# Control Valve Sizing Isa75

> >-

- **Type:** Skill
- **Install:** `agentstack add skill-jskherman-engg-skills-control-valve-sizing-isa75`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [jskherman](https://agentstack.voostack.com/s/jskherman)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** Apache-2.0
- **Upstream author:** [jskherman](https://github.com/jskherman)
- **Source:** https://github.com/jskherman/engg-skills/tree/main/skills/control-valve-sizing-isa75

## Install

```sh
agentstack add skill-jskherman-engg-skills-control-valve-sizing-isa75
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Control Valve Sizing (ISA 75.01.01)

## Overview

Wrapper around `fluids.control_valve.size_control_valve_l` (liquid) and
`size_control_valve_g` (gas) per the ISA 75.01.01 / IEC 60534 family of
sizing equations.

## Prerequisites

1. `uv` available.
2. On first use, the script writes `LICENSE_NOTIFICATION.txt`.

## When to Use

- Selecting a control valve size for liquid or gas service.
- Checking a vendor-supplied Cv.
- Comparing Cv against the operating envelope (min/normal/max flow).

## Don't use for

- Pressure relief / safety valves — use `relief-valve-sizing-api520`.
- On-off valves, ball-valve trim selection.
- Cryogenic, slurry, abrasive, or high-temperature service with
  vendor-specific corrections beyond the ISA standard.

## Utility Scripts

- `uv run scripts/cv.py liquid --rho 800 --P1 2000000 --P2 1700000 --Q 0.005 --mu 5e-4 --Psat 100000 --Pc 4.2e6 --output /tmp/liq.json`
- `uv run scripts/cv.py gas --T 300 --MW 30 --mu 1.2e-5 --gamma 1.3 --Z 0.92 --P1 800000 --P2 400000 --Q 0.6 --output /tmp/gas.json`

## Procedure

1. Determine min / normal / max flow rates for the service.
2. Get fluid properties at upstream conditions (rho, mu, Psat, gamma, Z).
3. Run sizing at each flow rate; the operating Cv should fall in the
   20-80% open range at the normal flow.
4. Review cavitation/flashing and choked-flow limits separately against the
   valve trim and vendor data.
5. Select the valve from vendor data such that the required Cv is met at
   max flow with margin.

## Pitfalls

- Sizing only for max flow; the valve may be unstable or hunt at min flow
  if it ends up too far closed.
- Using upstream density for downstream conditions when there is a large
  pressure drop and significant flashing.
- Treating cavitation onset as the same as choked flow. They are different:
  cavitation depends on pressure recovery (`FL`) and `Psat`; choked flow
  depends on pressure ratio and `gamma`.
- Confusing Kv (m³/hr) with Cv (US gpm); the ratio is ~1.156.
- Using a globe-valve `FL` for a butterfly-valve service. `FL` is
  trim-specific.
- Sizing with viscosity-corrected `FR` outside the correlation envelope.

## Fallback Strategies

- If `fluids.control_valve` is unavailable, surface to the user; the
  rigorous ISA equation is not reproduced here.
- For two-phase service, the standard ISA 75.01.01 does not apply
  directly; consult the vendor or use a specialised correlation.

## Verification

- Run the listed script with representative inputs and an `--output` file when a deterministic calculation is available.
- Confirm the JSON result contains `ok: true`, expected units, and no unhandled warnings.
- Check result magnitudes against the stated assumptions, references, and a hand calculation or known operating range before reporting them.

## References

- `references/equation_family.md` — pointers to ISA 75.01.01 / IEC 60534.
- `fluids.control_valve` docs: https://fluids.readthedocs.io/fluids.control_valve.html
- ISA 75.01.01-2012 — Industrial-process control valves — Flow capacity.
- IEC 60534-2-1 — Industrial-process control valves — Part 2-1: Flow capacity.

## Anti-Patterns

- Specifying a control valve by line size rather than by Cv requirement.
- Skipping the min-flow check.
- Ignoring cavitation/flashing on liquid service near `Psat`.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [jskherman](https://github.com/jskherman)
- **Source:** [jskherman/engg-skills](https://github.com/jskherman/engg-skills)
- **License:** Apache-2.0

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-jskherman-engg-skills-control-valve-sizing-isa75
- Seller: https://agentstack.voostack.com/s/jskherman
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.