IE Circular No. 78-07, Damaged Components of a Bergen-Paterson Series 25000 Hydraulic Test Stand

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                            WASHINGTON, D. C. 20555

IE Circular No. 78-07
Date: May 31, 1978
Page 1 of 2


During functional testing of hydraulic snubbers at a power reactor
facility,  test results were adversely influenced by the use of damaged
components in the  test stand connectors to the snubber being tested.

The following paragraphs are the manufacturer's (Bergen-Paterson)
description  of the problem together with recommended procedures to avoid
such problems in  the future:

"A number of HSSA-3 (Hydraulic Shock and Sway Arrester) Units, 1-1/2" bore
x  6" stroke, with 3,000 pound load rating, exhibited nonuniform
performance. The  bleed rates were erratic and in some instances a
structural lockup was  observed. A sample of units were disassembled and
found to be in proper  working order.

"Attention was then directed to the testing machine's fixturing. The
series  25000 test stand utilizes a 2 pin loading system to simulate
actual strut load  connections which does not allow transmission of
bending moments in the  vertical plane. Unlike the actual strut which
employs a ball bushing, the test  stand's fixturing is a simplified pin

"An inspection of the load pins and bushings during the review of the test 
fixturing indicated that they were damaged due to a prior overload
condition.  These damaged components induced bending moments into the test
units which  produced mechanical binding between the piston rod and its

"The noted moment type loading condition does not occur on units in
service  since all strut assemblies incorporate ball bushings in the
crosspin  connection at each end of the strut, providing a universal
action thereby  assuring pure axial loading.

"Bergen-Paterson recommends that the pinned connections and fixtures of
the  Series 25000 test stand or other test equipment used for snubber
testing be  periodically inspected and replaced if indications of damage
are noted."


IE Circular No. 78-07 
Date: May 31, 1978 
Page 2 of 2

Bergen-Paterson's recommended inspection frequency is as follows:

A. Prior to initial start of a Test Program.

B. After each 60 credits of units tested with credits assigned per the
following schedule:

UNIT SIZE                      CREDITS

 3                                1
10                                1
20                                2
30                                3
50                                5
70                                5

Inspection acceptance criteria for Test Fixture Components are:

Cross Pins       Straightness 0.015 in.
Bushings         Cylindricity 0.015 in.
Fit              .020 in. Max Diametral

While there are a limited number of this specific test stand currently in
use,  it is considered likely that similar hydraulic snubber test
equipment may have  comparable problems. All holders of Reactor Operating
Licenses or Construction  permits should consider the following items in
their review of this matter:

1. Review the snubber testing device utilized at your facility to
determine if  a comparable problem could develop in the mounting fixtures.

2. Consider the need for a periodic inspection and replacement of
components  that could adversely affect the test results.

No written response to this Circular is required. If you require
additional  information regarding this matter, contact the Director of the
appropriate NRC  Regional Office.


Page Last Reviewed/Updated Thursday, March 25, 2021