UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13D
                    Under the Securities Exchange Act of 1934
                                (Amendment No. 3)


                             NATCO GROUP INC. (NTG)
                                (Name of Issuer)

                                  Common Stock
                         (Title of Class of Securities)

                                   0001057693
                                 (CUSIP Number)

                                David Nierenberg
                               The D3 Family Funds
                               19605 NE 8th Street
                                 Camas, WA 98607
                                 (360) 604-8600

                                 With a copy to:

                               Henry Lesser, Esq.
                       DLA Piper Rudnick Gray Cary US LLP
                             2000 University Avenue
                            East Palo Alto, CA 94303
                                 (650) 833-2000

                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)


                                 March 25, 2008
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D and is filing this
schedule because of ss.ss. 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box |_|.



--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON

     The D3 Family Fund, L.P.
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                 (a)  |X|
                                                                 (b)  |_|
--------------------------------------------------------------------------------
3    SEC USE ONLY


--------------------------------------------------------------------------------
4    SOURCE OF FUNDS*

     WC
--------------------------------------------------------------------------------
5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
     PURSUANT TO ITEMS 2(d) OR 2(e)                                   |_|


--------------------------------------------------------------------------------
6    CITIZENSHIP OR PLACE OF ORGANIZATION

     Washington
--------------------------------------------------------------------------------
               7    SOLE VOTING POWER

                    251,249 Common shares (1.3%)
               -----------------------------------------------------------------
  NUMBER OF    8    SHARED VOTING POWER
   SHARES
BENEFICIALLY        0
  OWNED BY     -----------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
  REPORTING
   PERSON           251,249
    WITH       -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER

                    0
--------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     For the reporting person listed on this page, 251,249; for all
     reporting persons as a group, 1,270,388 shares (6.4%)
--------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  |_|


--------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     6.4%
--------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON*

     PN
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       2



--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON

     The D3 Family Bulldog Fund, L.P.
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                 (a)  |X|
                                                                 (b)  |_|
--------------------------------------------------------------------------------
3    SEC USE ONLY


--------------------------------------------------------------------------------
4    SOURCE OF FUNDS*

     WC
--------------------------------------------------------------------------------
5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
     PURSUANT TO ITEMS 2(d) OR 2(e)                                   |_|


--------------------------------------------------------------------------------
6    CITIZENSHIP OR PLACE OF ORGANIZATION

     Washington
--------------------------------------------------------------------------------
               7    SOLE VOTING POWER

                    740,294 common shares (3.7%)
               -----------------------------------------------------------------
  NUMBER OF    8    SHARED VOTING POWER
   SHARES
BENEFICIALLY        0
  OWNED BY     -----------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
  REPORTING
   PERSON           740,294
    WITH       -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER

                    0
--------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     For the reporting person listed on this page, 740,294; for all
     reporting persons as a group, 1,270,388 shares (6.4%)
--------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  |_|


--------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     6.4%
--------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON*

     PN
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       3



--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON

     The DIII Offshore Fund, L.P.
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                 (a)  |X|
                                                                 (b)  |_|
--------------------------------------------------------------------------------
3    SEC USE ONLY


--------------------------------------------------------------------------------
4    SOURCE OF FUNDS*

     WC
--------------------------------------------------------------------------------
5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
     PURSUANT TO ITEMS 2(d) OR 2(e)                                   |_|


--------------------------------------------------------------------------------
6    CITIZENSHIP OR PLACE OF ORGANIZATION

     Bahamas
--------------------------------------------------------------------------------
               7    SOLE VOTING POWER

                    278,795 common shares (1.4%)
               -----------------------------------------------------------------
  NUMBER OF    8    SHARED VOTING POWER
   SHARES
BENEFICIALLY        0
  OWNED BY     -----------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
  REPORTING
   PERSON           278,795
    WITH       -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER

                    0
--------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     For the reporting person listed on this page, 278,795; for all reporting
     persons as a group, 1,270,388 (6.4%)
--------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  |_|


--------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     6.4%
--------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON*

