---
kind: "section"
citation: "46 C.F.R. § 154.801"
title: "46"
number: "154.801"
heading: "Pressure relief systems."
url: "https://uscodex.org/cfr/46/154.801"
---

# §154.801. Pressure relief systems.

- (a) **Each cargo tank that has a volume of 20m 3 (706 ft.** 3) or less must have at least one pressure relief valve.
- (b) **Each cargo tank that has a volume of more than 20m 3 (706 ft.** 3) must have at least two pressure relief valves of the same nominal relieving capacity.
- (c) **Each pressure relief valve must—**
  - (1) Meet [Subpart 162.018](/cfr/46/subpart162.018.md) of this chapter or, if the valve is also capable of vacuum relief and the MARVS is 69 kPa gauge (10 psig) or less, [Subpart 162.017](/cfr/46/subpart162.017.md) of this chapter, and have at least the capacity required under [§ 154.806](/cfr/46/154.806.md);
  - (2) Not be set for a higher pressure than the MARVS;
  - (3) Have a fitting for sealing wire that prevents the set pressure from being changed without breaking the sealing wire;
  - (4) Be fitted on the cargo tank to remain in the vapor phase under conditions of 15° list and of 0.015 L trim by both the bow and stern;
  - (5) Vent to a vent mast under [§ 154.805](/cfr/46/154.805.md), except a relief valve may vent to a common tank relief valve header if the back pressure is included in determining the required capacity under [§ 154.806](/cfr/46/154.806.md);
  - (6) Not vent to a common header or common vent mast if the relief valves are connected to cargo tanks carrying chemically incompatible cargoes;
  - (7) Not have any stop valves or other means of isolating the cargo tank from its relief valve unless:
    - (i) The stop valves are interlocked or arranged so that only one pressure relief valve is out of service at any one time;
    - (ii) The interlock arrangement automatically shows the relief valve that is out of service; and
    - (iii) The other valves have the relieving capacity required under [§ 154.806](/cfr/46/154.806.md), or all relief valves on the cargo tank are the same size and there is a spare of the same size, or there is a spare for each relief valve on a cargo tank.
- (d) **The pressure relief system must—**
  - (1) If the design temperature is below 0 °C (32 °F), be designed to prevent the relief valve from becoming inoperative due to ice formation; and
  - (2) **Be designed to prevent chattering of the relief valve.**

## Notes

### Amendments

[CGD 74-289, 44 FR 26009, May 3, 1979; 44 FR 59234, Oct. 15, 1979]

### Authority

Authority: 46 U.S.C. 3703, 9101; Department of Homeland Security Delegation No. 0170.1.

### Source

Source: CGD 74-289, 44 FR 26009, May 3, 1979, unless otherwise noted.

### Amendments

[CGD 74-289, 44 FR 26009, May 3, 1979; 44 FR 59234, Oct. 15, 1979]