Samson 2371-10 Service manual

Mounting and
Operating Instructions
EB 2640 EN
Edition January 2016
Type 2371-11 Pressure Reducing Valve
Manual set point adjustment
Type 2371-10 Pressure Reducing Valve
Pneumatic set point adjustment
Series 2371 Pressure Regulators
Pressure reducing valves for the food and pharmaceutical
industries
Type2371-10·Pneumatic set point adjustment
Type2371-11·Manual set point adjustment

Denition of signal words
DANGER!
Hazardous situations which, if not
avoided, will result in death or seri-
ous injury
WARNING!
Hazardous situations which, if not
avoided, could result in death or se-
rious injury
NOTICE
Property damage message or mal-
function
Note:
Additional information
Tip:
Recommended action

2 EB 2640 EN

Contents
EB 2640 EN 3
1 General safety instructions.............................................................................4
2 Process medium and scope of application.......................................................5
2.1 Transportation and storage.............................................................................5
3 Design and principle of operation ..................................................................6
4 Installation..................................................................................................10
4.1 Mounting position........................................................................................10
4.2 Shut-off valve and pressure gauge.................................................................10
4.3 Safety valve.................................................................................................11
4.4 Leakage line connection ...............................................................................11
5 Operation...................................................................................................11
5.1 Start-up.......................................................................................................11
5.2 Adjusting the set point..................................................................................11
5.2.1 Setpoint·Type2371-11..............................................................................12
5.2.2 Setpoint·Type2371-10..............................................................................14
5.3 Operation ...................................................................................................14
5.4 Decommissioning.........................................................................................14
6 Cleaning and maintenance ..........................................................................15
6.1 Cleaning .....................................................................................................15
6.2 Maintenance·Replacingparts......................................................................19
6.3 Replacingtheplug .......................................................................................19
6.4 Replacingthediaphragmunit .......................................................................21
6.5 Replacingthetwodiaphragms......................................................................22
6.5.1 Replacingthesetpointsprings......................................................................24
7 Customer service.........................................................................................24
8 Nameplate..................................................................................................25
9 Technical data.............................................................................................26
10 Dimensions .................................................................................................27

4 EB 2640 EN
General safety instructions
1 General safety instructions
−The regulator is to be mounted, started up or serviced by fully trained and
qualiedpersonnelonly;theacceptedindustrycodesandpracticesareto
be observed. Make sure employees or third persons are not exposed to any
danger.
−Allsafetyinstructionsandwarningsgiveninthesemountingandoperating
instructions, particularly those concerning installation, start-up and mainte-
nance, must be strictly observed.
−According to these mounting and operating instructions, trained personnel
referstoindividualswhoareabletojudgetheworktheyareassignedto
and recognize possible dangers due to their specialized training, their
knowledgeandexperienceaswellastheirknowledgeoftheapplicable
standards.
−Toensureappropriateuse,onlyusetheregulatorinapplicationswherethe
operatingpressureandtemperaturesdonotexceedthespecicationsused
for sizing the regulator at the ordering stage.
−The manufacturer does not assume any responsibility for damage caused by
external forces or any other external factors.
−Any hazards that could be caused in the regulator by the process medium,
operating pressure or by moving parts are to be prevented by taking appro-
priate precautions.
−Proper transport, storage, installation, operation and maintenance are as-
sumed.
Note:
Non-electric actuators and control valve versions do not have their own
potential ignition source according to the ignition risk assessment stipu-
lated in EN13463-1: 2009, section 5.2, even in the rare incident of an
operating fault. Therefore, they do not fall within the scope of Directive
94/9/EC. For connection to the equipotential bonding system, observe
the requirements in section 6.3 of EN60079-14: 2014-10 (VDE0165
Part 1).