     PN
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       4


--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON

     Nierenberg Investment Management Company, Inc.
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                 (a)  |X|
                                                                 (b)  |_|
--------------------------------------------------------------------------------
3    SEC USE ONLY


--------------------------------------------------------------------------------
4    SOURCE OF FUNDS*

     AF
--------------------------------------------------------------------------------
5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
     PURSUANT TO ITEMS 2(d) OR 2(e)                                   |_|


--------------------------------------------------------------------------------
6    CITIZENSHIP OR PLACE OF ORGANIZATION

     Washington
--------------------------------------------------------------------------------
               7    SOLE VOTING POWER

                    0
               -----------------------------------------------------------------
  NUMBER OF    8    SHARED VOTING POWER
   SHARES
BENEFICIALLY        1,270,388 shares (6.4%)
  OWNED BY     -----------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
  REPORTING
   PERSON           0
    WITH       -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER

                    1,270,388 shares
--------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     For the reporting person listed on this page, 1,270,388; for all
     reporting persons as a group, 1,270,388 shares (6.4%)
--------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  |_|


--------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     6.4%
--------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON*

     CO
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       5



--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON

     Nierenberg Investment Management Offshore, Inc.
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                 (a)  |X|
                                                                 (b)  |_|
--------------------------------------------------------------------------------
3    SEC USE ONLY


--------------------------------------------------------------------------------
4    SOURCE OF FUNDS*

     AF
--------------------------------------------------------------------------------
5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
     PURSUANT TO ITEMS 2(d) OR 2(e)                                   |_|


--------------------------------------------------------------------------------
6    CITIZENSHIP OR PLACE OF ORGANIZATION

     Bahamas
--------------------------------------------------------------------------------
               7    SOLE VOTING POWER

                    0
               -----------------------------------------------------------------
  NUMBER OF    8    SHARED VOTING POWER
   SHARES
BENEFICIALLY        278,795 common shares (1.4%)
  OWNED BY     -----------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
  REPORTING
   PERSON           0
    WITH       -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER

                    278,795 common shares
--------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     For the reporting person listed on this page, 278,795; for all
     reporting persons as a group, 1,270,388 shares (6.4%)
--------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  |_|


--------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     6.4%
--------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON*

     CO
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       6



--------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON

     David Nierenberg
--------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                                 (a)  |X|
                                                                 (b)  |_|
--------------------------------------------------------------------------------
3    SEC USE ONLY


--------------------------------------------------------------------------------
4    SOURCE OF FUNDS*

     AF
--------------------------------------------------------------------------------
5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
     PURSUANT TO ITEMS 2(d) OR 2(e)                                   |_|


--------------------------------------------------------------------------------
6    CITIZENSHIP OR PLACE OF ORGANIZATION

     Washington
--------------------------------------------------------------------------------
               7    SOLE VOTING POWER

                    0
               -----------------------------------------------------------------
  NUMBER OF    8    SHARED VOTING POWER
   SHARES
BENEFICIALLY        1,270,388 common shares (6.4%)
  OWNED BY     -----------------------------------------------------------------
    EACH       9    SOLE DISPOSITIVE POWER
  REPORTING
   PERSON           0
    WITH       -----------------------------------------------------------------
               10   SHARED DISPOSITIVE POWER

                    1,270,388
--------------------------------------------------------------------------------
11   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     For the reporting person listed on this page, 1,270,388; for all
     reporting persons as a group, 1,270,388 shares (6.4%)
--------------------------------------------------------------------------------
12   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*  |_|


--------------------------------------------------------------------------------
13   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

     6.4%
--------------------------------------------------------------------------------
14   TYPE OF REPORTING PERSON*

     IN
--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                       7



      This Amendment No. 3 to Schedule 13D (this "Amendment") amends the
below-indicated items from the Schedule 13D previously filed by or on behalf of
the undersigned parties (the "Reporting Persons"), as previously amended (the
"Schedule 13D"), by supplementing such Items with the information below:

Item 2.  Identity and Background.

