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Maintenance procedure for interconnected strong motion
seismographs
MAINTENANCE PROCEDURE FOR INTERCONNECTED STRONG MOTION SEISMOGRAPHS
J.H. Rainer and E.C. Luctkar
PREFACE
Strong-motion seismographs installed on soil and rock and in civil engineering structures, such as buildings, dams, and bridges, provide valuable information on the nature of the ground motion and on the response of structures during moderate or strong earthquakes. In 1965 the Division of Building Research started a network, presently consisting of 10 seismographs, in the seismically active regions of Eastern Canada, in order to record the effects of such earthquakes. In addition, the Division has assisted other organizations, namely Hydro-Quebec, Atomic Energy of Canada Ltd., and the James Bay Power Corporation, with the installation and servicing of a total of 15 instruments in their respective facilities.
In order to ensure the operational readiness of these seismographs, proper maintenance at periodic intervals is vital. This guide has been prepared with the objective of facilitating the task of servicing these
instruments.
It is expected that this Report will be updated and amended
periodically in order to accommodate changing instrument technology and to incorporate improvements as a result of further operating experience.
Ottawa
January 1980
C
.
B. Crawford Director, DBR/NRCNATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH
DBR INTERNAL REPORT NO. 458
MAINTENANCE PROCEDURE FOR INTERCONNECTED STRONG MOTION SEISMOGRAPHS
by J.H. Rainer and E.C. Luctkar
Checked by: T.D.N. Approved by: L
.
W. G.
Date: January 1980Prepared for: Record Purposes
This procedure consists of three parts: Part I: Introductory Remarks; Part 11: Maintenance Procedure; Part 111: Maintenance Record.
PART I
INTRODUCTORY REMARKS
Purpose and Scope
This maintenance procedure has been prepared to facilitate the servicing of interconnected networks of strong-motion seismographs in Eastern Canada. It is based on information supplied by the instrument manufacturers and on experience gained in installing and servicing the Eastern Canadian Strong Motion Network over a number of years. The procedure applies specifically to the SMA-1 strong motion seismograph manufactured by Kinemetrics, Inc. of Pasadena, California, because at the time of writing only this instrument type was being used in interconnected networks in Eastern Canada. With little modification, however, this procedure should also be
applicable to film recording instruments supplied by other
components and f u n c t i o n s and on o p e r a t i n g p r o c e d u r e s , t h e i n s t r u c t i o n manuals f o r t h e i n s t r u m e n t s s h o u l d be c o n s u l t e d .
E x p l a n a t i o n o f Terms
"MastertT r e f e r s t o t h e i n s t r u m e n t which o r i g i n a t e s t h e t i m e s i g n a l common t o a l l i n s t r u m e n t s i n an i n t e r c o n n e c t e d network. There must be one, b u t o n l y one, " m a s t e r t t i n an i n t e r c o n n e c t e d network.
" S l a v e t t r e f e r s t o a l l i n s t r u m e n t s o t h e r t h a n t h e "master" i n an i n t e r c o n n e c t e d network.
