The Commissioner may designate special inspectors and contract fee inspectors to issue inspection certificates for boilers and pressure vessels they have inspected. If no defects are found or when the boiler or pressure vessel has been corrected in accordance with regulations, the designated special inspector or contract fee inspector shall issue a certificate on forms furnished by the Department. The designated special inspector or contract fee inspector shall collect the inspection certificate fee required under § 40.1-51.10 at the time of the issuance of the certificate and forward the fee and a duplicate of the certificate to the chief inspector immediately. Each designated special inspector or contract fee inspector may charge a fee as set under subsection A of § 40.1-51.15 for each certificate issued, but the charge shall not be mandatory. No charge shall be made unless the inspector has previously contracted therefor.