      David Nierenberg is hereby added as a Reporting Person; his business
address is 19605 NE 8th Street, Camas WA 98607; his principal occupation is
President of Nierenberg Investment Management Company, Inc. and Nierenberg
Investment Management Offshore, Inc, two of the other Reporting Persons; during
the past five years he has not been convicted in a criminal proceeding required
to be reported in response to Item 2(d), or a party to a civil proceeding
required to be reported in response to Item 2(e), of Schedule 13D; and he is a
citizen of the United States of America.

Item 3.  Source and Amount of Funds or Other Consideration.

      On March 25, 2008 the Reporting Persons acquired a total of 1,270,388
shares of NTG's common stock through conversion, in accordance with their terms
and without the payment of additional consideration, all of the shares of NTG
convertible preferred stock acquired by the Reporting Persons on April 7, 2006,
as previously reported, that they beneficially owned immediately prior
to conversion.

Item 4.  Purpose of the Transaction.

      Reference is made to the responses to Items 3 and 5, which are
incorporated herein by reference.

      The Reporting Persons hold their shares of NTG common stock for
investment. The Reporting Persons reserve the right to increase or decrease
their investment in NTG depending on market conditions, circumstances affecting
NTG and/or extrinsic factors such as developments in NTG' s industry and the
economic environment, and to discuss NTG and their investment in the shares of
NTG with the directors and executive officers of NTG and third parties, without
amending the Schedule 13D except as required by applicable rules.

Item 5.  Interest in Securities of the Issuer.

(a,b)  The Reporting Persons, in the aggregate, beneficially own 1,270,388
common shares, constituting approximately 6.4% of the outstanding Shares. The
Reporting Persons have determined their current individual and aggregate
percentages for purposes of this Amendment based on the sum of the number of
shares of NTG common stock reported to be outstanding on March 11 in NTG's
Annual Report on Form 10-K for the year ended December 31, 2007 plus the number
of shares of NTG common stock acquired by the Reporting Persons through
conversion of convertible preferred stock (see Item 3).

                                       8


      c) On March 25, 2008, the Reporting Persons acquired the following shares
of NTG common stock through conversion of convertible preferred stock (see Item
3):



                           Transaction       Common Shares      Preferred Shares
Portfolio Name                Date             Acquired            Converted
--------------             -----------       -------------      ----------------
D3 Family Fund LP           3/25/2008           251,249               1,961
D3 Family Bulldog Fund LP   3/25/2008           740,294               5,778
DIII Offshore Fund LP       3/25/2008           278,795               2,176

Item 7.  Material to be filed as Exhibits

      Exhibit 1 to this Schedule 13D is the Joint Filing Agreement among the
Reporting Persons dated March 5, 2008 pursuant to which all of the Reporting
Persons (and one of their affiliates that owns no NTG shares and is therefore
not a Reporting Person) have authorized the filing of Schedule 13D's and
amendments thereto as a group.

                                       9


                                    SIGNATURE


After reasonable inquiry and to the best of my knowledge and belief, each of the
undersigned certifies that the information set forth in the Statement is true,
complete and correct.

                                   D3 Family Fund, L.P., D3 Family Bulldog
                                   Fund, L.P., and D3 Family Canadian Fund, L.P.

                                   By: Nierenberg Investment Management
                                      Company, Inc.

                                   Its: General Partner

March 26, 2008                     By: /s/ David Nierenberg
-------------------------          ---------------------------------------------
                                           David Nierenberg, President

                                   DIII Offshore Fund, L.P.

                                   By: Nierenberg Investment Management
                                             Offshore, Inc.

                                   Its: General Partner

March 26, 2008                     By: /s/ David Nierenberg
-------------------------          ---------------------------------------------
                                           David Nierenberg, President

                                   Nierenberg Investment Management
                                          Company, Inc.

March 26, 2008                     By: /s/ David Nierenberg
-------------------------          ---------------------------------------------
                                           David Nierenberg, President

                                   Nierenberg Investment Management
                                          Offshore, Inc.

March 26, 2008                      By: /s/David Nierenberg
-------------------------           -------------------------------------------
                                           David Nierenberg, President

March 26, 2008                     /s/ David Nierenberg
--------------------------         ---------------------------------------------
                                       David Nierenberg

                                       10