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Answers for industry.

Sitrans F

Electromagnetic Flowmeters

Lining Material for Water Applications

White Paper 2009

Introduction

The choice of electromagnetic flowme-ter lining material is a potential sourceof confusion or even annoyance in

the water / wastewater industry as anumber of different liner options areavailable on the market, all havingtheir specific properties, strengths andweaknesses.This paper gives an overview of somebasic criteria for choosing lining mate-rial for the water / wastewater industryand furthermore provides a short de-scription of the properties, strengthsand weaknesses of EPDM, NBR, PURand Ebonite, i.e. the four types of lin-ing material most commonly used inthe water / wastewater industry.

Basic criteria for choosing liningmaterialDue to the functionality of the flowmeter, a non-conductive lining materi

is imperative, but other requiremenvary according to the specific featureof the intended application.

In general, the choice of lining materinormally mainly rests on the followincriteria:

Temperature resistance.•

Sensitivity to chemicals added, e.g•

on treatment plantsMechanical stability, e.g. resi•

tance towards swelling, shrinkinor other physical effects of interation with additives or solvents.Robustness and wear resistance•

Table of ContentsIntroduction

Basic criteria for choosing lining material EPDM

NBR

PUR

Ebonite

Summary



For drinking water applications, it is furthermore importantthat the lining material has been tested for:

Odor and flavor impact (liberation)•

Growth of biofilm•

Extraction of substances of concern to human health•

(e.g. metals, organic carbon or other trace substances)

A third category of criteria concerns main internationaldrinking water approvals:

The electromagnetic flowmeter with the lining material•

of choice must hold the relevant approvals, e.g. WRAS,ANSI/NSF Standard 61, ACS, DVGW, BelgAqua etc.

The four types of lining material describes in the followingare all suitable for the water / wastewater industry, but havediverse features making them more suited for some applica-tions than others.

EPDM

EPDM (ethylene propylene diene rubber) is a terpolymerconsisting of ethylene, propylene and a non conjugateddiene as third monomer.

EPDM shows an excellent resistance against ozone, oxygenas well as polar organic and inorganic chemicals, butlacks resistance to non-polar substances such as solvents,grease and mineral oils. It furthermore has an excellenttemperature? resistance and a good low temperatureflexibility, which ensures a high performance on a widetemperature range.

The strength of EPDM lies in its good temperature, weatherand seawater resistance as well as in its resistance topolar chemicals. Furthermore, EPDM is not reactive tochlorinated water. These features make EPDM very suitablefor all drinking water applications. EPDM fulfills the global

requirements of the different drinking water approvals.EPDM is less suitable for wastewater applications due tothe lack of resistance towards non-polar substances. Thismeans that EPDM cannot be recommended for wastewateapplications. EPDM can be used in process industrial waterapplications, if there is no hydrocarbon present in thewater.

NBR

NBR (nitrile butadiene rubber) is build up ofcopolymerization of acrylonitrile and butadiene in anemulsion process.

NBR shows an excellent swelling behavior when usedwith liquids containing non-polar solvents (e.g. mineraloil, grease, tar, gasoline and hydrocarbons). However,compared to EPDM, NBR is less resistant against polar

substances, and shows a relative lack of elasticity andlow temperature flexibility. The resistance against heat,weather, ozone and oxidizing substances such as chlorineis average.

The strength of NBR lies in its moderate costs, and goodresistance to swelling caused by hydrocarbons or acids.These features ensure that NBR is a cost-efficient andflexible all-round lining material fulfilling the needs of moindustrial water applications. Furthermore, NBR is verysuitable for wastewater applications, due to the resistanceto non-polar solvents.NBR can be used in drinking water applications, butonly has an average resistance to chlorinated water.

Performance in tests on odor and flavor impact and growtof biofilm is average. NBR can fulfill the requirements forNSF/ANSI Standard 61.

Copyright Siemens AG 2009

All rights reserved

of 4 Document no. SFIDK.PW.027.A1.0



PUR

Polyurethane rubber (AU) or Thermoplastic polyurethanerubber (TPU) is formed by the reaction of polyester orpolyetherdiols (soft segment) with diisocyanates.

PUR has a good low temperature flexibility as well asweather resistance. It is very resistant to mineral oil, grease

gasoline and aromatic hydrocarbons. Used with acidic andchlorine media, however, it has a low degree of stability.The temperature resistance of PUR is relatively low.PUR has a good resistance to swelling caused byhydrocarbons. This feature ensures that PUR can be used inmany industrial water applications. Furthermore, PUR canbe used for wastewater applications, due to the resistanceto non-polar solvents.The low hydrolysis stability of PUR makes it less suitablefor liquids containing ozone, chlorine or acid, e.g. treateddrinking water applications and process water.

Ebonite

Vulcanized natural rubber.

Ebonite is a non resilient material with an excellentresistance to ozone, oxygen, chemicals, and non polarsubstances such as solvents, grease and mineral oils.It furthermore has an excellent heat resistance, whileits low temperature flexibility is average. Resistance topulsation in flow and changes in pressure is moderate.

The strength of ebonite lies in its resistance to polarchemicals and oxidizing agents such as water based

chlorine solutions. This makes ebonite a good choicefor drinking water applications. Ebonite fulfills the

requirements of some drinking water approvals such asWRAS and ANSI/NSF 61.Ebonite is very suitable for process industrial waterapplications and for wastewater applications, due to itsresistance towards non-polar substances.

Summary

In accordance with the general properties strengths andweaknesses of the lining material described above, it maybe concluded that EPDM can be recommended for alldrinking water applications. Ebonite can be recommendedas a good alternative, but cannot hold the complete rangeof drinking water approvals. PUR and NBR can obtain a verlimited number of approvals and for that reason cannot berecommended as a preferred liner type.For wastewater and industrial water applications wherehydrocarbons/solvents can be present, NBR and Ebonite ar

the best fits of the evaluated lining materials, while PURhas some limitations due to its low hydrolysis stability.

Copyright Siemens AG 2009

All rights reserved

of 4 Document no. SFIDK.PW.027.A1.0

whitepaper lnining material water app e

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