EB 2640 EN 5
Process medium and scope of application
2 Process medium and scope of application
Pressure regulators for food processing and pharmaceutical industries for liquids and gases
inthetemperaturerangefrom0to160°C(32to320°F)·KVS0.1to16(CV0.12to20)
NominalsizeDN15to50(NPS½to2).
Forcontrollingtheoutputpressurep2totheadjustedsetpoint.Thevalvecloseswhenthe
downstreampressurerises.
WARNING!
The Type2371-10/-11 Regulators are designed as safety valves. Exceeding the max-
imum pressure (10bar/150psi) of the regulator may cause it to burst.
If necessary, a suitable overpressure protection must be installed on site in the plant
section.
Note:
The Type2371-10/-11 Regulators are shut-off devices that do not guarantee abso-
lute tight shut-off (leakage class according to DINEN60534-4 or ANSI/FCI 70-2,
see section9 on page26). As a result, the output pressure p2can rise to the same
level as the upstream pressure p1in a plant which does not have its own consump-
tion.
2.1 Transportation and storage
The regulators must be carefully handled, transported and stored. During storage and trans-
portationbeforeinstallation:Protecttheregulatorsagainstadverseinuences,suchasdirt,
moisture or temperatures outside the operating temperature range.


6 EB 2640 EN
Design and principle of operation
3 Design and principle of oper-
ation
TheType2371-10andType2371-11Re-
ducing Pressure Valves consist mainly of a
single-seatedanglevalvewithoperatingdia-
phragm and actuator housing.
ThesetpointoftheType2371-10isadjust-
ed pneumatically by an external air supply,
e.g. compressed air.
ThesetpointofType2371-11isadjusted
manually by tensioning the set point spring.
Themediumowsthroughthevalvebody(1)
inthedirectionindicatedbythearrow.The
positionoftheplug(3)determinestheow
rateacrosstheareareleasedbetweenplug
andvalveseat(2).Thevalvecloseswhenthe
downstreampressurep2rises above the ad-
justed set point. The resulting output pressure
p2dependsontheowrate.
Any medium escaping from the test connec-
tion(11)indicatesthattheoperatingdia-
phragm(4)maybeleakingorthedia-
phragm has ruptured. The test connection of
Type2371-10isconnectedtoaexiblepipe
elbowtodischargeanymediumescaping.
Type2371-11·Version with manual set
point adjustment (seealsosection5.2on
page11)
In the idle state, the valve is kept open by the
setpointsprings(7).Thevalvecloseswhen
the output pressure p2acting on the dia-
phragm(4)andtheresultingforceexceed
the force of the springs.
The set point is adjusted by an Allen key
(8mm),whichisinsertedthroughtheadjust-

mentopening(6.1)ontopofthehousing
ontothesetpointscrew(6).Theblanking
plugmustrstberemoved.Ifnecessary,the
setpointscrewcanbesecuredbythelock-
ingscrew(12)intheupperplugsectionto
preventthesetpointscrewfromloosening
due to vibrations, causing the set point to
change.
Thedisk(15)servesasabottomendstopto
protect the diaphragm from overload and to
prevent parts from falling apart inadvertently
whiletheregulatorisbeingdismantled.
Turningthesetpointscrewclockwisecauses
thespringplate(7.1)tomoveupwardsand
increases the spring force and the set point.
Turningthesetpointscrewcounterclockwise
relieves the spring tension and reduces the
set point.
Type2371-10·Version with pneumatic set
point adjustment (seealsosection5.2on
page11)
In the idle state, the valve is kept open by the
set point pressure pc(compressedair)ap-
plied as the control pressure.
When the force created by the output pres-
sure p2acting on the diaphragm exceeds the
force resulting from the set point pressure pc,
theplug(3)movestowardstheseat(2),clos-
ing the passage. In this case, the ratio be-
tweenp1and pcis not necessarily 1:1.
As the output pressure p2drops, the resulting
force reduces again. The valve is opened
againwhenthepressurefallsbelowtheset
point pressure pc.

EB 2640 EN 7
Design and principle of operation
Thetwodiaphragms(4.1)provideacertain
amountofsafetywhenoneofthedia-
phragms ruptures and prevents the process
medium and external pressure medium from
mixing.Thescrew(12)preventspartsfrom
fallingapartinadvertentlywhiletheregula-
tor is being dismantled.
Fig.1: Functional drawings of the regulators
p1
p2
pc
15
3
11
2
4.1
12
6.1
6
8
1
9
5
3
2
12
7.1
7
11
4
15
p
1
p2
1 Valve body 6 Setpointscrew 11 Test connection or leakage line
connection
2 Seat 6.1 Adjustmentopeningwithblankingplug 12 Lockingscrew
3 Plug 7Set point springs 15 Mechanicalstop(disk)
4 Operating
diaphragm
7.1 Spring plate p1Input pressure
4.1 Twodiaphragms 8 Actuator housing p2Output pressure
5Upper plug section 9Clamptting pCSetpointpressure(control
pressure),external
6
12
Type2371-10 Type2371-11
Type2371-11·Lockingscrewtolock
thesetpointscrewinposition

