Sour service hammer union seals resist hydrogen sulfide attack per NACE MR0175/ISO 15156 standards. Specially formulated Viton, HNBR, or AFLAS compounds prevent blistering and cracking from H2S exposure. Mandatory in wells with significant sour gas content to avoid catastrophic seal failure and ensure personnel safety. https://globalsealstech.com/product/hammer-union-seal-2/