You need to pre-set the voltage setting on your power supply. The bulk charging voltage for a 12V flooded battery is 14.8 V at 25°C; at different temperatures this needs to be adjusted by −0.005 V/°C. After the voltage is set, connect to the battery while avoiding sparks over the battery (i.e. connect leads to the battery first and the power supply last). At the bulk charge voltage the battery should not gas noticeably. If you hear gassing, there is a problem, perhaps a shorted cell as others have suggested. After bulk charging, the cells should be watered to the appropriate level (not overwatered) and equalized, although modern lead-calcium batteries do not provide an easy means to add water and so you can't equalize.
If your power supply does have a crowbar circuit, definitely follow Arthur Dent's advice about the diode. You will need to compensate for the 0.7V diode drop in the initial power supply setting. From my research, the 6237B does not have a crowbar, however.