8 EB 2640 EN
Design and principle of operation
Stem locking for CIP or SIP
Seesection6.1onpage15.
Type2371-10andType2371-11canbet-
tedwithastemlockingtokeeptheplugin
theopenposition.Thisallowstheregulator
tobecleaned(CIPorSIP)whilethevalveis
open.
The stem can be locked in place pneumati-
callybyanadditionalpneumaticunitwith
compressedairconnection(forTypes2371-
10and2371-11)ormanuallyusingaspe-
cialpin(forType2371-11only).
The pneumatic and manual stem locking do
not effect the control function of the valve,
provided the stem locking is not engaged.
The pneumatic unit for the pneumatic stem
locking is located on the top of the regulator.
The unit can be mounted in any position
sincetheaxialxtureoftheunitallowsitto
turn360°.
The pin of the manual stem locking is
screwedintotheadjustmentopeningin
place of the blanking plug.
Pneumatic stem locking·Types2371-10/-11 Manual stem locking·Type2371-11
Stem locking engaged
Fig.2: Stem locking
êpV∙G
1
/
8
connection
Pneumatic unit
Pin
Lock nut

EB 2640 EN 9
Design and principle of operation
Pneumatic stem locking
Type2371-10
To open the valve, apply a pressure pV
(=1bar)tothepneumaticunit.Thiscauses
theplugstemtomovetogetherwiththeplug
out of the valve seat. A set point pressure pC
must not be applied to the regulator in this
case.
Toswitchthevalvebacktoitscontrolfunc-
tion, remove the pressure pV(=1bar).
Type2371-11
To open the valve, apply a pressure pV
(=6bar)tothepneumaticunit.Thiscauses
theplugstemtomovetogetherwiththeplug
out of the valve seat, opposing the spring
force.
Toswitchthevalvebacktoitscontrolfunc-
tion, remove the pressure pV(=6bar).
Manual stem locking
Type2371-11 only
Tolockthestemintoplace,screwthepininto
the opening on top of the actuator housing
in place of the blanking plug. The end of the
pin comes to rest on the head of the set point
screw.Asthepinisscrewedintothevalve,it
pushes the plug into the open position over
thesetpointscrewandupperplugsection.
A mechanical stop prevents it from being
screwedinanyfurther,protectingthedia-
phragm from overstretching or rupturing. Se-
cure the position using the lock nut.
When the groove of the pin is completely
concealed,thestemlockingisactive,where-
as a visible groove means it is disengaged.

10 EB 2640 EN
Installation
4 Installation
NOTICE
Pay particular attention to correct hy-
giene and ensure that regulators for
the food and pharmaceutical indus-
tries are kept absolutely clean.
Used tools must be free of sol-
vents and grease. Only use a lubri-
cant suitable for foodstuffs (order no.
8150-9002) for parts that must be
lubricated.
Chooseaplaceofinstallationthatallows
you to freely access the regulator even after
the entire plant has been completed and al-
lowsunobstructedsetpointadjustment.
Before installing the regulator in the pipeline,
clean the pipeline thoroughly to remove any
foreignparticlesintheplantwhichcouldaf-
fect the regulator's proper functioning.
The plant must be designed and the pipe-
linesinstalledinsuchawaythattheregula-
torcanbemountedandoperatedwithout
any tension. If necessary, support the pipe-
line near to the connections. Do not attach
supports to the regulator itself.
Selectastraightsectionofpipelinewithout
any disturbances as the site of installation for
theregulator(toensurethatthecontrolfunc-
tionisnotaffectedbytheowconditions).
4.1 Mounting position
The regulator has an angle-style
valve body. The actuator hous-
ingmustfaceupwards.Asare-
sult, the outlet must face to the
side in the installed position.
−Directionofowmustmatchthedirec-
tionindicatedbythearrowonthebody
(inletatthebottomandoutletatthe
side).
4.2 Shut-off valve and pressure
gauge
Install a manually operated shut-off valve up-
streamanddownstreamoftheregulator.This
allowstheplanttobedepressurized,ifre-
quired. In addition, it serves to relieve the
operatingdiaphragmofpressurewhenthe
plant is not operated for extended periods.
Apressuregaugedownstreamoftheregula-
torallowsthesetpoint(tocontroltheoutput
pressure p2)tobemonitored.
13
1
2
p1
p2
Fig.3: Installation drawing (Type2371-11)
1 Shut-off valve
2 Pressure gauge
3 Safety valve
p1Input pressure
p2Output pressure
Type2371-11

