<PAGE>   1
                                                                EXHIBIT 10.22(b)


                                 AMENDMENT NO. 2
                                       TO
                                CREDIT AGREEMENT


          THIS AMENDMENT NO. 2 TO CREDIT AGREEMENT (the "Amendment") is made as
of March 26, 2001 by and among CHICAGO BRIDGE & IRON COMPANY N.V. (the
"Company"), CB&I CONSTRUCTORS, INC., CBI SERVICES, INC., CHICAGO BRIDGE & IRON
COMPANY (DELAWARE) and CB&I TYLER COMPANY (collectively, the "Subsidiary
Borrowers", and, together with the Company, the "Borrowers"), the financial
institutions listed on the signature pages hereof (the "Lenders"), BANK ONE, NA
(having its principal office in Chicago, Illinois), in its individual capacity
as a Lender and in its capacity as contractual representative (the
"Administrative Agent"), BANK OF AMERICA, N.A., as Syndication Agent, and HARRIS
TRUST AND SAVINGS BANK, as Documentation Agent, under that certain Credit
Agreement dated as of December 1, 2000 by and among the Borrowers, the financial
institutions party thereto, the Administrative Agent, the Syndication Agent, the
Documentation Agent and BANC ONE CAPITAL MARKETS, INC., as Lead Arranger and
Sole Book Runner (as amended by Amendment No. 1 dated February 6, 2001, and as
the same may be amended, restated, supplemented or otherwise modified from time
to time, the "Credit Agreement"). Defined terms used herein and not otherwise
defined herein shall have the meaning given to them in the Credit Agreement.

                                   WITNESSETH

          WHEREAS, the Borrowers, the Lenders, the Administrative Agent, the
Syndication Agent and the Documentation Agent are parties to the Credit
Agreement; and

          WHEREAS, the Borrowers have requested that the Administrative Agent,
the Syndication Agent, the Documentation Agent and the requisite number of
Lenders under Section 9.2 of the Credit Agreement amend the Credit Agreement on
the terms and conditions set forth herein; and

          WHEREAS, the Borrowers, the requisite number of Lenders under Section
9.2 of the Credit Agreement, the Administrative Agent, the Syndication Agent and
the Documentation Agent have agreed to amend the Credit Agreement on the terms
and conditions set forth herein;

          NOW, THEREFORE, in consideration of the premises set forth above, the
terms and conditions contained herein, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto have agreed to the following amendments to the Credit Agreement:

          1.   Amendments to the Credit Agreement. Effective as of March 26,
2001 and subject to the satisfaction of the conditions precedent set forth in
Section 2 below, the Credit Agreement is hereby amended as follows:

<PAGE>   2

          1.1. Section 2.5(B)(ii)(a) of the Credit Agreement is hereby amended
               to insert immediately after the phrase in the first parenthetical
               provision that currently reads "as all or part of the
               consideration for any Permitted Acquisition" the following:

               "and (iii) the sale to D.C. Capital Partners, L.P., Tinicum
               Capital Partners, L.P., Tinicum Capital Partners Parallel Fund,
               L.P., Tinicum Capital Partners Executive Fund I, L.L.C., Mr.
               Frederick A. Klingenstein and Mr. Jon Klingenstein of 807,356
               shares Capital Stock of the Company, 524,781 of which have been
               repurchased from Pitt-Des Moines, Inc. and were previously issued
               and delivered to Pitt-Des Moines, Inc. in connection with the PDM
               Acquisition and 282,575 of which were held by Pitt-Des Moines,
               Inc. to assure payment in connection with the PDM Acquisition but
               have been released and returned to the Company".

               2.   Conditions of Effectiveness. The effectiveness of this
Amendment is subject to the conditions precedent that the Administrative Agent
shall have received the following:

          (a)  duly executed originals of this Amendment from each of the
               Borrowers, the requisite number of Lenders under Section 9.2 of
               the Credit Agreement, the Administrative Agent, the Syndication
               Agent and the Documentation Agent;

          (b)  duly executed originals of a Reaffirmation in the form of
               Attachment A attached hereto from each of the Subsidiary
               Guarantors identified thereon;

          (c)  such other documents, instruments and agreements as the
               Administrative Agent may reasonably request.

