**Exhibit 31.2**


SECTION
      302
      CERTIFICATION






I, Mel G. Riggs, certify
      that:




1.    
I
      have reviewed this annual report on Form
      10-K of Southwest Royalties Institutional Income Fund X-B, L.P.




2.    
Based
      on my knowledge, this report does not
      contain any untrue statement of a material fact or omit to state a material
      fact
      necessary to make the statements made, in light of the circumstances under
      which
      such statements were made, not misleading with respect to the period covered
      by
      this report;




3.    
Based
      on my knowledge, the financial
      statements, and other financial information included in this report, fairly
      present in all material respects the financial condition, results of operations
      and cash flows of the registrant as of, and for, the periods presented in this
      report;




4.    
The
      registrant’s other certifying officer(s)
      and I are responsible for establishing and maintaining disclosure controls
      and
      procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the
      registrant and have:




a)    
Designed
      such disclosure controls and
      procedures, or caused such disclosure controls and procedures to be designed
      under our supervision, to ensure that material information relating to the
      registrant, including its consolidated subsidiaries, is made known to us by
      others within those entities, particularly during the period in which this
      report is being prepared;




b)   
Evaluated
      the effectiveness of the registrant’s
      disclosure controls and procedures and presented in this report our conclusions
      about the effectiveness of the disclosure controls and procedures, as of the
      end
      of the period covered by this report based on such evaluation; and




c)    
Disclosed
      in this report any change in the
      registrant’s internal control over financial reporting that occurred during the
      registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter
      in the case of an annual report) that has materially affected, or is reasonably
      likely to materially affect, the registrant’s internal control over financial
      reporting; and




5.    
The
      registrant’s other certifying officer(s)
      and I have disclosed, based on our most recent evaluation of internal control
      over financial reporting, to the registrant’s auditors and the audit committee
      of registrant’s board of directors (or persons performing the equivalent
      functions):




a)    
All
      significant deficiencies and material
      weaknesses in the design or operation of internal control over financial
      reporting which reasonably likely to adversely affect the registrant’s ability
      to record, process, summarize and report financial information; and




b)   
Any
      fraud, whether or not material, that involves
      management or other employees who have a significant role in the registrant’s
      internal control over financial reporting.




Date: 
April
                5, 2007
            /s/
                Mel
                G. RiggsMel
                G.
                RiggsVice
                President and Chief Financial Officer ofSouthwest
                Royalties, Inc., theManaging
                General Partner ofSouthwest
                Royalties Institutional Income Fund X-B,
                L.P.