EB 2640 EN 11
Operation
4.3 Safety valve
TheTypes2371-10/-11Regulatorsareshut-
off devices that do not guarantee absolute
tightshut-off(leakageclass,seesection9on
page26).
As a result, the output pressure p2can rise to
thesamelevelasthedownstreampressure
p1inaplantwhichdoesnothaveitsown
consumption.
WARNING!
The pressure in the entire system must
not exceed the maximum permissi-
ble pressure. Corresponding safety
equipment (e.g. safety valve) must be
installed downstream of the regula-
tor. Ensure that the pressure reducing
valve itself cannot exceed the spec-
ied maximum pressure of 10bar
(150psi).
The permissible temperature and pressure
limitsarespeciedontheregulator.
4.4 Leakage line connection
A leakage line can be connected to the regu-
latorwhentoxicordangerousmediaare
used. In the event of a defective diaphragm
(e.g.diaphragmrupture),anyprocessmedi-
um that escapes can be fed through a pipe
to a safe location.
Adapt the pipe diameter to the connection at
the regulator.
5 Operation
5.1 Start-up
Firststartuptheregulatoraftermountingall
parts.
Filltheplantslowlywiththeprocessmedium.
Avoid pressure surges. Open the shut-off
valvesrstontheupstreampressureside.
Afterwards,openallthevalvesonthecon-
sumerside(downstreamoftheregulator).
Tip:
For optimal control, the required
pressure set point must be within the
top end of the setting range.
5.2 Adjusting the set point
The set point must be adjusted on starting up
the plant running under normal operating
conditions.
Thepressuregaugelocatedonthedown-
stream(output)pressuresideallowsthead-
justed set point to be monitored.
−ThesetpointadjustmentinType2371-
10 is pneumatic1).
−ThesetpointofType2371-11isadjust-
ed manually by tensioning the set point
spring.
___
1) Externalsupplyair(e.g.compressedair,
pmax=8bar)required

12 EB 2640 EN
Operation
5.2.1 Set point·Type2371-11
Manualsetpointadjustment∙SeeFig.1on
page7.
Thesetpointisadjustedforthelowestoutput
pressure in the delivered state. The locking
screw(12)isnot tightened.
NOTICE
Set point screw screwed too tight!
The regulator is blocked and the me-
dium ow through it is restricted.
Pressure regulation is no longer pos-
sible.
Only screw the set point screw up to
the point where the spring tension
can still be felt.
How to proceed:
1. Removethestopper.UseanAllenkey
(3mm)toundothelockingscrew(12)if
itistightened(twoturnscounterclock-
wise).
2. UseanAllenkey(8mm)toremovethe
blankingplug(6.1).
3. Place the key through the opening to
reachthesetpointscrew(6).
4. Turnthesetpointscrew(totensiontheset
pointspring)toadjustthesetpoint:
−Turnclockwise: Increases the pressure
setpoint(theoutputpressurerises).
−Turncounterclockwise:Reducesthe
pressuresetpoint(theoutputpressure
drops).
Monitorthedownstreampressureatapres-
suregauge(seeFig.3onpage10).
Thevalvecloseswhentheoutputpressurep2
exceeds the adjusted set point.
5. Retightenthelockingscrew(12)topre-
ventthesetpointscrew(6)frombeing
turned.
−Reinsertthestopper.

EB 2640 EN 13
Operation
1.
Positionofthelockingscrew(12)withstopper
Fig.4: Set point adjustment of Type2371-11
3.
4.
Stopper∙Lockingscrew
(12)concealed
6.1
6
2.
5.