               3.   Representations and Warranties of the Borrowers.

          (a)  The Borrowers hereby represent and warrant that this Amendment,
               the attached Reaffirmations and the Credit Agreement, as
               previously executed and as amended hereby, constitute legal,
               valid and binding obligations of the Borrowers and the Subsidiary
               Guarantors parties thereto and are enforceable against the
               Borrowers and the Subsidiary Guarantors parties thereto in
               accordance with their terms (except as enforceability may be
               limited by bankruptcy, insolvency, or similar laws affecting the
               enforcement of creditors' rights generally).

          (b)  Upon the effectiveness of this Amendment and after giving effect
               hereto, (i) the Borrowers hereby reaffirm all covenants,
               representations and warranties made in the Credit Agreement as
               amended hereby, and agrees that all such covenants,
               representations and warranties shall be true and correct as of
               the effective date of this Amendment (unless such representation
               and warranty is made as of a specific date, in which case such
               representation and warranty shall be true and correct as of such
               date) and (ii) no Default or Unmatured Default has occurred and
               is continuing.


                                      -2-
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               4.   References to the Credit Agreement.

          (a)  Upon the effectiveness of Section 1 hereof, on and after the date
               hereof, each reference in the Credit Agreement (including any
               reference therein to "this Credit Agreement," "hereunder,"
               "hereof," "herein" or words of like import referring thereto) or
               in any other Loan Document shall mean and be a reference to the
               Credit Agreement as amended hereby.

          (b)  Except as specifically amended above, the Credit Agreement and
               all other documents, instruments and agreements executed and/or
               delivered in connection therewith, shall remain in full force and
               effect, and are hereby ratified and confirmed.

          (c)  The execution, delivery and effectiveness of this Amendment shall
               not, except as expressly provided herein, operate as a waiver of
               any right, power or remedy of the Administrative Agent or the
               Lenders, nor constitute a waiver of any provision of the Credit
               Agreement or any other documents, instruments and agreements
               executed and/or delivered in connection therewith.

               5.   GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS (INCLUDING 735 ILCS 105/5-1 ET
SEQ., BUT OTHERWISE WITHOUT REGARD TO THE CONFLICT OF LAW PROVISIONS) OF THE
STATE OF ILLINOIS.

               6.   Headings. Section headings in this Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Amendment for any other purpose.

               7.   Counterparts. This Amendment may be executed by one or more
of the parties to this Amendment on any number of separate counterparts and all
of said counterparts taken together shall be deemed to constitute one and the
same instrument.



                     [REMAINDER OF PAGE INTENTIONALLY BLANK]











                                      -3-
<PAGE>   4

          IN WITNESS WHEREOF, this Amendment has been duly executed as of the
day and year first above written.




                                        CHICAGO BRIDGE & IRON COMPANY
                                        N.V., as the Company
                                        By:  Chicago Bridge & Iron Company B.V.
                                        Its: Managing Director


                                        By: /s/ Gerald M. Glenn
                                            ----------------------------
                                          Name:  Gerald M. Glenn
                                          Title: Managing Director


                                        CB&I CONSTRUCTORS, INC., as a
                                        Subsidiary Borrower


                                        By: /s/ Timothy J.P. Moran
                                            ----------------------------
                                          Name:  Timothy J.P. Moran
                                          Title: Treasurer


                                        CBI SERVICES, INC., as a Subsidiary
                                        Borrower


                                        By: /s/ Dennis C. Planic
                                            ----------------------------
                                          Name:  Dennis C. Planic
                                          Title: Treasurer


                                        CHICAGO BRIDGE & IRON COMPANY
                                        (DELAWARE), as a Subsidiary Borrower


                                        By: /s/ Timothy J.P. Moran
                                            ----------------------------
                                          Name:  Timothy J.P. Moran
                                          Title: Treasurer

<PAGE>   5

                                        CB&I TYLER COMPANY, as a Subsidiary
                                        Borrower


                                        By: /s/ Timothy J.P. Moran
                                            ----------------------------
                                          Name:  Timothy J.P. Moran
                                          Title: Treasurer