" T r i g g e r t t r e f e r s t o t h e motion s e n s i n g d e v i c e t h a t s t a r t s t h e r e c o r d i n g o f a c c e l e r a t i o n when a c e r t a i n p r e - s e t t h r e s h o l d o f motion h a s been exceeded. An i n t e r c o n n e c t e d network n e e d s a t l e a s t one t r i g g e r , b u t can have more t h a n o n e . Any "master" o r " s l a v e t t i n s t r u m e n t can c o n t a i n a t r i g g e r . Both h o r i z o n t a l o r v e r t i c a l t r i g g e r s a r e i n u s e . TCG-1: Time-code g e n e r a t o r . By c o m b i n a t i o n s o f p u l s e l e n g t h s , t h e
TCG-1 g e n e r a t e s code on t h e t i m i n g t r a c e on t h e r i g h t edge o f t h e f i l m , c o n t a i n i n g t h e day, h o u r , m i n u t e , and second when t h e
i n s t r u m e n t i s t r i g g e r e d . I f a time-code g e n e r a t o r i s l o c a t e d i n t h e "master" l o c a t i o n , t h e same code w i l l a l s o a p p e a r on a l l
i n t e r c o n n e c t e d " s l a v e " u n i t s . S i n g l e I n s t r u m e n t s
T h i s Maintenance Procedure can a l s o be employed f o r i n s t r u m e n t s t h a t a r e n o t c o n n e c t e d t o any o t h e r i n s t r u m e n t . Note t h a t a s i n g l e u n i t always h a s t o be a "master" u n i t . The i n t e r i o r s w i t c h i s t h e r e f o r e on "MRSTER" (up) on i n s t r u m e n t s w i t h o u t a time-code g e n e r a t o r , o r on "TCG-1" (down) when equipped w i t h a time-code g e n e r a t o r . R e f e r e n c e s t o I t s l a v e t ' p o s i t i o n s and
i n t e r c o n n e c t i n g c a b l e s s h o u l d be i g n o r e d .
PART I1
MAINTENANCE PROCEDURE
1. Complete a Maintenance Record f o r each seismograph l o c a t i o n .
2 . S t a r t s e r v i c i n g t h e network a t t h e "master" l o c a t i o n .
3 . Check "EVENT INDICATOR" and n o t e whether i t i s w h i t e o r b l a c k . ("White"
means t h e u n i t h a s been t r i g g e r e d , a c c i d e n t a l l y o r by a ground motion.) 4 . Check number and c o u n t e r r e a d i n g on t h e e x t e r n a l m o n i t o r ( g r e y box) f o r
5 . Insert key in "master" seismograph and put a calibration record on whole network. .
A calibration record consists of one blank, then one calibration and one more blank.
Blank
-
turn key to "TEST" and back to "OFF." - wait 15 s or until motor stops.Calibration - turn key to "TEST" and count 1, 2, 3, 4.
- turn key to "CALIB" (calibrate) and count 1, 2, 3, 4.
-
turn key to 'INAT FREQ'I (natural frequency) andcount 1, 2, 3, 4.
-
turn key back to "CALIB'I and count 1, 2, 3, 4.- turn key directly to "OFF."
Disconnect interconnecting cables before proceeding with servicing of "master" unit.
6. At all locations other than "mastery1' turn key from "OPERATE" to "OFF" and disconnect interconnecting cable before putting a calibration record on the seismograph (this prevents triggering the whole network).
7. Open lid of seismograph and quickly turn some film into takeup magazine (clockwise).
8. Check that seismograph is securely fastened to mounting structure and is
level. Level is satisfactory if leveling bubble does not touch outer ring. If the unit is loose, look for reasons why it was not secure or level and tighten nut or readjust leveling shims.
9. Check alignment of traces using calibration scale and with lamp switch in
"TEST." 21 mm either side of guide lines is satisfactory. Adjust if necessary. Differentiate between 2 fixed traces (if they are present on the instrument) and accelerometer traces by temporarily blocking light path from the two fixed mirrors. Remove calibration scale.
10. Remove takeup magazine from mounting, cut film and check for label on film magazine with date and location of seismograph.
11. Place takeup magazine in plastic light-tight container, then into black plastic bag and seal bag with tape.
12. Insert new supply magazine if necessary (at least every 2 years or if less than half full). Amount of film in cassette isshown by indicator on side of magazine. Red dot = empty, Green dot = full.
13. Insert new takeup magazine which has been labeled with date and location of seismograph. 'Bend film end and attach to roller with a small piece of tape.
Battery condition - Check terminals for corrosion and measure battery voltage with 120 V AC disconnected. Record voltage.