14 EB 2640 EN
Operation
5.2.2 Set point·Type2371-10
Pneumaticsetpointadjustment∙SeeFig.1
onpage7.
How to proceed:
1. Connect the external set point pressure
lineattheG¼connection.Max.pres-
sure pc=8bar.
2. Adjust the set point pressure pcto obtain
and keep the required pressure constant.
Monitorthedownstreampressureatapres-
suregauge(seeFig.3onpage10).
Thevalvecloseswhentheoutputpressurep2
exceeds the adjusted set point.
Fig.5: Pneumatic set point adjustment
G¼connectionforthesetpointpressure
line at the side on the pneumatic unit
5.3 Operation
AcorrectlysizedType2371-10/-11Pres-
sureReducingValveworksautomatically
withinitscontrolrange.
We recommend after every start-up to check
that the regulator functions properly and to
adaptittonewoperatingconditions,ifnec-
essary.
5.4 Decommissioning
Close the shut-off valve upstream of the valve
andthenclosetheshut-offvalvedownstream
of the valve.
Note:
Before performing any work on the
regulator, make sure the relevant
plant section has been depressurized
and, depending on the process medi-
um, drained as well.


EB 2640 EN 15
Cleaning and maintenance
6 Cleaning and maintenance
The pressure reducing valves do not require
any maintenance. Nevertheless, they are
subjecttonaturalwear,particularlyatthe
seat, plug and operating diaphragm.
Depending on the operating conditions,
check the regulator at regular intervals to
avoid possible malfunctions.
WARNING!
Be aware of the risk on performing
work on pressurized or hot plant sec-
tions.
Hot process medium can escape un-
controlled on dismantling the regula-
tor. Risk of scalding!
Allow the regulator to cool down be-
fore depressurizing and draining it
and remove it from the pipeline.
Checktheseatandplugforwear.Checkthat
thePTFElayerofthediaphragm(seeFig.1,
Fig.12,andFig.13)isnotdamaged(e.g.
cracks,milkycoloringatthebends).Thisis
necessaryforcompliancewithEU
1935/2004.
If leakage still occurs and there is no visible
signs of damage on the diaphragm, check
theconnectionbetweentheplugsupportand
plug stem or the clamped connection be-
tweenthevalvebodyandbonnet(seesec-
tion6.2onpage19).
Tighten the connection to achieve a leak-
proof joint.
6.1 Cleaning
To clean inside the regulator, the plug can be
keptintheopenpositionintheversionwith
stemlockingtoallowthevalvetobecleaned
(CIP=CleaningInPlaceorSIP=Steriliza-
tionInPlace)whileitisopen(seeStemlock-
ingforCIPorSIPonpage8).
Stem locking:PneumaticforType2371-
10/-11·ManualforType2371-11
The disengaged stem locking does not affect
the regulator's control function.

16 EB 2640 EN
Cleaning and maintenance
Manual stem locking
Type2371-11
See Stem locking for CIP or SIP on page
8.
How to proceed:
1. Removetheblankingplugandscrewthe
pin(13)ofthestemlockingwiththelock
nut(14)intotheadjustmentopening.
−The end of the pin comes to rest on the
headofthesetpointscrewandkeepsthe
plug in the open position. A mechanical
stoppreventsitfrombeingscrewedin
any further, protecting the diaphragm
from being overloaded.
2. Usethelocknut(14)tokeepthisposi-
tion.
−When the groove of the pin is completely
concealed, the stem locking is active.
−A visible groove means it is disengaged.
−The control function of the valve is not af-
fectedwhenthestemlockingisdisen-
gaged.
14
13
6
8
7
Manualstemlocking·Type2371-11
6Setpointscrew
7Set point springs
8 ActuatorhousingofType2371-11
13 Pin
14 Lock nut
Fig.6: Manual stem locking

EB 2640 EN 17
Cleaning and maintenance
Pneumatic stem locking
Type2371-10 and Type2371-11
See Stem locking for CIP or SIP on page
8.
Type2371-11
The pressure pV=6bar applied to the pneu-
matic unit opens the valve. This causes the
plugstemtomovetogetherwiththeplugout
of the valve seat and opens the valve.
How to proceed:
1. Connectthepressurehosewithmin.
6mmdiametertotheG
1
/
8
connection.
2. Apply a pressure pv=6bartothepneu-
maticunit.Thiscausesthesetpointscrew
(6)tomoveandtheplugtomoveoutof
the valve seat and opens the valve.
3. Toswitchthevalvebacktoitscontrol
function, remove the pressure pV=6bar
to return the pressure back to atmospher-
ic pressure.
4. Thespring(16)pullstheactuatingunit
back,allowingtheplugstemtomove
again for the control task.
Pneumaticstemlocking·Type2371-11
6Setpointscrew
7Set point springs
8 ActuatorhousingofType2371-11
16 Spring
17 Actuatingunit/diaphragm
pVPressure for stem locking
Fig.7: Pneumatic stem locking
pV
17
16
8
6
7
Stem locking engaged
pV=6bar
Actuator housing
Stem locking
G
1
/
8
connection