AGENTS AND LENDERS:                     BANK ONE, NA (having its principal
                                        office in Chicago, Illinois), as
                                        Administrative Agent and as a Lender


                                        By: /s/ Suzanne Ergastolo
                                            ----------------------------
                                          Name:  Suzanne Ergastolo
                                          Title: Vice President


                                        BANK OF AMERICA, N.A., as Syndication
                                        Agent and as a Lender


                                        By: /s/ Charles F. Lilygren
                                            ----------------------------
                                          Name:  Charles F. Lilygren
                                          Title: Managing Director


                                        HARRIS TRUST AND SAVINGS BANK, as
                                        Documentation Agent and as a Lender


                                        By: /s/ David Rubin
                                            ----------------------------
                                          Name:  David Rubin
                                          Title: Managing Director


                                        ABN AMRO BANK N.V., as a Lender


                                        By: /s/ Thomas K. Peterson
                                            ----------------------------
                                          Name:  Thomas K. Peterson
                                          Title: Senior Vice President

                                        By: /s/ Jonathan F. Chiarieri
                                            ----------------------------
                                          Name:  Jonathan F. Chiarieri
                                          Title: Assistant Vice President


<PAGE>   6

                                        THE CHASE MANHATTAN BANK, as a Lender


                                        By:
                                            ----------------------------
                                          Name:
                                          Title:


<PAGE>   7

                                                                    ATTACHMENT A

                                  REAFFIRMATION

          Each of the undersigned hereby acknowledges receipt of a copy of the
foregoing Amendment No. 2 to the Credit Agreement dated as of December 1, 2000
by and among CHICAGO BRIDGE & IRON COMPANY N.V. (the "Company"), CB&I
CONSTRUCTORS, INC., CBI SERVICES, INC., CHICAGO BRIDGE & IRON COMPANY (DELAWARE)
and CB&I TYLER COMPANY (collectively, the "Subsidiary Borrowers", and, together
with the Company, the "Borrowers"), the financial institutions from time to time
party thereto (the "Lenders"), BANK ONE, NA (having its principal office in
Chicago, Illinois), in its individual capacity as a Lender and in its capacity
as contractual representative (the "Administrative Agent"), BANK OF AMERICA,
N.A., as Syndication Agent, and HARRIS TRUST AND SAVINGS BANK, as Documentation
Agent, and Banc One Capital Markets, Inc., as Lead Arranger and Sole Book Runner
(as amended by Amendment No. 1 dated February 6, 2001, and as the same may be
amended, restated, supplemented or otherwise modified from time to time, the
"Credit Agreement"), which Amendment No. 2 is dated as of March 26, 2001 (the
"Amendment"). Capitalized terms used in this Reaffirmation and not defined
herein shall have the meanings given to them in the Credit Agreement. Without in
any way establishing a course of dealing by the Administrative Agent or any
Lender, each of the undersigned reaffirms the terms and conditions of the
Guaranty, the Subsidiary Security Agreement, the Subsidiary Pledge Agreement and
any other Loan Document executed by it and acknowledges and agrees that such
agreement and each and every such Loan Document executed by the undersigned in
connection with the Credit Agreement remains in full force and effect and is
hereby reaffirmed, ratified and confirmed. All references to the Credit
Agreement contained in the above-referenced documents shall be a reference to
the Credit Agreement as so modified by the Amendment and as the same may from
time to time hereafter be amended, modified or restated.

Dated:  March 26, 2001




CHICAGO BRIDGE & IRON COMPANY


By /s/ Timothy J.P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer


CHICAGO BRIDGE & IRON COMPANY (DELAWARE)


By /s/ Timothy J.P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer

<PAGE>   8

CB&I TYLER COMPANY


By /s/ Timothy J.P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer


CB&I CONSTRUCTORS, INC.


By /s/ Timothy J.P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer


CBI SERVICES, INC.


By /s/ Dennis C. Planic
   -----------------------------
Name:     Dennis C. Planic
Title:    Treasurer


HORTON CBI, LIMITED


By /s/ James W. House
   -----------------------------
Name:     James W. House
Title:    Treasurer


CBI VENEZOLANA, S.A.


