-off gas in

a terminal and ran to 75,000 h quite inexpensively Some end-users experience close

or better time between overhauls (TBOs) See Table C-11

The process data for the compressor in this application are as follows:

of nickel-alloyed cast iron with laminar graphite.

Table C-12 indicates the outstanding thermal shock behavior of GGG Ni 35 inrelation to other candidate materials This is valuable, especially under transient

FIG C-115 Experimental rigs for R&D work (Source: Sulzer-Burckhardt.)