THERMINOL®

Heat Transfer Fluids By

+400°C

+350°C

+300°C

+250°C

+200°C

+150°C

+100°C

+50°C

+0°C

-50°C

-100°C

� FLUID LIFE

System design and operating conditionshave a critical influence on fluid life. Thegeneral design guidance in this leaflet isgiven to maximise fluid life and to promo-te safe operation.

All Therminol fluids have publishedrecommended maximum bulk and filmtemperatures. These maximum use tem-peratures are based on long term study ofthermal stability and should not be excee-ded.

Fluid thermal degradation generallyresults in the formation of volatile pro-ducts referred to as low boilers. Theseshould periodically be removed from thesystem, by venting via the expansion tank. Low boilers can be highly flammable therefore relief valves and vents should bepositioned at a safe distance from ignitionsources and personnel. Solutia recom-mends the collection and disposal of lowboilers.

In the event that products with highmolecular weight are formed, these arereferred to as high boilers and they aresoluble in the fluid and do not causecoking or fouling.

It should be noted that thermal and oxidative stability are radically differentissues. Whilst Therminol fluids show out-standing thermal stability at high tempera-tures, they will not withstand extensiveexposure to oxygen at such temperaturesfor prolonged periods.

� FLUID ANALYSIS

Regular monitoring of the fluid charac-teristics in the system enables detectionof deviations and correction. Analysis offluid samples is provided by Solutia.Reports indicate when corrective actionis considered necessary.

� FLUID DISPOSAL

Used fluid drained from the systemshould be disposed of in the way prescri-bed by the relevant legislation. In certaincases, reclamation may be possible.

System design

� MATERIALS OF CONSTRUCTION

The majority of metals and alloys nor-mally encountered in high-temperaturesystems can be used. However, the use ofcopper, aluminium and bronze should bekept to a minimum because of their redu-ced metallurgical strength at higher tem-peratures. Otherwise see DIN 4754 orequivalent norms for selection of materialsand design constraints.

� PUMPS

For large flow rates, centrifugal pumpsshould generally be used with cast or forged steel casings rated to 16 bar. Thespecification should be appropriate forthe temperature duty. A successful andstrongly recommended alternative toconventional centrifugal pumps withmechanical seals are magnetic drivepumps or canned motor pumps.Each pump should be fitted with acontrol device to cut off the heat sourcein the event of pump failure.

� VALVES

Cast steel globe valves with deep stuf-fing boxes have generally been found togive satisfactory service. Graphite pac-king is used to seal valve stems on high-temperature systems and generally fiverings are specified to assure a reaso-nable seal. Install valve stems horizontal-ly or in a downward position so that anystem leakage does not enter the insula-tion. An increasingly used alternativewhich ensures completely successfulsealing is the metal bellows stem sealedvalve.

� PIPEWORK AND FLANGES

The piping layout for Therminol sys-tems should be sized to provide therequired flow rate at an economical pres-sure drop. Drain valves should be provi-ded at the low points to facilitate cleaningand vent valve connections sited at allhigh points.

Stresses arising from expansionduring temperature changes may beavoided by use of loops and bellows. Ifexpansion loops are used in the pumpsuction piping, they should be horizon-tal or vertically downwards otherwisethey can collect air and vapour which canseriously hamper pump performance.

In high temperature systems, the entiresystem pipework should be of low carbonsteel to DIN 2401 part 12, St 35, St 35.8materials. These are equivalent respective-ly to ANSI B36.3 and ASTM A53 Tp S Gr B/ A106 Gr B and ASTM A312 Gr Tp 304 SS.When using heat transfer fluids at below-20°C, the pipework material should be304SS ASTM A312 Gr Type 304 or ASTM106 Gr B or ASTM A 333 Gr1.

The tendency to leak through jointsand fittings is a characteristic of mostorganic heat transfer fluids unless thesefittings are extremely tight. Monitoring ofpiping leaks is essential, since fluid satu-rated insulation may create a fire hazard(see Lagging). On new systems, it isstrongly recommended that a maximumnumber of connections are welded.

Where access is vital or a flangedconnection is unavoidable, raised faceflanges with weldneck joint material toDIN 2401 part 12, PN16 as per DIN 2633,PN 25 DIN 2634, DIN 2500, DIN 2512and ANSI B16.5 Class 300. Bolting as perDIN 2507 or other equivalent standardshould be used. Install flanges on hori-zontal pipe runs whenever possible. Onvertical runs where occasional leaks candevelop at flanges, install tight fittingcaps to divert any fluid leakage outsidethe insulation.

� GASKETS

For flange connections in high tempera-ture heat transfer systems where all welded construction is not possible, usestainless steel spiral wound gaskets with aflexible graphite insert. As an alternative,pure graphite gaskets may be used.Material is described in DIN 3754 part 1. Alist of manufacturers is available fromSolutia on request.

� FILTERS

Before startup of a new system, installa wire mesh strainer of approx. 120micron mesh size in the pump suction.

When operating where solids and conta-minants might enter or be generated in thesystem, it is advisable at the design stageto provide connection points to allow forlater installation of a bypass loop betweenthe discharge and suction sides of thepump. Filters that have generally beenused are glass fibre sting-wound car-tridges or sintered metal elements in the20-30 micron range.

THERMINOL®

System design and maintenance

� LAGGING

Insulating materials which have becomesaturated due to leakage of heat transferfluid are a potential fire hazard. The risk ofcombustion normally occurs at tempera-tures above 180°C.