By /s/ Mario D. Marquez
   -----------------------------
Name:     Mario D. Marquez
Title:    Vice President


CBI EASTERN ANSTALT


By /s/ John R. Edmonds
   -----------------------------
Name:     John R. Edmonds
Title:    Administrator and Vice President

<PAGE>   9

CBI CONSTRUCTORS PTY, LTD.


By /s/ David J. Cochrane
   -----------------------------
Name:     David J. Cochrane
Title:    Director


LEALAND FINANCE COMPANY B.V.


By /s/ Timothy J.P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Managing Director


CB&I (EUROPE) B.V.


By /s/ J. Hendrik Schurink
   -----------------------------
Name:     J. Hendrik Schurink
Title:    Managing Director


ARABIAN GULF MATERIAL SUPPLY COMPANY, LIMITED


By /s/ Kenneth W. Ford
   -----------------------------
Name:     Kenneth W. Ford
Title:    President


ASIA PACIFIC MATERIAL SUPPLY COMPANY LTD.


By /s/ Timothy J. P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer


CBI COMPANY LIMITED


By /s/ Timothy J. P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer

<PAGE>   10


CBI CONSTRUCCIONES S.A.


By /s/ Jose Manuel Tappata
   -----------------------------
Name:     Jose Manuel Tappata
Title:    President


CBI CONSTRUCTORS LIMITED


By /s/ J. Hendrik Schurink
   -----------------------------
Name:     J. Hendrik Schurink
Title:    Managing Director


CBI HOLDINGS (U.K.) LIMITED


By /s/ Melbourne A. Hamer
   -----------------------------
Name:     Melbourne A. Hamer
Title:    Director


CBI OVERSEAS, LLC


By /s/ Wong Keem Ming
   -----------------------------
Name:     Wong Keem Ming
Title:    Treasurer


CENTRAL TRADING COMPANY, LTD.


By /s/ Timothy J. P. Moran
   -----------------------------
Name:     Timothy J.P. Moran
Title:    Treasurer


CHICAGO BRIDGE & IRON (ANTILLES) N.V.


By /s/ Gerald M. Glenn
   -----------------------------
Name:     Gerald M. Glenn
Title:    Managing Director

<PAGE>   11


CHICAGO BRIDGE & IRON COMPANY B.V.


By /s/ Gerald M. Glenn
   -----------------------------
Name:     Gerald M. Glenn
Title:    Managing Director


CMP HOLDINGS B.V.


By /s/ J. Hendrik Schurink
   -----------------------------
Name:     J. Hendrik Schurink
Title:    Managing Director


PACIFIC RIM MATERIAL SUPPLY COMPANY, LTD.


By /s/ Kenneth W. Ford
   -----------------------------
Name:     Kenneth W. Ford
Title:    President


HOWE-BAKER INTERNATIONAL, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President and Chief Executive Officer


HOWE-BAKER ENGINEERS, LTD.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President


HOWE-BAKER HOLDINGS, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President and Chief Executive Officer


<PAGE>   12

HOWE-BAKER MANAGEMENT, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President


HOWE-BAKER, L.P.

By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President


MATRIX ENGINEERING, LTD.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President and Chief Executive Officer


HBI HOLDINGS, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President and Chief Executive Officer


HOWE-BAKER INTERNATIONAL MANAGEMENT, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    Chairman of the Board and Chief Executive Officer


A&B BUILDERS, LTD.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    Chairman of the Board and Chief Executive Officer

<PAGE>   13


MATRIX MANAGEMENT SERVICES, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    Chairman of the Board and Chief Executive Officer


CALLIDUS TECHNOLOGIES INTERNATIONAL, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    Chairman of the Board


CALLIDUS TECHNOLOGIES, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    Chairman of the Board


CONSTRUCTORS INTERNATIONAL, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President and Chief Executive Officer


PROCESS MANAGEMENT, L.L.C.


By /s/ Ronald D. Brazzel
   -----------------------------
Name:     Ronald D. Brazzel
Title:    President and Chief Executive Officer