18 EB 2640 EN
Cleaning and maintenance
Type2371-10
To open the valve, apply a pressure pV=
1bartothepneumaticunit.Thiscausesthe
plugstemtomovetogetherwiththeplugout
of the valve seat. A set point pressure pC
must not be applied to the regulator in this
case.
How to proceed:
1. Connectthepressurehosewithmin.
6mmdiametertotheG
1
/
8
connection.
2. Applyapressurepv=1bartothepneu-
matic stem locking. This causes the actu-
atingunit(17)tomovetheplugstemto-
getherwiththeplugoutofthevalveseat
and open the valve.
3. Toswitchthevalvebacktoitscontrol
function, remove the pressure pV(=
1bar)toreturnthepressurebacktoat-
mospheric pressure.
4. Thespring(16)pullstheactuatingunit
back,allowingtheplugstemtomove
again for the control task.
Pneumaticstemlocking·Type2371-10
8 ActuatorhousingofType2371-10
15 Upperplugsectionwithmechanicalstop
16 Spring
17 Actuatingunit/diaphragm
pVPressure for stem locking
Fig.8: Pneumatic stem locking
pV
17
16
15
8
G
1
/
8
connection
Stem locking disengaged
pV=Atmosphericpressure
Actuator housing
Stem locking

EB 2640 EN 19
Cleaning and maintenance
6.2 Maintenance·Replacing
parts
SeeFig.1onpage7.
Theregulatorissubjecttonaturalwear.De-
pending on the operating conditions and du-
ration of operation, regularly check the regu-
lator's ability to function.
Incasethedownstreampressurerises,for
example,whenalltheconsumersareclosed,
and the valve does not shut off tightly
enough.Thismayhappenwhenthetight
shut-off is impaired by either dirt or natural
wearontheseatandplug.However,itisim-
portant to take into account that a maximum
leakageof0.05%oftheKVS or CVcoef-
cient in the case of metal-seated plugs and
0.01%inthecaseofsoft-seatedplugsisstill
permissible(refertosection9on
page26).
6.3 Replacing the plug
Types2371-10/-11·Replacing the plug
Theplug(3)isscrewedintotheplugsupport
(3.1)andcanonlyberemovedthroughthe
inletport.Usetheappropriatesocketwrench
tounscrewtheplug.
How to proceed:
1. Loosentheplugusingthesocketwrench
−DN15to25(NPS½to1):width across
ats 10
DN32to50(NPS1¼to2):width
across ats 13
2. Unscrewtheplug(3)throughtheinlet
port p1.Removethetwowashersandthe
seal.
3. Priortoinstallinganewplug:Checkthe
seat and seat facing, so far as it is possi-
ble, for damage. In case of damage, the
regulator must be replaced or repaired.
Cutawaymodel·Unscrewingorscrewingintheplug
withasocketwrench
Screwed-inplug(3),plugsupport(3.1)seal
andwashers
Fig.9: Replacing the plug of Type2371-11
3
3.1
3
3.1
Input p1
Socketwrench

20 EB 2640 EN
Cleaning and maintenance
We recommend also checking the dia-
phragm for cracks and damage as a preven-
tivemeasure.Refertosection6.4on
page21.
Assemblethenewplug(3)inthereverseor-
der described for the disassembly. Insert the
twowashersintothethreadedholewiththe
concavesidesfacingawayfromeachother
(asshowninthedrawing).
−Do not forget the PEEK seal!
Tightening torque
−DN15to25:5Nm
(NPS½to1)
−DN32to50:20Nm
(NPS1¼to2) Insertwashersasshowninthediagram.
Type2371-11∙Insertingthewashers
Fig.10: Soft-seated plug with plug support
PEEKseal
O-ring
V-portplugwithEPDMsoftseal
Washers