<PAGE>   1
                                                                EXHIBIT 10.22(c)


                                 AMENDMENT NO. 3
                                       TO
                                CREDIT AGREEMENT


          THIS AMENDMENT NO. 3 TO CREDIT AGREEMENT (the "Amendment") is made as
of April 30, 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 as of February 6, 2001 and
an Amendment No. 2 dated as of March 26, 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:

<PAGE>   2

          1.   Amendments to the Credit Agreement. Effective as of December 1,
2000 and subject to the satisfaction of the conditions precedent set forth in
Section 2 below, the Credit Agreement is hereby amended as follows:

     1.1. Section 7.3(A)(viii) of the Credit Agreement is hereby deleted in its
          entirety and the following is substituted therefor:

               "(viii) Indebtedness (a) evidenced by letters of credit in an
          aggregate face amount not to exceed at any time $30,000,000 issued in
          the ordinary course of business to secure obligations of the Company
          and its Subsidiaries under workers' compensation and other social
          security programs, and Contingent Obligations with respect to any such
          permitted letters of credit, and (b) constituting payment or other
          obligations to Praxair or its Affiliates in respect of employee
          benefits under the Employee Benefits Disaffiliation Agreement dated
          January 1, 1997, between Chicago Bridge & Iron Company and Praxair, as
          amended from time to time;".

          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-
<PAGE>   3

          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/ R. Scott Russell
                                            -----------------------------
                                          Name:  R. Scott Russell
                                          Title: Secretary


                                        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/ R. Vernon Howard, Jr.
                                            -----------------------------
                                          Name:  R. Vernon Howard, Jr.
                                          Title: Managing Director


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


                                        By: /s/ S. Z. Shah
                                            -----------------------------
                                          Name:  S. Z. Shah
                                          Title: Managing Director


                                        ABN AMRO BANK N.V., as a Lender


                                        By: /s/ Laurie D. Flom
                                            -----------------------------
                                          Name:  Laurie D. Flom
                                          Title: Senior Vice President

                                        By: /s/ Mary L. Honda
                                            -----------------------------
                                          Name:  Mary L. Honda
                                          Title: Group 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. 3 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 an Amendment No. 2
dated as of March 26, 2001, and as the same may be amended, restated,
supplemented or otherwise modified from time to time, the "Credit Agreement"),
which Amendment No. 3 is dated as of April 30, 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: April 30, 2001



CHICAGO BRIDGE & IRON COMPANY


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

<PAGE>   8


CHICAGO BRIDGE & IRON COMPANY (DELAWARE)


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


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/ R. Scott Russell
   ---------------------------------
Name:     R. Scott Russell
Title:    Secretary


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

<PAGE>   9


CBI EASTERN ANSTALT


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


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/ Alan R. Black
   ---------------------------------
Name:     Alan R. Black
Title:    President


ASIA PACIFIC MATERIAL SUPPLY COMPANY LTD.


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

<PAGE>   10

CBI COMPANY LIMITED


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


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/ J. Robert McKenzie
   ---------------------------------
Name:     J. Robert McKenzie
Title:    Managing 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

<PAGE>   11

CHICAGO BRIDGE & IRON (ANTILLES) N.V.


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


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/ Alan R. Black
   ---------------------------------
Name:     Alan R. Black
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

<PAGE>   12

HOWE-BAKER HOLDINGS, L.L.C.


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


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

<PAGE>   13

A&B BUILDERS, LTD.


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


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


<PAGE>   14


PROCESS MANAGEMENT, L.L.C.


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