Reconnect transformer to 120 V AC, measure and record battery voltage (it should be equal when batteries are fully charged, or slightly higher); this checks that charger unit is working. If battery voltage is below 12 V, check operation of charger unit and 120 V AC supply. Check lamp voltage with switch in "TEST." Record reading. Adjust if
necessary. Record adjusted lamp voltage.
If unit contains time-code generator, take reading by attaching TCG-1 reader to seismograph TCG-1 printed circuit board. Attach ground lead first, then connector. Record old TCG-1 reading and corresponding reference time (watch)
.
Reset time-code generator to reference time and record setting.
Remove connector before ground lead upon completion of TCG-1 readings. Check position of timing switch. On units with time-code generator and
used as the "master" location, the switch should be in "TCG-1" position (down). In units without time-code generator and used as the "master" location, the switch is placed in the "MASTER" position (up). All others are placed in the "SLAVE" position (down).
Replace silica gel.
Replace seismograph cover.
For both "masterff and "slave" locations, put on a calibration record. Then with key in "OFF" position, reconnect interconnecting cable and return key to "OPERATE" position.
If the network is accidentally triggered after some instruments have been serviced, return to "master" location after all instruments are serviced, disconnect interconnecting cable and re-set "EVENT INDICATOR" to black. This is achieved by turning key from "OPERATE" to "OFF," to "TEST," to "OFF." Wait for 15 s or for motor to stop and turn to "OFF." Re-connect interconnecting cable and turn to "OPERATE." Remove key. Note the
location and number of accidental triggers on Maintenance Record.
Where the location is very damp, it is necessary to place a container with silica gel next to the connector on the interconnection cables and wrap with plastic and watertight tape.
Battery replacement - First disconnect charger transformer from 120 V AC. Unplug grey multi-pin CANNON connector inside seismograph before
removing batteries. Re-connect CANNON connector after new batteries have been installed and connected. This prevents damage to electronics
due to possible shorting of battery terminals. Apply some vaseline or
PART I 1 1 MAINTENANCE RECORD Date S e r v i c e d : Locat i o n : Number o f L o c a t i o n : I n s t r u m e n t Type: S e r i a l Number: S e r v i c e d by:
,
1. Event i n d i c a t o r : White (on)
a
Black ( o f f )n
2 . E x t e r n a l m o n i t o r ( g r e y box) number Counter r e a d i n g
3 . Number o f c a l i b r a t i o n r e c o r d s added t o o l d f i l m
Check t h a t seismograph i s s e c u r e l y mounted and l e v e l
n
Check t r a c e a l i g n m e n t - T V
D
La
t i m i n g marks(4
means 0 . K . , X a d j u s t m e n t r e q u i r e d ) B a t t e r y c o n d i t i o n ( t e r m i n a l s ) ; v o l t a g e r e a d i n g , c h a r g e r d i s c o n n e c t e d ; v o l t a g e r e a d i n g , c h a r g e r c o n n e c t e d 120 V AC power: ONn
OFFa
Lamp v o l t a g e ( s w i t c h t o "TEST"),
a d j u s t e d t o Does u n i t i n c l u d e t i m e code g e n e r a t o r , YESTime-code g e n e r a t o r r e a d i n g R e f e r e n c e t i m e r e a d i n g (watch)
Reset time-code g e n e r a t o r t o r e f e r e n c e t i m e and r e c o r d new r e a d i n g
Check p o s i t i o n o f t i m i n g s w i t c h MASTER (ZPPS)
[7
(up)SLAVE (TCG-1)
T r i g g e r l e v e l checked: YES
0
NO[7
s e t t i n gReplacement o f t a k e u p magazine: YES
[7
NO[7
l a b e l a p p l i e dReplacement o f s u p p l y magazine: YES
(
NOAmount o f f i l m i n s u p p l y magazine
Replacement o f s i l i c a g e l YES
n
NONumber o f c a l i b r a t i o n r e c o r d s on new t a k e u p magazine