Routine inspection and prompt elimina-tion of leakage is therefore essential. Theuse of cellular glass insulation (e.g.Foamglas-Pittsburgh Corning) whichresists saturation due to its closed cellstructure is particularly recommended inareas of potential leakage such as near instrument connections, valve packingglands, flanges and other connections.

� EXPANSION TANK

After the heater, the expansion tank is themost critical element and its design isdirectly connected with the design of theentire system. We therefore recommendthat a qualified engineering company or hea-ter manufacturer should be consulted.

The expansion tank layout illustrated inthe Figure performs the following functions:

1) maintains a static pump suction head 2) compensates for temperature related

volume and pressure changes3) provides a means of venting moisture

and low boilers4) prevents fluid oxidation

The expansion tank has to be positionedat the highest point of the system andconnected to the inlet side of the pump. It may also be connected to the main cir-culating loop at the lowest pressure point.

For heating circuits, the expansion tankshould be sized so that it is 1/4 full atambient temperature and 3/4 full whenthe system is at operating temperature;vice versa for cooling. Fluid expansion canbe 25% or more depending on the fluid choice and the operating temperaturerange.

The expansion tank volume has to com-ply with local national legislation and over-flow line may be usefull to reduce its sizesin many countries.

The expansion tank should also serve asthe main venting point for the system, andfor optimum venting it should be providedwith feed and discharge lines enabling theentire fluid flow to be directed via theexpansion tank. This “double-leg” designprovides higher flexibility in normal opera-tion when compared with the moresophisticated single leg design withdegassing vessel. However, with carefulattention to venting systems both will givesatisfactory service. The vent line shouldbe fitted with a valve E to facilitate the pur-ging of water and air when charging thesystem for the first time and all vent linesshould be routed to a safe area, preferablyvia a cooled condenser.

Protection of the heat transfer fluidagainst oxidation is essential. Contact withoxygen can occur in both the expansiontank and in the collection tank, if the latteris fitted. Unless the temperature in thesevessels can be limited to below 60°C theheat transfer fluid should be blanketedwith an inert gas or, if this is not feasible,air contact can be minimised by the use of

any cold seal trap. DIN 4754 describesthese options in detail.

Inert gas blanketing (usually with nitro-gen) is the most effective way of preventingfluid oxidation.

Supply and discharge of inert gas, con-trolled by pneumatic valves in the inert gassupply and tank venting line provide opti-mum protection.

Startup, venting andnormal operation ofthe system

The system should initially be chargedvia valve D with valves B, C and E open,so that optimum venting of any air in the system is ensured.

Before the first charge with heat trans-fer fluid there will usually be some mois-ture in the system, (for example due tocondensation in pipes and on the walls ofvessels) and during charging, the fluidmixes with this water which must be ven-ted via the expansion tank otherwisepump cavitation may occur. This is effec-ted by gradually heating the fluid and limi-ting the temperature in the expansion tankto approx. 130°C. The circulation can beregulated by partially opening and closingvalves A and B. Venting is complete whenno more fluid enters the catch pot. Thenormal fluid circuit is then established byfirst opening valve A and then closingvalves B, C and E. The inert gas pressurecan then be set.

The above process is also carried outfor venting «low boilers».

For normal system operation, valve Ais open and valves B, C, D, E, and F areclosed. Routine fluid replenishment canbe made via valve F or D.

THERMINOL®

Low-pressure Regulator

Inert gas0.3 bar over pressure

Fill Line - Operating

Pump

StrainerFill Line - initial(Low Point)

Relief Valve

Outlet Regulator

Catch Pot

Approx. 1/3Full Line Size

F

D

C B

E

A

Expansion Tank HLA=High Level AlarmLLA=Low Level Alarm

HLA

LLA

Vent Line

THERMINOL®

T.B.S 10-25 (E) (12/98) - PROVOC

Therminol is a trademark of Solutia. Therminol has now been adopted as a world-wide brand for the Solutia Heat Transfer Fluid range.Fluids known previously under the Santotherm and Gilotherm brands are identical in composition and performance to the correspondingTherminol brand fluids.

The information in this bulletin is to the best of our knowledge true and accurate but all instructions, recommendations or suggestions are made without guarantee. Since the conditions of use are beyondtheir control, Solutia Inc. and its subsidiaries disclaim any liability for loss or damage suffered from use of these data or suggestions. Furthermore no liability is accepted if use of any product in accor-dance with these data or suggestions infringes any patent.

P l e a s e c o n t a c t u s f o r m o r e i n f o r m a t i o n :

EuropeSolutia Europe S.A./N.V.

Rue Laid Burniat 3 - Parc Scientifique - Fleming B-1348 Louvain-la-Neuve (Sud) - Belgium

Tel.: (+32) 10 48 15 47 - Fax: (+32) 10 48 14 86http://www.solutia.com

North AmericaSolutia Inc.

10300 Olive Boulevard - PO Box 66760 St Louis, MO 63166-6760 - USA

Tel.: (+1) 314 674 10 00

AsiaSolutia Singapore Pte. Ltd.

101 Thomson Road - #19-00 United Square Singapore307591

Tel.: (+65) 355 7231 - Fax: (+65) 254 3138

Latin AmericaSolutia Brasil Ltda.

Rua Gomes de Carvalho 1306 - 60 andar - conj. 61 e 62 CEP : 04547-005 • Vila Olímpia - Sao Paulo, SP, BrasilPhone: (+55) 11-5087 3000 - Fax: (+55) 11-5087 3030

People’s Republic of ChinaSolutia Chemical Co. Ltd., Suzhou

9th floor, Kings Tower16 Shi Shan Road - Suzhou New District - Suzhou, PRC 215011

Phone: (+86) 512 8258167 - Fax: (+86) 512 8250417